Organic tanning agent free of formaldehyde and chromium and preparation method of organic tanning agent

Abstract

The invention provides an organic tanning agent free of formaldehyde and chromium and a preparation method of the organic tanning agent, and belongs to the technical field of leather chemical industry. The preparation method comprises the following steps: preparing the composite filler; preparing a modified composite filler; preparing a caesalpinia spinosa extract concentrated solution; fermenting the caesalpinia spinosa extract concentrated solution; and preparing the organic tanning agent. The preparation method comprises the following steps: firstly, respectively dissolving zinc nitrate and potassium hydroxide to prepare solutions, then adding dodecyl trimethyl ammonium bromide into the potassium hydroxide solution, adding diatomite into the zinc nitrate solution, mixing and reacting to prepare a diatomite-loaded petal-shaped nano-zinc oxide structure composite filler, adding the diatomite-loaded petal-shaped nano-zinc oxide structure composite filler into an organic tanning agent, and carrying out tanning treatment to obtain the tanning agent. And zinc ions on the surface of the tanning agent can be adsorbed on the surface of a bacterial cell membrane to destroy the normal function of the bacterial cell membrane so as to death bacteria, so that the leather is tanned by utilizing the organic tanning agent, and the antibacterial property of the leather can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of leather chemical industry, and in particular to an organic tanning agent free of formaldehyde and chromium elements and a preparation method thereof. Background Art

[0002] The production process of finished leather is complicated and tedious, and requires a series of processes such as degreasing, deliming, pickling, pre-tanning, correction, retanning, dyeing, greasing, and finishing. Among them, tanning is the most critical process in the leather processing process. By adding agents, the raw hide is converted into semi-finished leather or cooked leather, which is cut into multiple layers and retanned into each layer, which can transform the raw hide into a leather product with durability, stability and good performance.

[0003] Tanning agents used in traditional tanning processes usually contain formaldehyde or chromium. Formaldehyde, as a common tanning agent component, plays a cross-linking role in the tanning process and can effectively improve the softness and durability of leather. However, it is highly volatile and toxic. During the use of leather products, formaldehyde will be continuously released, which will not only irritate the human respiratory tract and skin, causing adverse reactions such as coughing, asthma, and skin allergies, but long-term contact may also increase the risk of cancer. Chrome tanning agents can give leather good flexibility, fullness and a higher shrinkage temperature, thereby meeting a variety of application requirements. However, the chrome tanning process will produce a large amount of chromium-containing wastewater, in which the chromium element mostly exists in the form of trivalent chromium and hexavalent chromium, which can easily pollute the soil, causing damage to the soil structure and reduced fertility, affecting the growth of crops, and being transmitted through the food chain, ultimately endangering human health.

[0004] Therefore, it is necessary to provide an organic tanning agent that does not contain formaldehyde and chromium elements and a preparation method thereof to achieve the purpose of being green and environmentally friendly. Summary of the invention

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide an organic tanning agent free of formaldehyde and chromium elements and a preparation method thereof.

[0006] A method for preparing an organic tanning agent free of formaldehyde and chromium elements comprises the following steps:

[0007] S1: Preparation of composite fillers

[0008] A zinc nitrate solution and a potassium hydroxide solution are prepared respectively, then dodecyltrimethylammonium bromide is added to the potassium hydroxide solution, diatomaceous earth is added to the zinc nitrate solution, and the mixture is mixed and reacted to obtain a composite filler;

[0009] S2: Preparation of modified composite fillers

[0010] Firstly, polyaspartic acid is prepared, and the surface of the composite filler is modified by using a silane coupling agent, and then the surface-modified composite filler is modified by using polyaspartic acid to obtain a modified composite filler;

[0011] S3: Preparation of concentrated Caesalpinia spinulosa extract

[0012] The thorny caltrops are crushed, passed through a 40-60 mesh sieve, added into distilled water at a solid-liquid ratio of 1:(15-20) mL, fully stirred and dispersed, heated and extracted at 80-90° C. for 2-4 hours, filtered and concentrated under reduced pressure to 1 / 4 of the original volume, to obtain a thorny caltrops extract concentrate;

[0013] S4: Fermented Caesalpinia spinulosa extract concentrate

[0014] Activating Streptomyces and Lactobacillus plantarum respectively, and then adding them to the above-mentioned concentrated solution of the thorny fruit extract to carry out heat preservation fermentation to obtain a fermentation solution of the thorny fruit extract;

[0015] S5: Preparation of organic tanning agent

[0016] Melamine and pentaerythritol are mixed and reacted to prepare melamine polymers, which are then dissolved in deionized water, and the fermentation liquid of the thorny calendula extract is added to react, and then the modified composite filler is added and mixed evenly to obtain an organic tanning agent.

[0017] Furthermore, S1 specifically includes the following steps:

[0018] S1.1: Add zinc nitrate and potassium hydroxide into deionized water respectively, stir and dissolve them thoroughly to prepare a 0.2 mol / L solution to obtain a zinc nitrate solution and a potassium hydroxide solution;

[0019] S1.2: Add dodecyltrimethylammonium bromide to the potassium hydroxide solution, stir thoroughly to dissolve, and obtain a mixed solution;

[0020] S1.3: Add diatomaceous earth to the above zinc nitrate solution at a solid-liquid ratio of 1g:(10-12)mL, stir and adsorb for 10-12h, heat to 70-80℃, add the above mixed solution while stirring, keep warm and stir for 1-2h, and let stand for 2-3h. Filter, wash, dry and crush to obtain a composite filler.

[0021] Furthermore, S2 specifically includes the following steps:

[0022] S2.1: Add aspartic acid to 2.5 mM sodium hydroxide solution at a solid-liquid ratio of 1 g: (12-16) mL, heat and stir at 60-70°C for 20-24 h, then add hydrochloric acid to adjust the pH to 7-8, precipitate with alcohol, centrifuge and dry to obtain polyaspartic acid;

[0023] S2.2: Dissolve the silane coupling agent KH550 in anhydrous ethanol at a solid-liquid ratio of 1 g: (90-100) mL, and heat at 60-70°C for 1-2 h. Then add the composite filler prepared in step S1.3 at a solid-liquid ratio of 1 g: (8-10) mL, keep warm and stir to react for 2-3 h, filter, wash and dry to obtain a surface-modified composite filler.

[0024] S2.3: Add the above-mentioned polyaspartic acid and the above-mentioned surface-modified composite filler into deionized water at a solid-liquid ratio of 1g:1g:(18-20)mL, and add hydrochloric acid to adjust the pH to 3.8-4.2, heat and stir under reflux at 70-80°C for 20-24h, cool, and centrifuge to obtain a modified composite filler.

[0025] Furthermore, S4 specifically includes the following steps:

[0026] S4.1: inoculate Streptomyces into ISP medium, culture at 28-32°C and 120-150rpm for 3-5 days for activation to obtain activated Streptomyces;

[0027] S4.2: inoculating Lactobacillus plantarum into MRS culture medium, culturing at 30-35° C. for 20-24 hours for activation, and obtaining activated Lactobacillus plantarum;

[0028] S4.3: Add the activated Streptomyces and activated Lactobacillus plantarum to the concentrated syringa extract obtained in step S3 at a mass ratio of (2.8-3.2):1, continue to ferment at 28-32°C for 16-18h, and obtain the syringa extract fermentation liquid after removing the precipitate by centrifugation.

[0029] Furthermore, S5 specifically includes the following steps:

[0030] S5.1: adding melamine and pentaerythritol in equal molar ratios into deionized water, stirring well to obtain a mixed reaction solution;

[0031] S5.2: Add stannous octoate to the mixed reaction solution, heat at 150-160°C for 4-5h, cool naturally to room temperature, filter, vacuum dehydrate, wash and dry to obtain a melamine polymer;

[0032] S5.3: Add the above melamine polymer to deionized water at a solid-liquid ratio of 1 g: (20-30) mL, heat and stir to dissolve, then add the fermentation broth of the thorny fruit extract obtained in step S4.3, stir and mix evenly, add acetic acid to adjust the pH to 4-5, heat and stir at 60-80°C for 3-4 hours to obtain a precursor solution;

[0033] S5.4: Add the modified composite filler obtained in step S2.3 to the above precursor solution, perform ultrasonic treatment for 20-30 minutes, and then stir for 2-3 hours to obtain an organic tanning agent.

[0034] Furthermore, the mass fraction of dodecyltrimethylammonium bromide in the mixed solution to the potassium hydroxide solution is 1-2wt%, and the molar ratio of potassium hydroxide in the mixed solution to zinc nitrate in the zinc nitrate solution is (2-3):1.

[0035] Furthermore, the total mass of activated Streptomyces and activated Lactobacillus plantarum accounts for 10-15wt% of the concentrated solution of the thorny fruit extract.

[0036] Furthermore, the solid-liquid ratio of melamine to deionized water is 1 g:(1.5-2.5) mL, and the molar ratio of stannous octoate to melamine is 1:(90-100).

[0037] Furthermore, the mass ratio of the melamine polymer to the fermentation broth of the thorny fruit extract is 1:(2-3), and the solid-liquid ratio of the modified composite filler to the precursor solution is 1 g:(45-55) mL.

[0038] Furthermore, an organic tanning agent free of formaldehyde and chromium elements is prepared by the method for preparing an organic tanning agent free of formaldehyde and chromium elements as described in any one of the above items.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] 1. The present invention prepares a solution by first dissolving zinc nitrate and potassium hydroxide separately, then adding dodecyltrimethylammonium bromide to the potassium hydroxide solution, and adding diatomaceous earth to the zinc nitrate solution, and then mixing and reacting to prepare a composite filler of diatomaceous earth loaded with petal-shaped nano zinc oxide structure. After adding the composite filler to an organic tanning agent, since the petal-shaped nano zinc oxide can interact with the cell membrane of bacteria, zinc ions on its surface can be adsorbed on the surface of the bacterial cell membrane, changing the permeability of the cell membrane, destroying the normal function of the bacterial cell membrane, thereby killing the bacteria. Diatomaceous earth has a porous structure and can adsorb bacteria, thereby making the contact between the bacteria and the nano zinc oxide closer, increasing the chance of the nano zinc oxide acting on the bacteria. Therefore, the antibacterial property of the leather can be effectively improved by tanning the leather with the organic tanning agent.

[0041] 2. The present invention prepares a thorny syrup extract concentrate by first extracting the thorny syrup with water, and ferments the thorny syrup extract concentrate with Streptomyces and Lactobacillus plantarum to prepare a thorny syrup extract fermentation liquid, and then uses melamine and pentaerythritol as raw materials to prepare a melamine polymer, and finally the thorny syrup extract fermentation liquid and the melamine polymer are mixed for reaction to prepare an organic tanning agent. Since the polyphenols in the thorny syrup extract fermentation liquid are combined with leather collagen through hydrogen bonds, and the melamine polymer is cross-linked with the collagen through chemical bonds, when the leather is tanned, the components in the thorny syrup extract fermentation liquid first perform preliminary fixation and filling of the leather fibers, and then the melamine polymer performs a deeper cross-linking reaction on the basis of the fermentation liquid to form a more complex and firm network structure, thereby achieving the effect of synergistically improving the tensile strength and shrinkage temperature of the leather.

[0042] 3. The present invention activates and cultures Streptomyces and Lactobacillus plantarum first, and then inoculates them into the concentrated solution of the thorny nut extract at a mass ratio of (2.8-3.2):1. When fermenting the concentrated solution, it can not only decompose the complex components in the plant cell walls and cells of the thorny nut extract, making the tannins in the thorny nut extract more easily dissolve to increase the tannin content and activity, but also effectively decompose the macromolecular substances in the tannins, so that the tanning agent can penetrate deeper into the leather fibers more quickly and be evenly distributed inside the leather, thereby further improving the tanning effect on the leather. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable those skilled in the relevant art to make and use the present disclosure.

[0044] Figure 1 This is a flow chart of the method for preparing an organic tanning agent free of formaldehyde and chromium elements used in an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The following describes in detail an organic tanning agent free of formaldehyde and chromium elements and a preparation method thereof provided by the present invention in conjunction with the accompanying drawings and specific embodiments.

[0046] Preparation Example

[0047] The steps for preparing ISP medium are as follows:

[0048] 10 g of glucose, 2 g of asparagine, 2 g of potassium hydrogen phosphate, 0.5 g of magnesium sulfate heptahydrate, 0.001 g of ferric sulfate heptahydrate and 20 g of agar were added to 1 L of distilled water, heated and stirred until completely dissolved, and sterilized by high pressure to obtain ISP medium.

[0049] The preparation steps of MRS medium are as follows:

[0050] 10 g of peptone, 10 g of beef extract, 5 g of yeast extract, 20 g of glucose, 5 g of sodium acetate, 2 g of potassium dihydrogen citrate, 2 g of diammonium hydrogen phosphate, 1 mL of Tween 80, 0.58 g of magnesium sulfate heptahydrate and 0.25 g of manganese sulfate tetrahydrate were added to 1 L of distilled water, heated and stirred until completely dissolved, and sterilized by high pressure to obtain MRS medium.

[0051] Example 1

[0052] A method for preparing an organic tanning agent free of formaldehyde and chromium, such as Figure 1 As shown, the following steps are included:

[0053] S1: Preparation of composite fillers

[0054] S1.1: Add zinc nitrate and potassium hydroxide into deionized water respectively, stir and dissolve them thoroughly to prepare a 0.2 mol / L solution to obtain a zinc nitrate solution and a potassium hydroxide solution;

[0055] S1.2: Add dodecyltrimethylammonium bromide to the potassium hydroxide solution, stir and dissolve thoroughly to obtain a mixed solution, wherein the mass fraction of dodecyltrimethylammonium bromide in the potassium hydroxide solution is 1wt%;

[0056] S1.3: Add diatomaceous earth to the zinc nitrate solution at a solid-liquid ratio of 1g:10mL, stir and adsorb for 10 hours, heat to 70°C, add the mixed solution while stirring, keep warm and stir for 1 hour, and let stand for 2 hours, filter, wash, dry and crush to obtain a composite filler, wherein the molar ratio of potassium hydroxide in the mixed solution to zinc nitrate in the zinc nitrate solution is 2:1;

[0057] S2: Preparation of modified composite fillers

[0058] S2.1: Add aspartic acid to 2.5 mM sodium hydroxide solution at a solid-liquid ratio of 1 g:12 mL, heat and stir at 60 °C for 20 h, then add hydrochloric acid to adjust the pH to 7, precipitate with alcohol, centrifuge and dry to obtain polyaspartic acid;

[0059] S2.2: Dissolve the silane coupling agent KH550 in anhydrous ethanol at a solid-liquid ratio of 1g:90mL, and heat at 60°C for 1h. Then add the composite filler prepared in step S1.3 at a solid-liquid ratio of 1g:8mL, keep warm and stir to react for 2h, filter, wash and dry to obtain a surface-modified composite filler;

[0060] S2.3: Add the polyaspartic acid and the surface-modified composite filler into deionized water at a solid-liquid ratio of 1g:1g:18mL, add hydrochloric acid to adjust the pH to 3.8, heat and stir under reflux at 70°C for 20h, cool, and centrifuge to obtain a modified composite filler;

[0061] S3: Preparation of concentrated Caesalpinia spinulosa extract

[0062] The thorny yam was crushed, passed through a 40-mesh sieve, and then added into distilled water at a solid-liquid ratio of 1:15 mL, fully stirred and dispersed, heated and extracted at 80° C. for 2 h, and then filtered and concentrated under reduced pressure to 1 / 4 of the original volume to obtain a thorny yam extract concentrate;

[0063] S4: Fermented Caesalpinia spinulosa extract concentrate

[0064] S4.1: inoculate Streptomyces into ISP medium, culture at 28°C and 120 rpm for 3 days for activation to obtain activated Streptomyces;

[0065] S4.2: inoculating Lactobacillus plantarum into MRS medium, culturing at 30° C. for 20 h for activation, and obtaining activated Lactobacillus plantarum;

[0066] S4.3: adding the activated Streptomyces and activated Lactobacillus plantarum to the concentrated solution of the thorny fruit extract obtained in step S3 at a mass ratio of 2.8:1, and continuing to ferment at 28°C for 16 hours, and obtaining a fermentation solution of the thorny fruit extract after removing the precipitate by centrifugation, wherein the total mass of the activated Streptomyces and activated Lactobacillus plantarum accounts for 10wt% of the concentrated solution of the thorny fruit extract;

[0067] S5: Preparation of organic tanning agent

[0068] S5.1: adding melamine and pentaerythritol in an equal molar ratio to deionized water, and stirring well to obtain a mixed reaction liquid, wherein the solid-liquid ratio of melamine to deionized water is 1 g:1.5 mL;

[0069] S5.2: Add stannous octoate to the mixed reaction liquid, heat at 150°C for 4 hours, cool naturally to room temperature, filter, vacuum dehydrate, wash and dry to obtain a melamine polymer, wherein the molar ratio of stannous octoate to melamine is 1:90;

[0070] S5.3: Add the above melamine polymer to deionized water at a solid-liquid ratio of 1g:20mL, heat and stir to dissolve, then add the fermentation liquid of the thorny nut extract obtained in step S4.3, stir and mix evenly, add acetic acid to adjust the pH to 4, heat and stir at 60°C for 3h to obtain a precursor solution, wherein the mass ratio of the melamine polymer to the fermentation liquid of the thorny nut extract is 1:2;

[0071] S5.4: Add the modified composite filler obtained in step S2.3 to the above-mentioned precursor solution, ultrasonically treat for 20 minutes, and then stir for 2 hours to obtain an organic tanning agent, wherein the solid-liquid ratio of the modified composite filler to the precursor solution is 1g:45mL.

[0072] Example 2

[0073] A method for preparing an organic tanning agent free of formaldehyde and chromium, such as Figure 1 As shown, the following steps are included:

[0074] S1: Preparation of composite fillers

[0075] S1.1: Add zinc nitrate and potassium hydroxide into deionized water respectively, stir and dissolve them thoroughly to prepare a 0.2 mol / L solution to obtain a zinc nitrate solution and a potassium hydroxide solution;

[0076] S1.2: Add dodecyltrimethylammonium bromide to the potassium hydroxide solution, stir and dissolve thoroughly to obtain a mixed solution, wherein the mass fraction of dodecyltrimethylammonium bromide in the potassium hydroxide solution is 1.5wt%;

[0077] S1.3: Add diatomaceous earth to the zinc nitrate solution at a solid-liquid ratio of 1g:11mL, stir and adsorb for 11h, heat to 75°C, add the mixed solution while stirring, keep warm and stir for 1.5h, and let stand for 2.5h, filter, wash, dry and crush to obtain a composite filler, wherein the molar ratio of potassium hydroxide in the mixed solution to zinc nitrate in the zinc nitrate solution is 2.5:1;

[0078] S2: Preparation of modified composite fillers

[0079] S2.1: Add aspartic acid to 2.5 mM sodium hydroxide solution at a solid-liquid ratio of 1 g:14 mL, heat and stir at 65 °C for 22 h, then add hydrochloric acid to adjust the pH to 7.5, precipitate with alcohol, centrifuge and dry to obtain polyaspartic acid;

[0080] S2.2: Dissolve the silane coupling agent KH550 in anhydrous ethanol at a solid-liquid ratio of 1g:95mL, and heat at 65°C for 1.5h. Then add the composite filler prepared in step S1.3 at a solid-liquid ratio of 1g:9mL, keep warm and stir to react for 2.5h, filter, wash and dry to obtain a surface-modified composite filler;

[0081] S2.3: Add the polyaspartic acid and the surface-modified composite filler into deionized water at a solid-liquid ratio of 1g:1g:19mL, add hydrochloric acid to adjust the pH to 4, heat and stir under reflux at 75°C for 22h, cool, and centrifuge to obtain a modified composite filler;

[0082] S3: Preparation of concentrated Caesalpinia spinulosa extract

[0083] The thorny yam was crushed, passed through a 50-mesh sieve, and then added into distilled water at a solid-liquid ratio of 1:17 mL, fully stirred and dispersed, heated and extracted at 85° C. for 3 h, and then filtered and concentrated under reduced pressure to 1 / 4 of the original volume to obtain a thorny yam extract concentrate;

[0084] S4: Fermented Caesalpinia spinulosa extract concentrate

[0085] S4.1: inoculate Streptomyces into ISP medium, culture at 30°C and 135 rpm for 4 days for activation to obtain activated Streptomyces;

[0086] S4.2: inoculating Lactobacillus plantarum into MRS medium, culturing at 32° C. for 22 h for activation, and obtaining activated Lactobacillus plantarum;

[0087] S4.3: adding the activated Streptomyces and activated Lactobacillus plantarum to the concentrated syringa extract obtained in step S3 at a mass ratio of 3:1, and continuing to ferment at 30°C for 17 hours, and removing the precipitate by centrifugation to obtain a fermented syringa extract, wherein the total mass of the activated Streptomyces and activated Lactobacillus plantarum accounts for 12.5wt% of the concentrated syringa extract;

[0088] S5: Preparation of organic tanning agent

[0089] S5.1: adding melamine and pentaerythritol in an equal molar ratio into deionized water, and stirring them thoroughly to obtain a mixed reaction liquid, wherein the solid-liquid ratio of melamine to deionized water is 1 g:2 mL;

[0090] S5.2: Add stannous octoate to the mixed reaction liquid, heat the mixture at 155°C for 4.5 hours, cool naturally to room temperature, filter, vacuum dehydrate, wash and dry to obtain a melamine polymer, wherein the molar ratio of stannous octoate to melamine is 1:95;

[0091] S5.3: Add the above melamine polymer to deionized water at a solid-liquid ratio of 1g:25mL, heat and stir to dissolve, then add the fermentation liquid of the thorny nut extract obtained in step S4.3, stir and mix evenly, add acetic acid to adjust the pH to 4.5, heat and stir at 70°C for 3.5h to obtain a precursor solution, wherein the mass ratio of the melamine polymer to the fermentation liquid of the thorny nut extract is 1:2.5;

[0092] S5.4: Add the modified composite filler obtained in step S2.3 to the above-mentioned precursor solution, ultrasonically treat for 25 minutes, and then stir for 2.5 hours to obtain an organic tanning agent, wherein the solid-liquid ratio of the modified composite filler to the precursor solution is 1g:50mL.

[0093] Example 3

[0094] A method for preparing an organic tanning agent free of formaldehyde and chromium, such as Figure 1 As shown, the following steps are included:

[0095] S1: Preparation of composite fillers

[0096] S1.1: Add zinc nitrate and potassium hydroxide into deionized water respectively, stir and dissolve them thoroughly to prepare a 0.2 mol / L solution to obtain a zinc nitrate solution and a potassium hydroxide solution;

[0097] S1.2: Add dodecyltrimethylammonium bromide to the potassium hydroxide solution, stir and dissolve thoroughly to obtain a mixed solution, wherein the mass fraction of dodecyltrimethylammonium bromide in the potassium hydroxide solution is 2wt%;

[0098] S1.3: Add diatomaceous earth to the zinc nitrate solution at a solid-liquid ratio of 1g:12mL, stir and adsorb for 12h, heat to 80°C, add the mixed solution while stirring, keep warm and stir for 2h, and let stand for 3h, filter, wash, dry and crush to obtain a composite filler, wherein the molar ratio of potassium hydroxide in the mixed solution to zinc nitrate in the zinc nitrate solution is 3:1;

[0099] S2: Preparation of modified composite fillers

[0100] S2.1: Add aspartic acid to 2.5 mM sodium hydroxide solution at a solid-liquid ratio of 1 g:16 mL, heat and stir at 70 °C for 24 h, then add hydrochloric acid to adjust the pH to 8, precipitate with alcohol, centrifuge and dry to obtain polyaspartic acid;

[0101] S2.2: Dissolve the silane coupling agent KH550 in anhydrous ethanol at a solid-liquid ratio of 1g:100mL, and heat at 70°C for 2h. Then add the composite filler prepared in step S1.3 at a solid-liquid ratio of 1g:10mL, keep warm and stir to react for 3h, filter, wash and dry to obtain a surface-modified composite filler;

[0102] S2.3: Add the polyaspartic acid and the surface-modified composite filler into deionized water at a solid-liquid ratio of 1g:1g:20mL, add hydrochloric acid to adjust the pH to 4.2, heat and stir under reflux at 80°C for 24h, cool, and centrifuge to obtain a modified composite filler;

[0103] S3: Preparation of concentrated Caesalpinia spinulosa extract

[0104] The thorny yam was crushed, passed through a 60-mesh sieve, added into distilled water at a solid-liquid ratio of 1:20 mL, fully stirred and dispersed, heated and extracted at 90° C. for 4 h, filtered and concentrated under reduced pressure to 1 / 4 of the original volume, to obtain a thorny yam extract concentrate;

[0105] S4: Fermented Caesalpinia spinulosa extract concentrate

[0106] S4.1: inoculate Streptomyces into ISP medium, culture at 32°C and 150 rpm for 5 days for activation, and obtain activated Streptomyces;

[0107] S4.2: inoculating Lactobacillus plantarum into MRS medium, culturing at 35° C. for 24 hours for activation, and obtaining activated Lactobacillus plantarum;

[0108] S4.3: adding the activated Streptomyces and activated Lactobacillus plantarum to the concentrated syringa extract obtained in step S3 at a mass ratio of 3.2:1, and continuing to ferment at 32°C for 18 hours, and obtaining a fermented syringa extract liquid after removing the precipitate by centrifugation, wherein the total mass of the activated Streptomyces and activated Lactobacillus plantarum accounts for 15wt% of the concentrated syringa extract;

[0109] S5: Preparation of organic tanning agent

[0110] S5.1: adding melamine and pentaerythritol in an equal molar ratio to deionized water, and stirring them thoroughly to obtain a mixed reaction liquid, wherein the solid-liquid ratio of melamine to deionized water is 1 g:2.5 mL;

[0111] S5.2: Add stannous octoate to the mixed reaction liquid, heat at 160°C for 5 hours, cool naturally to room temperature, filter, vacuum dehydrate, wash and dry to obtain a melamine polymer, wherein the molar ratio of stannous octoate to melamine is 1:100;

[0112] S5.3: Add the above melamine polymer to deionized water at a solid-liquid ratio of 1g:30mL, heat and stir to dissolve, then add the fermentation liquid of the thorny nut extract obtained in step S4.3, stir and mix evenly, add acetic acid to adjust the pH to 5, heat and stir at 80°C for 4h to obtain a precursor solution, wherein the mass ratio of the melamine polymer to the fermentation liquid of the thorny nut extract is 1:3;

[0113] S5.4: Add the modified composite filler obtained in step S2.3 to the above-mentioned precursor solution, ultrasonically treat for 30 minutes, and then stir for 3 hours to obtain an organic tanning agent, wherein the solid-liquid ratio of the modified composite filler to the precursor solution is 1g:55mL.

[0114] Comparative Example 1

[0115] The difference between Comparative Example 1 and Example 1 is that step S5.4 is removed, that is, no modified composite filler is added.

[0116] Comparative Example 2

[0117] The difference between Comparative Example 2 and Example 1 is that the dodecyltrimethylammonium bromide in step S1.2 is removed.

[0118] Comparative Example 3

[0119] The difference between Comparative Example 3 and Example 1 is that the fermentation liquid of the thorny fruit extract in step S5.3 is replaced by an equal mass of melamine polymer.

[0120] Comparative Example 4

[0121] The difference between Comparative Example 4 and Example 1 is that the melamine polymer in step S5.3 is replaced by an equal mass of the fermentation liquid of the extract of Celastrus spinulosa.

[0122] Comparative Example 5

[0123] The difference between Comparative Example 5 and Example 1 is that the mass ratio of activated Streptomyces to activated Lactobacillus plantarum is adjusted to 2.5:1.

[0124] Comparative Example 6

[0125] The difference between Comparative Example 6 and Example 1 is that the mass ratio of activated Streptomyces to activated Lactobacillus plantarum is adjusted to 3.5:1.

[0126] Test Case

[0127] The deacidified rawhide was cut into slices of equal weight along the spine line, and tanned using the organic tanning agents prepared in Examples 1-3 and Comparative Examples 1-6 according to the international leather tanning method.

[0128] Test 1: First, the Staphylococcus aureus stock solution was activated with liquid culture medium for 12 hours (about 10 8 CFU / mL, and then dilute the bacterial stock solution with PBS (about 10 5 CFU / mL). 1 mL of the diluted Staphylococcus aureus solution was taken respectively, and cultured with the leather tanned with the organic tanning agent prepared in Example 1-3 and Comparative Example 1-2 at 37°C in a water bath with shaking for 12 h, then applied to the solid culture medium with an applicator, cultured in a constant temperature incubator at 37°C, the growth of the colonies was observed, and the antibacterial rate was calculated. The results are shown in Table 1.

[0129] Table 1: Test results of antibacterial rate of leather tanned with organic tanning agent obtained in Examples 1-3 and Comparative Examples 1-2

[0130] Antibacterial rate (%) Example 1 99.2 Example 2 99.1 Example 3 99.4 Comparative Example 1 53.6 Comparative Example 2 87.3

[0131] As can be seen from Table 1, the leather obtained by tanning raw cowhide with the organic tanning agent prepared without adding the modified composite filler in Comparative Example 1 has an antibacterial rate of about 53.6%, which is much lower than that of Examples 1, 2 and 3, indicating that the antibacterial property of the leather can be effectively improved by first dissolving zinc nitrate and potassium hydroxide into solutions, then adding dodecyltrimethylammonium bromide to the potassium hydroxide solution, and adding diatomaceous earth to the zinc nitrate solution, and then mixing and reacting to prepare a composite filler with a petal-shaped nano zinc oxide structure loaded with diatomaceous earth, adding the composite filler to the organic tanning agent, and using the organic tanning agent to tan the leather;

[0132] In addition, after dodecyltrimethylammonium bromide is removed in Comparative Example 2, the obtained nano zinc oxide has a non-petal-shaped structure. After tanning raw cowhide with an organic tanning agent prepared by adding a modified composite filler composed of the non-petal-shaped nano zinc oxide and diatomaceous earth, the antibacterial rate of the leather is about 87.3%, which is also lower than that of Examples 1-3. It can be seen that the petal-shaped nano zinc oxide has a higher antibacterial effect after being compounded with diatomaceous earth.

[0133] Test 2: The shrinkage temperature of the leather tanned with the organic tanning agent obtained in Examples 1-3 and Comparative Examples 3-6 was measured using a shrinkage temperature measuring instrument. The results are shown in Table 2.

[0134] Test 3: The tensile strength and tear strength of the leather tanned with organic tanning agent obtained in Examples 1-3 and Comparative Examples 3-6 were tested using a tensile testing machine. The results are shown in Table 2.

[0135] Table 2: Test results of shrinkage temperature, tensile strength and tear strength of tanned leather

[0136] Shrinkage temperature(℃) Tensile strength(MPa) Tear strength(N / mm) Example 1 82.3 14.2 59.8 Example 2 82.5 13.9 58.1 Example 3 82.2 14.1 58.5 Comparative Example 3 74.8 11.6 52.7 Comparative Example 4 70.7 10.5 43.6 Comparative Example 5 76.3 11.7 54.3 Comparative Example 6 78.6 12.3 53.2

[0137] As can be seen from Table 2, after tanning raw cowhide with a single melamine polymer and an organic tanning agent prepared by a single fermentation liquid of the thorny wormwood extract in Comparative Examples 3 and 4, the shrinkage temperature, tensile strength and tear strength of the leather obtained are lower than those in Examples 1-3. This shows that by first extracting the thorny wormwood with water to prepare a thorny wormwood extract concentrate, fermenting the thorny wormwood extract concentrate with Streptomyces and Lactobacillus plantarum to prepare a thorny wormwood extract fermentation liquid, and then using melamine and pentaerythritol as raw materials to prepare a melamine polymer, and finally mixing the thorny wormwood extract fermentation liquid with the melamine polymer to react to prepare an organic tanning agent, the effect of synergistically improving the tensile strength and shrinkage temperature of the leather can be achieved.

[0138] In addition, in Comparative Examples 5 and 6, after the mass ratio of activated Streptomyces to activated Lactobacillus plantarum was adjusted to 2.5:1 and 3.5:1, the shrinkage temperature, tensile strength and tear strength of the leather after tanning raw cowhide with the obtained organic tanning agent were also lower than those in Examples 1-3. This shows that by first activating and culturing Streptomyces and Lactobacillus plantarum, and then inoculating them into the concentrated solution of the spinulosa fruit extract at a mass ratio of (2.8-3.2):1 and fermenting it, the tanning effect of the leather can be further improved. That is to say, when the inoculation mass ratio of activated Streptomyces to activated Lactobacillus plantarum is (2.8-3.2):1, the obtained mail tanning agent has the best tanning effect.

[0139] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing an organic tanning agent free of formaldehyde and chromium, characterized in that: The steps include: S1: Preparation of composite fillers A zinc nitrate solution and a potassium hydroxide solution are prepared respectively, then dodecyltrimethylammonium bromide is added to the potassium hydroxide solution, diatomaceous earth is added to the zinc nitrate solution, and the mixture is mixed and reacted to obtain a composite filler; S2: Preparation of modified composite fillers Firstly, polyaspartic acid is prepared, and the surface of the composite filler is modified by using a silane coupling agent, and then the surface-modified composite filler is modified by using polyaspartic acid to obtain a modified composite filler; S3: Preparation of concentrated Caesalpinia spinulosa extract The thorny caltrops are crushed, passed through a 40-60 mesh sieve, added into distilled water at a solid-liquid ratio of 1:(15-20) mL, fully stirred and dispersed, heated and extracted at 80-90° C. for 2-4 hours, filtered and concentrated under reduced pressure to 1 / 4 of the original volume, to obtain a thorny caltrops extract concentrate; S4: Fermented Caesalpinia spinulosa extract concentrate Activating Streptomyces and Lactobacillus plantarum respectively, and then adding them to the above-mentioned concentrated solution of the thorny fruit extract to carry out heat preservation fermentation to obtain a fermentation solution of the thorny fruit extract; S5: Preparation of organic tanning agent Melamine and pentaerythritol are mixed and reacted to prepare melamine polymers, which are then dissolved in deionized water, and the fermentation liquid of the thorny calendula extract is added to react, and then the modified composite filler is added and mixed evenly to obtain an organic tanning agent.

2. The method for preparing a formaldehyde-free and chromium-free organic tanning agent according to claim 1, characterized in that: S1 includes the following steps: S1.1: Add zinc nitrate and potassium hydroxide into deionized water respectively, stir and dissolve them thoroughly to prepare a 0.2 mol / L solution to obtain a zinc nitrate solution and a potassium hydroxide solution; S1.2: Add dodecyltrimethylammonium bromide to the potassium hydroxide solution, stir thoroughly to dissolve, and obtain a mixed solution; S1.3: Add diatomaceous earth to the above zinc nitrate solution at a solid-liquid ratio of 1g:(10-12)mL, stir and adsorb for 10-12h, heat to 70-80℃, add the above mixed solution while stirring, keep warm and stir for 1-2h, and let stand for 2-3h. Filter, wash, dry and crush to obtain a composite filler.

3. The method for preparing a formaldehyde-free and chromium-free organic tanning agent according to claim 2, characterized in that: S2 includes the following steps: S2.1: Add aspartic acid to 2.5 mM sodium hydroxide solution at a solid-liquid ratio of 1 g: (12-16) mL, heat and stir at 60-70°C for 20-24 h, then add hydrochloric acid to adjust the pH to 7-8, precipitate with alcohol, centrifuge and dry to obtain polyaspartic acid; S2.2: Dissolve the silane coupling agent KH550 in anhydrous ethanol at a solid-liquid ratio of 1g:(90-100)mL, and heat at 60-70℃ for 1-2h, then add the composite filler prepared in step S1.3 at a solid-liquid ratio of 1g:(8-10)mL, keep warm and stir to react for 2-3h, filter, wash and dry to obtain a surface-modified composite filler; S2.3: Add the above-mentioned polyaspartic acid and the above-mentioned surface-modified composite filler into deionized water at a solid-liquid ratio of 1g:1g:(18-20)mL, add hydrochloric acid to adjust the pH to 3.8-4.2, heat and stir under reflux at 70-80℃ for 20-24h, cool, and centrifuge to obtain a modified composite filler.

4. The method for preparing a formaldehyde-free and chromium-free organic tanning agent according to claim 3, characterized in that: S4 includes the following steps: S4.1: inoculate Streptomyces into ISP medium, culture at 28-32°C and 120-150rpm for 3-5 days for activation to obtain activated Streptomyces; S4.2: inoculating Lactobacillus plantarum into MRS culture medium, culturing at 30-35° C. for 20-24 hours for activation, and obtaining activated Lactobacillus plantarum; S4.3: Add the activated Streptomyces and activated Lactobacillus plantarum to the mixture in step S4.3 according to the mass ratio (2.8-3.2):

1. The concentrated solution of the thorny fruit extract obtained in S3 is fermented at 28-32° C. for 16-18 hours, and the precipitate is removed by centrifugation to obtain a fermentation solution of the thorny fruit extract.

5. The method for preparing a formaldehyde-free and chromium-free organic tanning agent according to claim 4, characterized in that: S5 specifically includes the following steps: S5.1: adding melamine and pentaerythritol in equal molar ratios into deionized water, and stirring well to obtain a mixed reaction solution; S5.2: Add stannous octoate to the mixed reaction solution, heat at 150-160°C for 4-5h, cool naturally to room temperature, filter, vacuum dehydrate, wash and dry to obtain a melamine polymer; S5.3: Add the above melamine polymer to deionized water at a solid-liquid ratio of 1 g: (20-30) mL, heat and stir to dissolve, then add the fermentation broth of the thorny fruit extract obtained in step S4.3, stir and mix evenly, add acetic acid to adjust the pH to 4-5, heat and stir at 60-80°C for 3-4 hours to obtain a precursor solution; S5.4: Add the modified composite filler obtained in step S2.3 to the above precursor solution, perform ultrasonic treatment for 20-30 minutes, and then stir for 2-3 hours to obtain an organic tanning agent.

6. The method for preparing an organic tanning agent free of formaldehyde and chromium according to claim 2, characterized in that: The mass fraction of dodecyltrimethylammonium bromide in the mixed solution to the potassium hydroxide solution is 1-2wt%, and the molar ratio of the potassium hydroxide in the mixed solution to the zinc nitrate in the zinc nitrate solution is (2-3):

1.

7. The method for preparing an organic tanning agent free of formaldehyde and chromium according to claim 4, characterized in that: The total weight of the activated Streptomyces and the activated Lactobacillus plantarum accounts for 10-15 wt % of the concentrated solution of the thorny fruit extract.

8. The method for preparing an organic tanning agent free of formaldehyde and chromium according to claim 5, characterized in that: The solid-liquid ratio of melamine to deionized water is 1 g:(1.5-2.5) mL, and the molar ratio of stannous octoate to melamine is 1:(90-100).

9. The method for preparing an organic tanning agent free of formaldehyde and chromium according to claim 5, characterized in that: The mass ratio of melamine polymer to the fermentation liquid of the thorny calamus extract is 1:(2-3), and the solid-liquid ratio of the modified composite filler to the precursor solution is 1g:(45-55)mL.

10. An organic tanning agent free of formaldehyde and chromium, characterized in that: The tanning agent is prepared by the method for preparing an organic tanning agent free of formaldehyde and chromium elements as described in any one of claims 1 to 9.

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