A kind of processing method of crocodile leather

Abstract

The invention discloses a method for processing crocodile leather, and relates to the technical field of leather processing. When processing crocodile leather, the present invention undergoes soaking, fleshing, degreasing, liming, re-liming, bleaching and fading, deacidification, pre-tanning, tanning, shaving, degreasing, neutralization, retanning-fat-dyeing, and post-processing processes, and uses a synthetic terminal epoxy hyperbranched polymer in the pre-tanning process, and uses a synthetic amphiphilic polymer retanning-fat-liquor in the retanning-fat-dyeing process. The crocodile leather prepared by the present invention has a higher shrinkage temperature, good tensile strength and elongation at break, and also has good antibacterial and flame retardant properties. At the same time, the use of chrome-containing tanning agents is avoided during the processing, the use of salt is reduced, and the difficulty and pressure of wastewater treatment are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of leather processing, in particular to a method for processing crocodile leather. Background Art

[0002] Crocodiles have high nutritional value, medicinal value, ecological significance and ornamental value. They contain a variety of amino acids, fatty acids, minerals and vitamins, and are rare protein materials. As one of the iconic luxury goods in the high-end leather products industry, crocodile leather products are sought after by all parties for their unique patterns and rarity.

[0003] Leather manufacturing is the main technology to achieve sustainable utilization of animal hide biomass resources. However, leather products are usually produced by traditional chrome tanning. The discharge of chromium-containing waste and the introduction of neutral salts in the pickling process make it difficult to treat tanning wastewater, posing a potential threat to the environment and public health. In view of the environmental pollution problems caused by chrome tanning in the current leather making process, the development of chrome-free ecological leather manufacturing technology has become the most important development direction in the leather industry in recent years.

[0004] Therefore, eliminating pollution from the source and implementing chrome-free tanning and salt-free pickling are important measures to manufacture ecological leather products and realize the transformation and upgrading of the leather industry. However, most chrome-free organic tanning agents currently face problems such as low shrinkage temperature of tanned leather, quality defects of finished leather, and potential aldehyde / chlorine pollution. In addition, chrome-free organic tanning reduces the positive charge of collagen fibers after tanning, resulting in a reduction in the binding sites of most anionic dyeing and finishing materials in the traditional chrome tanning system, which leads to a significant decrease in the absorption and chemical binding rate of dyeing and finishing materials, resulting in problems such as discoloration and poor feel of the finished leather, which cannot meet the new development needs of the tanning system. Summary of the invention

[0005] The purpose of the present invention is to provide a method for processing crocodile leather to solve the problems existing in the prior art.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for processing crocodile leather, characterized in that it mainly comprises the following processing steps: soaking, fleshing, degreasing, liming, reliming, bleaching and fading, deacidification, pretanning, tanning, shaving, degreasing, neutralization, retanning-fatting-dyeing, and post-treatment, wherein the pretanning process uses a synthetic terminal epoxy hyperbranched polymer, and the retanning-fatting-dyeing process uses a synthetic amphiphilic polymer retanning-fatting agent;

[0008] The epoxy-terminated hyperbranched polymer is prepared by first reacting trimethylolpropane with succinic anhydride and diethanolamine to obtain a hydroxy-terminated hyperbranched polymer, and then reacting the polymer with epichlorohydrin.

[0009] The amphiphilic polymer retanning-fatting agent is prepared by reacting palmitic acid with epibromohydrin to obtain 3-bromo-2-hydroxypropyl palmitate, which is then reacted with N-allylimidazole to obtain modified allyl imidazole, copolymerizing the modified allyl imidazole with diallyldimethylammonium chloride and allylphosphonic acid to obtain an amphiphilic polymer, and finally compounding the amphiphilic polymer with castor oil, rapeseed oil and fatty acid methyl ester.

[0010] As an optimization, the crocodile skin is taken from the abdomen of artificially cultivated Siamese crocodiles or Nile crocodiles.

[0011] As an optimization, the soaking, fleshing, degreasing, liming, reliming, bleaching and fading are the pretreatment steps for crocodile leather, and the detailed operations are carried out with reference to the document "Practical Leather and Fur Production Technology (Continued)" (Volume 30, Issue 5, 2013).

[0012] As an optimization, the processing method of crocodile leather mainly includes the following steps:

[0013] All the following dosages are based on the quality of pre-treated crocodile leather;

[0014] (1) Deacidification: 200-300% pure water, 2-4r / min, add 7-8% sodium chloride, add crocodile skin after 10 minutes, add 2-3% sodium bicarbonate every 15 minutes until the pH is greater than 7.5, continue to drum for 30-40 minutes, and change the liquid for washing;

[0015] (2) Pretanning: 100-200% pure water, 1% hexamethylenetetramine, rotate at 2-4 rpm for 2 h; adjust the pH to 6.8-7.2, rotate at 25-30°C for 30 min, add 8-10% terminal epoxy hyperbranched polymer, 1% sodium dodecyl sulfate, rotate for 8-10 h; add a mixture of sodium bicarbonate and sodium carbonate in a mass ratio of 1:1, add 1% each time, add once every 20 min, adjust the pH to 8.0-8.4, heat to 30-35°C, rotate for 2-3 h, let stand for 10-12 h, change the solution and wash with water;

[0016] (3) Tanning: 150-200% pure water, 1-2% formic acid, adjust pH to 2.4-3.0, let stand for 3-4 hours; add 6-7% aluminum tanning agent, 2-4r / min, turn and stop for 5-6 hours, heat to 35-40°C, add sodium bicarbonate in batches, 1% each time, 1 hour interval, adjust pH to 4.0-4.2, turn for 2-3 hours, let stand for 24-30 hours, turn for another 10-15 minutes, change liquid and wash, remove from drum, and ride for 20-24 hours;

[0017] (4) Shaving: Adjust the thickness according to product requirements;

[0018] (5) Degreasing: pure water 200-300%, degreasing agent 1%, let stand for 2-3 hours, add oxalic acid 0.5-0.8%, let stand for 1-1.5 hours, change the solution and wash with water;

[0019] (6) Neutralization: 100-150% pure water, temperature 35-40°C, 0.5-1.0% sodium formate, 0.4-0.8% sodium bicarbonate, add in portions to adjust the pH to 5.5-5.8, let stand for 10-12 hours, and change the solution for washing;

[0020] (7) Retanning-fatliquor-dyeing: 150-200% pure water, 45-50°C, 18-20% amphiphilic polymer retanning-fatliquor, 2-3% dye, 2-4 rpm, turn and stop for 10-12 h, add formic acid to adjust pH to 3.5-3.8, let stand for 5-6 h, change the solution and wash with water;

[0021] (8) Post-processing: Horse riding, nail board drying to obtain crocodile leather.

[0022] As an optimization, the preparation method of the epoxy-terminated hyperbranched polymer in step (2) is as follows:

[0023] (I) 5-6 parts of trimethylolpropane are weighed by weight, heated at 70-80° C. under a nitrogen atmosphere until the trimethylolpropane is completely melted, 1.48-2 parts of p-toluenesulfonic acid are added, stirred at 300-400 r / min for 10-15 min, 33.5-45.8 parts of succinic anhydride and 35.2-48 parts of diethanolamine are simultaneously added dropwise at a rate of 50-60 drops / min, reacted at 120° C. for 4-6 h after the addition is completed, vacuum-reduced for 15 min every 45 min, cooled naturally to room temperature after the reaction is completed, and vacuum-dried at 70-80° C. for 10-12 h to obtain a hydroxyl-terminated hyperbranched polymer;

[0024] (II) 17-19 parts of a hydroxyl-terminated hyperbranched polymer and 20-24 parts of tetrahydrofuran were weighed and mixed uniformly, stirred at 300-400 r / min at room temperature until dissolved, 0.76-0.85 parts of boron trifluoride etherate were added, 10.9-11.8 parts of epichlorohydrin were added dropwise at 50-60 drops / min, after the addition was completed, the mixture was refluxed in an oil bath at 70-75° C. for 2-3 h, cooled to 30° C., and the epichlorohydrin was removed by reduced pressure distillation, 20.7-22.4 parts of a 25 wt % sodium hydroxide solution were added dropwise at 5-6 drops / s, after the addition was completed, the mixture was reacted at 50-60° C. and 300-400 r / min for 3-4 h, filtered, distilled under reduced pressure, centrifuged at 6000-8000 rpm for 12-15 min, the liquid phase was collected, and vacuum dried at 50-60° C. for 6-8 h to obtain an epoxy-terminated hyperbranched polymer.

[0025] As an optimization, the reaction process of the hydroxyl-terminated hyperbranched polymer in step (I) is as follows:

[0026]

[0027] As an optimization, the reaction process of the epoxy-terminated hyperbranched polymer in step (II) is as follows:

[0028]

[0029] As an optimization, the aluminum tanning agent in step (3) is aluminum sulfate 18hydrate.

[0030] As an optimization, the degreasing agent in step (5) is DESOAGEN N309.

[0031] As an optimization, the preparation method of the amphiphilic polymer retanning-fatting agent in step (7) is as follows:

[0032] (a) palmitic acid, epibromopropane and cetyltrimethylammonium bromide are uniformly mixed in a mass ratio of 1: (0.64-0.8): (0.0016-0.0018), stirred at 60-65°C and 300-400 r / min until completely dissolved, reacted at 100-105°C and 300-400 r / min for 5-6 hours, washed with pure water at 70-80°C for 3-5 times, and vacuum dried at 50-60°C for 6-8 hours to obtain 3-bromo-2-hydroxypropyl palmitate;

[0033] (b) 3-bromo-2-hydroxypropyl palmitate, N-allylimidazole and ethyl acetate are mixed uniformly in a mass ratio of 1:(0.315-0.345):(5-7), stirred at room temperature at 200-300 r / min until dissolved, refluxed at 65-70° C. and 300-400 r / min for 24-26 h, filtered, washed with ethyl acetate for 5-6 times, distilled under reduced pressure, and vacuum dried at 30-35° C. for 24-28 h to obtain modified allyl imidazole;

[0034] (c) uniformly mixing modified allyl imidazole, diallyl dimethyl ammonium chloride, allyl phosphonic acid, n-dodecyl mercaptan and anhydrous ethanol in a mass ratio of 1:(1.25-1.32):(0.22-0.27):(0.0303-0.0305):(10-15), stirring at 300-400 r / min under a nitrogen atmosphere until dissolved, adding 10 wt% azobisisobutyronitrile ethanol solution (8.3 times the mass of n-dodecyl mercaptan) at 60-70° C. and 300-400 r / min at a rate of 5-6 drops per second, reacting for 6-7 hours after the addition, removing the solvent by rotary evaporation, dialyzing in ethanol aqueous solution for 36-40 hours, changing the ethanol aqueous solution every 4 hours, and vacuum drying at 50-60° C. for 12-15 hours to obtain an amphiphilic polymer;

[0035] (d) Weigh 2 to 3 parts of an amphiphilic polymer, 2 to 3 parts of castor oil, 3 to 4 parts of rapeseed oil and 4 to 6 parts of fatty acid methyl ester by weight, mix them evenly, stir them in an oil bath at 60 to 70° C. and 500 to 600 r / min for 30 to 40 min, adjust the pH to 6.5 with a 10 wt % triethanolamine acetic acid solution, add 99 to 180 parts of pure water at 60 to 70° C., stir them at 500 to 600 r / min for 30 to 40 min, stop heating, and cool them naturally to room temperature to obtain an amphiphilic polymer retanning-fatting agent.

[0036] As an optimization, the reaction process of 3-bromo-2-hydroxypropyl palmitate in step (a) is as follows:

[0037]

[0038] As an optimization, the reaction process of the modified allyl imidazole in step (b) is as follows:

[0039]

[0040] As an optimization, the volume ratio of ethanol to aqueous solution for dialysis in step (c) is 1:1, and the dialysis bag used is MD-44 with a molecular weight cutoff of 500.

[0041] As an optimization, the reaction process of the amphiphilic polymer in step (c) is as follows:

[0042]

[0043] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0044] When processing crocodile leather, the crocodile leather is processed through the following steps: soaking, fleshing, degreasing, liming, reliming, bleaching and fading, deacidification, pretanning, tanning, shaving, degreasing, neutralization, retanning-fatting-dyeing and post-treatment, wherein the pretanning step uses a synthetic terminal epoxy hyperbranched polymer, and the retanning-fatting-dyeing step uses a synthetic amphiphilic polymer retanning-fatting agent.

[0045] Firstly, a self-made terminal epoxy hyperbranched polymer is used to pre-tan the pre-treated crocodile skin before tanning. The terminal epoxy hyperbranched polymer is prepared by reacting trimethylolpropane with succinic anhydride and diethanolamine to obtain a terminal hydroxyl hyperbranched polymer, which is then reacted with epichlorohydrin. The abundant epoxy groups on the terminal epoxy hyperbranched polymer can undergo a ring-opening cross-linking reaction with the amino groups in the crocodile skin, and at the same time, the volume expansion caused by acid immersion can be suppressed. In addition, the excellent water solubility of the terminal epoxy hyperbranched polymer enables it to penetrate into the crocodile skin well for reaction, thereby avoiding uneven reaction. The terminal epoxy hyperbranched polymer is rich in nitrogen and oxygen elements, and at the same time, the hydroxyl groups left after the epoxy ring-opening reaction can also well complex metal ions, thereby promoting the tanning of the subsequent aluminum tanning agent and improving its effect. However, before using the terminal epoxy hyperbranched polymer for pre-tanning, the crocodile skin needs to be treated with hexamethylenetetramine for a period of time, otherwise the terminal epoxy hyperbranched polymer has almost no effect.

[0046] Secondly, the amphiphilic polymer retanning-fatting agent used in the retanning-fatting-dyeing process is prepared by first reacting palmitic acid and epibromopropane under the action of a catalyst, hexadecyltrimethylammonium bromide, to obtain 3-bromo-2-hydroxypropyl palmitate; reacting 3-bromo-2-hydroxypropyl palmitate with N-allylimidazole to obtain modified allyl imidazole; copolymerizing the modified allyl imidazole with diallyldimethylammonium chloride and allylphosphonic acid under the action of a chain transfer agent, n-dodecyl mercaptan, and an initiator, azobisisobutyronitrile, to obtain The amphiphilic polymer is prepared; the amphiphilic polymer is compounded with castor oil, rapeseed oil and fatty acid methyl ester to obtain an amphiphilic polymer retanning-fatting agent; the brominated alkane long chain introduced into the modified allyl imidazole makes it lipophilic, and the lipophilic alkyl long chain structure can weaken the hydrogen bond and van der Waals force between fibers, widen the molecular distance between fibers, and make the leather have good fullness and softness; the nitrogen cation on the imidazole ring provides a binding point for the anionic dye, which can improve the performance of the leather caused by the use of organic chrome-free tanning agents. The positive charge of the leather decreases, thereby improving the dyeing performance of the crocodile leather; the allylphosphonic acid monomer introduced into the amphiphilic polymer can improve the hydrophilicity of the polymer, so that it can penetrate into the middle of the leather fiber, form hydrogen bonds and ionic bonds with the collagen fiber peptide chain, increase the fullness and elasticity of the leather, and improve the utilization rate of the crust leather. At the same time, the phosphorus element contained in it can also improve the flame retardant performance of the crust leather; the diallyldimethylammonium chloride monomer will form a five-membered ring structure in the copolymerization, which improves the tensile and tear resistance of the leather, and the quaternary ammonium group on it can also bring antibacterial ability to the leather, avoiding mildew caused by bacteria during processing and storage, and the quaternary ammonium group is positively charged, which can provide a binding site for anionic dyeing and finishing materials, and can form an electrostatic bond with the negative charge of the phosphonic acid group to improve the mechanical properties of the leather; because the synthesized amphiphilic polymer contains both hydrophilic and lipophilic groups, it can be fattened while retanning the crocodile leather, and can be used as an excellent retanning-fatliquor after compounding with common oils and fats. DETAILED DESCRIPTION

[0047] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0048] The crocodile skins used in all the following examples and comparative examples are all from the belly skins of artificially cultivated Nile crocodiles and have been pretreated.

[0049] Example 1

[0050] A method for processing crocodile leather, the method mainly comprising the following steps:

[0051] All the following dosages are based on the quality of pre-treated crocodile leather;

[0052] (1) Deacidification: 200% pure water, 2r / min, add 7% sodium chloride, add crocodile skin after 10 minutes, add 2% sodium bicarbonate every 15 minutes until the pH is greater than 7.5, continue to rotate the drum for 30 minutes, and change the liquid for washing;

[0053] (2) Pretanning: 100% pure water, 1% hexamethylenetetramine, rotate at 2r / min for 2h; adjust pH to 6.8, 25°C, rotate for 30min, add 8% end-epoxy hyperbranched polymer, 1% sodium dodecyl sulfate, rotate for 8h; add a mixture of sodium bicarbonate and sodium carbonate in a mass ratio of 1:1, add 1% each time, add once every 20min, adjust pH to 8.0, heat to 30°C, rotate for 2h, let stand for 10h, change the solution and wash with water;

[0054] (3) Tanning: 150% pure water, 1% formic acid, adjust pH to 3.0, let stand for 3 hours; add 6% aluminum tanning agent, 2r / min, turn and stop for 5 hours, heat to 35°C, add sodium bicarbonate in batches, 1% each time, 1 hour interval, adjust pH to 4.0, turn for 2 hours, let stand for 24 hours, turn for 10 minutes, change liquid and wash, remove from drum, and ride for 20 hours;

[0055] (4) Shaving: Adjust the thickness according to product requirements;

[0056] (5) Degreasing: 200% pure water, 1% degreasing agent, let stand for 2 h, add 0.5% oxalic acid, let stand for 1 h, change the solution and wash with water;

[0057] (6) Neutralization: 100% pure water, temperature 35°C, 0.5% sodium formate, 0.4% sodium bicarbonate, add in portions to adjust the pH to 5.5, let stand for 10 h, change the solution and wash with water;

[0058] (7) Retanning-fatliquor-dyeing: pure water 150%, temperature 45°C, amphiphilic polymer retanning-fatliquor 18%, dye 2%, 2r / min, turn and stop for 12h, add formic acid to adjust pH to 3.5, stand for 5h, change liquid and wash;

[0059] (8) Post-processing: Horse riding, nail board drying to obtain crocodile leather.

[0060] The preparation method of the epoxy-terminated hyperbranched polymer is as follows:

[0061] (I) 5 parts of trimethylolpropane were weighed by mass, heated at 70° C. under a nitrogen atmosphere until the trimethylolpropane was completely melted, 1.48 parts of p-toluenesulfonic acid were added, and stirred at 300 r / min for 15 min. 33.5 parts of succinic anhydride and 35.2 parts of diethanolamine were simultaneously added dropwise at a rate of 50 drops / min. After the addition was completed, the mixture was reacted at 120° C. for 4 h, and vacuum-reduced for 15 min every 45 min. After the reaction was completed, the mixture was naturally cooled to room temperature, and vacuum-dried at 70° C. for 12 h to obtain a hydroxyl-terminated hyperbranched polymer;

[0062] (II) 17 parts of a hydroxyl-terminated hyperbranched polymer and 20 parts of tetrahydrofuran were weighed and mixed uniformly, stirred at 300 r / min at room temperature until dissolved, 0.76 parts of boron trifluoride etherate were added, 10.9 parts of epichlorohydrin were added dropwise at 50 drops / min, after the addition was completed, the mixture was refluxed in an oil bath at 70° C. for 2 h, cooled to 30° C., and the epichlorohydrin was removed by reduced pressure distillation, 20.7 parts of a 25 wt % sodium hydroxide solution were added dropwise at 5 drops / s, after the addition was completed, the mixture was reacted at 50° C. and 300 r / min for 4 h, filtered, distilled under reduced pressure, centrifuged at 6000 rpm for 15 min, the liquid phase was collected, and vacuum dried at 50° C. for 8 h to obtain an epoxy-terminated hyperbranched polymer.

[0063] The preparation method of the amphiphilic polymer retanning-fatting agent is as follows:

[0064] (a) palmitic acid, epibromopropane and cetyltrimethylammonium bromide were mixed uniformly in a mass ratio of 1:0.64:0.0016, stirred at 60°C and 300 r / min until completely dissolved, reacted at 100°C and 300 r / min for 6 hours, washed with 70°C pure water for 3 times, and vacuum dried at 50°C for 8 hours to obtain 3-bromo-2-hydroxypropyl palmitate;

[0065] (b) 3-bromo-2-hydroxypropyl palmitate, N-allylimidazole and ethyl acetate were mixed uniformly in a mass ratio of 1:0.315:5, stirred at room temperature at 200 r / min until dissolved, refluxed at 65° C. and 300 r / min for 26 h, filtered, washed with ethyl acetate 5 times, distilled under reduced pressure, and dried in vacuo at 30° C. for 28 h to obtain modified allyl imidazole;

[0066] (c) Modified allyl imidazole, diallyl dimethyl ammonium chloride, allyl phosphonic acid, n-dodecyl mercaptan, and anhydrous ethanol were mixed uniformly in a mass ratio of 1:1.25:0.27:0.0303:10, stirred at 300 r / min under a nitrogen atmosphere until dissolved, and a 10 wt% azobisisobutyronitrile ethanol solution (8.3 times the mass of n-dodecyl mercaptan) was added dropwise at 60° C. and 300 r / min at a rate of 5 drops per second. After the addition was completed, the reaction was continued for 7 hours, the solvent was removed by rotary evaporation, and dialyzed in an ethanol aqueous solution for 36 hours, the ethanol aqueous solution was changed every 4 hours, and vacuum dried at 50° C. for 15 hours to obtain an amphiphilic polymer;

[0067] (d) Weigh 2 parts of amphiphilic polymer, 2 parts of castor oil, 3 parts of rapeseed oil and 4 parts of fatty acid methyl ester by mass, mix them evenly, stir them in an oil bath at 60° C. and 500 r / min for 40 min, adjust the pH to 6.5 with 10 wt % triethanolamine acetic acid solution, add 99 parts of 60° C. pure water, stir them at 500 r / min for 40 min, stop heating, and cool them naturally to room temperature to obtain an amphiphilic polymer retanning-fatting agent.

[0068] Example 2

[0069] A method for processing crocodile leather, the method mainly comprising the following steps:

[0070] All the following dosages are based on the quality of pre-treated crocodile leather;

[0071] (1) Deacidification: 250% pure water, 3r / min, add 7.5% sodium chloride, add crocodile skin after 10 minutes, add 2.5% sodium bicarbonate every 15 minutes until the pH is greater than 7.5, continue to rotate the drum for 35 minutes, and change the liquid for washing;

[0072] (2) Pretanning: 150% pure water, 1% hexamethylenetetramine, rotate at 3 rpm for 2 h; adjust pH to 7.0, 28°C, rotate for 30 min, add 9% end-epoxy hyperbranched polymer, 1% sodium dodecyl sulfate, rotate for 9 h; add a mixture of sodium bicarbonate and sodium carbonate in a mass ratio of 1:1, add 1% each time, add once every 20 min, adjust pH to 8.2, heat to 33°C, rotate for 2.5 h, let stand for 11 h, change the solution and wash with water;

[0073] (3) Tanning: 175% pure water, 1.5% formic acid, adjust pH to 2.7, let stand for 3.5 hours; add 6.5% aluminum tanning agent, 3r / min, turn and stop for 5.5 hours, heat to 38°C, add sodium bicarbonate in batches, 1% each time, 1 hour interval, adjust pH to 4.1, turn for 2.5 hours, let stand for 27 hours, turn for another 12 minutes, change liquid and wash, remove from drum, and ride for 22 hours;

[0074] (4) Shaving: Adjust the thickness according to product requirements;

[0075] (5) Degreasing: 250% pure water, 1% degreasing agent, let stand for 2.5 hours, add 0.65% oxalic acid, let stand for 1 hour, change the solution and wash with water;

[0076] (6) Neutralization: 125% pure water, temperature 38°C, 0.8% sodium formate, 0.6% sodium bicarbonate, add in portions to adjust the pH to 5.7, let stand for 11 h, change the solution and wash with water;

[0077] (7) Retanning-fatliquor-dyeing: pure water 175%, temperature 48°C, amphiphilic polymer retanning-fatliquor 19%, dye 2.5%, 3 rpm, turn-on / off combination for 11 h, add formic acid to adjust pH to 3.6, stand for 5.5 h, change liquid and wash;

[0078] (8) Post-processing: Horse riding, nail board drying to obtain crocodile leather.

[0079] The preparation method of the epoxy-terminated hyperbranched polymer is as follows:

[0080] (I) 5.5 parts of trimethylolpropane were weighed by mass, heated at 75° C. under a nitrogen atmosphere until the trimethylolpropane was completely melted, 1.72 parts of p-toluenesulfonic acid were added, and stirred at 350 r / min for 12 min. 39.3 parts of succinic anhydride and 41.3 parts of diethanolamine were simultaneously added dropwise at a rate of 55 drops / min. After the addition was completed, the mixture was reacted at 120° C. for 5 h, and vacuum-reduced for 15 min every 45 min. After the reaction was completed, the mixture was naturally cooled to room temperature, and vacuum-dried at 75° C. for 11 h to obtain a hydroxyl-terminated hyperbranched polymer;

[0081] (II) 18 parts of a hydroxyl-terminated hyperbranched polymer and 22 parts of tetrahydrofuran were weighed and mixed uniformly, stirred at 350 r / min at room temperature until dissolved, 0.81 parts of boron trifluoride etherate were added, 11.26 parts of epichlorohydrin were added dropwise at 55 drops / min, after the addition was completed, the reaction was refluxed in an oil bath at 70° C. for 2.5 h, cooled to 30° C., and the epichlorohydrin was removed by vacuum distillation, 21.4 parts of a 25 wt% sodium hydroxide solution were added dropwise at 5 drops / s, after the addition was completed, the reaction was carried out at 55° C. and 350 r / min for 3.5 h, filtered, vacuum distilled, centrifuged at 7000 rpm for 14 min, the liquid phase was collected, and vacuum dried at 55° C. for 7 h to obtain an epoxy-terminated hyperbranched polymer.

[0082] The preparation method of the amphiphilic polymer retanning-fatting agent is as follows:

[0083] (a) palmitic acid, epibromopropane and cetyltrimethylammonium bromide were mixed uniformly in a mass ratio of 1:0.72:0.0017, stirred at 65°C and 350 r / min until completely dissolved, reacted at 105°C and 350 r / min for 5.5 h, washed with 75°C pure water for 4 times, and vacuum dried at 55°C for 7 h to obtain 3-bromo-2-hydroxypropyl palmitate;

[0084] (b) 3-bromo-2-hydroxypropyl palmitate, N-allylimidazole and ethyl acetate were mixed uniformly in a mass ratio of 1:0.33:6, stirred at room temperature at 250 r / min until dissolved, refluxed at 70° C. and 350 r / min for 25 h, filtered, washed with ethyl acetate 6 times, distilled under reduced pressure, and dried in vacuo at 35° C. for 26 h to obtain modified allyl imidazole;

[0085] (c) Modified allyl imidazole, diallyl dimethyl ammonium chloride, allyl phosphonic acid, n-dodecyl mercaptan, and anhydrous ethanol were mixed in a mass ratio of 1:1.29:0.24:0.0304:12, stirred at 350 r / min under a nitrogen atmosphere until dissolved, and a 10 wt% azobisisobutyronitrile ethanol solution (8.3 times the mass of n-dodecyl mercaptan) was added dropwise at 65° C. and 350 r / min at a rate of 6 drops per second. After the addition was completed, the reaction was continued for 6.5 h, the solvent was removed by rotary evaporation, and dialyzed in an ethanol aqueous solution for 38 h, the ethanol aqueous solution was changed every 4 h, and vacuum dried at 55° C. for 13 h to obtain an amphiphilic polymer;

[0086] (d) 2.5 parts of an amphiphilic polymer, 2.5 parts of castor oil, 3.5 parts of rapeseed oil and 5 parts of fatty acid methyl ester were weighed and mixed uniformly, and stirred at 550 r / min for 35 min in an oil bath at 65° C., the pH was adjusted to 6.5 with a 10 wt % triethanolamine acetic acid solution, 150 parts of pure water at 65° C. were added, and stirred at 550 r / min for 35 min. The heating was stopped, and the mixture was naturally cooled to room temperature to obtain an amphiphilic polymer retanning-fatting agent.

[0087] Example 3

[0088] A method for processing crocodile leather, the method mainly comprising the following steps:

[0089] All the following dosages are based on the quality of pre-treated crocodile leather;

[0090] (1) Deacidification: 300% pure water, 4r / min, add 8% sodium chloride, add crocodile skin after 10min, add 3% sodium bicarbonate every 15min until the pH is greater than 7.5, continue to drum for 40min, change the liquid and wash with water;

[0091] (2) Pretanning: 200% pure water, 1% hexamethylenetetramine, rotate at 4 rpm for 2 h; adjust pH to 7.2, 30°C, rotate for 30 min, add 10% end-epoxy hyperbranched polymer, 1% sodium dodecyl sulfate, rotate for 10 h; add a mixture of sodium bicarbonate and sodium carbonate in a mass ratio of 1:1, add 1% each time, add once every 20 min, adjust pH to 8.4, heat to 35°C, rotate for 3 h, let stand for 12 h, change the solution and wash with water;

[0092] (3) Tanning: 200% pure water, 2% formic acid, adjust pH to 2.4, let stand for 4 hours; add 7% aluminum tanning agent, 4r / min, turn and stop for 5 hours, heat to 40°C, add sodium bicarbonate in batches, 1% each time, 1 hour interval, adjust pH to 4.2, turn for 3 hours, let stand for 30 hours, turn for another 15 minutes, change liquid and wash, remove from drum, and ride for 24 hours;

[0093] (4) Shaving: Adjust the thickness according to product requirements;

[0094] (5) Degreasing: 300% pure water, 1% degreasing agent, let stand for 3 hours, add 0.8% oxalic acid, let stand for 1.5 hours, change the solution and wash with water;

[0095] (6) Neutralization: 150% pure water, temperature 40°C, 1.0% sodium formate, 0.8% sodium bicarbonate, add in portions to adjust the pH to 5.8, let stand for 12 h, change the solution and wash with water;

[0096] (7) Retanning-fatliquor-dyeing: 200% pure water, 50°C, 20% amphiphilic polymer retanning-fatliquor, 3% dye, 4 rpm, 12 h of rotation, pH adjusted to 3.8 with formic acid, let stand for 6 h, and then change the solution and wash with water;

[0097] (8) Post-processing: Horse riding, nail board drying to obtain crocodile leather.

[0098] The preparation method of the epoxy-terminated hyperbranched polymer is as follows:

[0099] (I) 6 parts of trimethylolpropane were weighed by weight, heated at 80° C. under a nitrogen atmosphere until the trimethylolpropane was completely melted, 2 parts of p-toluenesulfonic acid were added, stirred at 400 r / min for 10 min, 45.8 parts of succinic anhydride and 48 parts of diethanolamine were simultaneously added dropwise at 60 drops / min, reacted at 120° C. for 6 h, vacuum-reduced for 15 min every 45 min, cooled naturally to room temperature after the reaction was completed, and vacuum-dried at 80° C. for 10 h to obtain a hydroxyl-terminated hyperbranched polymer;

[0100] (II) 19 parts of hydroxyl-terminated hyperbranched polymer and 24 parts of tetrahydrofuran were weighed and mixed uniformly, stirred at 400 r / min at room temperature until dissolved, 0.85 parts of boron trifluoride etherate were added, 11.8 parts of epichlorohydrin were added dropwise at 60 drops / min, after the addition was completed, the mixture was refluxed in an oil bath at 75°C for 3 h, cooled to 30°C, and the epichlorohydrin was removed by reduced pressure distillation, 22.4 parts of 25 wt% sodium hydroxide solution were added dropwise at 6 drops / s, after the addition was completed, the mixture was reacted at 60°C and 400 r / min for 3 h, filtered, distilled under reduced pressure, centrifuged at 8000 rpm for 12 min, the liquid phase was collected, and vacuum dried at 60°C for 6 h to obtain an epoxy-terminated hyperbranched polymer.

[0101] The preparation method of the amphiphilic polymer retanning-fatting agent is as follows:

[0102] (a) palmitic acid, epibromopropane and cetyltrimethylammonium bromide were mixed uniformly in a mass ratio of 1:0.8:0.0018, stirred at 65°C and 400 r / min until completely dissolved, reacted at 105°C and 400 r / min for 5 h, washed with 80°C pure water for 5 times, and vacuum dried at 60°C for 6 h to obtain 3-bromo-2-hydroxypropyl palmitate;

[0103] (b) 3-bromo-2-hydroxypropyl palmitate, N-allylimidazole and ethyl acetate were mixed uniformly in a mass ratio of 1:0.345:7, stirred at room temperature at 300 r / min until dissolved, refluxed at 70° C. and 400 r / min for 24 h, filtered, washed with ethyl acetate 6 times, distilled under reduced pressure, and dried in vacuo at 35° C. for 24 h to obtain modified allyl imidazole;

[0104] (c) Modified allyl imidazole, diallyl dimethyl ammonium chloride, allyl phosphonic acid, n-dodecyl mercaptan, and anhydrous ethanol were mixed in a mass ratio of 1:1.32:0.22:0.0305:15, stirred at 400 r / min under a nitrogen atmosphere until dissolved, and a 10 wt% azobisisobutyronitrile ethanol solution (8.3 times the mass of n-dodecyl mercaptan) was added dropwise at 70°C and 400 r / min at a rate of 6 drops per second. After the addition was completed, the reaction was continued for 7 hours, the solvent was removed by rotary evaporation, and dialyzed in an ethanol aqueous solution for 40 hours, the ethanol aqueous solution was changed every 4 hours, and vacuum dried at 60°C for 12 hours to obtain an amphiphilic polymer;

[0105] (d) Weigh 3 parts of an amphiphilic polymer, 3 parts of castor oil, 4 parts of rapeseed oil and 6 parts of fatty acid methyl ester by mass, mix them evenly, stir them in an oil bath at 70° C. and 600 r / min for 30 min, adjust the pH to 6.5 with a 10 wt % triethanolamine acetic acid solution, add 180 parts of pure water at 70° C., stir them at 600 r / min for 30 min, stop heating, and naturally cool to room temperature to obtain an amphiphilic polymer retanning-fatting agent.

[0106] Comparative Example 1

[0107] A method for processing crocodile leather, the method mainly comprising the following steps:

[0108] All the following dosages are based on the quality of pre-treated crocodile leather;

[0109] (1) Deacidification: 250% pure water, 3r / min, add 7.5% sodium chloride, add crocodile skin after 10 minutes, add 2.5% sodium bicarbonate every 15 minutes until the pH is greater than 7.5, continue to rotate the drum for 35 minutes, and change the liquid for washing;

[0110] (2) Pretanning: 150% pure water, 1% hexamethylenetetramine, rotate at 3 rpm for 2 h; adjust pH to 7.0, 28°C, rotate for 30 min, add 9% end-epoxy hyperbranched polymer, 1% sodium dodecyl sulfate, rotate for 9 h; add a mixture of sodium bicarbonate and sodium carbonate in a mass ratio of 1:1, add 1% each time, add once every 20 min, adjust pH to 8.2, heat to 33°C, rotate for 2.5 h, let stand for 11 h, change the solution and wash with water;

[0111] (3) Tanning: 175% pure water, 1.5% formic acid, adjust pH to 2.7, let stand for 3.5 hours; add 6.5% aluminum tanning agent, 3r / min, turn and stop for 5.5 hours, heat to 38°C, add sodium bicarbonate in batches, 1% each time, 1 hour interval, adjust pH to 4.1, turn for 2.5 hours, let stand for 27 hours, turn for another 12 minutes, change liquid and wash, remove from drum, and ride for 22 hours;

[0112] (4) Shaving: Adjust the thickness according to product requirements;

[0113] (5) Degreasing: 250% pure water, 1% degreasing agent, let stand for 2.5 hours, add 0.65% oxalic acid, let stand for 1 hour, change the solution and wash with water;

[0114] (6) Neutralization: 125% pure water, temperature 38°C, 0.8% sodium formate, 0.6% sodium bicarbonate, add in portions to adjust the pH to 5.7, let stand for 11 h, change the solution and wash with water;

[0115] (7) Retanning-fatliquoring-dyeing: pure water 175%, temperature 48°C, Desopon LQ-5 fatliquor 19%, dye 2.5%, 3 rpm, turn-on / off for 11 h, add formic acid to adjust pH to 3.6, let stand for 5.5 h, change the liquid and wash with water;

[0116] (8) Post-processing: Horse riding, nail board drying to obtain crocodile leather.

[0117] The preparation method of the epoxy-terminated hyperbranched polymer is as follows:

[0118] (I) 5.5 parts of trimethylolpropane were weighed by mass, heated at 75° C. under a nitrogen atmosphere until the trimethylolpropane was completely melted, 1.72 parts of p-toluenesulfonic acid were added, and stirred at 350 r / min for 12 min. 39.3 parts of succinic anhydride and 41.3 parts of diethanolamine were simultaneously added dropwise at a rate of 55 drops / min. After the addition was completed, the mixture was reacted at 120° C. for 5 h, and vacuum-reduced for 15 min every 45 min. After the reaction was completed, the mixture was naturally cooled to room temperature, and vacuum-dried at 75° C. for 11 h to obtain a hydroxyl-terminated hyperbranched polymer;

[0119] (II) 18 parts of a hydroxyl-terminated hyperbranched polymer and 22 parts of tetrahydrofuran were weighed and mixed uniformly, stirred at 350 r / min at room temperature until dissolved, 0.81 parts of boron trifluoride etherate were added, 11.26 parts of epichlorohydrin were added dropwise at 55 drops / min, after the addition was completed, the reaction was refluxed in an oil bath at 70° C. for 2.5 h, cooled to 30° C., and the epichlorohydrin was removed by vacuum distillation, 21.4 parts of a 25 wt% sodium hydroxide solution were added dropwise at 5 drops / s, after the addition was completed, the reaction was carried out at 55° C. and 350 r / min for 3.5 h, filtered, vacuum distilled, centrifuged at 7000 rpm for 14 min, the liquid phase was collected, and vacuum dried at 55° C. for 7 h to obtain an epoxy-terminated hyperbranched polymer.

[0120] Comparative Example 2

[0121] A method for processing crocodile leather, the method mainly comprising the following steps:

[0122] All the following dosages are based on the quality of pre-treated crocodile leather;

[0123] (1) Deacidification: 250% pure water, 3r / min, add 7.5% sodium chloride, add crocodile skin after 10 minutes, add 2.5% sodium bicarbonate every 15 minutes until the pH is greater than 7.5, continue to rotate the drum for 35 minutes, and change the liquid for washing;

[0124] (2) Pretanning: 150% pure water, 1% hexamethylenetetramine, rotate at 3 rpm for 2 h; adjust pH to 7.0, 28°C, rotate for 30 min, add 9% end-epoxy hyperbranched polymer, 1% sodium dodecyl sulfate, rotate for 9 h; add a mixture of sodium bicarbonate and sodium carbonate in a mass ratio of 1:1, add 1% each time, add once every 20 min, adjust pH to 8.2, heat to 33°C, rotate for 2.5 h, let stand for 11 h, change the solution and wash with water;

[0125] (3) Tanning: 175% pure water, 1.5% formic acid, adjust pH to 2.7, let stand for 3.5 hours; add 6.5% aluminum tanning agent, 3r / min, turn and stop for 5.5 hours, heat to 38°C, add sodium bicarbonate in batches, 1% each time, 1 hour interval, adjust pH to 4.1, turn for 2.5 hours, let stand for 27 hours, turn for another 12 minutes, change liquid and wash, remove from drum, and ride for 22 hours;

[0126] (4) Shaving: Adjust the thickness according to product requirements;

[0127] (5) Degreasing: 250% pure water, 1% degreasing agent, let stand for 2.5 hours, add 0.65% oxalic acid, let stand for 1 hour, change the solution and wash with water;

[0128] (6) Neutralization: 125% pure water, temperature 38°C, 0.8% sodium formate, 0.6% sodium bicarbonate, add in portions to adjust the pH to 5.7, let stand for 11 h, change the solution and wash with water;

[0129] (7) Retanning-fatliquor-dyeing: pure water 175%, temperature 48°C, amphiphilic polymer retanning-fatliquor 19%, dye 2.5%, 3 rpm, turn-on / off combination for 11 h, add formic acid to adjust pH to 3.6, stand for 5.5 h, change liquid and wash;

[0130] (8) Post-processing: Horse riding, nail board drying to obtain crocodile leather.

[0131] The preparation method of the epoxy-terminated hyperbranched polymer is as follows:

[0132] (I) 5.5 parts of trimethylolpropane were weighed by mass, heated at 75° C. under a nitrogen atmosphere until the trimethylolpropane was completely melted, 1.72 parts of p-toluenesulfonic acid were added, and stirred at 350 r / min for 12 min. 39.3 parts of succinic anhydride and 41.3 parts of diethanolamine were simultaneously added dropwise at a rate of 55 drops / min. After the addition was completed, the mixture was reacted at 120° C. for 5 h, and vacuum-reduced for 15 min every 45 min. After the reaction was completed, the mixture was naturally cooled to room temperature, and vacuum-dried at 75° C. for 11 h to obtain a hydroxyl-terminated hyperbranched polymer;

[0133] (II) 18 parts of a hydroxyl-terminated hyperbranched polymer and 22 parts of tetrahydrofuran were weighed and mixed uniformly, stirred at 350 r / min at room temperature until dissolved, 0.81 parts of boron trifluoride etherate were added, 11.26 parts of epichlorohydrin were added dropwise at 55 drops / min, after the addition was completed, the reaction was refluxed in an oil bath at 70° C. for 2.5 h, cooled to 30° C., and the epichlorohydrin was removed by vacuum distillation, 21.4 parts of a 25 wt% sodium hydroxide solution were added dropwise at 5 drops / s, after the addition was completed, the reaction was carried out at 55° C. and 350 r / min for 3.5 h, filtered, vacuum distilled, centrifuged at 7000 rpm for 14 min, the liquid phase was collected, and vacuum dried at 55° C. for 7 h to obtain an epoxy-terminated hyperbranched polymer.

[0134] The preparation method of the amphiphilic polymer retanning-fatting agent is as follows:

[0135] (a) N-allylimidazole, diallyldimethylammonium chloride, allylphosphonic acid, n-dodecyl mercaptan, and anhydrous ethanol were mixed in a mass ratio of 1:1.29:0.24:0.0304:12, stirred at 350 r / min under a nitrogen atmosphere until dissolved, and a 10 wt% azobisisobutyronitrile ethanol solution (8.3 times the mass of n-dodecyl mercaptan) was added dropwise at 65° C. and 350 r / min at a rate of 6 drops per second. After the addition was completed, the reaction was continued for 6.5 hours, the solvent was removed by rotary evaporation, and dialyzed in an ethanol aqueous solution for 38 hours, the ethanol aqueous solution was changed every 4 hours, and vacuum dried at 55° C. for 13 hours to obtain an amphiphilic polymer;

[0136] (b) 2.5 parts of an amphiphilic polymer, 2.5 parts of castor oil, 3.5 parts of rapeseed oil and 5 parts of fatty acid methyl ester were weighed and mixed uniformly, and stirred at 550 r / min for 35 min in an oil bath at 65° C., the pH was adjusted to 6.5 with a 10 wt % triethanolamine acetic acid solution, 150 parts of pure water at 65° C. were added, and stirred at 550 r / min for 35 min. The heating was stopped, and the mixture was naturally cooled to room temperature to obtain an amphiphilic polymer retanning-fatting agent.

[0137] Comparative Example 3

[0138] A method for processing crocodile leather, the method mainly comprising the following steps:

[0139] All the following dosages are based on the quality of pre-treated crocodile leather;

[0140] (1) Deacidification: 250% pure water, 3r / min, add 7.5% sodium chloride, add crocodile skin after 10 minutes, add 2.5% sodium bicarbonate every 15 minutes until the pH is greater than 7.5, continue to rotate the drum for 35 minutes, and change the liquid for washing;

[0141] (2) Pretanning: 150% pure water, 1% hexamethylenetetramine, rotate at 3 rpm for 2 h; adjust pH to 7.0, 28°C, rotate for 30 min, add 9% end-epoxy hyperbranched polymer, 1% sodium dodecyl sulfate, rotate for 9 h; add a mixture of sodium bicarbonate and sodium carbonate in a mass ratio of 1:1, add 1% each time, add once every 20 min, adjust pH to 8.2, heat to 33°C, rotate for 2.5 h, let stand for 11 h, change the solution and wash with water;

[0142] (3) Tanning: 175% pure water, 1.5% formic acid, adjust pH to 2.7, let stand for 3.5 hours; add 6.5% aluminum tanning agent, 3r / min, turn and stop for 5.5 hours, heat to 38°C, add sodium bicarbonate in batches, 1% each time, 1 hour interval, adjust pH to 4.1, turn for 2.5 hours, let stand for 27 hours, turn for another 12 minutes, change liquid and wash, remove from drum, and ride for 22 hours;

[0143] (4) Shaving: Adjust the thickness according to product requirements;

[0144] (5) Degreasing: 250% pure water, 1% degreasing agent, let stand for 2.5 hours, add 0.65% oxalic acid, let stand for 1 hour, change the solution and wash with water;

[0145] (6) Neutralization: 125% pure water, temperature 38°C, 0.8% sodium formate, 0.6% sodium bicarbonate, add in portions to adjust the pH to 5.7, let stand for 11 h, change the solution and wash with water;

[0146] (7) Retanning-fatliquor-dyeing: pure water 175%, temperature 48°C, amphiphilic polymer retanning-fatliquor 19%, dye 2.5%, 3 rpm, turn-on / off combination for 11 h, add formic acid to adjust pH to 3.6, stand for 5.5 h, change liquid and wash;

[0147] (8) Post-processing: Horse riding, nail board drying to obtain crocodile leather.

[0148] The preparation method of the epoxy-terminated hyperbranched polymer is as follows:

[0149] (I) 5.5 parts of trimethylolpropane were weighed by mass, heated at 75° C. under a nitrogen atmosphere until the trimethylolpropane was completely melted, 1.72 parts of p-toluenesulfonic acid were added, and stirred at 350 r / min for 12 min. 39.3 parts of succinic anhydride and 41.3 parts of diethanolamine were simultaneously added dropwise at a rate of 55 drops / min. After the addition was completed, the mixture was reacted at 120° C. for 5 h, and vacuum-reduced for 15 min every 45 min. After the reaction was completed, the mixture was naturally cooled to room temperature, and vacuum-dried at 75° C. for 11 h to obtain a hydroxyl-terminated hyperbranched polymer;

[0150] (II) 18 parts of a hydroxyl-terminated hyperbranched polymer and 22 parts of tetrahydrofuran were weighed and mixed uniformly, stirred at 350 r / min at room temperature until dissolved, 0.81 parts of boron trifluoride etherate were added, 11.26 parts of epichlorohydrin were added dropwise at 55 drops / min, after the addition was completed, the reaction was refluxed in an oil bath at 70° C. for 2.5 h, cooled to 30° C., and the epichlorohydrin was removed by vacuum distillation, 21.4 parts of a 25 wt% sodium hydroxide solution were added dropwise at 5 drops / s, after the addition was completed, the reaction was carried out at 55° C. and 350 r / min for 3.5 h, filtered, vacuum distilled, centrifuged at 7000 rpm for 14 min, the liquid phase was collected, and vacuum dried at 55° C. for 7 h to obtain an epoxy-terminated hyperbranched polymer.

[0151] The preparation method of the amphiphilic polymer retanning-fatting agent is as follows:

[0152] (a) palmitic acid, epibromopropane and cetyltrimethylammonium bromide were mixed uniformly in a mass ratio of 1:0.72:0.0017, stirred at 65°C and 350 r / min until completely dissolved, reacted at 105°C and 350 r / min for 5.5 h, washed with 75°C pure water for 4 times, and vacuum dried at 55°C for 7 h to obtain 3-bromo-2-hydroxypropyl palmitate;

[0153] (b) 3-bromo-2-hydroxypropyl palmitate, N-allylimidazole and ethyl acetate were mixed uniformly in a mass ratio of 1:0.33:6, stirred at room temperature at 250 r / min until dissolved, refluxed at 70° C. and 350 r / min for 25 h, filtered, washed with ethyl acetate 6 times, distilled under reduced pressure, and dried in vacuo at 35° C. for 26 h to obtain modified allyl imidazole;

[0154] (c) The modified allyl imidazole, allylphosphonic acid, n-dodecyl mercaptan and anhydrous ethanol were mixed in a mass ratio of 1:0.24:0.0304:12, stirred at 350 r / min under a nitrogen atmosphere until dissolved, and a 10 wt% azobisisobutyronitrile ethanol solution (8.3 times the mass of n-dodecyl mercaptan) was added dropwise at 65° C. and 350 r / min at a rate of 6 drops per second. After the addition was completed, the reaction was carried out for 6.5 hours, the solvent was removed by rotary evaporation, and dialyzed in an ethanol aqueous solution for 38 hours, the ethanol aqueous solution was changed every 4 hours, and vacuum dried at 55° C. for 13 hours to obtain an amphiphilic polymer;

[0155] (d) 2.5 parts of an amphiphilic polymer, 2.5 parts of castor oil, 3.5 parts of rapeseed oil and 5 parts of fatty acid methyl ester were weighed and mixed uniformly, and stirred at 550 r / min for 35 min in an oil bath at 65° C., the pH was adjusted to 6.5 with a 10 wt % triethanolamine acetic acid solution, 150 parts of pure water at 65° C. were added, and stirred at 550 r / min for 35 min. The heating was stopped, and the mixture was naturally cooled to room temperature to obtain an amphiphilic polymer retanning-fatting agent.

[0156] Comparative Example 4

[0157] A method for processing crocodile leather, the method mainly comprising the following steps:

[0158] All the following dosages are based on the quality of pre-treated crocodile leather;

[0159] (1) Deacidification: 250% pure water, 3r / min, add 7.5% sodium chloride, add crocodile skin after 10 minutes, add 2.5% sodium bicarbonate every 15 minutes until the pH is greater than 7.5, continue to rotate the drum for 35 minutes, and change the liquid for washing;

[0160] (2) Pretanning: 150% pure water, 1% hexamethylenetetramine, rotate at 3 rpm for 2 h; adjust pH to 7.0, 28°C, rotate for 30 min, add 9% end-epoxy hyperbranched polymer, 1% sodium dodecyl sulfate, rotate for 9 h; add a mixture of sodium bicarbonate and sodium carbonate in a mass ratio of 1:1, add 1% each time, add once every 20 min, adjust pH to 8.2, heat to 33°C, rotate for 2.5 h, let stand for 11 h, change the solution and wash with water;

[0161] (3) Tanning: 175% pure water, 1.5% formic acid, adjust pH to 2.7, let stand for 3.5 hours; add 6.5% aluminum tanning agent, 3r / min, turn and stop for 5.5 hours, heat to 38°C, add sodium bicarbonate in batches, 1% each time, 1 hour interval, adjust pH to 4.1, turn for 2.5 hours, let stand for 27 hours, turn for another 12 minutes, change liquid and wash, remove from drum, and ride for 22 hours;

[0162] (4) Shaving: Adjust the thickness according to product requirements;

[0163] (5) Degreasing: 250% pure water, 1% degreasing agent, let stand for 2.5 hours, add 0.65% oxalic acid, let stand for 1 hour, change the solution and wash with water;

[0164] (6) Neutralization: 125% pure water, temperature 38°C, 0.8% sodium formate, 0.6% sodium bicarbonate, add in portions to adjust the pH to 5.7, let stand for 11 h, change the solution and wash with water;

[0165] (7) Retanning-fatliquor-dyeing: pure water 175%, temperature 48°C, amphiphilic polymer retanning-fatliquor 19%, dye 2.5%, 3 rpm, turn-on / off combination for 11 h, add formic acid to adjust pH to 3.6, stand for 5.5 h, change liquid and wash;

[0166] (8) Post-processing: Horse riding, nail board drying to obtain crocodile leather.

[0167] The preparation method of the epoxy-terminated hyperbranched polymer is as follows:

[0168] (I) 5.5 parts of trimethylolpropane were weighed by mass, heated at 75° C. under a nitrogen atmosphere until the trimethylolpropane was completely melted, 1.72 parts of p-toluenesulfonic acid were added, and stirred at 350 r / min for 12 min. 39.3 parts of succinic anhydride and 41.3 parts of diethanolamine were simultaneously added dropwise at a rate of 55 drops / min. After the addition was completed, the mixture was reacted at 120° C. for 5 h, and vacuum-reduced for 15 min every 45 min. After the reaction was completed, the mixture was naturally cooled to room temperature, and vacuum-dried at 75° C. for 11 h to obtain a hydroxyl-terminated hyperbranched polymer;

[0169] (II) 18 parts of a hydroxyl-terminated hyperbranched polymer and 22 parts of tetrahydrofuran were weighed and mixed uniformly, stirred at 350 r / min at room temperature until dissolved, 0.81 parts of boron trifluoride etherate were added, 11.26 parts of epichlorohydrin were added dropwise at 55 drops / min, after the addition was completed, the reaction was refluxed in an oil bath at 70° C. for 2.5 h, cooled to 30° C., and the epichlorohydrin was removed by vacuum distillation, 21.4 parts of a 25 wt% sodium hydroxide solution were added dropwise at 5 drops / s, after the addition was completed, the reaction was carried out at 55° C. and 350 r / min for 3.5 h, filtered, vacuum distilled, centrifuged at 7000 rpm for 14 min, the liquid phase was collected, and vacuum dried at 55° C. for 7 h to obtain an epoxy-terminated hyperbranched polymer.

[0170] The preparation method of the amphiphilic polymer retanning-fatting agent is as follows:

[0171] (a) palmitic acid, epibromopropane and cetyltrimethylammonium bromide were mixed uniformly in a mass ratio of 1:0.72:0.0017, stirred at 65°C and 350 r / min until completely dissolved, reacted at 105°C and 350 r / min for 5.5 h, washed with 75°C pure water for 4 times, and vacuum dried at 55°C for 7 h to obtain 3-bromo-2-hydroxypropyl palmitate;

[0172] (b) 3-bromo-2-hydroxypropyl palmitate, N-allylimidazole and ethyl acetate were mixed uniformly in a mass ratio of 1:0.33:6, stirred at room temperature at 250 r / min until dissolved, refluxed at 70° C. and 350 r / min for 25 h, filtered, washed with ethyl acetate 6 times, distilled under reduced pressure, and dried in vacuo at 35° C. for 26 h to obtain modified allyl imidazole;

[0173] (c) Modified allyl imidazole, diallyl dimethyl ammonium chloride, acrylic acid, n-dodecyl mercaptan, and anhydrous ethanol were mixed uniformly in a mass ratio of 1:1.29:0.144:0.0304:12, stirred at 350 r / min under a nitrogen atmosphere until dissolved, and a 10 wt% azobisisobutyronitrile ethanol solution (8.3 times the mass of n-dodecyl mercaptan) was added dropwise at 65° C. and 350 r / min at a rate of 6 drops per second. After the addition was completed, the reaction was carried out for 6.5 hours, the solvent was removed by rotary evaporation, and the mixture was dialyzed in an ethanol aqueous solution for 38 hours, the ethanol aqueous solution was changed every 4 hours, and the mixture was vacuum dried at 55° C. for 13 hours to obtain an amphiphilic polymer;

[0174] (d) 2.5 parts of an amphiphilic polymer, 2.5 parts of castor oil, 3.5 parts of rapeseed oil and 5 parts of fatty acid methyl ester were weighed and mixed uniformly, and stirred at 550 r / min for 35 min in an oil bath at 65° C., the pH was adjusted to 6.5 with a 10 wt % triethanolamine acetic acid solution, 150 parts of pure water at 65° C. were added, and stirred at 550 r / min for 35 min. The heating was stopped, and the mixture was naturally cooled to room temperature to obtain an amphiphilic polymer retanning-fatting agent.

[0175] Test Example 1

[0176] Leather shrinkage temperature test: The shrinkage temperature of the prepared crocodile leather was measured according to QB / T 2713-2005. Each group was tested 3 times and the average value was recorded.

[0177] The results are shown in Table 1.

[0178] Table 1

[0179] Shrinkage temperature / ℃ Shrinkage temperature / ℃ Example 1 100.5 Comparative Example 1 88.7 Example 2 100.3 Comparative Example 2 95.6 Example 3 100.4 Comparative Example 3 92.4 Comparative Example 4 100.2

[0180] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 4 in Table 1, it can be found that the crocodile leather prepared by the present invention has a higher shrinkage temperature.

[0181] By comparison, the shrinkage temperatures of Examples 1 to 3 are greater than that of Comparative Example 1, indicating that the amphiphilic polymer retanning-fatting agent has a good retanning effect. Its amphiphilic properties not only improve the permeability, but also retan the crocodile leather, forming intermolecular hydrogen bonds and ionic bonds with the collagen fibers in the crocodile leather, thereby increasing the shrinkage temperature.

[0182] By comparison, the shrinkage temperatures of Examples 1 to 3 are greater than that of Comparative Example 2, indicating that grafting long carbon chain alkanes onto N-allylimidazole can enhance its filling effect and increase the shrinkage temperature.

[0183] By comparison, the shrinkage temperatures of Examples 1 to 3 are greater than that of Comparative Example 3, indicating that the addition of diallyldimethylammonium chloride increases the shrinkage temperature of the prepared crocodile leather, and the nitrogen cations thereon form intermolecular hydrogen bonds with the collagen fibers, thereby improving the retanning effect and increasing the shrinkage temperature.

[0184] Test Example 2

[0185] Mechanical strength determination: The tensile strength and elongation at break of the prepared crocodile leather were determined in accordance with QB / T 2710-2018 to evaluate the mechanical properties of the prepared crocodile leather. Each group was tested 3 times and the average value was recorded.

[0186] The results are shown in Table 2.

[0187] Table 2

[0188] Tensile strength / MPa Elongation at break Example 1 65.74 73.15％ Example 2 68.49 76.48％ Example 3 66.28 69.77％ Comparative Example 1 61.32 61.96％ Comparative Example 2 63.82 49.24％ Comparative Example 3 58.73 57.44％ Comparative Example 4 55.34 61.83％

[0189] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 4 in Table 2, it can be found that the crocodile leather prepared by the present invention has good tensile strength and elongation at break.

[0190] By comparison, the tensile strength and elongation at break of Examples 1 to 3 are greater than those of Comparative Examples 1 to 4, indicating that the amphiphilic polymer retanning-fatting agent has a good retanning effect. The nitrogen cations carried thereon form an electrostatic binding effect with the phosphate anions, which improves the mechanical strength of the crocodile leather. At the same time, the phosphate groups contained therein form intermolecular hydrogen bonds and ionic bonds with the collagen fibers in the crocodile leather, which also improve the mechanical strength. Diallyl dimethyl ammonium chloride forms a five-membered ring structure after copolymerization, which has higher structural strength and can also improve the mechanical strength.

[0191] Test Example 3

[0192] Dye absorbance determination: Use Trumpier's TRUPOCORYELLOW BB dye for retanning-fatliquoring-dyeing process. Prepare the dye used in the process into a standard solution of a certain concentration, use an ultraviolet spectrophotometer to determine its maximum absorption wavelength and draw a standard curve; collect the liquid at the beginning and end of dyeing, dilute and measure the absorbance respectively, calculate the dye content in the liquid through the standard curve, and repeat the measurement 3 times to take the average value.

[0193] The results are shown in Table 3.

[0194] Table 3

[0195] Dye absorption Dye absorption Example 1 99.32％ Comparative Example 1 86.72％ Example 2 99.48％ Comparative Example 2 91.52％ Example 3 99.15％ Comparative Example 3 93.76％ Comparative Example 4 99.07％

[0196] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 4 in Table 3, it can be found that the crocodile leather prepared by the present invention has a good dye absorption rate.

[0197] By comparison, the dye absorption rate of Examples 1 to 3 is greater than that of Comparative Example 1, indicating that the amphiphilic polymer retanning-fatting agent is successfully fixed inside the crocodile leather, and the nitrogen cations it carries give it more anionic dye binding sites, and its dye absorption rate is higher than that of commercially available fatliquors.

[0198] By comparison, the dye absorption rates of Examples 1 to 3 are greater than that of Comparative Example 2, indicating that the modification of N-allylimidazole makes it amphiphilic, and the nitrogen cations thereon provide more anionic dye binding sites, thereby improving the dye absorption rate and reducing dye waste.

[0199] By comparison, the dye absorption rates of Examples 1 to 3 are greater than that of Comparative Example 3, indicating that the nitrogen cations on diallyldimethylammonium chloride provide binding sites for anionic dyes, so that the prepared crocodile leather can better absorb the dye for coloring and reduce the occurrence of color fading.

[0200] Test Example 4

[0201] Determination of antibacterial properties: Referring to the oscillation method in GB / T 20944, cut the crocodile leather into 0.75±0.05g sample, mix it with the bacterial solution and oscillate it for 5 minutes. Take the oscillated bacterial solution to culture in agar medium, and determine the antibacterial rate of crocodile leather against Escherichia coli and Staphylococcus aureus by the number of growing colonies. Record the average value of three repetitions.

[0202] The results are shown in Table 4.

[0203] Table 4

[0204] Escherichia coli inhibition rate Staphylococcus aureus inhibition rate Example 1 95.49％ 93.27％ Example 2 96.24％ 94.11％ Example 3 95.86％ 93.58％ Comparative Example 1 12.68％ 9.46％ Comparative Example 2 64.28％ 58.14％ Comparative Example 3 18.35％ 11.24％ Comparative Example 4 95.17％ 93.47％

[0205] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 4 in Table 4, it can be found that the crocodile leather prepared by the present invention has good antibacterial properties.

[0206] By comparison, the antibacterial rates of Examples 1 to 3 are greater than that of Comparative Example 1, indicating that the amphiphilic polymer retanning-fatting agent is successfully fixed inside the crocodile leather, and the quaternary ammonium groups carried thereon give the crocodile leather good antibacterial properties.

[0207] By comparison, the antibacterial rates of Examples 1 to 3 are greater than that of Comparative Example 2, indicating that the modification of N-allylimidazole improves its lipophilicity, and the lipophilic long-chain alkane can better adhere to the bacterial surface, so that the antibacterial properties of the quaternary ammonium group can be better exerted.

[0208] By comparison, the antibacterial rates of Examples 1 to 3 are greater than that of Comparative Example 3, indicating that the antibacterial property is mainly derived from diallyldimethylammonium chloride, and the quaternary ammonium group brings about good antibacterial performance.

[0209] Test Example 5

[0210] Flame retardant performance determination: Refer to GB / T 2406.1-2008 to test the limiting oxygen index of the prepared crocodile leather with an oxygen index instrument. The sample size is 150mm×10mm×3mm. Each group is tested 3 times and the average value is recorded.

[0211] The results are shown in Table 5.

[0212] Table 5

[0213] Limiting oxygen index Limiting oxygen index Example 1 29.4 Comparative Example 1 21.4 Example 2 30.1 Comparative Example 2 28.9 Example 3 29.2 Comparative Example 3 29.1 Comparative Example 4 20.7

[0214] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 4 in Table 5, it can be found that the crocodile leather prepared by the present invention has good flame retardant properties.

[0215] By comparison, the limiting oxygen index of Examples 1 to 3 is greater than that of Comparative Example 1, indicating that the amphiphilic polymer retanning-fatting agent successfully enters the interior of the crocodile leather and is fixed inside the crocodile leather through intermolecular forces, and the phosphate groups therein improve the flame retardancy.

[0216] By comparison, the limiting oxygen index of Examples 1 to 3 is greater than that of Comparative Example 4, indicating that the introduction of allylphosphonic acid improves the flame retardancy.

[0217] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for processing crocodile leather, characterized in that: The process mainly includes the following steps: soaking, fleshing, degreasing, liming, reliming, bleaching and fading, deacidification, pretanning, tanning, shaving, degreasing, neutralization, retanning-fatliquoring-dyeing, and post-treatment, wherein the pretanning process uses a synthetic epoxy-terminated hyperbranched polymer, and the retanning-fatliquoring-dyeing process uses a synthetic amphiphilic polymer retanning-fatliquoring agent; The epoxy-terminated hyperbranched polymer is prepared by first reacting trimethylolpropane with succinic anhydride and diethanolamine to obtain a hydroxy-terminated hyperbranched polymer, and then reacting the polymer with epichlorohydrin. The amphiphilic polymer retanning-fatting agent is prepared by reacting palmitic acid with epibromohydrin to obtain 3-bromo-2-hydroxypropyl palmitate, which is then reacted with N-allylimidazole to obtain modified allyl imidazole, copolymerizing the modified allyl imidazole with diallyldimethylammonium chloride and allylphosphonic acid to obtain an amphiphilic polymer, and finally compounding the amphiphilic polymer with castor oil, rapeseed oil and fatty acid methyl ester.

2. The method for processing crocodile leather according to claim 1, characterized in that: The processing method of the crocodile leather mainly comprises the following steps: All subsequent dosages are based on the quality of the pre-treated crocodile leather; (1) Deacidification: 200-300% pure water, 2-4r / min, add 7-8% sodium chloride, add crocodile skin after 10 minutes, add 2-3% sodium bicarbonate every 15 minutes until the pH is greater than 7.5, continue to drum for 30-40 minutes, and change the liquid for washing; (2) Pretanning: 100-200% pure water, 1% hexamethylenetetramine, rotate at 2-4 rpm for 2 h; adjust the pH to 6.8-7.2, rotate at 25-30°C for 30 min, add 8-10% terminal epoxy hyperbranched polymer, 1% sodium dodecyl sulfate, rotate for 8-10 h; add a mixture of sodium bicarbonate and sodium carbonate in a mass ratio of 1:1, add 1% each time, add once every 20 min, adjust the pH to 8.0-8.4, heat to 30-35°C, rotate for 2-3 h, let stand for 10-12 h, change the solution and wash with water; (3) Tanning: 150-200% pure water, 1-2% formic acid, adjust pH to 2.4-3.0, let stand for 3-4 hours; add 6-7% aluminum tanning agent, 2-4r / min, turn and stop for 5-6 hours, heat to 35-40°C, add sodium bicarbonate in batches, 1% each time, 1 hour interval, adjust pH to 4.0-4.2, turn for 2-3 hours, let stand for 24-30 hours, turn for another 10-15 minutes, change liquid and wash, remove from drum, and ride for 20-24 hours; (4) Shaving: Adjust the thickness according to product requirements; (5) Degreasing: pure water 200-300%, degreasing agent 1%, let stand for 2-3 hours, add oxalic acid 0.5-0.8%, let stand for 1-1.5 hours, change the solution and wash with water; (6) Neutralization: 100-150% pure water, temperature 35-40°C, 0.5-1.0% sodium formate, 0.4-0.8% sodium bicarbonate, add in portions to adjust the pH to 5.5-5.8, let stand for 10-12 hours, and change the solution for washing; (7) Retanning-fatliquor-dyeing: 150-200% pure water, 45-50°C, 18-20% amphiphilic polymer retanning-fatliquor, 2-3% dye, 2-4 rpm, turn and stop for 10-12 h, add formic acid to adjust pH to 3.5-3.8, let stand for 5-6 h, change the solution and wash with water; (8) Post-processing: Horse riding, nail board drying to obtain crocodile leather.

3. The method for processing crocodile leather according to claim 2, characterized in that: The preparation method of the epoxy-terminated hyperbranched polymer in step (2) is as follows: (I) 5-6 parts of trimethylolpropane are weighed by weight, heated at 70-80° C. under a nitrogen atmosphere until the trimethylolpropane is completely melted, 1.48-2 parts of p-toluenesulfonic acid are added, stirred at 300-400 r / min for 10-15 min, 33.5-45.8 parts of succinic anhydride and 35.2-48 parts of diethanolamine are simultaneously added dropwise at a rate of 50-60 drops / min, reacted at 120° C. for 4-6 h after the addition is completed, vacuum-reduced for 15 min every 45 min, cooled naturally to room temperature after the reaction is completed, and vacuum-dried at 70-80° C. for 10-12 h to obtain a hydroxyl-terminated hyperbranched polymer; (II) 17-19 parts of a hydroxyl-terminated hyperbranched polymer and 20-24 parts of tetrahydrofuran were weighed and mixed uniformly, stirred at 300-400 r / min at room temperature until dissolved, 0.76-0.85 parts of boron trifluoride etherate were added, 10.9-11.8 parts of epichlorohydrin were added dropwise at 50-60 drops / min, after the addition was completed, the mixture was refluxed in an oil bath at 70-75° C. for 2-3 h, cooled to 30° C., and the epichlorohydrin was removed by reduced pressure distillation, 20.7-22.4 parts of a 25 wt % sodium hydroxide solution were added dropwise at 5-6 drops / s, after the addition was completed, the mixture was reacted at 50-60° C. and 300-400 r / min for 3-4 h, filtered, distilled under reduced pressure, centrifuged at 6000-8000 rpm for 12-15 min, the liquid phase was collected, and vacuum dried at 50-60° C. for 6-8 h to obtain an epoxy-terminated hyperbranched polymer.

4. The method for processing crocodile leather according to claim 2, characterized in that: The aluminum tanning agent in step (3) is aluminum sulfate 18hydrate.

5. The method for processing crocodile leather according to claim 2, characterized in that: The degreasing agent in step (5) is DESOAGEN N309.

6. The method for processing crocodile leather according to claim 2, characterized in that: The preparation method of the amphiphilic polymer retanning-fatting agent described in step (7) is as follows: (a) palmitic acid, epibromopropane and cetyltrimethylammonium bromide are uniformly mixed in a mass ratio of 1: (0.64-0.8): (0.0016-0.0018), stirred at 60-65°C and 300-400 r / min until completely dissolved, reacted at 100-105°C and 300-400 r / min for 5-6 hours, washed with pure water at 70-80°C for 3-5 times, and vacuum dried at 50-60°C for 6-8 hours to obtain 3-bromo-2-hydroxypropyl palmitate; (b) 3-bromo-2-hydroxypropyl palmitate, N-allylimidazole and ethyl acetate are mixed uniformly in a mass ratio of 1:(0.315-0.345):(5-7), stirred at room temperature at 200-300 r / min until dissolved, refluxed at 65-70° C. and 300-400 r / min for 24-26 h, filtered, washed with ethyl acetate for 5-6 times, distilled under reduced pressure, and vacuum dried at 30-35° C. for 24-28 h to obtain modified allyl imidazole; (c) uniformly mixing modified allyl imidazole, diallyl dimethyl ammonium chloride, allyl phosphonic acid, n-dodecyl mercaptan and anhydrous ethanol in a mass ratio of 1:(1.25-1.32):(0.22-0.27):(0.0303-0.0305):(10-15), stirring at 300-400 r / min under a nitrogen atmosphere until dissolved, adding 10 wt% azobisisobutyronitrile ethanol solution (8.3 times the mass of n-dodecyl mercaptan) at 60-70° C. and 300-400 r / min at a rate of 5-6 drops per second, reacting for 6-7 hours after the addition, removing the solvent by rotary evaporation, dialyzing in ethanol aqueous solution for 36-40 hours, changing the ethanol aqueous solution every 4 hours, and vacuum drying at 50-60° C. for 12-15 hours to obtain an amphiphilic polymer; (d) Weigh 2 to 3 parts of an amphiphilic polymer, 2 to 3 parts of castor oil, 3 to 4 parts of rapeseed oil and 4 to 6 parts of fatty acid methyl ester by weight, mix them evenly, stir them in an oil bath at 60 to 70° C. and 500 to 600 r / min for 30 to 40 min, adjust the pH to 6.5 with a 10 wt % triethanolamine acetic acid solution, add 99 to 180 parts of pure water at 60 to 70° C., stir them at 500 to 600 r / min for 30 to 40 min, stop heating, and cool them naturally to room temperature to obtain an amphiphilic polymer retanning-fatting agent.

7. The method for processing crocodile leather according to claim 6, characterized in that: The volume ratio of ethanol to aqueous solution for dialysis in step (c) is 1:1, and the dialysis bag used is MD-44 with a molecular weight cut-off of 500.

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