Method for preparing acrylic resin retanning agent

Abstract

The invention relates to the technical field of leather retanning agents, and particularly discloses a method for preparing an acrylic resin retanning agent. Acrylic acid, methyl methacrylate, itaconic acid, acrylamide, methacrylic acid-2-hydroxyethyl ester, modified graphene oxide / polystyrene composite microspheres and ammonium chloride modified silicon dioxide are used as reaction monomers; under the action of an initiator and an assistant, a polymerization reaction is carried out to obtain an acrylic resin retanning agent, modified graphene oxide / polystyrene composite microspheres and ammonium chloride modified silicon dioxide surface double bonds participate in copolymerization, the phase separation problem of physical blending is avoided, and through chemical modification and an in-situ polymerization technology, the high-temperature-resistant acrylic resin retanning agent is obtained. The acrylic resin retanning agent with a network structure is constructed, crust leather can be filled and retanned by the retanning agent, the comprehensive performance of the crust leather can be effectively improved, and the leather processed by the retanning agent has excellent mechanical performance and is green and environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of leather retanning agents, in particular to a method for preparing an acrylic resin retanning agent. Background Art

[0002] Retanning is a key step in leather processing, improving its physical and mechanical properties, feel, and appearance. The properties of the retanning agents used during retanning directly impact the quality and performance of the leather. Acrylic resin retanning agents are widely used due to their excellent water dispersibility, leather-bonding ability, and filling properties. However, traditional acrylic resin retanning agents suffer from a single molecular structure, resulting in insufficient bonding with leather fibers, poor softness, and poor filling properties.

[0003] There are many improved acrylic resin retanning agents in the prior art, but they still have significant shortcomings. Chinese patent application CN115449569A discloses a method for preparing and applying a keratin-based high-performance filler-enhanced acrylic resin retanning agent. Keratin is extracted from waste cattle hair and modified with glyoxylic acid before being compounded with a polycarboxyl ligand and nitrate to obtain a high-performance filler. The high-performance filler is then ball-milled with acrylic resin, boric acid, sodium carboxymethyl cellulose, and sodium tripolyphosphate to obtain a keratin-based high-performance filler-enhanced acrylic resin retanning agent. The leather processed from this retanning agent has good physical and mechanical properties, while also having certain safety and health properties. However, the prepared high-performance filler has poor dispersion uniformity in the acrylic resin, which affects the retanning effect and has a long preparation cycle. Chinese patent application CN103255243A discloses a soft acrylic resin leather retanning agent and its preparation method. The agent is based on an esterification reaction between methyl ricinoleate and maleic anhydride, followed by neutralization with sodium hydroxide to obtain a sodium salt monomer of methyl ricinoleate maleate monoester. This monomer is then free radical copolymerized with a vinyl monomer in an aqueous system to produce an acrylic resin retanning agent containing a long-chain lipophilic group from the methyl ricinoleate structure in the side chain. This retanning agent has low toxicity, can fill and retan crust leather, softens crust leather fibers, and has a certain waterproofing effect on chrome-tanned crust leather. However, without the addition of reinforcing fillers, the agent has poor filling properties, average mechanical properties, and poor acid and alkali resistance.

[0004] Therefore, it is of great significance to develop an acrylic resin retanning agent that is environmentally friendly, low-toxic, has good filling properties and strong bonding strength. Summary of the Invention

[0005] (1) Technical problems solved In view of the deficiencies of the prior art, the present invention provides a method for preparing an acrylic resin retanning agent, and provides an acrylic resin retanning agent with excellent filling properties and strong bonding with crust leather, which can effectively improve the comprehensive properties of crust leather.

[0006] (2) Technical solution In order to achieve the above object, the present invention discloses a method for preparing an acrylic resin retanning agent, comprising the following steps: Step 1, ultrasonically dispersing the graphene oxide / polystyrene composite microspheres in anhydrous ethanol to form a uniform dispersion, adding acetic acid to adjust the pH to 3.5-4.5, adding γ-methacryloxypropyltrimethoxysilane, stirring and mixing, heating, reacting, centrifuging, washing with deionized water and anhydrous ethanol until neutral, and drying to obtain modified graphene oxide / polystyrene composite microspheres; Step 2: Add nano-silica, xylene, maleic anhydride, and triethylamine into a reactor, stir and mix, react, centrifuge after the reaction, wash with anhydrous ethanol and deionized water, and dry to obtain carboxyl-modified silica; Step 3: uniformly mix carboxyl-modified silica, N,N-dimethylformamide, N,N-dimethylethanolamine, and p-toluenesulfonic acid, heat, react, and after the reaction, perform vacuum distillation, adjust the pH to 6.5-7.5 with a 30% by mass sodium hydroxide solution, and dry to obtain modified silica; Step 4: ultrasonically disperse the modified silica in N,N-dimethylformamide, mix well, add chlorododecane, react, and after the reaction is completed, distill under reduced pressure, wash with acetone, and vacuum dry at 60° C. for 12 hours to obtain ammonium chloride modified silica; Step 5. Add acrylic acid, methyl methacrylate, itaconic acid, acrylamide, 2-hydroxyethyl methacrylate, modified graphene oxide / polystyrene composite microspheres, and ammonium chloride-modified silica to a reaction vessel, ultrasonically disperse, and mix evenly to obtain a monomer mixture. Mix deionized water and an auxiliary composition evenly to obtain a mixture, add the mixture to the monomer mixture, stir and mix in a nitrogen atmosphere, and then add an initiator to react. After the reaction is completed, cool and slowly neutralize with a sodium hydroxide solution to obtain an acrylic resin retanning agent.

[0007] Preferably, in the step 1, the addition ratio of graphene oxide / polystyrene composite microspheres, anhydrous ethanol, and γ-methacryloxypropyltrimethoxysilane is 10 g: 550-700 mL: 0.2-1 g.

[0008] Preferably, the reaction temperature in step 1 is 75-85° C., and the reaction time is 24-32 h.

[0009] Furthermore, the preparation method of the graphene oxide / polystyrene composite microspheres comprises the following steps: Anhydrous ethanol and deionized water in a mass ratio of 4:1 were mixed evenly to obtain a mixed solvent, polyvinyl pyrrolidone was added, and the mixture was stirred and mixed until completely dissolved. Styrene and azobisisobutyronitrile were added, and the mixture was stirred and mixed in a nitrogen atmosphere. The mixture was reacted at 70°C for 2 hours. Graphene oxide dispersion was added, and the concentration of the graphene oxide dispersion was 0.1% (w / v). The mixture was stirred and mixed, and the reaction was continued for 12 hours to terminate the reaction. The mass ratio of the mixed solvent, polyvinyl pyrrolidone, styrene and azobisisobutyronitrile, and graphene oxide dispersion was 560:33:100:1:280. The mixture was centrifuged, washed with anhydrous ethanol and deionized water, respectively, and dried to obtain graphene oxide / polystyrene composite microspheres.

[0010] Preferably, in the step 2, the addition ratio of nano-silica, xylene, maleic anhydride and triethylamine is 10g:350-400mL:15-18g:0.5-1g.

[0011] Preferably, the reaction temperature in step 2 is 105-115° C., and the reaction time is 24-36 h.

[0012] Preferably, in the step 3, the addition ratio of carboxyl-modified silica, N,N-dimethylformamide, N,N-dimethylethanolamine, and p-toluenesulfonic acid is 10 g: 200-250 mL: 4-7 g: 0.2-0.5 g.

[0013] Preferably, the reaction temperature in step 3 is 95-105° C., and the reaction time is 6-8 h.

[0014] Preferably, in step 4, the addition ratio of modified silica, N,N-dimethylformamide, and chlorododecane is 10 g:380-420 mL:14-25 g.

[0015] Preferably, the reaction temperature in step 4 is 80-85° C., and the reaction time is 24-32 h.

[0016] Preferably, in the step 5, the addition ratio of acrylic acid, methyl methacrylate, itaconic acid, acrylamide, 2-hydroxyethyl methacrylate, modified graphene oxide / polystyrene composite microspheres, ammonium chloride-modified silica, deionized water, initiator, and auxiliary agent composition is 100g:60-80g:10-16g:20-35g:6-10g:5-9g:3-6g:90-120mL:0.8-2g:6-12g.

[0017] Preferably, the reaction temperature in step 5 is 70-75° C., the reaction time is 3-5 h, and the stirring speed during the reaction is 240-300 r / min.

[0018] Preferably, the auxiliary agent composition in step 5 is composed of sodium dodecylbenzenesulfonate and polyvinyl alcohol in a mass ratio of 2:3.

[0019] Preferably, the initiator in step five is ammonium persulfate.

[0020] (3) Beneficial technical effects Compared with the prior art, the present invention has the following beneficial effects: (1) In the present invention, graphene oxide / polystyrene composite microspheres are modified by using γ-methacryloxypropyltrimethoxysilane to introduce alkenyl groups to participate in the polymerization reaction. Nano-silica is surface-modified, maleic anhydride and the hydroxyl groups on the surface of the silica undergo an esterification reaction, carboxyl groups and alkenyl groups are introduced, and the carboxyl groups undergo an esterification reaction with N,N-dimethylethanolamine to obtain modified silica, which is then reacted with chlorododecane to obtain ammonium chloride-modified silica. Acrylic acid, methyl methacrylate, itaconic acid, acrylamide, 2-hydroxyethyl methacrylate, modified graphene oxide / polystyrene composite microspheres, and ammonium chloride-modified silica are used as reaction monomers. In the presence of an initiator and an auxiliary agent, a polymerization reaction is performed to obtain an acrylic resin retanning agent.

[0021] (2) In the present invention, an acrylic resin retanning agent with a network structure is constructed by chemical modification and in-situ polymerization technology. The high specific surface area of ​​graphene oxide can provide a large number of adsorption sites, forming hydrogen bonds and ionic bonds with the amino groups of leather collagen. After modification, it is evenly dispersed and can effectively disperse local stress when subjected to external force, thereby improving tear strength and preventing local breakage of the leather. The elastic buffering effect of polystyrene microspheres elastically expands in the gaps between leather fibers, playing the role of elastic filling and enhancing the bending resistance of leather. The quaternary ammonium salt in ammonium chloride modified silica forms strong electrostatic adsorption with leather fibers (negatively charged) and can destroy bacterial cell membranes, thereby improving the antibacterial properties of the leather. The introduced long-chain alkyl chain enhances hydrophobicity and improves water resistance. Nano-silica has excellent wear resistance and heat resistance. It enters the gaps between leather fibers and can effectively prevent fiber slippage. Graphene oxide and nano-silica synergistically have good filling properties and can effectively improve the mechanical properties and heat resistance of leather. Furthermore, the introduction of 2-hydroxyethyl methacrylate into the retanning agent can improve the solubility of the retanning agent in water, enhance the leather's ability to absorb and retain moisture, prevent the leather from hardening after drying, and at the same time make the polymer chain segments more mobile, giving the leather a soft feel. The large number of carboxyl groups introduced can form multiple ionic bonds with the leather fibers, improving the binding fastness of the retanning agent and increasing the thickening rate. Sodium dodecylbenzenesulfonate acts as an anionic emulsifier to reduce surface tension, and polyvinyl alcohol acts as a protective colloid to prevent particle agglomeration, making the polymerization system stable.

[0022] (3) The modified graphene oxide / polystyrene composite microspheres and ammonium chloride-modified silica surface double bonds in the present invention participate in the copolymerization, thus avoiding the phase separation problem of physical blending. The synergistic effect between the raw materials effectively improves the comprehensive performance of the retanning agent. The retanning agent can form hydrogen bonds with the raw leather, with strong binding force. After the retanning agent is processed into leather, it has excellent mechanical properties and is green and environmentally friendly. The shrinkage temperature of the raw leather is increased, and the wet heat stability is excellent. At the same time, it also has certain antistatic and antibacterial properties. DETAILED DESCRIPTION

[0023] To facilitate understanding of the present invention, the present invention will be described in more detail below. Preferred embodiments of the present invention are provided below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention. Example

[0024] A method for preparing an acrylic resin retanning agent comprises the following steps: Step 1: ultrasonically disperse 10 g of graphene oxide / polystyrene composite microspheres in 550 mL of anhydrous ethanol to form a uniform dispersion, add acetic acid to adjust the pH to 3.5, add 0.2 g of γ-methacryloxypropyltrimethoxysilane, stir and mix, heat, react at 75 ° C for 32 h, centrifuge, wash with deionized water and anhydrous ethanol until neutral, and dry to obtain modified graphene oxide / polystyrene composite microspheres; Step 2: 10 g of nano-silica, 350 mL of xylene, 15 g of maleic anhydride, and 0.5 g of triethylamine were added to a reactor, stirred and mixed, and reacted at 105° C. for 36 h. After the reaction was completed, the mixture was centrifuged, washed with anhydrous ethanol and deionized water, and dried to obtain carboxyl-modified silica; Step 3: 10 g of carboxyl-modified silica, 200 mL of N,N-dimethylformamide, 4 g of N,N-dimethylethanolamine, and 0.2 g of p-toluenesulfonic acid were mixed evenly, heated, and reacted at 95 ° C for 8 h. After the reaction, vacuum distillation was performed, and the pH was adjusted to 6.5 with a 30% mass fraction of sodium hydroxide solution, and dried to obtain modified silica; Step 4: ultrasonically disperse 10 g of modified silica into 380 mL of N,N-dimethylformamide, mix well, add 14 g of chlorododecane, react at 80° C. for 32 h, and after the reaction is completed, distill under reduced pressure, wash with acetone, and vacuum dry at 60° C. for 12 h to obtain ammonium chloride modified silica; Step 5. Add 100g of acrylic acid, 60g of methyl methacrylate, 10g of itaconic acid, 20g of acrylamide, 6g of 2-hydroxyethyl methacrylate, 5g of modified graphene oxide / polystyrene composite microspheres, and 3g of ammonium chloride-modified silica to a reaction vessel, ultrasonically disperse, and mix evenly to obtain a monomer mixture. Mix 90mL of deionized water and 6g of an auxiliary composition, wherein the auxiliary composition consists of sodium dodecylbenzenesulfonate and polyvinyl alcohol in a mass ratio of 2:3 to obtain a mixture, add the mixture to the monomer mixture, stir and mix in a nitrogen atmosphere, and then add 0.8g of initiator ammonium persulfate. During the reaction, the stirring speed is 240r / min, and the reaction is carried out at 70°C for 5h. After the reaction is completed, cool and slowly neutralize with sodium hydroxide solution to obtain an acrylic resin retanning agent. Example

[0025] A method for preparing an acrylic resin retanning agent comprises the following steps: Step 1: ultrasonically disperse 10 g of graphene oxide / polystyrene composite microspheres in 650 mL of anhydrous ethanol to form a uniform dispersion, add acetic acid to adjust the pH to 4, add 0.8 g of γ-methacryloxypropyltrimethoxysilane, stir and mix, heat, react at 80 ° C for 30 h, centrifuge, wash with deionized water and anhydrous ethanol until neutral, and dry to obtain modified graphene oxide / polystyrene composite microspheres; Step 2: 10 g of nano-silica, 380 mL of xylene, 17 g of maleic anhydride, and 0.8 g of triethylamine were added to a reactor, stirred and mixed, and reacted at 110° C. for 32 h. After the reaction was completed, the mixture was centrifuged, washed with anhydrous ethanol and deionized water, and dried to obtain carboxyl-modified silica; Step 3: 10 g of carboxyl-modified silica, 240 mL of N,N-dimethylformamide, 5 g of N,N-dimethylethanolamine, and 0.4 g of p-toluenesulfonic acid were mixed evenly, heated, and reacted at 100 ° C for 7 h. After the reaction, vacuum distillation was performed, and the pH was adjusted to 6 with a 30% mass fraction of sodium hydroxide solution, and dried to obtain modified silica; Step 4: ultrasonically disperse 10 g of modified silica into 400 mL of N,N-dimethylformamide, mix well, add 21 g of chlorododecane, react at 82° C. for 30 h, and after the reaction is completed, distill under reduced pressure, wash with acetone, and vacuum dry at 60° C. for 12 h to obtain ammonium chloride modified silica; Step 5. Add 100g of acrylic acid, 68g of methyl methacrylate, 12g of itaconic acid, 28g of acrylamide, 7g of 2-hydroxyethyl methacrylate, 6g of modified graphene oxide / polystyrene composite microspheres, and 4g of ammonium chloride-modified silica to a reaction vessel, ultrasonically disperse, and mix evenly to obtain a monomer mixture. Mix 105mL of deionized water and 8g of an auxiliary composition, wherein the auxiliary composition consists of sodium dodecylbenzenesulfonate and polyvinyl alcohol in a mass ratio of 2:3 to obtain a mixture, add the mixture to the monomer mixture, stir and mix in a nitrogen atmosphere, and then add 1.4g of initiator ammonium persulfate. During the reaction, the stirring speed is 280r / min, and the reaction is carried out at 72°C for 4h. After the reaction is completed, cool and slowly neutralize with sodium hydroxide solution to obtain an acrylic resin retanning agent. Example

[0026] A method for preparing an acrylic resin retanning agent comprises the following steps: 100 g of acrylic acid, 75 g of methyl methacrylate, 15 g of itaconic acid, 32 g of acrylamide, 9 g of 2-hydroxyethyl methacrylate, 7 g of modified graphene oxide / polystyrene composite microspheres, and 5 g of ammonium chloride-modified silica were added to a reaction container, ultrasonically dispersed, and mixed uniformly to obtain a monomer mixture. 105 mL of deionized water and 10 g of an auxiliary composition were mixed uniformly, wherein the auxiliary composition consisted of sodium dodecylbenzenesulfonate and polyvinyl alcohol in a mass ratio of 2:3 to obtain a mixture, which was added to the monomer mixture. The mixture was stirred in a nitrogen atmosphere, and 1.8 g of initiator ammonium persulfate was added. The stirring speed during the reaction was 280 r / min, and the reaction was carried out at 72° C. for 4 h. After the reaction was completed, the mixture was cooled and slowly neutralized with a sodium hydroxide solution to obtain an acrylic resin retanning agent.

[0027] The preparation method of the modified graphene oxide / polystyrene composite microspheres and ammonium chloride-modified silica is exactly the same as the preparation method of the modified graphene oxide / polystyrene composite microspheres and ammonium chloride-modified silica in Example 2. Example

[0028] A method for preparing an acrylic resin retanning agent comprises the following steps: Step 1: ultrasonically disperse 10 g of graphene oxide / polystyrene composite microspheres in 700 mL of anhydrous ethanol to form a uniform dispersion, add acetic acid to adjust the pH to 4.5, add 1 g of γ-methacryloxypropyltrimethoxysilane, stir and mix, heat, react at 85 ° C for 24 h, centrifuge, wash with deionized water and anhydrous ethanol until neutral, and dry to obtain modified graphene oxide / polystyrene composite microspheres; Step 2: 10 g of nano-silica, 400 mL of xylene, 18 g of maleic anhydride, and 1 g of triethylamine were added to a reactor, stirred and mixed, and reacted at 115° C. for 24 h. After the reaction was completed, the mixture was centrifuged, washed with anhydrous ethanol and deionized water, and dried to obtain carboxyl-modified silica; Step 3: 10 g of carboxyl-modified silica, 250 mL of N,N-dimethylformamide, 7 g of N,N-dimethylethanolamine, and 0.5 g of p-toluenesulfonic acid were mixed evenly, heated, and reacted at 105 ° C for 6 h. After the reaction, vacuum distillation was performed, and the pH was adjusted to 7.5 with a 30% mass fraction of sodium hydroxide solution, and dried to obtain modified silica; Step 4: ultrasonically disperse 10 g of modified silica into 420 mL of N,N-dimethylformamide, mix well, add 25 g of chlorododecane, react at 85° C. for 24 h, and after the reaction is completed, distill under reduced pressure, wash with acetone, and vacuum dry at 60° C. for 12 h to obtain ammonium chloride modified silica; Step 5. Add 100g of acrylic acid, 80g of methyl methacrylate, 16g of itaconic acid, 35g of acrylamide, 10g of 2-hydroxyethyl methacrylate, 9g of modified graphene oxide / polystyrene composite microspheres, and 6g of ammonium chloride-modified silica to a reaction vessel, ultrasonically disperse, and mix evenly to obtain a monomer mixture. Mix 120mL of deionized water and 12g of an auxiliary composition, wherein the auxiliary composition consists of sodium dodecylbenzenesulfonate and polyvinyl alcohol in a mass ratio of 2:3 to obtain a mixture, add the mixture to the monomer mixture, stir and mix in a nitrogen atmosphere, and then add 2g of initiator ammonium persulfate. During the reaction, the stirring speed is 300r / min, and the reaction is carried out at 75°C for 3h. After the reaction is completed, cool and slowly neutralize with sodium hydroxide solution to obtain an acrylic resin retanning agent.

[0029] Comparative Example 1 A method for preparing an acrylic resin retanning agent comprises the following steps: 100 g of acrylic acid, 75 g of methyl methacrylate, 15 g of itaconic acid, 32 g of acrylamide, 9 g of 2-hydroxyethyl methacrylate, 7 g of graphene oxide / polystyrene composite microspheres, and 5 g of ammonium chloride-modified silica were added to a reaction container, ultrasonically dispersed, and mixed uniformly to obtain a monomer mixture. 105 mL of deionized water and 10 g of an auxiliary composition were mixed uniformly, wherein the auxiliary composition consisted of sodium dodecylbenzenesulfonate and polyvinyl alcohol in a mass ratio of 2:3 to obtain a mixture, which was added to the monomer mixture. The mixture was stirred in a nitrogen atmosphere, and 1.8 g of initiator ammonium persulfate was added. The stirring speed during the reaction was 280 r / min, and the reaction was carried out at 72° C. for 4 h. After the reaction was completed, the mixture was cooled and slowly neutralized with a sodium hydroxide solution to obtain an acrylic resin retanning agent.

[0030] The preparation method of ammonium chloride modified silica is exactly the same as the preparation method of ammonium chloride modified silica in Example 2.

[0031] Comparative Example 2 A method for preparing an acrylic resin retanning agent comprises the following steps: Step 1: ultrasonically disperse 10 g of graphene oxide / polystyrene composite microspheres in 650 mL of anhydrous ethanol to form a uniform dispersion, add acetic acid to adjust the pH to 4, add 0.8 g of γ-methacryloxypropyltrimethoxysilane, stir and mix, heat, react at 80 ° C for 30 h, centrifuge, wash with deionized water and anhydrous ethanol until neutral, and dry to obtain modified graphene oxide / polystyrene composite microspheres; Step 2: 10 g of nano-silica, 380 mL of xylene, 17 g of maleic anhydride, and 0.8 g of triethylamine were added to a reactor, stirred and mixed, and reacted at 110° C. for 32 h. After the reaction was completed, the mixture was centrifuged, washed with anhydrous ethanol and deionized water, and dried to obtain carboxyl-modified silica; Step 3, 100g of acrylic acid, 75g of methyl methacrylate, 15g of itaconic acid, 32g of acrylamide, 9g of 2-hydroxyethyl methacrylate, 7g of modified graphene oxide / polystyrene composite microspheres, and 5g of carboxyl-modified silica were added to a reaction vessel, ultrasonically dispersed, and mixed evenly to obtain a monomer mixture. 105mL of deionized water and 10g of an auxiliary composition were mixed evenly, wherein the auxiliary composition consisted of sodium dodecylbenzenesulfonate and polyvinyl alcohol in a mass ratio of 2:3 to obtain a mixture, which was added to the monomer mixture. In a nitrogen atmosphere, the mixture was stirred and mixed, and 1.8g of initiator ammonium persulfate was added. The stirring speed during the reaction was 280r / min, and the reaction was carried out at 72°C for 4h. After the reaction was completed, the mixture was cooled and slowly neutralized with sodium hydroxide solution to obtain an acrylic resin retanning agent.

[0032] Comparative Example 3 A method for preparing an acrylic resin retanning agent comprises the following steps: 100 g of acrylic acid, 75 g of methyl methacrylate, 15 g of itaconic acid, 32 g of acrylamide, 9 g of 2-hydroxyethyl methacrylate, 7 g of graphene oxide / polystyrene composite microspheres, and 5 g of nano-silica were added to a reaction container, ultrasonically dispersed, and mixed uniformly to obtain a monomer mixture. 105 mL of deionized water and 10 g of an auxiliary composition were mixed uniformly, wherein the auxiliary composition consisted of sodium dodecylbenzenesulfonate and polyvinyl alcohol in a mass ratio of 2:3 to obtain a mixture, which was added to the monomer mixture. The mixture was stirred in a nitrogen atmosphere, and 1.8 g of initiator ammonium persulfate was added. The stirring speed during the reaction was 280 r / min, and the reaction was carried out at 72° C. for 4 h. After the reaction was completed, the mixture was cooled and slowly neutralized with a sodium hydroxide solution to obtain an acrylic resin retanning agent.

[0033] The preparation method of the graphene oxide / polystyrene composite microspheres described in the examples and comparative examples of the present invention comprises the following steps: Anhydrous ethanol and deionized water in a mass ratio of 4:1 were mixed evenly to obtain a mixed solvent, polyvinyl pyrrolidone was added, and the mixture was stirred and mixed until completely dissolved. Styrene and azobisisobutyronitrile were added, and the mixture was stirred and mixed in a nitrogen atmosphere. The mixture was reacted at 70°C for 2 hours. Graphene oxide dispersion was added, and the concentration of the graphene oxide dispersion was 0.1% (w / v). The mixture was stirred and mixed, and the reaction was continued for 12 hours to terminate the reaction. The mass ratio of the mixed solvent, polyvinyl pyrrolidone, styrene and azobisisobutyronitrile, and graphene oxide dispersion was 560:33:100:1:280. The mixture was centrifuged, washed with anhydrous ethanol and deionized water, respectively, and dried to obtain graphene oxide / polystyrene composite microspheres.

[0034] The graphene oxide used in the examples and comparative examples of the present invention was purchased from Suzhou Tanfeng Graphite Technology Co., Ltd.; nanosilica was purchased from Jiangsu Lianyungang Pengrui Chemical Co., Ltd. with a particle size of 15 nm; polyvinyl alcohol was purchased from Alfa Aesar (Tianjin) Chemical Co., Ltd.; other raw materials and reagents not specified were commercially available.

[0035] The acrylic resin retanning agents prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to relevant performance tests. Wet cowhide leather was shaved and whitened, TWS tanned, and had a thickness of 1.2 mm. Samples were taken symmetrically along the ridge line and weighed. The crust leather sample size was 20 cm × 30 cm. The conventional retanning process was used. The amount of retanning agent was 4 wt % of the crust leather sample. The sample tests were as follows: The tear strength of the crust leather samples was tested according to the QB / T 2711-2005 standard, the bursting strength of the crust leather samples was tested according to the QB / T 2712-2005 standard, the shrinkage temperature of the crust leather samples was tested according to the QB / T 2713-2005 standard, and the thickening rate was tested according to the QB / T 2709-2005 standard. Each group of the above tests was tested three times and the average value was taken. The test results are shown in Table 1: Table 1 Test items Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tear strength (N / mm) 41.7 46.9 50.3 47.8 29.8 32.7 22.5 Collapse strength (N) 380.1 418.4 429.2 416.7 326.9 364.8 302.5 Shrinkage temperature (℃) 82.4 85.7 88.5 91.0 76.8 79.5 72.1 Thickening rate (%) 19.6 21.8 23.5 22.9 16.9 18.0 15.3 As can be seen from the test results of Table 1, the samples corresponding to Examples 1-4 of the present invention have excellent mechanical properties, higher shrinkage temperatures, and increased thickening rates after treatment, indicating that the retanning agent has excellent comprehensive properties. Graphene oxide / polystyrene composite microspheres were not modified in Comparative Example 1 and were directly added to the matrix as monomers, resulting in a deterioration in dispersibility and easy detachment from the polymer network, resulting in a deterioration in comprehensive properties. Quaternary ammonium salt was not introduced in Comparative Example 2, resulting in a significant decrease in electrostatic attraction and mechanical strength. Nanoparticles were easily agglomerated in Comparative Example 3, resulting in poor compatibility between the raw materials, a significant reduction in mechanical properties, a weakening of the reactive force between the crust leather, a decrease in thickening rate, and a reduction in heat resistance.

[0036] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and that all equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing an acrylic resin retanning agent, characterized in that: The steps include: Step 1, ultrasonically dispersing the graphene oxide / polystyrene composite microspheres in anhydrous ethanol to form a uniform dispersion, adding acetic acid to adjust the pH to 3.5-4.5, adding γ-methacryloxypropyltrimethoxysilane, stirring and mixing, heating, reacting, centrifuging, washing, and drying to obtain modified graphene oxide / polystyrene composite microspheres; Step 2: Add nano-silica, xylene, maleic anhydride, and triethylamine into a reactor, stir and mix, react, centrifuge, wash, and dry after the reaction to obtain carboxyl-modified silica; Step 3: uniformly mix carboxyl-modified silica, N,N-dimethylformamide, N,N-dimethylethanolamine, and p-toluenesulfonic acid, heat, react, and after the reaction is completed, perform vacuum distillation, add sodium hydroxide solution to adjust the pH to 6.5-7.5, and dry to obtain modified silica; Step 4: ultrasonically dispersing the modified silica into N,N-dimethylformamide, mixing evenly, adding chlorododecane to react, and after the reaction is completed, distilling under reduced pressure, washing, and drying to obtain ammonium chloride modified silica; Step 5. Add acrylic acid, methyl methacrylate, itaconic acid, acrylamide, 2-hydroxyethyl methacrylate, modified graphene oxide / polystyrene composite microspheres, and ammonium chloride-modified silica to a reaction vessel, ultrasonically disperse, and mix evenly to obtain a monomer mixture. Mix deionized water and an auxiliary composition evenly to obtain a mixture, add the mixture to the monomer mixture, stir and mix in a nitrogen atmosphere, and then add an initiator to react. After the reaction is completed, cool and slowly neutralize with a sodium hydroxide solution to obtain an acrylic resin retanning agent.

2. A method for preparing an acrylic resin retanning agent according to claim 1, characterized in that: In the step 1, the addition ratio of graphene oxide / polystyrene composite microspheres, anhydrous ethanol, and γ-methacryloxypropyltrimethoxysilane is 10 g:550-700 mL:0.2-1 g, the reaction temperature is 75-85° C., and the reaction time is 24-32 h.

3. A method for preparing an acrylic resin retanning agent according to claim 1, characterized in that: In the step 2, the addition ratio of nano-silica, xylene, maleic anhydride and triethylamine is 10g:350-400mL:15-18g:0.5-1g, the reaction temperature is 105-115°C, and the reaction time is 24-36h.

4. A method for preparing an acrylic resin retanning agent according to claim 1, characterized in that: In the step 3, the addition ratio of carboxyl-modified silica, N,N-dimethylformamide, N,N-dimethylethanolamine, and p-toluenesulfonic acid is 10 g: 200-250 mL: 4-7 g: 0.2-0.5 g.

5. A method for preparing an acrylic resin retanning agent according to claim 1, characterized in that: The reaction temperature in step 3 is 95-105° C., and the reaction time is 6-8 h.

6. A method for preparing an acrylic resin retanning agent according to claim 1, characterized in that: In the step 4, the addition ratio of modified silica, N,N-dimethylformamide, and chlorododecane is 10 g:380-420 mL:14-25 g, the reaction temperature is 80-85° C., and the reaction time is 24-32 h.

7. A method for preparing an acrylic resin retanning agent according to claim 1, characterized in that: In the step 5, the addition ratio of acrylic acid, methyl methacrylate, itaconic acid, acrylamide, 2-hydroxyethyl methacrylate, modified graphene oxide / polystyrene composite microspheres, ammonium chloride modified silica, deionized water, initiator, and auxiliary agent composition is 100g:60-80g:10-16g:20-35g:6-10g:5-9g:3-6g:90-120mL:0.8-2g:6-12g.

8. A method for preparing an acrylic resin retanning agent according to claim 1, characterized in that: The reaction temperature in step 5 is 70-75° C., the reaction time is 3-5 h, and the stirring speed during the reaction is 240-300 r / min.

9. A method for preparing an acrylic resin retanning agent according to claim 1, characterized in that: The auxiliary agent composition in step 5 is composed of sodium dodecylbenzenesulfonate and polyvinyl alcohol in a mass ratio of 2:

3.

10. The method for preparing an acrylic resin retanning agent according to claim 1, wherein: In the step 5, the initiator is ammonium persulfate.