A wear-resistant and scratch-resistant leather finishing agent and preparation method thereof

Abstract

The present invention relates to the technical field of leather finishing agents, specifically a wear-resistant and scratch-resistant leather finishing agent and a preparation method thereof. The present invention first uses succinic anhydride and diethanolamine as raw materials to react and prepare an intermediate, reacts the intermediate with 1,2-epoxy-7-octene to obtain a dihydroxy crosslinking monomer; then the dihydroxy crosslinking monomer, chitosan quaternary ammonium salt, acrylic acid, butyl acrylate, and methyl methacrylate are mixed, and polymerized under the action of an initiator to obtain a chitosan quaternary ammonium salt-based acrylate emulsion; then the chitosan quaternary ammonium salt-based acrylate emulsion is added to a polyurethane prepolymer to prepare a modified polyurethane; finally, the modified polyurethane, carboxylated modified graphene oxide, a defoamer, a thickener, and a wetting agent are mixed to obtain a leather finishing agent. The leather finishing agent prepared by the present invention has good film-forming performance and has antibacterial, wear-resistant, scratch-resistant, water-washable and other properties.

Description

Technical Field

[0001] The invention relates to the technical field of leather finishing agents, in particular to a wear-resistant and scratch-resistant leather finishing agent and a preparation method thereof. Background Art

[0002] Leather finishing agents are additives used for leather surface finishing, protection and beautification, and have good film-forming and coloring properties. When used, they are usually applied to the leather surface by wiping, brushing, spraying, etc. After curing, a coating with adhesive strength and mechanical strength can be formed, thereby achieving the effect of increasing the appearance of the leather, extending the use time of the leather, and improving the quality and grade of leather products. Therefore, in leather finishing agents, film-forming substances determine the maintenance effect of the finishing agent on the leather to a certain extent.

[0003] Common film-forming substances used for leather finishing agents include polyacrylic acid resin, polyurethane resin, etc. Among them, polyacrylic acid resin has good water resistance, light stability, and weather resistance, but has problems such as poor wear resistance, hot stickiness and cold brittleness, and solvent resistance, while water-based polyurethane resin has high wear resistance and good mechanical properties, but poor water resistance. Polyacrylic acid resin and polyurethane resin are organically combined to take advantage of each other's strengths and make up for each other's weaknesses to prepare a new type of wear-resistant and scratch-resistant leather finishing agent. Summary of the invention

[0004] The object of the present invention is to provide a wear-resistant and scratch-resistant leather finishing agent and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a wear-resistant and scratch-resistant leather finishing agent and a preparation method thereof, comprising the following steps:

[0006] Step 1:

[0007] S11: mixing chitosan quaternary ammonium salt, acrylic acid, butyl acrylate, and methyl methacrylate and stirring for 10 to 15 minutes, and adding a dihydroxy crosslinking monomer to obtain a monomer mixture; wherein the mass fraction of the hydroxyl group in the monomer mixture is 0.8 to 1.3%;

[0008] S12: dispersing the monomer mixture in deionized water, adding an emulsifier, stirring for 30 to 40 minutes, adding an initiator, and polymerizing at 70 to 80° C. for 3 to 5 hours to obtain a chitosan quaternary ammonium salt-based acrylate emulsion;

[0009] Step 2:

[0010] S21: polypropylene glycol 1000, dimethylol propionic acid and isophorone diisocyanate are mixed, dibutyltin dilaurate is used as a catalyst, the temperature is raised to 70-80° C. for reaction for 1-2 hours to obtain a polyurethane prepolymer; chitosan quaternary ammonium salt-based acrylate emulsion is added to the polyurethane prepolymer while keeping the temperature, and the reaction is continued for 2-3 hours to obtain a modified polyurethane prepolymer;

[0011] S22: adding 1,4-butanediol to the modified polyurethane prepolymer at 40-50° C. and reacting for 1-2 hours; adding acetone and triethylamine and stirring to react for 30-40 minutes; adding water for emulsification and then evaporating the acetone under reduced pressure to obtain a modified polyurethane emulsion;

[0012] Step 3:

[0013] The modified polyurethane emulsion, carboxyl modified graphene oxide, defoamer, thickener and wetting agent are mixed to obtain a wear-resistant and scratch-resistant leather finishing agent.

[0014] Furthermore, in S11, in the monomer mixture, the contents of each component are, by weight, 10 to 15 parts of chitosan quaternary ammonium salt, 12 to 15 parts of acrylic acid, 21 to 24 parts of butyl acrylate, 27 to 32 parts of methyl methacrylate, and the remainder is a dihydroxy crosslinking monomer.

[0015] Furthermore, the preparation method of the dihydroxy cross-linking monomer is as follows: succinic anhydride and diethanolamine are dispersed in anhydrous methanol in a molar ratio of 1:1, the temperature is raised to 60-70°C under nitrogen protection, the anhydrous methanol is removed by reduced pressure distillation, and the intermediate is obtained by drying; the intermediate and 1,2-epoxy-7-octene are mixed in a ratio of 1:1 between carboxyl and epoxy groups, a catalyst triphenylphosphine and an inhibitor are added, and the mixture is reacted at 120-130°C for 5-8h to obtain the dihydroxy cross-linking monomer.

[0016] Furthermore, in S12, in the chitosan quaternary ammonium salt-based acrylate, the amounts of the components are, by weight, 80 to 100 parts of the monomer mixture and 1 to 2 parts of the emulsifier; the solid content of the chitosan quaternary ammonium salt-based acrylate emulsion is 30 to 35%.

[0017] Furthermore, in S21, in the polyurethane prepolymer, the amount of each component is calculated by weight, 180 to 200 parts of polypropylene glycol 1000, 20 to 30 parts of dihydroxymethylpropionic acid, and 110 to 120 parts of isophorone diisocyanate; in the modified polyurethane prepolymer, the mass ratio of chitosan quaternary ammonium salt acrylate to polyurethane prepolymer is 1:(4 to 9).

[0018] Furthermore, in S22, the amounts of the components are calculated by weight: 100 parts of modified polyurethane prepolymer, 1 to 1.5 parts of 1,4-butanediol, 18 to 25 parts of acetone, and 4 to 7 parts of triethylamine.

[0019] Furthermore, in S22, the solid content of the modified polyurethane emulsion is 30-35%.

[0020] Furthermore, in step 3, the content of each component in the wear-resistant and scratch-resistant leather finishing agent is calculated by weight: 100 parts of modified polyurethane emulsion, 2 to 3 parts of carboxylated modified graphene oxide, 0.5 to 1 part of defoaming agent, 0.5 to 1 part of thickener, and 1 to 2 parts of wetting agent.

[0021] Furthermore, in step 3, the preparation method of carboxylated modified graphene oxide is: adding graphene oxide to deionized water, mixing the graphene oxide dispersion obtained by ultrasonic dispersion; adding sodium hydroxide to the graphene oxide dispersion, stirring and adding bromoacetic acid to react for 3 to 5 hours, letting it stand and filtering the precipitate to separate it, washing the filter cake with dilute hydrochloric acid and distilled water, and then vacuum drying to obtain carboxylated modified graphene oxide.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the present invention provides a method for preparing a wear-resistant and scratch-resistant leather finishing agent. Succinic anhydride and diethanolamine are used as raw materials to react and prepare an intermediate, and the intermediate is reacted with 1,2-epoxy-7-octene to obtain a dihydroxy cross-linking monomer; chitosan quaternary ammonium salt, acrylic acid, butyl acrylate, methyl methacrylate, and dihydroxy cross-linking monomer are mixed, and polymerized under the action of an initiator to obtain a chitosan quaternary ammonium salt-based acrylate emulsion; the chitosan quaternary ammonium salt-based acrylate emulsion is added to a polyurethane prepolymer to prepare a modified polyurethane. The modified polyurethane, carboxylated modified graphene oxide, a defoamer, a thickener, and a wetting agent are mixed to obtain a wear-resistant and scratch-resistant leather finishing agent with good antibacterial and film-forming properties.

[0023] In the present invention, a dihydroxy crosslinking monomer is added when preparing the chitosan quaternary ammonium salt-based acrylate emulsion, which can react with the isocyanate group in the polyurethane prepolymer to form a chemical bond, thereby improving the compatibility between the two molecules. However, in the research and development process, researchers found that in the chitosan quaternary ammonium salt-based acrylate, the high mass fraction of hydroxyl groups will cause the modified polyurethane latex particle size to become larger and the viscosity of the emulsion to increase, and the prepared leather finishing agent has poor film-forming performance and obvious granularity. After repeated experiments, it was found that the modification effect is best when the mass fraction of hydroxyl groups in the chitosan quaternary ammonium salt-based acrylate is controlled to be 0.8-1.3%. In order to avoid the high content of chitosan quaternary ammonium salt-based acrylate, which leads to a decrease in its compatibility with polyurethane and affects the performance of the finishing agent, the present invention mixes chitosan quaternary ammonium salt-based acrylate with the polyurethane prepolymer in a mass ratio of 1: (4-9).

[0024] In addition, the present invention introduces polar carboxyl functional groups on the surface of graphene oxide, and the latex particles of the finishing agent also contain carboxyl groups, which enable the graphene oxide to achieve a stable and uniform dispersion effect through electrostatic repulsion, and after curing, a graphene oxide layer is formed in the coating and attached to the leather surface. When the leather is rubbed and scratched, the graphene oxide layer plays a boundary lubrication and protection effect, thereby giving the leather a wear-resistant and scratch-resistant effect. DETAILED DESCRIPTION

[0025] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0026] Materials and sources used in the present invention: chitosan quaternary ammonium salt (substitution degree ≥ 90%) comes from Nantong Lvshen Bioengineering Co., Ltd.; the inhibitor is inhibitor 701; the emulsifier is dodecyltrimethylammonium bromide; the initiator is ammonium persulfate; the defoamer comes from Evonik Industries AG, item number 810 defoamer; the thickener comes from Anhui Yuanchen New Materials Technology Co., Ltd., item number YC-100A; the wetting agent comes from Shanghai Sangjing Chemical Co., Ltd., item number 440 wetting agent; and graphene oxide comes from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., item number XF033.

[0027] Embodiment 1: A wear-resistant and scratch-resistant leather finishing agent and a preparation method thereof, comprising the following steps:

[0028] Step 1:

[0029] S11: Disperse succinic anhydride and diethanolamine in anhydrous methanol in a molar ratio of 1:1, heat to 60°C under nitrogen protection, remove anhydrous methanol by reduced pressure distillation, and dry to obtain an intermediate; mix the intermediate and 1,2-epoxy-7-octene in a ratio of 1:1 between carboxyl and epoxy groups, add catalyst triphenylphosphine and polymerization inhibitor, and react at 120°C for 5h to obtain a dihydroxy crosslinking monomer;

[0030] S12: 13 g of chitosan quaternary ammonium salt, 12 g of acrylic acid, 24 g of butyl acrylate, and 31 g of methyl methacrylate were mixed and stirred for 10 min, and a dihydroxy crosslinking monomer was added to obtain a monomer mixture; wherein the mass fraction of hydroxyl groups in the monomer mixture was 1.3%;

[0031] S13: 100 g of the monomer mixture was dispersed in deionized water, 1 g of an emulsifier was added, and after stirring for 30 min, an initiator was added, and polymerization was carried out at 70° C. for 3 h to obtain a chitosan quaternary ammonium salt-based acrylate emulsion with a solid content of 30%;

[0032] Step 2:

[0033] S21: 200 g of polypropylene glycol 1000, 20 g of dimethylol propionic acid and 120 g of isophorone diisocyanate were mixed, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 70° C. and the mixture was reacted for 1 hour to obtain a polyurethane prepolymer; chitosan quaternary ammonium salt-based acrylate emulsion was added to the polyurethane prepolymer while keeping the temperature, and the reaction was continued for 2 hours to obtain a modified polyurethane prepolymer; in the modified polyurethane prepolymer, the mass ratio of chitosan quaternary ammonium salt-based acrylate to polyurethane prepolymer was 1:9;

[0034] S22: adding 1.2 g of 1,4-butanediol to 100 g of the modified polyurethane prepolymer at 40° C. and reacting for 1 h; adding 20 g of acetone and 5 g of triethylamine and stirring to react for 30 min; adding water for emulsification and then evaporating the acetone under reduced pressure to obtain a modified polyurethane emulsion with a solid content of 35%;

[0035] Step 3:

[0036] S31: adding 5 g of graphene oxide to deionized water; mixing the graphene oxide dispersion obtained by ultrasonic dispersion; adding 40 g of sodium hydroxide to the graphene oxide dispersion, stirring and adding 73 g of bromoacetic acid to react for 3 h, standing and filtering the precipitate to separate it, washing the filter cake with dilute hydrochloric acid and distilled water, and vacuum drying to obtain carboxylated modified graphene oxide;

[0037] S32: 100 g of modified polyurethane emulsion, 3 g of carboxylated modified graphene oxide, 0.8 g of defoaming agent, 1 g of thickener, and 1.4 g of wetting agent are mixed to obtain a wear-resistant and scratch-resistant leather finishing agent.

[0038] Embodiment 2: A wear-resistant and scratch-resistant leather finishing agent and a preparation method thereof, comprising the following steps:

[0039] Step 1:

[0040] S11: Disperse succinic anhydride and diethanolamine in anhydrous methanol in a molar ratio of 1:1, heat to 65°C under nitrogen protection, remove anhydrous methanol by vacuum distillation, and dry to obtain an intermediate; mix the intermediate with 1,2-epoxy-7-octene in a ratio of 1:1 between carboxyl and epoxy groups, add catalyst triphenylphosphine and polymerization inhibitor, and react at 125°C for 6 hours to obtain a dihydroxy crosslinking monomer;

[0041] S12: 13 g of chitosan quaternary ammonium salt, 12 g of acrylic acid, 24 g of butyl acrylate, and 31 g of methyl methacrylate were mixed and stirred for 12 min, and a dihydroxy crosslinking monomer was added to obtain a monomer mixture; wherein the mass fraction of hydroxyl groups in the monomer mixture was 1.3%;

[0042] S13: 100 g of the monomer mixture was dispersed in deionized water, 1 g of an emulsifier was added, and after stirring for 35 min, an initiator was added, and polymerization was carried out at 75° C. for 4 h to obtain a chitosan quaternary ammonium salt-based acrylate emulsion with a solid content of 30%;

[0043] Step 2:

[0044] S21: 200 g of polypropylene glycol 1000, 20 g of dimethylol propionic acid and 120 g of isophorone diisocyanate were mixed, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 75° C. and the reaction was carried out for 1.5 h to obtain a polyurethane prepolymer; chitosan quaternary ammonium salt-based acrylate emulsion was added to the polyurethane prepolymer while keeping the temperature, and the reaction was continued for 2.5 h to obtain a modified polyurethane prepolymer; in the modified polyurethane prepolymer, the mass ratio of chitosan quaternary ammonium salt-based acrylate to polyurethane prepolymer was 1:7;

[0045] S22: adding 1.2 g of 1,4-butanediol to 100 g of the modified polyurethane prepolymer at 45° C. and reacting for 1.5 h; adding 20 g of acetone and 5 g of triethylamine and stirring and reacting for 35 min; adding water for emulsification and then evaporating the acetone under reduced pressure to obtain a modified polyurethane emulsion with a solid content of 35%;

[0046] Step 3:

[0047] S31: adding 5 g of graphene oxide to deionized water; mixing the graphene oxide dispersion obtained by ultrasonic dispersion; adding 40 g of sodium hydroxide to the graphene oxide dispersion, stirring and adding 73 g of bromoacetic acid, reacting for 4 h, standing and filtering the precipitate, washing the filter cake with dilute hydrochloric acid and distilled water, and vacuum drying to obtain carboxylated modified graphene oxide;

[0048] S32: 100 g of modified polyurethane emulsion, 3 g of carboxylated modified graphene oxide, 0.8 g of defoaming agent, 1 g of thickener, and 1.4 g of wetting agent are mixed to obtain a wear-resistant and scratch-resistant leather finishing agent.

[0049] Embodiment 3: A wear-resistant and scratch-resistant leather finishing agent and a preparation method thereof, comprising the following steps:

[0050] Step 1:

[0051] S11: Disperse succinic anhydride and diethanolamine in anhydrous methanol in a molar ratio of 1:1, heat to 70°C under nitrogen protection, remove anhydrous methanol by reduced pressure distillation, and dry to obtain an intermediate; mix the intermediate with 1,2-epoxy-7-octene in a ratio of 1:1 between carboxyl and epoxy groups, add catalyst triphenylphosphine and polymerization inhibitor, and react at 130°C for 8h to obtain a dihydroxy crosslinking monomer;

[0052] S12: 13 g of chitosan quaternary ammonium salt, 12 g of acrylic acid, 24 g of butyl acrylate, and 31 g of methyl methacrylate were mixed and stirred for 15 min, and a dihydroxy crosslinking monomer was added to obtain a monomer mixture; wherein the mass fraction of hydroxyl groups in the monomer mixture was 1.3%;

[0053] S13: 100 g of the monomer mixture was dispersed in deionized water, 1 g of an emulsifier was added, and after stirring for 40 min, an initiator was added, and polymerization was carried out at 80° C. for 5 h to obtain a chitosan quaternary ammonium salt-based acrylate emulsion with a solid content of 30%;

[0054] Step 2:

[0055] S21: 200 g of polypropylene glycol 1000, 20 g of dimethylol propionic acid and 120 g of isophorone diisocyanate were mixed, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 80° C. and the mixture was reacted for 2 h to obtain a polyurethane prepolymer; chitosan quaternary ammonium salt-based acrylate emulsion was added to the polyurethane prepolymer while keeping the temperature, and the reaction was continued for 3 h to obtain a modified polyurethane prepolymer; in the modified polyurethane prepolymer, the mass ratio of chitosan quaternary ammonium salt-based acrylate to polyurethane prepolymer was 1:4;

[0056] S22: adding 1.2 g of 1,4-butanediol to 100 g of the modified polyurethane prepolymer at 50° C. and reacting for 2 h; adding 20 g of acetone and 5 g of triethylamine and stirring and reacting for 40 min; adding water for emulsification and then evaporating the acetone under reduced pressure to obtain a modified polyurethane emulsion with a solid content of 35%;

[0057] Step 3:

[0058] S31: adding 5 g of graphene oxide to deionized water; mixing the graphene oxide dispersion obtained by ultrasonic dispersion; adding 40 g of sodium hydroxide to the graphene oxide dispersion, stirring and adding 73 g of bromoacetic acid, reacting for 5 h, standing and filtering the precipitate, washing the filter cake with dilute hydrochloric acid and distilled water, and vacuum drying to obtain carboxylated modified graphene oxide;

[0059] S32: 100 g of modified polyurethane emulsion, 3 g of carboxylated modified graphene oxide, 0.8 g of defoaming agent, 1 g of thickener, and 1.4 g of wetting agent are mixed to obtain a wear-resistant and scratch-resistant leather finishing agent.

[0060] Comparative Example 1: The graphene oxide was not modified, and the other parameters were the same as those in Example 1.

[0061] Step 1:

[0062] S11: Disperse succinic anhydride and diethanolamine in anhydrous methanol in a molar ratio of 1:1, heat to 60°C under nitrogen protection, remove anhydrous methanol by reduced pressure distillation, and dry to obtain an intermediate; mix the intermediate and 1,2-epoxy-7-octene in a ratio of 1:1 between carboxyl and epoxy groups, add catalyst triphenylphosphine and polymerization inhibitor, and react at 120°C for 5h to obtain a dihydroxy crosslinking monomer;

[0063] S12: 13 g of chitosan quaternary ammonium salt, 12 g of acrylic acid, 24 g of butyl acrylate, and 31 g of methyl methacrylate were mixed and stirred for 10 min, and a dihydroxy crosslinking monomer was added to obtain a monomer mixture; wherein the mass fraction of hydroxyl groups in the monomer mixture was 1.3%;

[0064] S13: 100 g of the monomer mixture was dispersed in deionized water, 1 g of an emulsifier was added, and after stirring for 30 min, an initiator was added, and polymerization was carried out at 70° C. for 3 h to obtain a chitosan quaternary ammonium salt-based acrylate emulsion with a solid content of 30%;

[0065] Step 2:

[0066] S21: 200 g of polypropylene glycol 1000, 20 g of dimethylol propionic acid and 120 g of isophorone diisocyanate were mixed, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 70° C. and the mixture was reacted for 1 hour to obtain a polyurethane prepolymer; chitosan quaternary ammonium salt-based acrylate emulsion was added to the polyurethane prepolymer while keeping the temperature, and the reaction was continued for 2 hours to obtain a modified polyurethane prepolymer; in the modified polyurethane prepolymer, the mass ratio of chitosan quaternary ammonium salt-based acrylate to polyurethane prepolymer was 1:9;

[0067] S22: adding 1.2 g of 1,4-butanediol to 100 g of the modified polyurethane prepolymer at 40° C. and reacting for 1 h; adding 20 g of acetone and 5 g of triethylamine and stirring to react for 30 min; adding water for emulsification and then evaporating the acetone under reduced pressure to obtain a modified polyurethane emulsion with a solid content of 35%;

[0068] Step 3:

[0069] 100 g of modified polyurethane emulsion, 3 g of graphene oxide, 0.8 g of defoamer, 1 g of thickener, and 1.4 g of wetting agent were mixed to obtain a wear-resistant and scratch-resistant leather finishing agent.

[0070] Comparative Example 2: The mass fraction of hydroxyl groups in the monomer mixture was increased to , and the other parameters were the same as those in Example 2.

[0071] Step 1:

[0072] S11: Disperse succinic anhydride and diethanolamine in anhydrous methanol in a molar ratio of 1:1, heat to 65°C under nitrogen protection, remove anhydrous methanol by vacuum distillation, and dry to obtain an intermediate; mix the intermediate with 1,2-epoxy-7-octene in a ratio of 1:1 between carboxyl and epoxy groups, add catalyst triphenylphosphine and polymerization inhibitor, and react at 125°C for 6 hours to obtain a dihydroxy crosslinking monomer;

[0073] S12: 13 g of chitosan quaternary ammonium salt, 12 g of acrylic acid, 24 g of butyl acrylate, and 31 g of methyl methacrylate were mixed and stirred for 12 min, and a dihydroxy crosslinking monomer was added to obtain a monomer mixture; wherein the mass fraction of hydroxyl groups in the monomer mixture was 2%;

[0074] S13: 100 g of the monomer mixture was dispersed in deionized water, 1 g of an emulsifier was added, and after stirring for 35 min, an initiator was added, and polymerization was carried out at 75° C. for 4 h to obtain a chitosan quaternary ammonium salt-based acrylate emulsion with a solid content of 30%;

[0075] Step 2:

[0076] S21: 200 g of polypropylene glycol 1000, 20 g of dimethylol propionic acid and 120 g of isophorone diisocyanate were mixed, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 75° C. and the reaction was carried out for 1.5 h to obtain a polyurethane prepolymer; chitosan quaternary ammonium salt-based acrylate emulsion was added to the polyurethane prepolymer while keeping the temperature, and the reaction was continued for 2.5 h to obtain a modified polyurethane prepolymer; in the modified polyurethane prepolymer, the mass ratio of chitosan quaternary ammonium salt-based acrylate to polyurethane prepolymer was 1:7;

[0077] S22: adding 1.2 g of 1,4-butanediol to 100 g of the modified polyurethane prepolymer at 45° C. and reacting for 1.5 h; adding 20 g of acetone and 5 g of triethylamine and stirring and reacting for 35 min; adding water for emulsification and then evaporating the acetone under reduced pressure to obtain a modified polyurethane emulsion with a solid content of 35%;

[0078] Step 3:

[0079] S31: adding 5 g of graphene oxide to deionized water; mixing the graphene oxide dispersion obtained by ultrasonic dispersion; adding 40 g of sodium hydroxide to the graphene oxide dispersion, stirring and adding 73 g of bromoacetic acid, reacting for 4 h, standing and filtering the precipitate, washing the filter cake with dilute hydrochloric acid and distilled water, and vacuum drying to obtain carboxylated modified graphene oxide;

[0080] S32: 100 g of modified polyurethane emulsion, 3 g of carboxylated modified graphene oxide, 0.8 g of defoaming agent, 1 g of thickener, and 1.4 g of wetting agent are mixed to obtain a wear-resistant and scratch-resistant leather finishing agent.

[0081] Comparative Example 3: The dosage of chitosan quaternary ammonium salt acrylate was increased, and the other parameters were the same as those in Example 3.

[0082] Step 1:

[0083] S11: Disperse succinic anhydride and diethanolamine in anhydrous methanol in a molar ratio of 1:1, heat to 70°C under nitrogen protection, remove anhydrous methanol by reduced pressure distillation, and dry to obtain an intermediate; mix the intermediate with 1,2-epoxy-7-octene in a ratio of 1:1 between carboxyl and epoxy groups, add catalyst triphenylphosphine and polymerization inhibitor, and react at 130°C for 8h to obtain a dihydroxy crosslinking monomer;

[0084] S12: 13 g of chitosan quaternary ammonium salt, 12 g of acrylic acid, 24 g of butyl acrylate, and 31 g of methyl methacrylate were mixed and stirred for 15 min, and a dihydroxy crosslinking monomer was added to obtain a monomer mixture; wherein the mass fraction of hydroxyl groups in the monomer mixture was 1.3%;

[0085] S13: 100 g of the monomer mixture was dispersed in deionized water, 1 g of an emulsifier was added, and after stirring for 40 min, an initiator was added, and polymerization was carried out at 80° C. for 5 h to obtain a chitosan quaternary ammonium salt-based acrylate emulsion with a solid content of 30%;

[0086] Step 2:

[0087] S21: 200 g of polypropylene glycol 1000, 20 g of dimethylol propionic acid and 120 g of isophorone diisocyanate were mixed, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 80° C. and the mixture was reacted for 2 h to obtain a polyurethane prepolymer; chitosan quaternary ammonium salt-based acrylate emulsion was added to the polyurethane prepolymer while keeping the temperature, and the reaction was continued for 3 h to obtain a modified polyurethane prepolymer; in the modified polyurethane prepolymer, the mass ratio of chitosan quaternary ammonium salt-based acrylate to polyurethane prepolymer was 1:3;

[0088] S22: adding 1.2 g of 1,4-butanediol to 100 g of the modified polyurethane prepolymer at 50° C. and reacting for 2 h; adding 20 g of acetone and 5 g of triethylamine and stirring and reacting for 40 min; adding water for emulsification and then evaporating the acetone under reduced pressure to obtain a modified polyurethane emulsion with a solid content of 35%;

[0089] Step 3:

[0090] S31: adding 5 g of graphene oxide to deionized water; mixing the graphene oxide dispersion obtained by ultrasonic dispersion; adding 40 g of sodium hydroxide to the graphene oxide dispersion, stirring and adding 73 g of bromoacetic acid, reacting for 5 h, standing and filtering the precipitate, washing the filter cake with dilute hydrochloric acid and distilled water, and vacuum drying to obtain carboxylated modified graphene oxide;

[0091] S32: 100 g of modified polyurethane emulsion, 3 g of carboxylated modified graphene oxide, 0.8 g of defoaming agent, 1 g of thickener, and 1.4 g of wetting agent are mixed to obtain a wear-resistant and scratch-resistant leather finishing agent.

[0092] Experiment: The performance of the wear-resistant and scratch-resistant leather finishing agents prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was tested. A 3 cm×3 cm square leather block was taken, the surface of which was coated with the wear-resistant and scratch-resistant leather finishing agent, and cured to form a coating with a thickness of 100 μm.

[0093] Film-forming properties: Observe the coating morphology on the surface of the square leather block. If the coating is smooth and has no granularity, the film-forming properties are good, otherwise they are poor.

[0094] Antibacterial performance and washing resistance: According to GB / T 21510-2008, Escherichia coli was used as the test strain, and the strain was placed in a culture dish at 37°C for 18 hours to make a concentration of 10 3 mol / L bacterial solution; a square leather block was placed in 300mL of bacterial solution and shaken for antibacterial performance test. After the test, the square leather was washed with deionized water and the antibacterial performance was tested again.

[0095] Wear resistance: Refer to GB / T39507-2020 and conduct a wear resistance test on a square leather block. Observe the changes on the surface of the sample after every 100 friction tests, and record the number of wear points on the coating surface until 4 or more wear points appear, and record the number of frictions at this time.

[0096] The test results are shown in Table 1.

[0097] Table 1. Test results of various properties of wear-resistant and scratch-resistant leather finishing agents

[0098]

[0099] Conclusion: The data of Examples 1 to 3 show that the wear-resistant and scratch-resistant leather finishing agent prepared by the present invention has good performance. The data of Example 1 and Comparative Example 1 show that after the graphene oxide is carboxylated, its dispersibility in the finishing agent is improved, and agglomeration is avoided, so the various properties of the finishing agent are improved. The data of Example 2 and Comparative Example 2 show that increasing the mass fraction of hydroxyl groups in the monomer mixture to increase the degree of crosslinking between the chitosan quaternary ammonium salt acrylate emulsion and polyurethane will increase, which will increase the viscosity of the emulsion on the one hand, and on the other hand, the particle size of the latex molecules will become larger, and the film-forming performance will be poor. The data of Example 3 and Comparative Example 3 show that excessive use of chitosan quaternary ammonium salt acrylate will lead to reduced compatibility with polyurethane, thereby affecting the performance of the finishing agent.

[0100] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a wear-resistant and scratch-resistant leather finishing agent, characterized in that: The following steps are involved: Step 1: S11: mixing chitosan quaternary ammonium salt, acrylic acid, butyl acrylate and methyl methacrylate and stirring for 10 to 15 minutes, adding a dihydroxy crosslinking monomer to obtain a monomer mixture; the mass fraction of hydroxyl in the monomer mixture is 0.8 to 1.3%; S12: dispersing the monomer mixture in deionized water, adding an emulsifier, stirring for 30 to 40 minutes, adding an initiator, and polymerizing at 70 to 80° C. for 3 to 5 hours to obtain a chitosan quaternary ammonium salt-based acrylate emulsion; Step 2: S21: polypropylene glycol 1000, dimethylol propionic acid and isophorone diisocyanate are mixed, dibutyltin dilaurate is used as a catalyst, the temperature is raised to 70-80° C. for reaction for 1-2 hours to obtain a polyurethane prepolymer; chitosan quaternary ammonium salt-based acrylate emulsion is added to the polyurethane prepolymer while keeping the temperature, and the reaction is continued for 2-3 hours to obtain a modified polyurethane prepolymer; S22: adding 1,4-butanediol to the modified polyurethane prepolymer at 40-50° C. and reacting for 1-2 hours; adding acetone and triethylamine and stirring to react for 30-40 minutes; adding water for emulsification and then evaporating the acetone under reduced pressure to obtain a modified polyurethane emulsion; Step 3: The modified polyurethane emulsion, carboxyl modified graphene oxide, defoamer, thickener and wetting agent are mixed to obtain a wear-resistant and scratch-resistant leather finishing agent.

2. The method for preparing a wear-resistant and scratch-resistant leather finishing agent according to claim 1, characterized in that: In S11, the content of each component in the monomer mixture is, by weight, 10 to 15 parts of chitosan quaternary ammonium salt, 12 to 15 parts of acrylic acid, 21 to 24 parts of butyl acrylate, 27 to 32 parts of methyl methacrylate, and the remainder is a dihydroxy crosslinking monomer.

3. The method for preparing a wear-resistant and scratch-resistant leather finishing agent according to claim 1, characterized in that: In S11, the preparation method of the dihydroxy cross-linking monomer is as follows: succinic anhydride and diethanolamine are dispersed in anhydrous methanol in a molar ratio of 1:1, the temperature is raised to 60-70°C under nitrogen protection, the anhydrous methanol is removed by reduced pressure distillation, and the intermediate is obtained by drying; the intermediate and 1,2-epoxy-7-octene are mixed in a ratio of 1:1 between carboxyl and epoxy groups, a catalyst triphenylphosphine and an inhibitor are added, and the mixture is reacted at 120-130°C for 5-8h to obtain the dihydroxy cross-linking monomer.

4. The method for preparing a wear-resistant and scratch-resistant leather finishing agent according to claim 1, characterized in that: In S12, the amount of each component in the chitosan quaternary ammonium salt-based acrylate is calculated by weight: 80 to 100 parts of the monomer mixture and 1 to 2 parts of the emulsifier; the solid content of the chitosan quaternary ammonium salt-based acrylate emulsion is 30 to 35%.

5. The method for preparing a wear-resistant and scratch-resistant leather finishing agent according to claim 1, characterized in that: In S21, in the polyurethane prepolymer, the amount of each component is calculated by weight, 180-200 parts of polypropylene glycol 1000, 20-30 parts of dihydroxymethylpropionic acid, and 110-120 parts of isophorone diisocyanate; in the modified polyurethane prepolymer, the mass ratio of chitosan quaternary ammonium salt acrylate to polyurethane prepolymer is 1:(4-9).

6. The method for preparing a wear-resistant and scratch-resistant leather finishing agent according to claim 1, characterized in that: In S22, the amounts of the components are calculated by weight: 100 parts of modified polyurethane prepolymer, 1 to 1.5 parts of 1,4-butanediol, 18 to 25 parts of acetone, and 4 to 7 parts of triethylamine.

7. The method for preparing a wear-resistant and scratch-resistant leather finishing agent according to claim 1, characterized in that: In S22, the solid content of the modified polyurethane emulsion is 30-35%.

8. The method for preparing a wear-resistant and scratch-resistant leather finishing agent according to claim 1, characterized in that: In step 3, the content of each component in the wear-resistant and scratch-resistant leather finishing agent is calculated by weight: 100 parts of modified polyurethane emulsion, 2 to 3 parts of carboxylated modified graphene oxide, 0.5 to 1 part of defoaming agent, 0.5 to 1 part of thickener, and 1 to 2 parts of wetting agent.

9. The method for preparing a wear-resistant and scratch-resistant leather finishing agent according to claim 1, characterized in that: In step 3, the preparation method of carboxylated modified graphene oxide is: adding graphene oxide to deionized water, mixing the graphene oxide dispersion obtained by ultrasonic dispersion; adding sodium hydroxide to the graphene oxide dispersion, stirring and adding bromoacetic acid to react for 3 to 5 hours, standing and filtering the precipitate to separate it, washing the filter cake with dilute hydrochloric acid and distilled water, and then vacuum drying to obtain carboxylated modified graphene oxide.

10. The wear-resistant and scratch-resistant leather finishing agent prepared by the preparation method according to any one of claims 1 to 9.

Images