Leather antifouling paint, modified leather material and shoes for women

Abstract

The invention discloses a leather antifouling coating, a modified leather material and shoes for women. The leather antifouling coating comprises the following raw materials in parts by mass besides a solvent: 60-85 parts by mass of carboxylated cellulose nanofibers, 5-15 parts by mass of a fluorosilane grafted modifier, 3-10 parts by mass of polyethyleneimine and 0.4-0.55 part by mass of an initiator, the preparation method comprises the following steps: firstly, enabling carboxylated cellulose nanofibers to react with a fluorosilane grafting modifier for grafting modification, then mixing the carboxylated cellulose nanofibers with polyethyleneimine, and dispersing the mixture in a solvent. The antifouling performance adaptive change is achieved through chemical structure dynamic reconstruction and multi-scale interface regulation and control, dust adsorption caused by static electricity accumulation in a dry environment is avoided, the antifouling durability is good, and the antifouling requirement of the leather surface of women's shoes is met.

Description

Technical Field

[0001] The present application relates to women's shoes, and in particular to a leather anti-fouling coating, a modified leather material and women's shoes. Background Art

[0002] The anti-fouling treatment of the surface of women's shoe leather has always been one of the key points of the quality of women's shoe products. In current technologies, a hydrophobic coating is mostly used to coat the leather surface to form a coating to achieve anti-fouling.

[0003] The following problems exist in the actual application process: For the hydrophobic coating, its principle lies in that the coating contains a large number of highly hydrophobic organic groups, which has a good anti-fouling effect on water stains. However, in a dry environment, static electricity is accumulated on its surface during daily wearing, adsorbing solid dust (such as pollen and dander), resulting in the shoe surface becoming dull and "old".

[0004] Different from other fields, women's shoes will encounter different types of stains in different environments. For example, water stains may be more common in rainy days, while daily dust may be more in dry times. Therefore, it is necessary to develop an anti-fouling coating to meet the needs of women's shoes. Summary of the Invention

[0005] In order to solve the changing requirements of women's shoes for anti-fouling objects, a leather anti-fouling coating, a modified leather material and women's shoes are provided.

[0006] The above first object of the present invention is achieved by the following technical solutions: A leather anti-fouling coating, the raw materials of which, except for the solvent, further include the following raw materials in parts by mass: 60-85 parts by mass of carboxylated cellulose nanofibers (CCNF), 5-15 parts by mass of fluorosilane grafting modifier, 3-10 parts by mass of polyethyleneimine, 0.4-0.55 parts by mass of initiator; The carboxylated cellulose nanofibers are first reacted with the fluorosilane grafting modifier for grafting modification, and then mixed with polyethyleneimine and dispersed in the solvent.

[0007] By adopting the above technical solutions, first, the carboxylated cellulose nanofibers of the present application can form a nanostructured protrusion microstructure on the coating surface, so that the coating surface has a certain anti-fouling effect through the structural interface; In addition, the carboxyl groups carried by the carboxylated cellulose nanofibers through hydroxylation have dynamic protonation properties, which can sense the surface conditions of the coating and change the coating surface microstructure and its own surface energy: In a dry environment, when the coating contacts the free moisture in the air, the pH is neutral, the carboxyl groups (-COO-) on the surface of CCNF ionize to form a hydrophilic interface, reducing the electrostatic accumulation. Moreover, the nanofibers swell and the spacing shrinks, and the microstructure formed by the fibers on the coating surface closes, making the hydrophobicity of the coating surface weak and reducing the possibility of dust adhesion. After direct contact with rainwater or sweat, the infiltration on the coating surface is enhanced, the carboxyl groups are protonated (-COOH), the surface charge density of the coating decreases, and the hydrophobicity is enhanced. Moreover, the nanofibers shrink, the surface microstructure opens, and the height of the nano-protrusions increases, which is beneficial to reducing the liquid infiltration by the liquid surface tension. The fluorosilane grafted on the carboxylated cellulose nanofibers can combine with the carboxyl groups with dynamic protonation performance and can amplify the hydrophobicity when hydrophobicity is required: Protonation causes the surface energy of CCNF to decrease, and the fluorocarbon chains of the grafted fluorosilane are induced to stretch, thereby enhancing the hydrophobicity of the coating surface. Moreover, the fluorocarbon chains form a dense molecular barrier, reducing the surface energy reduction of the coating and further reducing the liquid infiltration. Polyethyleneimine serves as a coating stabilizer. The amino groups (-NH2) in polyethyleneimine can form reversible cross-links with the carboxyl groups of CCNF. When the pH changes, the cross-linking network reorganizes through hydrogen bonds to buffer the stress and prevent the coating from cracking. Therefore, due to the synergistic effect of carboxylated cellulose nanofibers (CCNF), fluorosilane graft modifiers, and polyethyleneimine in this application, an intelligent response of "enhanced hydrophobicity when encountering water" is achieved through the dynamic reconstruction of chemical structures and multi-scale interface regulation, avoiding the problem of electrostatic dust adsorption of hydrophobic coatings in dry environments. Moreover, when dry, the microstructure formed by the fibers on the coating surface closes and the coating surface has luster. Thus, the anti-fouling performance of the coating cured by coating this application changes adaptively, meeting the anti-fouling requirements of the leather surface of women's shoes.

[0008] In addition, through detection and verification, the anti-fouling performance of the existing hydrophobic coating decays when the coating surface is exposed to wet and dry conditions repeatedly for a long time. However, the dynamic response anti-fouling coating of this application can still maintain long-term anti-fouling performance during the infiltration and drying cycles.

[0009] Optionally, the fluorosilane graft modifier is heptadecafluorodecyltrimethoxysilane.

[0010] By adopting the above technical solution, when the fluorocarbon chains of the grafted fluorosilane are induced to stretch, the surface energy of the coating is lower, the liquid contact angle is larger, and the anti-fouling performance is better.

[0011] Optionally, the reaction grafting step of the carboxylated cellulose nanofibers and the fluorosilane graft modifier is as follows: Mix and stir the CCNF suspension with γ-aminopropyltriethoxysilane to react to obtain amino-functionalized CCNF; After pre-hydrolyzing the fluorosilane graft modifier in an ethanol / water system, amino-functionalized CCNF was added for grafting reaction. After the reaction, separation and washing were carried out to obtain fluorosilane-modified CCNF.

[0012] By adopting the above technical solution, γ-aminopropyltriethoxysilane was first used to graft with CCNF to introduce amino groups. On the one hand, the amino groups can guide the directional arrangement of fluorosilane molecules through hydrogen bonds, reducing steric hindrance. On the other hand, the positive charge of the amino groups attracts the negative charge of the silicon hydroxyl groups of fluorosilane and catalyzes the condensation as a weak base, accelerating the grafting reaction of the fluorosilane graft modifier. Thus, the stability of the grafting reaction of the fluorosilane graft modifier can be reduced, the fluorosilane grafting rate can be increased, and the antifouling effect and antifouling stability of the coating can be improved.

[0013] Optionally, the volume ratio of ethanol / water in the ethanol / water system used for pre-hydrolyzing the fluorosilane graft modifier is 70:30 to 90:10, and the reaction temperature for the grafting reaction of amino-functionalized CCNF is 50 to 70 °C.

[0014] By adopting the technical solution, a high ethanol ratio inhibits the excessive hydrolysis of fluorosilane, reduces side reactions, and improves the grafting efficiency. An appropriate reaction temperature can accelerate the hydrolysis and condensation kinetics, while avoiding the fracture of CCNF fibers and the decline of the coating durability and stability caused by high temperature.

[0015] Optionally, it further includes 0.07 to 0.12 parts by mass of hydroxyethyl cellulose.

[0016] By adopting the above technical solution, as a thixotropic agent, it optimizes the coating viscosity, prevents the coating from sagging during spraying or dipping, enhances the flatness of the wet film, and thus improves the antifouling performance and durability of the coating.

[0017] Optionally, the carboxyl content of the carboxylated cellulose nanofibers is 1.0 to 2.0 mmol / g.

[0018] By adopting the above technical solution, too low carboxyl content leads to slow pH response, while too high carboxyl content reduces the fluorosilane grafting rate due to electrostatic repulsion. Balancing the pH responsiveness and hydrophobicity amplification performance can further improve the comprehensive antifouling performance.

[0019] The above other invention objects of the present invention are achieved through the following technical solutions: A modified leather material includes a leather layer and an antifouling coating covering the surface of the leather layer. The antifouling coating is obtained by coating and curing the above leather antifouling paint.

[0020] A women's shoe includes a shoe upper, and the shoe upper is made of the above modified leather material.

[0021] By adopting the above technical solution, the upper leather of the women's shoes in this application has self-adaptive adjustable antifouling performance, with good and stable antifouling performance.

[0022] In summary, the present application has at least the following beneficial effects: 1. The synergistic effect of carboxylated cellulose nanofibers (CCNF), fluorosilane graft modifiers, and polyethyleneimine in the present application realizes an intelligent response of "enhanced hydrophobicity when encountering water" through chemical structure dynamic reconstruction and multi-scale interface regulation, avoiding the problem of electrostatic dust adsorption of hydrophobic coatings in dry environments. Moreover, when dry, the microstructure formed by the fibers on the coating surface is closed, and the coating surface has luster. Therefore, the coating formed by coating and curing the coating of the present application has self-adaptive changes in the anti-fouling object, meeting the anti-fouling requirements of the leather surface of women's shoes; 2. The dynamic response type anti-fouling coating of the present application can still maintain long-term anti-fouling performance during the wetting and drying cycles; 3. The upper leather of the women's shoes of the present application has self-adaptive adjustable anti-fouling performance, with good and stable anti-fouling performance. Specific Embodiments

[0023] Raw materials: Cotton pulp, a product of Shandong Yinying Chemical Fiber, with α-cellulose of 90 wt%, moisture ≤ 8 wt%, and ash content ≤ 0.2 wt%.

[0024] Hydroxyethyl cellulose is Ashland NATROSOL 250HHR.

[0025] Polyethyleneimine, branched PEI, Mw = 10 kDa, degree of branching 50%, Sigma-Aldrich 408727.

[0026] Polyacrylic acid, Mw = 50 kDa, Sigma-Aldrich product 306231.

[0027] TEMPO, 2,2,6,6-tetramethylpiperidine 1-oxyl, purity ≥ 98%, CAS No. 2564-83-2.

[0028] Hydrochloric acid and NaClO solution are obtained by diluting commercially available products.

[0029] The initiator is Irgacure 2959.

[0030] Ethanol, NaOH, NaBr, and ethyl acetate are commercially available analytical pure products.

[0031] γ-Aminopropyltriethoxysilane is a commercially available product with a purity greater than 99 wt%.

[0032] The fluorosilane graft modifier heptadecafluorodecyltrimethoxysilane / tridecafluorooctyltriethoxysilane is a commercially available product with a purity greater than 99 wt%.

[0033] Preparation Example 1 A carboxylated cellulose nanofiber, the preparation process is as follows: Add 500 g of cotton pulp with a particle size of 0.5 mm to a 0.1 mol / L NaOH solution. The mass ratio of cotton pulp to NaOH solution is 1:20. Stir and react at 60 °C for 2 h, filter, and wash with water until neutral to obtain pretreated cellulose. Disperse the pretreated cellulose in deionized water, stir magnetically and apply ultrasonic treatment (40 kHz) to disperse evenly, and prepare a 1 wt% cellulose suspension. Add TEMPO and NaBr to the cellulose suspension. The addition amount of TEMPO is 0.1 mmol / g of cellulose, and the addition amount of NaBr is 1 mmol / g of cellulose. Stir at 2 °C for 30 min, then slowly dropwise add a 10 wt% NaClO solution. The addition amount of NaClO is 5 mmol / g of cellulose, and at the same time dropwise add a 0.1 mol / L sodium hydroxide solution to maintain the pH at 10. After continuous reaction for 6.5 h, add ethanol accounting for 10% of the volume of the remaining materials to obtain the reaction materials. Process the reaction materials through a high-pressure homogenizer (150 MPa, 3 cycles) to obtain carboxylated cellulose nanofibers with a diameter of 15 ± 3 nm.

[0034] It is detected that the carboxyl content of the carboxylated cellulose nanofibers in Preparation Example 1 is 1.7 mmol / g.

[0035] Preparation Example 2 A carboxylated cellulose nanofiber, the preparation process is as follows: Add 500 g of cotton pulp with a particle size of 0.5 mm to a 0.1 mol / L NaOH solution. The mass ratio of cotton pulp to NaOH solution is 1:20. Stir and react at 60 °C for 2 h, filter, and wash with water until neutral to obtain pretreated cellulose. Disperse the pretreated cellulose in deionized water, stir magnetically and apply ultrasonic treatment (40 kHz) to disperse evenly, and prepare a 1 wt% cellulose suspension. Process the 1 wt% cellulose suspension through a high-pressure homogenizer (150 MPa, 3 cycles) to obtain cellulose nanofibers with a diameter of 15 ± 3 nm.

[0036] Preparation Example 3 A carboxylated cellulose nanofiber, different from Preparation Example 1 in that the reaction time is 3 h.

[0037] It is detected that the carboxyl content of the carboxylated cellulose nanofibers in Preparation Example 3 is 0.75 mmol / g.

[0038] Preparation Example 4 A carboxylated cellulose nanofiber, which is different from Preparation Example 1 in that the reaction time is 4.5 h.

[0039] It was detected that the carboxyl content of the carboxylated cellulose nanofiber in Preparation Example 4 was 1.0 mmol / g.

[0040] Preparation Example 5 A carboxylated cellulose nanofiber, which is different from Preparation Example 1 in that the reaction time is 7 h.

[0041] It was detected that the carboxyl content of the carboxylated cellulose nanofiber in Preparation Example 5 was 2.0 mmol / g.

[0042] Preparation Example 6 A carboxylated cellulose nanofiber, which is different from Preparation Example 1 in that the reaction time is 8.2 h.

[0043] It was detected that the carboxyl content of the carboxylated cellulose nanofiber in Preparation Example 6 was 2.5 mmol / g.

[0044] Example 1 A leather antifouling coating, the raw materials of which, in addition to the solvent, also include 75 g of carboxylated cellulose nanofiber, 12 g of fluorosilane graft modifier, 6 g of polyethyleneimine, 0.5 g of initiator, and 0.1 g of hydroxyethyl cellulose.

[0045] The carboxylated cellulose nanofiber was prepared according to Preparation Example 1.

[0046] The fluorosilane graft modifier is heptadecafluorodecyltrimethoxysilane.

[0047] The solvent is ethanol, and the amount of the solvent is determined according to the required viscosity of the coating.

[0048] The preparation method of the leather antifouling coating is as follows. S1: Take the carboxylated cellulose nanofiber and disperse it evenly in deionized water to obtain a 0.5 wt% CCNF suspension; Add γ-aminopropyltriethoxysilane accounting for 10% of the mass of CCNF to the 0.5 wt% CCNF suspension. After mixing evenly, add ethanol to adjust the volume ratio of ethanol to water to 4:1, add acetic acid to control the pH to 5.5, stir and react at 50 °C for 24 h. After the reaction is completed, let it stand, centrifuge to discard the supernatant, and then wash and centrifuge repeatedly with ethanol to obtain amino-functionalized CCNF; S2: Prepare an ethanol / water mixture according to the volume ratio of ethanol:water = 85:15. Add 12 g of heptadecafluorodecyltrimethoxysilane to 500 mL of the ethanol / water mixture, dropwise add 0.1 mol / L hydrochloric acid, adjust the pH to 4.0, and stir and react at 50 °C for 1 h to obtain a pre-hydrolyzed solution. The aminated CCNF was added to the pre-hydrolyzed solution and dispersed with the assistance of ultrasonic waves at 40 kHz. The grafting reaction was carried out at 60 °C for 24 h. The supernatant was discarded by centrifugation, and the precipitate was repeatedly washed with ethanol and centrifuged to remove the free fluorosilane. Then it was dried in vacuo at 60 °C to obtain fluorosilane-modified CCNF; S3: The fluorosilane-modified CCNF was dispersed in an ethanol / water solution (volume ratio 30:70) at a ratio of 500 ml of ethanol / water solution per 100 g of fluorosilane-modified CCNF to prepare a fluorosilane-modified CCNF suspension; Polyethyleneimine was added to the fluorosilane-modified CCNF suspension, stirred and mixed. 0.1 mol / L hydrochloric acid was added to adjust the pH to 6.5, and the reaction was carried out at 60 °C for 4 h to obtain a cross-linked material; S4: Hydroxyethyl cellulose was added to the cross-linked material and stirred for 2 h. An initiator was added and stirred in the dark for 30 min, and then the mixture was degassed in vacuo to obtain a coating composition; S5: Ethanol was added to the coating composition to adjust the viscosity to 0.9 Pa·s to obtain a leather stain-proof coating.

[0049] Comparative Example 1 A leather stain-proof coating, which is different from Example 1 in that carboxylated cellulose nanofibers are replaced by an equal mass of carboxymethyl cellulose nanofibers prepared in Preparation Example 2.

[0050] Comparative Example 2 A leather stain-proof coating, which is different from Example 1 in that the amount of the fluorosilane grafting modifier is 0, that is, no fluorosilane grafting modifier is added.

[0051] Comparative Example 3 A leather stain-proof coating, which is different from Example 1 in that polyacrylic acid is used to replace the polyethyleneimine cross-linking agent in equal mass.

[0052] Comparative Example 4 A leather stain-proof coating, in addition to the solvent, the raw materials also include 80 g of PTFE emulsion, 15 g of hydrophobic silica nanoparticles, 5 g of epoxy resin, and 0.5 g of leveling agent.

[0053] The PTFE emulsion is DuPont TM PTFE, the hydrophobic silica nanoparticles are R812, the epoxy resin is E-44, the leveling agent is BYK-333, and the solvent is ethyl acetate.

[0054] The preparation method is as follows: The PTFE emulsion and the hydrophobic silica nanoparticles were mixed, and ethyl acetate was added to adjust the solid content to 30%, and the mixture was continuously mixed until the hydrophobic silica nanoparticles were evenly dispersed; After adding epoxy resin and stirring for 1 h, then adding a leveling agent and continuing to stir for 30 min, a leather antifouling coating is obtained.

[0055] Example 2 A leather antifouling coating, which is different from Example 1 in that tridecafluorooctyltriethoxysilane is used to replace perfluorodecyltrimethoxysilane in an equimolar amount.

[0056] Example 3 A leather antifouling coating, which is different from Example 1 in that the steps S1 and S2 of the preparation method are different.

[0057] The contents of steps S1 and S2 of the preparation method of Example 3 are as follows: Prepare an ethanol / water mixture according to the volume ratio of ethanol: water = 85:15. Add 12 g of perfluorodecyltrimethoxysilane to 500 mL of the ethanol / water mixture, dropwise add 0.1 mol / L hydrochloric acid, adjust the pH to 4.0, and stir and react at 50 °C for 1 h to obtain a pre-hydrolyzed solution; Add CCNF to the pre-hydrolyzed solution, assist in dispersion with ultrasonic waves at 40 kHz, carry out grafting reaction at 60 °C for 24 h, centrifuge to discard the supernatant, repeatedly wash with ethanol and centrifuge the precipitate to remove free fluorosilane, and then vacuum dry at 60 °C to obtain fluorosilane-modified CCNF; Example 4 A leather antifouling coating, which is different from Example 1 in that the volume ratio of ethanol to water in the ethanol / water mixture used to prepare the pre-hydrolyzed solution in S2 is 50:50.

[0058] Example 5 A leather antifouling coating, which is different from Example 1 in that the volume ratio of ethanol to water in the ethanol / water mixture used to prepare the pre-hydrolyzed solution in S2 is 70:30.

[0059] Example 6 A leather antifouling coating, which is different from Example 1 in that the volume ratio of ethanol to water in the ethanol / water mixture used to prepare the pre-hydrolyzed solution in S2 is 90:10.

[0060] Example 7 A leather antifouling coating, which is different from Example 1 in that the volume ratio of ethanol to water in the ethanol / water mixture used to prepare the pre-hydrolyzed solution in S2 is 98:2.

[0061] Example 8 A leather antifouling coating, which is different from Example 1 in that the reaction stability of the grafting reaction of amino-functionalized CCNF in S2 is controlled at 40 °C.

[0062] Example 9 A leather anti-fouling coating, which is different from that of Example 1 in that the reaction stability of the amination CCNF grafting reaction in S2 is controlled at 50 °C.

[0063] Example 10 A leather anti-fouling coating, which is different from that of Example 1 in that the reaction stability of the amination CCNF grafting reaction in S2 is controlled at 70 °C.

[0064] Example 11 A leather anti-fouling coating, which is different from that of Example 1 in that the reaction stability of the amination CCNF grafting reaction in S2 is controlled at 80 °C.

[0065] Example 12 A leather anti-fouling coating, which is different from that of Example 1 in that the dosage of hydroxyethyl cellulose is 0, that is, no hydroxyethyl cellulose is added.

[0066] Example 13 A leather anti-fouling coating, which is different from that of Example 1 in that the carboxylated cellulose nanofibers are prepared by Preparation Example 3.

[0067] Example 14 A leather anti-fouling coating, which is different from that of Example 1 in that the carboxylated cellulose nanofibers are prepared by Preparation Example 4.

[0068] Example 15 A leather anti-fouling coating, which is different from that of Example 1 in that the carboxylated cellulose nanofibers are prepared by Preparation Example 5.

[0069] Example 16 A leather anti-fouling coating, which is different from that of Example 1 in that the carboxylated cellulose nanofibers are prepared by Preparation Example 6.

[0070] Example 17 A leather anti-fouling coating, which is different from that of Example 1 in that the raw material dosage is different. In its raw materials, the carboxylated cellulose nanofibers are 60 g, the fluorosilane grafting modifier is 8 g, the polyethyleneimine is 3 g, the initiator is 0.4 g, and the hydroxyethyl cellulose is 0.07 g.

[0071] Example 18 A leather anti-fouling coating, which is different from that of Example 1 in that the raw material dosage is different. In its raw materials, the carboxylated cellulose nanofibers are 85 g, the fluorosilane grafting modifier is 15 g, the polyethyleneimine is 10 g, the initiator is 0.55 g, and the hydroxyethyl cellulose is 0.12 g.

[0072] The leather anti-fouling coatings of Examples 1 to 18 and Comparative Examples 1 to 4 were painted and tested.

[0073] Coating method of the coating on the specimen: Coated by the dipping method, the wet film thickness of the coating is 70 μm, dried at 80 °C for 30 min after coating, and then cured at 120 °C for 1 h to obtain the coating.

[0074] Hydrophobicity test: Dry environment contact angle test and wet environment contact angle test.

[0075] The dry environment contact angle test is detected according to ASTM D7334. The test liquid is deionized water, the droplet volume is 2 μL ± 0.1 μL, 25 °C ± 1 °C, RH = 30% ± 2%. The value is taken 10 s after the droplet is stable, repeated 3 times, and the test result is the average value ± standard deviation; The wet environment contact angle test is detected according to ASTM D7334. The test liquid is hydrochloric acid solution with pH = 5.0, the droplet volume is 2 μL ± 0.1 μL, 25 °C ± 1 °C, RH = 85% ± 3%. The value is taken 10 s after the droplet is stable, repeated 3 times, and the test result is the average value ± standard deviation.

[0076] Electrostatic adsorption test (dry environment): Detected according to ISO 18562, constant temperature and humidity chamber (RH = 20% ± 2%), the dust type is ISO 12103-1A2 fine ash (median particle size 5 μm), exposure time 24 h, adsorption amount = (W2 - W1) / area, unit μg / cm 2 。

[0077] Anti-fouling cycle durability (after 50 wet and dry cycles) test: Referring to ISO 11997, the test cycle is immersed in water and dried 50 times. Each immersion is in deionized water at 25 °C for 4 h, and each drying is in an oven at 60 °C for 2 h. After the cycle ends, the wet contact angle is measured, and the performance retention rate is calculated (wet contact angle after cycle / initial contact angle × 100%).

[0078] The test results are shown in the following table.

[0079] Table 1. Detection result table of Examples 1-18 and Comparative Examples 1-4 Combined with Table 1, by comparing Example 1 and Comparative Example 4, it can be seen that: The wet contact angle (145° ± 3°) of Comparative Example 4 is similar to the dry contact angle (146° ± 2°) of Comparative Example 4.

[0080] The wetting contact angle of Example 1 (152°±3°) increased significantly compared to the dry contact angle of Example 1 (78°±2°), and the wetting contact angle of Example 1 was greater than that of Comparative Example 4. Therefore, it can be known that the coating cured by the coating of Example 1 can adaptively adjust its hydrophobicity in different humidity environments, that is, it exhibits weak hydrophobicity in a dry environment and strong hydrophobicity in a wet environment.

[0081] At the same time, the electrostatic adsorption amount of Example 1 was significantly less than that of Comparative Example 4. Therefore, Example 1 is significantly less likely to accumulate static electricity and adsorb dust in a dry environment compared to Comparative Example 4.

[0082] Moreover, in the cyclic durability, the contact angle retention rate of Example 1 (95.3%) was significantly greater than that of Comparative Example 4 (78.2%). Therefore, the cyclic durability of the coating cured by the coating of Example 1 was significantly greater than that of Comparative Example 4.

[0083] Combined with Comparative Examples 1-2, in Comparative Example 1, uncarboxylated cellulose nanofibers were used to replace hydroxylated cellulose nanofibers compared to Example 1, and in Comparative Example 2, the carboxylated cellulose nanofibers were not grafted and modified with fluorosilane compared to Example 1.

[0084] In the test results, the dry contact angles of Comparative Examples 1-2 were in the range of 60-90°. The wetting contact angles of Comparative Examples 1-3 did not show a significant increase compared to the dry contact angles, and were significantly lower than the dry and wet contact angles of Comparative Example 4. Therefore, Comparative Examples 1-2 did not have the required hydrophobicity in either a dry or wet environment.

[0085] Combined with Comparative Example 3 again, in Comparative Example 3, polyacrylic acid was used to replace polyethyleneimine. The wetting contact angle of Comparative Example 3 (130°±4°) increased significantly compared to the dry contact angle of Comparative Example 3 (74°±3°), but the contact angle retention rate of Comparative Example 4 (68.2%) in the cyclic durability was lower than that of Example 1 and Comparative Example 4, and the durability of the coating was significantly decreased compared to Example 1.

[0086] From this, it can be known that: compared with Comparative Example 4, Example 1 can adaptively adjust its hydrophobicity in different humidity environments, is not easy to adsorb dust in a dry environment, and has long-term durability due to the synergistic effect of carboxylated cellulose nanofibers (CCNF), fluorosilane graft modifier and polyethyleneimine in this application. Specifically as follows: The carboxyl groups carried by the hydroxylated carboxylated cellulose nanofibers have dynamic protonation properties, which can sense the surface conditions of the coating and change the surface microstructure and its own surface energy: in a dry environment, the coating contacts the free moisture in the air, the pH is neutral, the carboxyl groups (-COO-) on the surface of CCNF ionize, forming a hydrophilic interface, reducing electrostatic accumulation, and the nanofibers swell, the spacing shrinks, the microstructure formed by the fibers on the coating surface closes, the hydrophobicity of the coating surface is weak, and the possibility of dust adhesion is reduced; after direct contact with rain or sweat, the infiltration of the coating surface is enhanced, the carboxyl groups are protonated (-COOH), the surface charge density of the coating decreases, the hydrophobicity is enhanced, and the nanofibers contract, the surface microstructure opens, and the height of the nano-protrusions increases, which is beneficial to reducing the liquid infiltration by the liquid surface tension; The fluorosilane grafted onto the carboxylated cellulose nanofibers combines with the dynamic protonation properties of the carboxyl groups, and can amplify the hydrophobicity when hydrophobicity is required: protonation causes the surface energy of CCNF to decrease, and the fluorocarbon chains of the grafted fluorosilane are induced to stretch, thereby enhancing the hydrophobicity of the coating surface, and the fluorocarbon chains form a dense molecular barrier, reducing the surface energy drop of the coating, and further reducing liquid infiltration; Polyethyleneimine serves as a coating stabilizer. The amino groups (-NH2) in polyethyleneimine can form reversible crosslinks with the carboxyl groups of CCNF. When the pH changes, the crosslinking network reorganizes through hydrogen bonds to buffer stress and prevent the coating from cracking; Thus, through the dynamic reconstruction of the chemical structure and the multi-scale interface regulation, the intelligent response of "enhancing hydrophobicity when encountering water" is realized, avoiding the problem that the hydrophobic coating accumulates static electricity and adsorbs dust in a dry environment, and when dry, the microstructure formed by the fibers on the coating surface closes and the coating surface is shiny. Therefore, the antifouling performance of the coating coated and cured by the coating of the present application changes adaptively, meeting the antifouling requirements of the leather surface of women's shoes, and still being able to maintain long-term antifouling performance during the wetting and drying cycles.

[0087] Comparing Example 1 and Example 2, the wetting contact angle of Example 1 is greater than that of Example 2, and the cycle durability of Example 1 is greater than that of Example 2. This is because the fluorocarbon chain grafted with heptadecafluorodecyltrimethoxysilane in Example 1 is longer. When it is induced to stretch, the surface energy of the coating is lower, the liquid contact angle is larger, and the antifouling performance is better. Therefore, the fluorosilane graft modifier of heptadecafluorodecyltrimethoxysilane is relatively superior.

[0088] In addition, the electrostatic adsorption amount of Example 1 is less than that of Example 2, further verifying that the hydrophobic mechanism of the present application is different from that of Comparative Example 4, and the improvement of hydrophobicity in a wet environment will not affect the performance of preventing electrostatic adsorption of dust in a dry environment.

[0089] Comparing Comparative Example 1 and Example 3, it can be seen that the wetting contact angle of Example 1 is significantly greater than that of Example 3, and the cycle durability of Example 1 is greater than that of Example 3. Therefore, in this application, γ-aminopropyltriethoxysilane is first used to graft with CCNF to introduce amino groups. On the one hand, the amino groups can guide the directional arrangement of fluorosilane molecules through hydrogen bonds, reducing steric hindrance. On the other hand, the positive charge of the amino groups attracts the negative charge of the silanol groups of fluorosilane and catalyzes the condensation as a weak base, accelerating the grafting reaction of the fluorosilane graft modifier. Thus, the stability of the grafting reaction of the fluorosilane graft modifier can be reduced, the fluorosilane grafting rate can be increased, and the antifouling effect and antifouling stability of the coating can be improved.

[0090] Comparing Comparative Example 1, Examples 4 to 7, it can be seen that in Examples 4, 5, 1, 6, and 7, the volume ratio of ethanol in the pre-hydrolysis system of the fluorosilane graft modifier gradually increases. The wetting contact angles of Examples 1, 6, 5, 7, and 4 decrease in turn, and the cycle durabilities of Examples 1, 6, 5, 4, and 7 decrease in turn. The reason is that a high ethanol ratio inhibits the excessive hydrolysis of fluorosilane, reduces side reactions, and improves the grafting efficiency. Therefore, in this application, the volume ratio of ethanol / water during the pre-hydrolysis of the fluorosilane graft modifier is preferably 70:30 to 90:10.

[0091] Combining Example 1 and Examples 8 to 11, it can be seen that when the grafting reaction of amino-functionalized CCNF is carried out in Examples 8, 9, 1, 10, and 11, the temperature gradually increases. The wetting contact angles of Examples 1, 10, 9, 11, and 8 decrease in turn, and the cycle durabilities of Examples 1, 10, 9, 8, and 11 decrease in turn. The reason is that an appropriate reaction temperature can accelerate the hydrolysis and condensation kinetics, while avoiding the fracture of CCNF fibers and the decline of the durability and stability of the coating caused by high temperature. Therefore, in this application, the reaction temperature during the grafting reaction of amino-functionalized CCNF is preferably 50 to 70 °C.

[0092] Comparing Comparative Example 1 and Example 12, it can be seen that compared with Example 12, hydroxyethyl cellulose is also added to the coating in Example 1. The wetting contact angle of Example 1 is greater than that of Example 12, the electrostatic adsorption amount of Example 1 is less than that of Example 2, and the cycle durability of Example 1 is greater than that of Example 12. Therefore, adding hydroxyethyl cellulose as a thixotropic agent can optimize the coating viscosity, prevent the coating from sagging during spraying or dipping, enhance the flatness of the wet film, and thus improve the antifouling performance and durability of the coating.

[0093] Comparing Comparative Example 1 with Examples 13 to 16, it can be seen from the test results that the wetting contact angles of Example 1, Example 15, Example 14, Example 16, and Example 13 decrease in turn. The applicant's further research found that this is because the carboxyl content in the carboxylated cellulose nanofibers will affect the sensitivity of the coating to the wet environment. At the same time, with the enhancement of carboxylation, the strength of the cellulose nanofibers will also decrease, and the grafting rate of fluorosilane will be affected by electrostatic repulsion - too low carboxyl content leads to slow pH response, and too high carboxyl content reduces the grafting rate of fluorosilane.

[0094] Therefore, balancing the pH responsiveness and the amplification performance of hydrophobicity can improve the comprehensive anti-fouling performance of the cured coating of the coating in this application. The carboxyl content of the carboxylated cellulose nanofibers in this application is preferably 1.0 - 2.0 mmol / g.

[0095] Example 19 A modified leather material, comprising a leather layer and an anti-fouling coating covering the surface of the leather layer.

[0096] The anti-fouling coating is obtained by coating and curing a leather anti-fouling coating, and the leather anti-fouling coating is one of Examples 1 to 18.

[0097] Example 20 A women's shoe, comprising a shoe upper and a sole. The shoe upper is obtained by cutting and splicing the modified leather material of Example 19.

[0098] The upper leather of the women's shoe in this application has self-adaptive adjustable anti-fouling performance, with good and stable anti-fouling performance.

[0099] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope claimed by the present invention, it is protected by the patent law.

Claims

1. A leather antifouling coating, characterized in that: Its raw materials include the following raw materials in parts by weight in addition to the solvent: Carboxylated cellulose nanofibers (CCNF) 60-85 parts by weight, 5-15 parts by weight of fluorosilane grafting modifier, 3-10 parts by weight of polyethyleneimine, Initiator 0.4~0.55 parts by mass; The carboxylated cellulose nanofibers are firstly reacted with a fluorosilane grafting modifier for grafting modification, and then mixed with polyethyleneimine and dispersed in a solvent.

2. The leather antifouling coating according to claim 1, characterized in that: The fluorosilane grafting modifier is heptadecafluorodecyltrimethoxysilane.

3. The leather antifouling coating according to claim 1, characterized in that: The steps of reacting and grafting the carboxylated cellulose nanofibers with the fluorosilane grafting modifier are as follows: The CCNF suspension is mixed with γ-aminopropyltriethoxysilane and stirred to react to obtain amino CCNF; The fluorosilane grafting modifier is pre-hydrolyzed in an ethanol / water system, and then added to the aminated CCNF for grafting reaction. After the reaction, the fluorosilane-modified CCNF is obtained after separation and washing.

4. The leather antifouling coating according to claim 3, characterized in that: The volume ratio of ethanol / water in the ethanol / water system used for pre-hydrolysis of the fluorosilane grafting modifier is 70:30-90:10, and the reaction temperature during the grafting reaction of the amination CCNF is 50-70°C.

5. The leather antifouling coating according to claim 1, characterized in that: It also includes 0.07-0.12 parts by weight of hydroxyethyl cellulose.

6. The leather antifouling coating according to claim 1, characterized in that: The carboxyl content of the carboxylated cellulose nanofibers is 1.0-2.0 mmol / g.

7. A modified leather material, characterized in that: The invention comprises a leather layer and an antifouling coating covering the surface of the leather layer, wherein the antifouling coating is obtained by coating and curing the leather antifouling coating according to any one of claims 1 to 6.

8. A pair of women's shoes, characterized in that: The shoe comprises an upper, wherein the upper is made of the modified leather material according to claim 7.

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