CN-122013551-A - Preparation method of scratch-resistant leather

CN122013551ACN 122013551 ACN122013551 ACN 122013551ACN-122013551-A

Abstract

The invention discloses a preparation method of scratch-resistant leather, and belongs to the technical field of leather functionalization treatment. The method comprises four core steps of preparing double dynamic covalent bond self-repairing polyurethane emulsion, constructing a bionic lamellar anti-cracking reinforcing phase, forming a flexible self-repairing composite coating and preparing a gradient modulus surface hardening layer, and constructing a multi-mechanism cooperative composite coating with dynamic covalent network self-repairing, lamellar bionic structure crack resistance, low friction cooperative scratch resistance and surface gradient hardening scratch resistance on the leather surface. The invention solves the problems of contradiction between the hardness and flexibility, irreparable scratch, insufficient durability and the like of the traditional scratch-resistant leather, realizes the remarkable improvement of the scratch-resistant performance and long-term use stability while the leather keeps flexible hand feeling, and is suitable for the field of leather products with high durability.

Inventors

CHEN FEI
XU XIANGJIN
GU WEIMIN
LI RONG
GAO DELIANG
LIU BIN

Assignees

浙江通天星集团股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260318

Claims (9)

1. The preparation method of the scratch-resistant leather is characterized by comprising the following steps of: the preparation of matrix self-repairing polyurethane emulsion comprises the steps of preparing polyurethane prepolymer by taking polycarbonate diol as soft segment polyol and aliphatic diisocyanate as hard segment raw materials, introducing diamine chain extender containing disulfide bond structure and chain extender monomer containing ortho-diol structure for chain extension reaction, adding phenylboronic acid or derivative monomer thereof into the system, enabling S-S dynamic covalent bond network and B-O reversible borate bond network to be formed in the obtained polyurethane molecular chain at the same time, and obtaining double-dynamic self-repairing aqueous polyurethane emulsion by neutralization and emulsification; S2, constructing a bionic lamellar anti-cracking reinforcing phase, namely adding hexagonal boron nitride nano-sheets into the emulsion obtained in the step S1 after carrying out surface hydroxylation treatment, and enabling the boron nitride nano-sheets to be arranged in a directional manner along a shearing direction under the action of a high shearing field to form a lamellar orientation structure parallel to the surface of a coating; S3, forming a composite coating, namely coating the composite emulsion obtained in the step S2 on the surface of the animal leather subjected to liming, softening, tanning and retanning treatment by roller, and drying and curing to form a flexible self-repairing composite layer; And S4, constructing a gradient modulus surface hardening layer, namely, applying hardening liquid containing a silane coupling agent, silica sol and a photoinitiator on the surface of the composite layer, and inducing sol-gel reaction through ultraviolet irradiation to form a decreasing structure with the crosslinking density from the surface to the inside in the thickness direction of the coating, so as to construct the gradient modulus structure with the continuous transition between the surface high-modulus siloxane crosslinking layer and the bottom flexible polyurethane layer.
2. The method of claim 1, wherein the dual-dynamic network comprising an S-S dynamic covalent bond network and a B-O reversible borate bond network in step S1 further comprises a hydrogen bond donor-acceptor structural unit, so that multiple hydrogen bond physical cross-linking networks are formed between polyurethane molecular chains, thereby forming a "dynamic covalent bond+reversible hydrogen bond" triple cooperative self-repairing system.
3. The method for preparing scratch resistant leather according to claim 1, wherein in step S2, the boron nitride nano-sheets and polyimide nano-fibers are present cooperatively, and the nano-fibers are aligned along a stress direction when subjected to an external force, so as to construct a stress response reinforcing structure.
4. The method for preparing scratch-resistant leather according to claim 1, wherein the graphene quantum dots in the step S2 are further modified by surface carboxyl groups or hydroxyl groups to form interface hydrogen bonding with polyurethane chain segments, so as to construct lubrication micro-regions capable of generating interface sliding in the scratch process.
5. The method of claim 1, wherein the silicone crosslink density is exponentially decreasing in the thickness direction in the gradient modulus structure formed in step S4.
6. The method for producing scratch-resistant leather according to claim 1, wherein the hardening liquid of step S4 further contains a small amount of side chain structural units of a silicone-fluorine hybrid polysiloxane to lower the surface energy of the coating.
7. The method for preparing scratch-resistant leather according to claim 1, wherein in the step S2, the boron nitride sheet layer forms a multi-level stacked structure in the thickness direction of the coating layer, and the spacing between the sheet layers is distributed in a gradient manner from micron level to nanometer level, so as to construct a multi-level crack deflection path.
8. The method for preparing scratch resistant leather according to claim 1, wherein a trace amount of photo-thermal response component is introduced into the composite coating, so that the coating is locally heated under the condition of illumination or frictional heating, and the recombination rate of the double dynamic covalent network is promoted.
9. The preparation method of the scratch-resistant leather according to claim 1, wherein the preferable technical parameters of the steps S1-S4 are that disulfide bond chain extender accounts for 5-20wt% of the total chain extender, phenylboronic acid monomer is used for 0.5-3wt% of polyurethane solid content, polyurethane emulsion solid content is 25-40wt%, hexagonal boron nitride nanosheets are 200-800nm in size and 1-20nm in thickness, resin solid content is 1-6wt%, graphene quantum dot particle size is 2-10nm, composite coating thickness is 10-40 mu m, surface siloxane hardened layer thickness is 0.5-5 mu m, and surface layer modulus is 2-8 times of the bottom layer.

Description

Preparation method of scratch-resistant leather Technical Field The invention relates to the technical field of leather functionalization treatment, in particular to a preparation method of scratch-resistant leather. Background In the daily use process of leather products, the leather products are subjected to the effects of hard object scraping, particle friction and bending stress for a long time, so that the quality problems of surface scratch, coating cracking, light loss, structural damage and the like are very easy to occur, and the appearance and the service life of the leather products are seriously influenced. The existing scratch-resistant leather preparation technology generally adopts two ideas, namely, improving the hardness of a coating, improving the scratch resistance of the surface by adding high-modulus resin, and blocking crack propagation by adding inorganic nano filler and utilizing the reinforcing effect of the filler. However, the above technology has obvious defects: the hardness is improved and the flexibility is naturally contradicted, the high-hardness coating is easy to crack in the bending process, and the natural hand feeling of leather is lost; In the nanoparticle reinforced system, the filler is easy to agglomerate, the bonding force between the filler and the matrix resin interface is weak, the reinforcing effect is limited, the surface of the coating is easy to be rough, the coating has no self-repairing capability after scratch, the damage is irreversible, the durability of leather products is insufficient, and the comprehensive performance requirements of scratch resistance, crack resistance, low friction and the like are difficult to be simultaneously met by a single reinforcing mechanism. Therefore, there is a need to develop a composite coating system that integrates self-healing, crack-resistant, low-friction, scratch-resistant functions, solving the pain points of the conventional art. Disclosure of Invention The invention aims to provide a preparation method of scratch-resistant leather, which aims to solve the problems of poor scratch resistance and cracking resistance of the existing leather. The technical scheme for solving the technical problems is as follows: the preparation method of the scratch-resistant leather specifically comprises the following steps: S1, preparing a matrix self-repairing polyurethane emulsion, namely taking polycarbonate diol as a soft segment polyol and aliphatic diisocyanate as hard segment raw materials, reacting for 1.5-3 hours under the condition of 70-90 ℃ in a nitrogen atmosphere to prepare a polyurethane prepolymer, introducing a diamine chain extender containing a disulfide bond structure and a chain extender monomer containing an ortho-diol structure into the prepolymer, performing chain extension reaction for 1-2 hours at 60-80 ℃, then adding phenylboronic acid or derivative monomers thereof, continuously reacting for 0.5-1 hour to simultaneously form an S-S dynamic covalent bond network and a B-O reversible boric acid ester bond network in a polyurethane molecular chain, finally adding a neutralizer to adjust pH to 7-8, and performing high-speed emulsification dispersion to obtain the double-dynamic self-repairing aqueous polyurethane emulsion. S2, constructing a bionic layered anti-cracking reinforcing phase, namely placing hexagonal boron nitride nano-sheets in a sodium hydroxide solution, heating in a water bath at 80-90 ℃ for 2-4 hours, carrying out surface hydroxylation treatment, washing and drying for later use, adding the modified boron nitride nano-sheets into the emulsion obtained in the step S1, dispersing for 20-40 minutes under the action of a high-shear emulsifying machine (the rotating speed is 6000-10000 r/min), enabling the boron nitride nano-sheets to be aligned along the shearing direction to form a lamellar orientation structure parallel to the surface of a coating, simultaneously adding graphene quantum dots, and carrying out ultrasonic dispersion for 10-20 minutes to enable the quantum dots to be adsorbed on the boundary area of the boron nitride sheets, thereby forming the low-friction synergistic reinforcing composite phase. S3, forming a composite coating, namely uniformly applying the composite emulsion obtained in the step S2 on the surface of the animal leather subjected to liming, softening, tanning and retanning treatment through a roller coating process, wherein the roller coating amount is 15-30g/m < 2 >, and drying the coated leather in a 50-70 ℃ oven for 1-2 hours, and curing to form the flexible self-repairing composite layer. S4, constructing a gradient modulus surface hardening layer, preparing hardening liquid containing a silane coupling agent, silica sol and a photoinitiator, uniformly coating the hardening liquid on the surface of the composite layer with the coating amount of 2-5g/m < 2 >, irradiating ultraviolet light (wavelength 365nm, energy density 800-1200mJ/cm < 2 >) for 5-15S,