CN113214735B - Water-based UV gloss oil for leather and preparation method and application thereof - Google Patents

Abstract

The invention discloses aqueous UV gloss oil for leather and a preparation method and application thereof. The water-based UV gloss oil for leather is prepared from the following components in parts by weight: 10-50 parts of urethane acrylate prepolymer, 1-10 parts of epoxy acrylate, 1-20 parts of dipentaerythritol hexaacrylate, 1-20 parts of tripropylene glycol diacrylate, 5-50 parts of mercaptan, 0.01-0.5 part of nitrogen-doped modified graphene, 1-10 parts of photoinitiator, 0.3-3 parts of other additives and 15-70 parts of solvent. The aqueous UV gloss oil for leather disclosed by the invention is characterized in that a polyurethane acrylate prepolymer is taken as a main body resin, epoxy acrylate, dipentaerythritol hexaacrylate and tripropylene glycol diacrylate are taken as acrylic active monomers, and mercaptan and nitrogen are doped to modify graphene and other components, so that the aqueous UV gloss oil is excellent in wear resistance, good in bending resistance and high in photocuring rate.

Description

Water-based UV gloss oil for leather and preparation method and application thereof

Technical Field

The invention relates to the technical field of high polymer materials, and particularly relates to water-based UV gloss oil for leather, and a preparation method and application thereof.

Background

Natural leather is widely used in the production of daily necessities and industrial goods due to its excellent natural characteristics, but the increase in the world population has multiplied the demand for leather by humans, and the limited amount of natural leather has not been able to meet the demand of people for a long time. Compared with natural leather, the synthetic leather has the advantages of environmental protection, easily obtained raw materials, no damage to ecological environment and the like, so that the synthetic leather can be widely applied to the fields of shoes, boots, bags, sofas and the like. The synthetic leather is an artificially synthesized textile material prepared by simulating the composition and structure of natural leather by using a high molecular chemical material, and generally adopts an impregnated non-woven fabric net layer as a base fabric layer, then a PU layer containing functional fillers is coated on the base fabric layer, and finally a layer of UV gloss oil is coated on the PU layer as a protective layer.

Since synthetic leather is generally used for the surfaces of shoes, boots, bags, and sofa seats, it is required that the synthetic leather has certain abrasion resistance and flex resistance. In addition, as the national environmental protection prevention and control force is gradually increased, the synthetic leather manufacturing industry is also developing towards the water-based synthetic leather. However, the aqueous UV gloss oil has the disadvantages of poor abrasion resistance, poor flexing resistance, slow drying rate and the like.

Penghui test et al (Penghui test, good for construction, etc.) Synthesis and application of organosilicon modified waterborne polyurethane for synthetic leather [ J ] Chinese leather, 2016,45(002):65-68,73.) adopt a prepolymer method to introduce polyether modified hydroxyl silicone oil to prepare organosilicon modified waterborne polyurethane for synthetic leather. The research considers that when the isocyanate value is 1.6, the poly (2-methyl propylene glycol adipate) is selected as the polyester polyol soft segment, and the addition amount of the polyether modified hydroxyl silicone oil is 6 percent, the obtained waterborne polyurethane is the optimal scheme of the research. However, despite this, the wear resistance of the aqueous synthetic leather prepared in the best solution can only meet the requirement of polyurethane synthetic leather for clothing, namely > 150 turns. For the synthetic leather of the luggage and the automobile seat, the requirement on the wear resistance is higher, wherein the wear resistance of the automobile seat needs to be more than or equal to 500 turns (the test standard uses QB/T2726-.

Therefore, it is required to develop a water-based UV varnish for leather having excellent abrasion resistance.

Disclosure of Invention

The invention provides the water-based UV gloss oil for leather, which overcomes the defect of poor wear resistance in the prior art, and the water-based UV gloss oil for leather takes urethane acrylate prepolymer as main resin, takes epoxy acrylate, dipentaerythritol hexaacrylate and tripropylene glycol diacrylate as acrylic active monomers, and is matched with mercaptan, nitrogen-doped modified graphene and other components, so that the water-based UV gloss oil has excellent wear resistance, good bending resistance and high photocuring rate.

The invention also aims to provide a preparation method of the water-based UV gloss oil for leather.

The invention also aims to provide application of the water-based UV gloss oil for leather in preparation of a protective layer of synthetic leather for bags and/or automobile seats.

In order to solve the technical problems, the invention adopts the technical scheme that:

the waterborne UV gloss oil for leather is prepared from the following components in parts by weight:

10-50 parts of urethane acrylate prepolymer, 1-10 parts of epoxy acrylate, 1-20 parts of dipentaerythritol hexaacrylate, 1-20 parts of tripropylene glycol diacrylate, 5-50 parts of mercaptan, 0.01-0.5 part of nitrogen-doped modified graphene, 1-10 parts of photoinitiator, 0.3-3 parts of other additives and 15-70 parts of solvent.

According to the water-based UV gloss oil, the polyurethane acrylate prepolymer is used as a main body resin, the epoxy acrylate, the dipentaerythritol hexaacrylate and the tripropylene glycol diacrylate are used as acrylic active monomers, and the mercaptan and nitrogen-doped modified graphene and other components are matched, so that the water-based UV gloss oil is excellent in wear resistance, good in bending resistance and high in photocuring speed.

The wear resistance and the flexing resistance of the water-based UV gloss oil can be greatly improved by adding a small amount of the nitrogen-doped modified graphene. The graphene has a honeycomb six-membered ring structure, is a two-dimensionally expanded carbon material, has excellent mechanical strength, has the elastic modulus of 1TPa and the ultimate strength of 130GPa which is 300 times that of steel, and can be used together with the polyurethane acrylate prepolymer to enhance the mechanical property of the graphene, so that the wear resistance of the aqueous UV gloss oil for leather is enhanced.

The nitrogen atoms have the size which is closer to carbon atoms than other inorganic nonmetal atoms, so the nitrogen atoms have better compatibility with graphene, and the doping of the nitrogen elements can generate N-C bonds and can be easily doped into crystal lattices of the graphene to obtain the stable nitrogen-doped modified graphene.

By carrying out nitrogen doping modification on graphene, the nitrogen-doped graphene shows more excellent mechanical properties than unmodified graphene. The modified graphene is in a folded gauze shape after being doped with nitrogen, and partial sheets are laminated together to form a multilayer structure in a spatial structure, so that the dispersibility of the aqueous UV gloss oil can be improved when the modified graphene is used in the aqueous UV gloss oil, the uniformity of the mechanical strength of each part of a film layer formed by the aqueous UV gloss oil is higher, and the overall mechanical property is more excellent.

Preferably, the molar ratio of nitrogen to graphene in the nitrogen-doped modified graphene is 1 (30-50).

More preferably, the molar ratio of nitrogen to graphene in the nitrogen-doped modified graphene is 1: 40.

The amount of nitrogen elements in the nitrogen-doped modified graphene is increased to a certain extent, the space structure of the graphene can be better improved, and the mechanical property improvement effect on the UV gloss oil is better; however, when the amount of nitrogen element is too large, a lattice defect of graphene is also caused, and mechanical properties are reduced.

When the molar ratio of nitrogen to graphene in the nitrogen-doped modified graphene is 1 (30-50), excellent mechanical properties can be obtained, and the lattice defect of the graphene can be avoided. When the molar ratio of nitrogen to graphene is 1:40, the mechanical property of the UV gloss oil is better.

The nitrogen-doped modified graphene is prepared by the following method:

dispersing graphene in an amino-containing compound, heating at 200-250 ℃ for 10-15 h, and performing post-treatment to obtain the graphene.

Preferably, the amino group-containing compound is ammonia.

Specifically, the preparation method of the nitrogen-doped modified graphene may be:

adding graphene into an ammonia water solution, and performing ultrasonic dispersion to obtain a graphene dispersion liquid;

and (3) placing the graphene dispersion liquid in a hydrothermal kettle, heating for 10-15 h at 200-250 ℃, cooling, washing to be neutral, and drying to obtain the nitrogen-doped modified graphene.

The thiol is a non-aromatic compound containing a thiol functional group (-SH), on one hand, the thiol in the thiol can be crosslinked with dipentaerythritol hexaacrylate and tripropylene glycol diacrylate in the photocuring process to generate compact macromolecules, and on the other hand, the thiol can generate a thioether structure with epoxy acrylate, so that the crosslinking density and compactness of the whole aqueous UV gloss oil system are improved, and further the bending resistance and the photocuring rate of the aqueous UV gloss oil are improved.

Preferably, the mercaptan is one or more of ethanethiol, diethylmercaptan, 1-propanethiol or 1, 3-propanedithiol.

More preferably, the thiol is ethyl mercaptan and/or 1-propyl mercaptan.

The mercaptan with the smaller molecular weight contains more mol of sulfydryl groups under the condition of the same mass, can better react with the acrylate to generate crosslinking, and has better physical properties, particularly better wear resistance and bending resistance after the film is formed by crosslinking the UV gloss oil.

Preferably, the polyurethane acrylate prepolymer is a polyurethane acrylate prepolymer with a functionality of 2-6.

The multifunctional urethane acrylate prepolymer has more groups capable of participating in photocuring reaction, and can provide a faster curing rate and a higher crosslinking density in the aqueous UV gloss oil system, and the mechanical properties, especially the wear resistance and the bending resistance, of the film after film formation are better. However, too high functionality urethane acrylate prepolymers have a high viscosity and a reduced processability. Therefore, a 2-6 functionality urethane acrylate prepolymer is preferred.

Preferably, the urethane acrylate prepolymer is an aliphatic urethane acrylate prepolymer.

For the aqueous UV gloss oil for leather, the aliphatic polyurethane acrylate prepolymer has better weather resistance and gloss and color retention. Under the irradiation of ultraviolet rays, the polyurethane is easy to decompose to produce amine, and after the aromatic urethane acrylate prepolymer generates aromatic amine, the aromatic amine is oxidized to generate quinone chromophoric groups, so that yellowing and discoloration are caused; even if the aliphatic urethane acrylate prepolymer is decomposed into aliphatic amine, the aliphatic amine has better oxidation resistance because the aliphatic amine does not have benzene ring conjugation as a chromophore, so that the aliphatic amine is not easy to discolor, and has better weather resistance and color retention.

Alternatively, the urethane acrylate prepolymer may be a difunctional aliphatic urethane acrylate prepolymer and/or a hexafunctional urethane acrylate prepolymer.

Preferably, the urethane acrylate prepolymer is a mixture of a difunctional aliphatic urethane acrylate prepolymer and a hexafunctional urethane acrylate prepolymer.

More preferably, the mass ratio of the difunctional aliphatic polyurethane acrylate prepolymer to the hexafunctional polyurethane acrylate prepolymer is (0.5-2) to 1.

Further preferably, the mass ratio of the difunctional aliphatic urethane acrylate prepolymer to the hexafunctional urethane acrylate prepolymer is 1.5: 1.

Preferably, the photoinitiator is one or more of 2-isopropyl thioxanthone, 2-benzyl-2-dimethylamino-1- (4-morpholinylphenyl) butanone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexyl phenyl ketone or phenyl bis (2,4, 6-trimethylbenzoyl) phosphine oxide.

More preferably, the photoinitiator is 2-isopropyl thioxanthone and 2-hydroxy-2-methyl-1-phenyl-1-acetone according to the mass ratio of 1: (1-3) in the above-mentioned manner.

Further preferably, the photoinitiator is 2-isopropyl thioxanthone and 2-hydroxy-2-methyl-1-phenyl-1-acetone in a mass ratio of 1: 2.

Preferably, the other auxiliary agent is a leveling agent and/or an antifoaming agent.

The leveling agent can be a leveling agent commonly used in aqueous UV gloss oil.

Preferably, the leveling agent is polyether modified polydimethylsiloxane.

More preferably, the leveling agent is a polyether modified acrylic functional polydimethylsiloxane. The leveling agent contains acrylic functional groups, can participate in a crosslinking reaction under UV photocuring, has high surface smoothness and adhesive tape stripping property, can improve the leveling property of the water-based UV gloss oil, and is suitable for long-term storage of synthetic leather.

Optionally, the polyether modified acrylic functional polydimethylsiloxane can be one or more of BYK-UV3500, BYK-UV3530 or BYK-UV 3570.

The defoamer may be a defoamer commonly used in aqueous UV varnish.

Optionally, the defoaming agent is one or more of nopcoNXZ, TEGO Airex 980, TEGO Airex 986 or BYK 085.

Preferably, the solvent is ethanol and/or water.

Ethanol as an aqueous solvent can improve the surface dryness and sagging property of the aqueous UV gloss oil.

The invention also provides a preparation method of the water-based UV gloss oil for leather, which comprises the following steps:

dissolving urethane acrylate prepolymer, epoxy acrylate, dipentaerythritol hexaacrylate and tripropylene glycol diacrylate in a solvent to obtain a mixed solution A;

dispersing the nitrogen-doped modified graphene, mercaptan, a photoinitiator and other auxiliaries in a solvent to obtain a mixed solution B;

and mixing and stirring the mixed solution A and the mixed solution B to obtain the water-based UV gloss oil for the leather.

The invention also protects the application of the water-based UV gloss oil for leather in preparing a synthetic leather protective layer for bags and/or automobile seats.

Compared with the prior art, the invention has the beneficial effects that:

the aqueous UV gloss oil for leather disclosed by the invention is characterized in that a polyurethane acrylate prepolymer is taken as a main body resin, epoxy acrylate, dipentaerythritol hexaacrylate and tripropylene glycol diacrylate are taken as acrylic active monomers, and mercaptan and nitrogen are doped to modify graphene and other components, so that the aqueous UV gloss oil is excellent in wear resistance, good in bending resistance and high in photocuring rate.

The synergistic effect of the mercaptan, dipentaerythritol hexaacrylate, tripropylene glycol diacrylate and epoxy acrylate enables the anti-bending property and the photocuring rate of the water-based UV gloss oil to be excellent; the wear resistance and flexing resistance of the water-based UV gloss oil are enhanced by the nitrogen-doped modified graphene.

Detailed Description

The present invention will be further described with reference to the following embodiments.

The starting materials in the examples and comparative examples are all commercially available, wherein:

hexafunctionality urethane acrylate prepolymer, purchased from chemical company R-1219, zhongshanjie, inc;

difunctional aliphatic urethane acrylate prepolymer: purchased from alder synthesis chemical ltd R4265;

epoxy acrylate: procured from south-male Shang good photochemical technology, Inc. DH-306;

dipentaerythritol hexaacrylate: purchased from Shanghai Guangyi technology Ltd;

tripropylene glycol diacrylate: procurement from Pangain (Shanghai) International trade, Inc.;

leveling agent: BYK-UV3500, BYK-UV3530, BYK-UV3570, BYK-333, BYK-344, BYK-345, BYK-346 and BYK085, purchased from Bike chemical company, Germany;

defoaming agent: NopcoNXZ, purchased from Santa Nuo Puke, Japan; TEGO Airex 980, TEGO Airex 986, available from Digaku industries Ltd.

Mercaptan: ethanethiol, diethylmercaptan, 1-propanethiol or 1, 3-propanedithiol, available from Shunhui Biotech, Inc., Shanghai;

the nitrogen-doped modified graphene is prepared by self-making, and the preparation method comprises the following steps:

adding 10g of graphene into 30mL of ammonia water solution with the concentration of 3 wt.%, performing ultrasonic dispersion to obtain graphene dispersion liquid, transferring the graphene dispersion liquid into a stainless steel hydrothermal kettle, heating at 220 ℃ for 10 hours, cooling, washing the contents of the stainless steel hydrothermal kettle to be neutral, and drying to obtain nitrogen-doped modified graphene A; theoretically calculating to obtain a molar ratio of nitrogen to graphene of 1:33, but as nitrogen elements in the ammonia water solution are not completely doped into the graphene, the molar ratio of nitrogen to graphene in the nitrogen-doped modified graphene A is 1:40 through X-ray photoelectron spectroscopy (XPS) detection;

according to the preparation method, the molar ratio of nitrogen to graphene in the nitrogen-doped modified graphene can be adjusted by changing the mass of the graphene and the ammonia water solution:

the dosage of the raw material of the nitrogen-doped modified graphene B is 10g of graphene, 30mL of 5 wt.% ammonia water solution, and the molar ratio of nitrogen of the nitrogen-doped modified graphene B to graphene is 1:30 through XPS detection;

the dosage of the raw material of the nitrogen-doped modified graphene C is 10g of graphene, 30mL of 1.8 wt.% ammonia water solution, and the mole ratio of nitrogen of the nitrogen-doped modified graphene C to graphene is 1:50 through XPS detection;

the dosage of the raw material of the nitrogen-doped modified graphene D is 10g of graphene and 30mL of 1.5 wt.% ammonia water solution, and the molar ratio of nitrogen of the nitrogen-doped modified graphene D to graphene is 1:60 through XPS detection;

the nitrogen-doped modified graphene A is used in the examples 1 to 11, the comparative examples 1 to 4 and the comparative example 8; example 12 used was nitrogen-doped modified graphene B; example 13 used nitrogen-doped modified graphene C, and comparative example 9 used nitrogen-doped modified graphene D.

Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Examples 1 to 5

Embodiments 1 to 5 provide an aqueous UV varnish, the preparation method including the steps of:

dissolving urethane acrylate prepolymer, epoxy acrylate, dipentaerythritol hexaacrylate and tripropylene glycol diacrylate in water, and stirring at 2000r/min for 30min to obtain a mixed solution A;

dispersing the nitrogen-doped modified graphene, mercaptan, a photoinitiator and other auxiliaries into ethanol, and mixing to obtain a mixed solution B;

and mixing the mixed solution A and the mixed solution B, stirring at 500r/min for 8min, and standing to obtain the aqueous UV gloss oil.

The contents of the components in examples 1 to 5 are shown in Table 1.

TABLE 1 contents (parts by weight) of each component in examples 1 to 5

Examples 6 to 13

Examples 6 to 13 provide aqueous UV varnish, the preparation method is the same as in examples 1 to 5, and the difference between the component content and the component content in example 4 is:

example 6 the photoinitiator was 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone;

example 7 the photoinitiator was 2-hydroxy-2-methyl-1-phenyl-1-propanone;

in example 8, the photoinitiator was a mixture of 2-isopropylthioxanthone and 2-hydroxy-2-methyl-1-phenyl-1-propanone in a mass ratio of 1: 2;

the leveling agent in the example 9 is a mixture of BYK-UV3530 and BYK-UV3570, and the mass ratio of the two is 5: 3;

the leveling agent in example 10 is BYK-333;

the antifoam in example 11 is TEGO Airex 980;

in example 12, the nitrogen-doped modified graphene is nitrogen-doped modified graphene B, and the molar ratio of nitrogen to graphene is 1: 30;

the nitrogen-doped modified graphene in example 13 is nitrogen-doped modified graphene C, wherein the molar ratio of nitrogen to graphene is 1: 50.

Comparative examples 1 to 6

Comparative examples 1 to 6 provide an aqueous UV gloss oil, the preparation method is the same as that of example 5, and the difference is that:

in comparative example 1, no mercaptan was added, and the other components and contents were the same as those in example 5;

in comparative example 2, no epoxy acrylate was added, and the other components and contents were the same as those in example 5;

in comparative example 3, dipentaerythritol hexaacrylate and tripropylene glycol diacrylate were not added, and the other components and contents were the same as in example 5;

in comparative example 4, dipentaerythritol hexaacrylate and tripropylene glycol diacrylate were not added, and 20 parts by weight of pentaerythritol triacrylate was added, that is, only in contrast to example 5, dipentaerythritol hexaacrylate and tripropylene glycol diacrylate, etc., were replaced by pentaerythritol triacrylate in terms of mass;

in the comparative example 5, no nitrogen-doped modified graphene is added, and other components and contents are consistent with those in the example 5;

in the comparative example 6, the nitrogen-doped modified graphene and other components are replaced by the unmodified graphene, and the other components and the content are consistent with those in the example 5;

in comparative example 7, the nitrogen-doped modified graphene and other substances are replaced by oxidized modified graphene, and the modification method comprises the following steps:

preparing graphite oxide by adopting a Hummers method, assembling a 500mL flask in an ice-water bath, adding 23mL concentrated sulfuric acid, adding a mixture of 4g of graphite powder and 2g of sodium nitrate solid while stirring, adding 12g of potassium permanganate for multiple times under the condition that the reaction temperature is controlled not to exceed 20 ℃, stirring for reaction for 10min, heating to 35 ℃, continuing stirring for 30min, slowly adding 25mL of deionized water, stirring for 20min, adding hydrogen peroxide until the solution becomes bright yellow, filtering while hot, washing with a 5% HCl solution, washing with deionized water, repeatedly washing until no sulfate radical is detected in the filtrate, and finally vacuum-drying the filtrate to obtain the graphite oxide; the other components and amounts were the same as in example 5.

Comparative example 8

Comparative example 8 provides an aqueous UV varnish having the same composition and content as in example 5, except that:

comparative example 8 was prepared by mixing the ingredients according to the amount of example 5 directly and stirring at 1800 rpm for 30min to give the aqueous UV varnish of comparative example 8.

Comparative example 9

Comparative example 9 provides an aqueous UV varnish prepared in the same manner as in example 5, except that:

the nitrogen-doped modified graphene of comparative example 9 is nitrogen-doped modified graphene D, and the molar ratio of nitrogen to graphene is 1: 60.

Performance testing

The performance tests were carried out on the aqueous UV gloss oils prepared in the above examples and comparative examples: firstly, preparing a PU layer on a polyester layer base fabric, then coating pigment on release paper, drying at 140-160 ℃ after coating glue, transferring to the PU layer, finally coating aqueous UV gloss oil on the PU layer, and curing.

The curing rate and adhesion of the aqueous UV varnish were tested, wherein,

curing rate test method: detecting the curing time (unit is s) by using a light curing machine under the conditions of an 80W/cm mercury lamp and a lamp distance of 25cm, carrying out parallel test on each sample for 6 times, and averaging the results;

the adhesion test method comprises the following steps: the test was carried out according to GB/T9286-.

And (3) carrying out wear-resisting and flexing-resisting performance tests on the leather product with the cured water-based UV gloss oil layer:

the wear resistance test method comprises the following steps: using a Taber abrasion tester to test by adopting a CS10 grinding wheel, setting the number of test cycles to be 5000 times, recording the quality of the leather product before and after the cycle test, and calculating the Taber abrasion rate by the following calculation formula: i ═ [ (a-B) × 1000 ]/C. Wherein I is the wear index; a is the mass of the sample before abrasion; b is the mass of the sample after abrasion; c is the number of test cycles;

the method for testing the flexing resistance comprises the following steps: and (3) performing a bending resistance test by using a leather bending resistance tester by referring to a standard SATRA TM, and judging that the leather product is qualified if no macroscopic damage exists on the surface of the leather product after 5 ten thousand bending tests at normal temperature, or judging that the leather product is unqualified.

The test results are shown in tables 2 and 3.

Table 2 adhesion and cure rate test results

The adhesive force of the water-based UV gloss oil for the leather in the embodiments 1-13 can reach 0 grade, and the adhesive force performance is good; the curing can be completed within 1.2-2.2 s under a light curing machine, which shows that the light curing speed is high, the production time can be shortened in industrial production, and the industrial production practicability is strong. The aqueous UV varnish of comparative example 1, without the addition of thiol, had a reduced adhesion compared to example 5 and a slower cure rate of 9.1 s. The reason is probably that the thiol containing the sulfydryl can be rapidly crosslinked with the acrylate active monomer to generate compact macromolecules, and meanwhile, the epoxy acrylate can also generate a thioether structure with the sulfydryl, so that the crosslinking density and compactness of the whole formula system are improved, and the speed of the aqueous UV gloss oil in the curing process is improved. Comparative example 2 no epoxy acrylate was added to the aqueous UV varnish, which was soft and tacky, and slow in cure rate, requiring an average of 10.4 seconds to cure completely. Comparative example 3 no dipentaerythritol hexaacrylate and tripropylene glycol diacrylate were added to the aqueous UV varnish, the thiol could not crosslink with more acrylate monomers, and the adhesion of the photocured aqueous UV varnish layer was poor. Comparative example 4 leather was prepared by replacing dipentaerythritol hexaacrylate and tripropylene glycol diacrylate in the formulation with pentaerythritol triacrylate using an aqueous UV varnish, and from the experimental results, the adhesion and cure rate were not as good as in example 5. In comparative example 8, all the raw materials were directly mixed and stirred during the preparation process of the aqueous UV varnish, rather than preparing the two-component formulation first and then mixing as in the preparation method of the present invention, it can be obtained from experimental results that the two-component preparation method can better allow the active monomer to be rapidly cured, thereby increasing the curing rate.

TABLE 3 abrasion and flex resistance test results

According to the test results in Table 3, after the aqueous UV gloss oil layer on the surface of the synthetic leather is prepared from the aqueous UV gloss oil in each embodiment of the invention, after 5000 times of wear resistance tests, the surface of the leather product is observed by naked eyes without macroscopic damage or wear, the wear rate is less than or equal to 3.8mg, and the requirement of the synthetic leather for bags and automobile seats on high wear resistance is met; in certain embodiments, the wear rate may be up to 2.5mg or less. After 5 ten thousand bending tests using a leather flex tester, the leather products of examples 1 to 13 had no visible damage to their surfaces. This demonstrates the excellent wear and flex resistance of the aqueous UV varnish of the present invention.

According to comparative examples 1-3 and 5, when any one of thiol, epoxy acrylate, dipentaerythritol hexaacrylate, tripropylene glycol diacrylate or nitrogen-doped modified graphene is not added into the aqueous UV gloss oil, the wear resistance and the flexing resistance of the aqueous UV gloss oil are poor, the wear rate reaches more than 12mg, and the flexing resistance test is not qualified. From comparative example 4, when dipentaerythritol hexaacrylate and tripropylene glycol diacrylate were replaced with pentaerythritol triacrylate, the abrasion resistance of the aqueous UV varnish was somewhat reduced.

Compared with the comparative examples 1 to 13, the wear rates of the comparative examples 6 to 7 are still higher, namely 6.2mg and 4.8mg, respectively, and the bending resistance test of the aqueous UV gloss oil of the comparative example 6 is unqualified, although the wear resistance of the aqueous UV gloss oil is improved compared with that of the comparative examples 1 to 3 and 5 when the nitrogen-doped modified graphene and other qualities are replaced by the unmodified graphene or the oxidized modified graphene. In the comparative example 9, the nitrogen doping amount of the nitrogen-doped modified graphene is low, so that the wear resistance of the UV gloss oil is difficult to be obviously improved, and the requirement of high wear resistance that the wear rate is less than or equal to 3.8mg is not met.

Therefore, the waterborne UV gloss oil for leather, which is excellent in wear resistance and flexing resistance and high in photocuring rate, is prepared by carrying out composite modification on epoxy acrylate, dipentaerythritol hexaacrylate, tripropylene glycol diacrylate and urethane acrylate through mercaptan and nitrogen-doped modified graphene and by virtue of the synergistic interaction among the components.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (10)

1. The aqueous UV gloss oil for leather is characterized by being prepared from the following components in parts by weight:

10-50 parts of urethane acrylate prepolymer, 1-10 parts of epoxy acrylate, 1-20 parts of dipentaerythritol hexaacrylate, 1-20 parts of tripropylene glycol diacrylate, 5-50 parts of mercaptan, 0.01-0.5 part of nitrogen-doped modified graphene, 1-10 parts of photoinitiator, 0.3-3 parts of other additives and 15-70 parts of solvent.

2. The water-based UV gloss oil for leather as claimed in claim 1, wherein the molar ratio of nitrogen to graphene in the nitrogen-doped modified graphene is 1 (30-50).

3. The aqueous UV gloss oil for leather according to claim 1 or 2, wherein the nitrogen-doped modified graphene is prepared by the following method: dispersing graphene in an amino-containing compound, heating at 200-250 ℃ for 10-15 h, and performing post-treatment to obtain the graphene.

4. The aqueous UV gloss oil for leather as claimed in claim 1, wherein the urethane acrylate prepolymer is a urethane acrylate prepolymer having a functionality of 2-6.

5. The aqueous UV varnish for leather, according to claim 4, wherein the urethane acrylate prepolymer is a difunctional aliphatic urethane acrylate prepolymer and/or a hexafunctional urethane acrylate prepolymer.

6. The aqueous UV gloss oil for leather as claimed in claim 1, wherein the thiol is one or more of ethanethiol, ethanedithiol, 1-propanethiol or 1, 3-propanedithiol.

7. Aqueous UV varnish for leather, according to claim 6, characterized in that the thiol is ethyl-thiol and/or 1-propyl-thiol.

8. The aqueous UV gloss oil for leather according to claim 1, wherein the other auxiliary agent is a leveling agent and/or a defoaming agent, and the leveling agent is polyether modified acrylic functional polydimethylsiloxane.

9. The preparation method of the water-based UV gloss oil for leather according to any one of claims 1 to 8, which is characterized by comprising the following steps:

dissolving urethane acrylate prepolymer, epoxy acrylate, dipentaerythritol hexaacrylate and tripropylene glycol diacrylate in a solvent to obtain a mixed solution A;

dispersing the nitrogen-doped modified graphene, mercaptan, a photoinitiator and other auxiliaries in a solvent to obtain a mixed solution B;

and mixing and stirring the mixed solution A and the mixed solution B to obtain the water-based UV gloss oil for the leather.

10. Use of the aqueous UV gloss oil for leather according to any one of claims 1 to 8 for the production of protective layers for synthetic leather for luggage and/or automobile seats.