Antique style leather and tanning agent-free short-process manufacturing method thereof

Abstract

The invention belongs to the technical field of leather processing, and discloses a tanning agent-free short-process manufacturing method for antique-style leather. The method comprises the following steps: using bare hide or white wet leather as raw material, first dehydrating with anhydrous ethanol, and then treating with cashew nut shell liquid and nano zirconium dioxide; wherein, based on the weight of the bare hide or white wet leather, the moisture content in the bare hide or white wet leather after dehydration is 4-12 wt%; the addition amount of the cashew nut shell liquid is 2-12 wt%; and the addition amount of the nano zirconium dioxide is 0.2-1.5 wt%. In the present invention, the nano zirconium dioxide can catalyze the oxidation of unsaturated double bonds in the cashew nut shell liquid to form covalent bonds with amino groups of skin collagen, while the phenolic hydroxyl groups in the cashew nut shell liquid can form hydrogen bonds with the skin collagen. Under the synergistic effect of hydrogen bonding and covalent bonding, the cashew nut shell liquid is stably fixed on the skin collagen fibers, thereby improving the hydrophobic modification effect of the cashew nut shell liquid on the skin collagen fibers, and finally obtaining a soft, plump, natural cinnamon-colored, and rich nutty antique crust leather product.

Description

Technical Field

[0001] The invention belongs to the technical field of leather processing, and particularly relates to an antique-style leather and a tanning agent-free short-process manufacturing method thereof. Background Art

[0002] The leather industry is a traditional pillar industry of the light industry and plays an important role in satisfying people's better lives and promoting social and economic development. However, the sustainable and healthy development of the leather industry faces the following two problems: (1) Leather manufacturing currently generally adopts chrome tanning technology, which produces chromium-containing wastewater and solid waste, which poses potential ecological and environmental risks; (2) The leather manufacturing process is long, energy-intensive, consumes a lot of chemicals, and is costly. Therefore, developing new environmentally friendly leather-making technologies, reducing the use of chemicals, and shortening the leather-making process are urgent challenges that need to be overcome for the sustainable development of the leather industry.

[0003] Chinese patent CN109385493B, "A Method for Preparing Wet-White Leather," discloses a method for producing porous wet-white leather using organic solvent dehydration to disperse fibers. While this method produces wet-white leather with the porosity, formability, and flex resistance of leather, it suffers from fiber stickiness and reduced porosity upon contact with water, sometimes even reverting to a raw hide state, limiting its application. To overcome the water resistance of dehydrated leather, Chinese patent CN109234477B, "A method for preparing chrome-free leather," discloses a method for blocking the hydrophilic groups of dehydrated leather using a reactive substance containing isocyanate groups; Chinese patent CN113265493B, "A method for preparing leather without tanning agents," discloses a method for hydrophobicizing dehydrated leather using oxides and polydimethylsiloxane; and Chinese patent CN109234476B, "A method for preparing chrome-free tanned leather with a hydrophobic, highly dispersed leather fiber structure," discloses a method for constructing a micro-nano rough structure on the surface of dehydrated leather using nanoparticles and polymers to reduce its surface energy. While all of these methods can improve the hydrophobicity of dehydrated leather, allowing collagen fibers to remain highly dispersed upon contact with water, the resulting leather exhibits poor softness and fullness, making it difficult to meet the high physical property demands of today's leather products. Furthermore, these hydrophobic modification agents primarily utilize petrochemicals as their base synthetic material, which, from a sustainable development perspective, does not meet the requirements of modern green chemistry. Chinese patent CN115747388A, "A method for producing metal-free leather by hydrophobic modification and the resulting leather product," discloses a method for hydrophobic modification of dehydrated leather stock using a long-chain silane coupling agent. The long-chain silane coupling agent used in this method has strong lubrication but weak filling properties, resulting in a leather stock that is soft but lacks fullness. Furthermore, the long-chain silane coupling agent must be bonded to the leather collagen fibers at high temperatures (60-120°C) for 2-6 hours, which inevitably results in additional energy and time consumption. Furthermore, the cost of long-chain silane coupling agents is currently high. These issues hinder the industrial application of the "solvent dehydration + hydrophobic modification" tanning agent-free leather technology.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] In order to solve the problems in the background technology, the present invention aims to provide a tanning agent-free short-process method for manufacturing antique-style leather. The hydrophobic modification reagent used in the method is green, environmentally friendly and low-cost. The manufacturing process is carried out at room temperature and is short in time. The obtained leather is soft and plump, and has a strong classical style due to its natural cinnamon color and rich nutty aroma.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A tanning agent-free, short-process manufacturing method for antique-style leather, using bare leather or wet-white leather as raw materials, first dehydrated with anhydrous ethanol, and then treated with cashew nut shell liquid and nano zirconium dioxide;

[0008] wherein the moisture content of the bare hide or wet white leather after dehydration is 4-12 wt% based on the weight of the bare hide or wet white leather;

[0009] The amount of cashew nut shell liquid added is 2-12 wt%;

[0010] The addition amount of the nano zirconium dioxide is 0.2-1.5 wt%.

[0011] Preferably, the bare skin raw material includes but is not limited to any one of delimed bare skin, softened bare skin, pickled bare skin and bare skin obtained by pickling-depickling process.

[0012] Preferably, the wet white leather raw material is any one of leathers tanned using a non-chrome metal tanning agent or an organic tanning agent.

[0013] More preferably, the leather tanned using a non-chrome metal tanning agent includes but is not limited to any one of aluminum tanned leather, zirconium tanned leather, iron tanned leather, zeolite tanned leather and multi-metal tanning agent tanned leather.

[0014] More preferably, the leather tanned using an organic tanning agent includes but is not limited to any one of vegetable tanned leather, aldehyde tanned leather, active chlorine tanned leather, synthetic tanning agent tanned leather and polymer tanning agent tanned leather.

[0015] Preferably, the anhydrous ethanol dehydration method includes but is not limited to any one or more of natural immersion and mechanical rotation.

[0016] Preferably, the dehydration time of anhydrous ethanol is 0.5-4 h.

[0017] Preferably, the particle size of the nano zirconium dioxide is 20-50 nm.

[0018] Preferably, the step of treating the dehydrated leather blank with cashew nut shell liquid and nano zirconium dioxide is: mixing the cashew nut shell liquid and nano zirconium dioxide, and applying the mixture to the flesh surface of the dehydrated leather blank;

[0019] The coating method includes but is not limited to any one or more of brush coating, roller coating and mechanical roller coating.

[0020] Preferably, the cashew nut shell liquid and nano zirconium dioxide are treated for a dehydrated crust for 5-60 min.

[0021] Preferably, after the dehydrated leather blank is treated with cashew nut shell oil and nano zirconium dioxide, the method further comprises drying, rehydrating and softening the treated leather blank.

[0022] The present invention also discloses antique-style leather obtained by adopting any of the above-mentioned tanning agent-free short-process manufacturing methods.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention uses cashew nut shell liquid and nano zirconium dioxide to simultaneously treat dehydrated leather. Zirconium dioxide catalyzes the oxidation of unsaturated double bonds in cashew nut shell liquid to form covalent bonds with the amino groups of leather collagen, while the phenolic hydroxyl groups in cashew nut shell liquid can form hydrogen bonds with the leather collagen. Under the synergistic effect of hydrogen bonding and covalent bonding, cashew nut shell liquid can be stably fixed on the leather collagen fibers, thereby enhancing the hydrophobic modification effect of cashew nut shell liquid on the leather collagen fibers. Finally, a soft, plump, natural cinnamon-colored, and rich nutty aroma imitation leather product is produced.

[0025] (2) In the tanning agent-free leather making technology system constructed by the present invention, the synergistic combination effect of "cashew nut shell liquid and nano zirconium dioxide" enables the cashew nut shell liquid to simultaneously play the role of filling, coloring and lubricating. Compared with traditional technologies, there is no need for retanning, dyeing and fatliquoring operations, which greatly shortens the leather making process.

[0026] (3) In the tanning agent-free leather making technology system constructed by the present invention, the solvent dehydration and hydrophobic modification operations are both carried out at room temperature, and the two-step operation takes a short time, which greatly reduces the time and energy consumption compared with the existing leather making technology.

[0027] (4) The present invention uses green, renewable and low-cost cashew nut shell oil as a hydrophobic modification agent, which not only improves the ecological nature of tanning agent-free leather making technology, but also significantly reduces the manufacturing cost of tanning agent-free leather, making it easier for tanneries to accept it than existing technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The chemical structure of the main component of cashew nut shell liquid. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments.It should be understood that these descriptions are exemplary only, and are not intended to limit the scope of the present invention.In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.Unindicated specific conditions in the embodiment are carried out according to the conditions of normal conditions or manufacturer's advice.Reagents used or instruments are not indicated by manufacturers, and are conventional products that can be obtained by commercial purchase.

[0030] The present invention provides a tanning agent-free short-process method for manufacturing antique-style leather, which uses bare leather or wet white leather as raw material, first dehydrates it with anhydrous ethanol, and then treats it with cashew nut shell liquid and nano zirconium dioxide;

[0031] wherein the moisture content of the bare hide or wet white leather after dehydration is 4-12 wt% based on the weight of the bare hide or wet white leather;

[0032] The amount of cashew nut shell liquid added is 2-12 wt%;

[0033] The addition amount of the nano zirconium dioxide is 0.2-1.5 wt%.

[0034] The cashew nut shell liquid used in the present invention is a dark brown oily liquid extracted from the shell of the tropical plant cashew nut. It is a low-priced and abundant agricultural by-product. Its main component, cardanol, is a natural phenolic compound with an unsaturated C15 long side chain, accounting for 60-90% of the total content. Other components are anacardic acid, cardol, 2-methyl cardic acid, etc. The chemical structures of each component are shown in Figure 1 . The rigid structure of the benzene ring in cashew nut shell liquid has a filling and thickening effect, which can play a role similar to the retanning process in leather making; the long carbon chain structure in cashew nut shell liquid has excellent hydrophobicity and lubricating effect, which can play a role similar to the fatliquoring process in leather making; the natural dark brown color of cashew nut shell liquid has a dyeing effect on collagen fibers, which can play a role similar to the dyeing process in leather making. It is precisely because of the unique molecular structure and color characteristics of cashew nut shell liquid that the present invention does not require modification operations on cashew nut shell liquid, and does not require tedious retanning, dyeing and fatliquoring operations on the raw leather, and can obtain antique-style leather with cinnamon color, excellent softness and fullness.

[0035] The present invention utilizes a combination of "CNSL + nano-zirconium dioxide" rather than CNSL alone to treat dehydrated leather. This is because the phenolic hydroxyl groups in CNSL are limited (e.g., one molecule of cardanol contains only one phenolic hydroxyl group) and cannot form multiple bonds with leather collagen. This results in insufficient bond strength between CNSL and collagen and easy migration within the collagen fibers, ultimately leading to an oily leather surface and poor softness and fullness. The applicant unexpectedly discovered in experiments that adding nano-zirconium dioxide to CNSL significantly enhances the bond strength between CNSL and collagen. This is due to the fact that nano-zirconium dioxide is a photocatalyst that catalyzes the oxidation of unsaturated double bonds in CNSL, forming covalent bonds with amino groups in collagen. Furthermore, the phenolic hydroxyl groups in CNSL can form hydrogen bonds with collagen. Under the synergistic effect of phenolic hydroxyl groups and unsaturated double bonds forming hydrogen bonds and covalent bonds with skin collagen, the fixation fastness of cashew nut shell liquid on skin collagen fibers is significantly enhanced, thereby improving the hydrophobic modification effect of cashew nut shell liquid on skin collagen fibers, ultimately obtaining a soft, plump, natural cinnamon-colored antique leather product with a rich nutty aroma.

[0036] Since cashew nut shell liquid is insoluble in water but soluble in ethanol, in order to allow cashew nut shell liquid to quickly and fully infiltrate the skin collagen fibers, it is necessary to first use anhydrous ethanol to dehydrate the bare skin or wet leather to a moisture content of 4-12 wt%. If the moisture content in the bare skin or wet leather exceeds 12 wt%, the infiltration effect of cashew nut shell liquid is poor. It should be noted that the moisture content of 4 wt% is close to the minimum value of the moisture content in the dehydrated leather blank. This part of water is the bound water of the skin collagen fibers and is difficult to remove by anhydrous ethanol. As can be seen from the above content, the amount of anhydrous ethanol used and the dehydration time do not need to be specifically limited. Those skilled in the art can use an appropriate amount of anhydrous ethanol for dehydration according to the degree of dehydration required. For example, based on the weight of the bare skin or wet leather, the amount of anhydrous ethanol used can be 50-800 wt%, and the dehydration time can be 0.5-4 h.

[0037] The dehydration method of anhydrous ethanol is a commonly used dehydration method in the art, for example, natural immersion or mechanical rotation can be used.

[0038] In an embodiment of the present invention, the amount of cashew nut shell liquid added is 2-12 wt%, and the amount of nano zirconium dioxide added is 0.2-1.5 wt%. The antique style leather prepared within this amount range has excellent softness and fullness. If the amount of cashew nut shell liquid is less than 2 wt%, the lubricating effect of the cashew nut shell liquid is insufficient, resulting in poor softness and fullness of the crust leather; if the amount of cashew nut shell liquid exceeds 12 wt%, the crust leather will produce a greasy feeling due to excessive cashew nut shell liquid; if the amount of nano zirconium dioxide is less than 0.2 wt%, it is difficult to catalyze the oxidation of the unsaturated double bonds in the cashew nut shell liquid to form a covalent bond with the collagen amino group of the skin, and it is impossible to produce a synergistic effect of covalent bonding and hydrogen bonding, resulting in insufficient bonding strength between the cashew nut shell liquid and the collagen fiber of the skin; if the amount of nano zirconium dioxide exceeds 1.5 wt%, the cost is increased, and the second is difficult to mix with the cashew nut shell liquid. After brushing, nano zirconium dioxide is even deposited on the crust leather.

[0039] It should be noted that the raw material of bare skin is a raw material of bare skin obtained according to a conventional process in the art. In some preferred embodiments, the raw material of bare skin includes but is not limited to any one of delimed bare skin, softened bare skin, pickled bare skin and bare skin obtained by pickling-depickling process;

[0040] The wet white leather raw material is any one of non-chrome metal tanned leather and organic tanning agent tanned leather obtained according to conventional processes in the art;

[0041] Wherein, the leather obtained by tanning with the non-chromium metal tanning agent includes but is not limited to any one of aluminum tanned leather, zirconium tanned leather, iron tanned leather, zeolite tanned leather and multi-metal tanning agent tanned leather;

[0042] The leather obtained by tanning with the organic tanning agent includes but is not limited to any one of vegetable tanned leather, aldehyde tanned leather, active chlorine tanned leather, synthetic tanning agent tanned leather and polymer tanning agent tanned leather.

[0043] In some preferred embodiments, in order to further improve the catalytic effect of nano-zirconium dioxide, nano-zirconium dioxide with a particle size range of 20-50 nm is selected.

[0044] In some embodiments, the method of using cashew nut shell liquid and nano zirconium dioxide treatment is to mix cashew nut shell liquid and nano zirconium dioxide, apply to the flesh surface of dehydrated crust, treat the dehydrated crust, and obtain a hydrophobic crust. The time of the treatment can be selected by those skilled in the art according to the hydrophobicity of the crust. For example, the dehydrated crust can be treated for 5-60 min.

[0045] The treatment method is preferably to cover the cashew nut shell liquid and nano zirconium dioxide on the surface of the dehydrated shell blank by brushing. In some preferred embodiments, the brushing method includes but is not limited to any one or more of brushing, rolling and mechanical roller coating.

[0046] In order to further improve the performance of the prepared antique style leather, after the hydrophobic treatment with cashew nut shell oil and nano zirconium dioxide, the hydrophobic leather blank can be dried, moisturized and softened according to conventional processes.

[0047] In order to better understand the technical solution provided by the present invention, the following uses a number of specific examples to illustrate the antique-style tanning agent-free short-process leather manufacturing technology and performance testing provided by the above-mentioned embodiment of the present invention.

[0048] The cashew nut shell liquid and zirconium dioxide used in the following examples and comparative examples are conventional commercially available unmodified reagents, and the bare hide and wet white leather are materials obtained by conventional tanning process, and their moisture content is 40-60 wt%.

[0049] In the following examples and comparative examples, the sensory evaluation method for tanning agent-free crust leather is as follows:

[0050] Five evaluators with at least three years of experience in leather sensory testing were invited to evaluate the color, odor, and greasiness of the tanning agent-free crust leather. The tanning agent-free crust leather was also graded for its antique quality. Excellent: 5 points; Good: 4 points; Fair: 3 points; Fair: 2 points; Poor: 1 point.

[0051] In the following examples and comparative examples, a softness tester was used to measure the softness of the prepared leather samples.

[0052] In the following examples and comparative examples, the fullness of the tanning agent-free crust leather is characterized by compression rate and rebound rate, and the specific measurement method is as follows:

[0053] Use a thickness gauge to measure the thickness of the crust leather under unloaded conditions T 0 Add an additional load of 5 N to the thickness gauge to measure the thickness of the crust leather. T 1 Remove the 5 N load of the thickness gauge and measure the thickness of the leather. T 2 The calculation formulas for the compression rate and rebound rate of crust leather are as follows:

[0054] ;

[0055] .

[0056] In the following examples and comparative examples, the binding strength of the oil component to the leather collagen fibers was characterized by measuring the total organic carbon content of the waste liquid after washing the tanning agent-free crust leather in alkali solution. The specific testing method is as follows:

[0057] The crust leather was placed in a rotating drum. 200 wt% deionized water and 4 wt% soda ash were added based on the weight of the crust leather. The drum was rotated at 30°C for 60 min. The waste liquid was collected and the total organic carbon content of the waste liquid was measured using a total organic carbon analyzer to reflect the amount of oil washed out of the crust leather.

[0058] Example 1

[0059] The acid-soaked leather was placed in anhydrous ethanol and mechanically rotated for dehydration to obtain a dehydrated leather blank with a moisture content of 6.3 wt%. 7 wt% of cashew nut shell liquid and 0.2 wt% of nano-zirconium dioxide with a particle size of 30 nm were mixed and brushed on the flesh surface of the dehydrated leather blank for 60 min. The hydrophobic leather blank was then dried, moisturized and softened according to conventional processes to obtain antique-style leather.

[0060] Sensory evaluation and instrumental measurement showed that the leather had a natural cinnamon color, a rich nutty aroma, and a dry, non-greasy body. The antique grade was 5 points, the softness was 8.2 mm, the compression rate was 12.2%, the rebound rate was 4.1%, and the total organic carbon content of the alkaline washing wastewater was 78.5 mg / L. The specific results are shown in Table 1.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that Comparative Example 1 only performs dehydration with anhydrous ethanol, and does not perform cashew nut shell liquid and nano zirconium dioxide treatment. The detailed process steps are as follows:

[0063] The pickled bare hide was placed in anhydrous ethanol and mechanically rotated for dehydration to obtain a dehydrated leather crust with a moisture content of 6.3 wt% based on the weight of the pickled bare hide; the hydrophobic leather crust was dried, moistened and softened according to conventional processes to obtain a tanning agent-free crust leather.

[0064] Sensory evaluation and instrumental testing revealed that the crust leather was white, had a natural protein aroma, and was dry and non-greasy. Its antique grade was 1, with a softness of 5.1 mm, a compressibility of 7.3%, and a rebound of 2.4%. Because the crust leather is not waterproof, it reverts to its rawhide state and undergoes alkaline expansion when exposed to alkali. Therefore, the total organic carbon content of the alkali wash wastewater was not measured. The specific results are shown in Table 1.

[0065] Comparative Example 2

[0066] The difference from Example 1 is that Comparative Example 2 only undergoes cashew nut shell liquid treatment, and does not undergo anhydrous ethanol dehydration and nano zirconium dioxide treatment. The detailed process steps are as follows:

[0067] 7 wt% of cashew nut shell liquid (CNSL) was brush-coated on the flesh surface of the pickled bare hide for 60 min, thereby obtaining a CNSL-treated leather. The CNSL-treated leather was then dried, moisturized, and softened according to conventional processes to obtain a tanning agent-free leather.

[0068] The crust leather is dark brown and has a strong nutty aroma, but the leather is very greasy and even difficult to dry, making it unusable. Therefore, the antique grade, softness, fullness, and alkaline wash resistance of the crust leather were not evaluated or measured. The specific results are shown in Table 1.

[0069] Comparative Example 3

[0070] The difference from Example 1 is that Comparative Example 3 only undergoes nano-zirconium dioxide treatment, and does not undergo anhydrous ethanol dehydration and cashew nut shell liquid treatment. The detailed process steps are as follows:

[0071] 0.2 wt% of nano-zirconium dioxide with a particle size of 30 nm was brush-coated on the flesh surface of the pickled bare hide for 60 min, thereby obtaining a leather blank treated with nano-zirconium dioxide. The leather blank treated with nano-zirconium dioxide was then dried, moisturized, and softened according to conventional processes to obtain a tanning agent-free crust leather.

[0072] The crust leather was gray, had a natural protein smell, and was dry and non-greasy. However, it was severely gelled and very stiff, making it unusable. Therefore, the antique grade, softness, fullness, and alkaline wash resistance of the crust leather were not evaluated or measured. The specific results are shown in Table 1.

[0073] Comparative Example 4

[0074] The difference from Example 1 is that Comparative Example 4 only undergoes cashew nut shell liquid and nano zirconium dioxide treatment, and no anhydrous ethanol dehydration is performed. The detailed process steps are as follows:

[0075] 7 wt% of cashew nut shell liquid and 0.2 wt% of nano-zirconium dioxide with a particle size of 30 nm were mixed and evenly applied to the flesh surface of the pickled leather. The mixing and application took 60 min to obtain a leather blank treated with cashew nut shell liquid and nano-zirconium dioxide. The leather blank treated with cashew nut shell liquid and nano-zirconium dioxide was dried, moisturized and softened according to conventional processes to obtain tanning agent-free leather.

[0076] The crust leather is dark brown and has a strong nutty aroma, but the leather is very greasy and even difficult to dry, making it unusable. Therefore, the antique grade, softness, fullness, and alkaline wash resistance of the crust leather were not evaluated or measured. The specific results are shown in Table 1.

[0077] Comparative Example 5

[0078] The difference from Example 1 is that Comparative Example 5 only undergoes anhydrous ethanol dehydration and cashew nut shell liquid treatment, and does not undergo nano zirconium dioxide treatment. The detailed process steps are as follows:

[0079] The pickled leather was placed in anhydrous ethanol and mechanically rotated to dehydrate it, obtaining a dehydrated leather with a moisture content of 6.3 wt%. 7 wt% cashew nut shell liquid was brushed onto the flesh surface of the dehydrated leather for 60 min to obtain a hydrophobic leather. The hydrophobic leather was then dried, moisturized, and softened according to conventional processes to obtain tanning agent-free leather.

[0080] Sensory evaluation and instrumental measurement showed that the leather had a natural cinnamon color, a strong nutty aroma, and was slightly oily. The antique grade was 3 points, the softness was 6.5 mm, the compression rate was 9.8%, the rebound rate was 3.2%, and the total organic carbon content of the alkaline washing wastewater was 435.6 mg / L. The specific results are shown in Table 1.

[0081] Comparative Example 6

[0082] The difference from Example 1 is that Comparative Example 6 only undergoes anhydrous ethanol dehydration and nano-zirconium dioxide treatment, and does not undergo cashew nut shell liquid treatment. The detailed process steps are as follows:

[0083] The pickled leather was placed in anhydrous ethanol and mechanically rotated for dehydration to obtain a dehydrated leather blank with a moisture content of 6.3 wt% based on the weight of the pickled leather. 0.2 wt% of nano-zirconium dioxide with a particle size of 30 nm was brush-coated on the flesh surface of the dehydrated leather blank for 60 min to obtain a nano-zirconium dioxide-treated leather blank. The nano-zirconium dioxide-treated leather blank was then dried, moisturized and softened according to conventional processes to obtain a tanning agent-free leather blank.

[0084] Sensory evaluation and instrumental testing revealed that the crust leather was white, had a natural protein aroma, and was dry and non-greasy. Its antique grade was 1, with a softness of 5.1 mm, a compressibility of 7.4%, and a rebound of 2.4%. Because the crust leather is not waterproof, it reverts to its raw state and undergoes alkaline expansion when exposed to alkali. Therefore, the total organic carbon content of the alkali wash wastewater was not measured. The specific results are shown in Table 1.

[0085] Comparative Example 7

[0086] The difference from Example 1 is that in Comparative Example 7, cashew nut shell liquid is replaced with rapeseed oil, and dehydration is first performed with anhydrous ethanol, and then rapeseed oil and nano zirconium dioxide are treated. The detailed process steps are as follows:

[0087] The pickled leather was placed in anhydrous ethanol and mechanically rotated for dehydration to obtain a dehydrated leather blank with a moisture content of 6.3 wt%. 7 wt% rapeseed oil and 0.2 wt% nano-zirconium dioxide with a particle size of 30 nm were mixed and brushed on the flesh surface of the dehydrated leather blank for 60 min to obtain a hydrophobic leather blank. The hydrophobic leather blank was dried, moistened and softened according to conventional processes to obtain tanning agent-free leather.

[0088] Sensory evaluation and instrumental measurement showed that the leather was white, had a rapeseed oil smell, and was relatively greasy. The antique grade was 2 points, the softness was 6.2 mm, the compression rate was 9.2%, the rebound rate was 2.9%, and the total organic carbon content of the alkaline washing wastewater was 1316.2 mg / L. The specific results are shown in Table 1.

[0089] Comparative Example 8

[0090] The difference from Example 1 is that in Comparative Example 8, cashew nut shell liquid is replaced with plant tannins (wattle bark tannin) and rapeseed oil, and dehydration is first performed with anhydrous ethanol, and then rapeseed oil and nano zirconium dioxide are treated. The detailed process steps are as follows:

[0091] The pickled leather was placed in anhydrous ethanol and mechanically rotated for dehydration to obtain a dehydrated leather crust with a moisture content of 6.3 wt%. 5 wt% rapeseed oil, 2 wt% vegetable tannins and 0.2 wt% nano-zirconium dioxide with a particle size of 30 nm were mixed and brushed on the flesh surface of the dehydrated leather crust. The mixing and brushing process took 60 min to obtain a hydrophobic leather crust. The hydrophobic leather crust was then dried, moisturized and softened according to conventional processes to obtain tanning agent-free leather crust.

[0092] Sensory evaluation and instrumental testing revealed that the crust leather was light brown, had a tannin and rapeseed oil aroma, and was relatively greasy. Its antique grade was 2, with a softness of 6.0 mm, a compressibility of 8.9%, and a rebound of 2.7%. Because vegetable tannins can affect the total organic carbon content in the crust leather alkali wash wastewater, this indicator was not measured. The specific results are shown in Table 1.

[0093] According to the sensory evaluation and instrument test results of Example 1 and Comparative Examples 1-8, it can be seen that the comparative example 1 uses anhydrous ethanol for dehydration, the crust leather is white, has a natural protein taste, and the leather body is dry and not greasy. The antique grade is 1 point, and the softness is as low as 5.1. mm, the compression rate is only 7.3%, the rebound rate is only 2.4%, and it is not water-resistant; Comparative Example 2 is treated with cashew nut shell oil, and the crust leather is dark brown and has a strong nutty aroma, but the leather body is very greasy, and it cannot even be dried, so it has no use value; Comparative Example 3 is treated with nano zirconium dioxide, and the crust leather is gray, has a natural protein taste, and the leather body is dry and not greasy, but it is severely gelled and very stiff, and has no use value; Comparative Example 4 is treated with cashew nut shell oil and nano zirconium dioxide, and the crust leather is dark brown and has a strong nutty aroma, but the leather body is still very greasy, and it cannot be dried, so it has no use value; Comparative Example 5 is first dehydrated with anhydrous ethanol and then treated with cashew nut shell oil. The crust leather is natural cinnamon color, has a strong nutty aroma, and the leather body is slightly greasy. The antique grade is 3 points, the softness is 6.5 mm, the compression rate is 9.8%, the rebound rate is 3.2%, and the total organic carbon content of the alkali washing waste liquid is 435.6 mg / L; Comparative Example 6 first uses anhydrous ethanol for dehydration and then uses nano-zirconium dioxide for treatment. The crust leather is white, has a natural protein smell, the leather body is dry and not greasy, the antique grade is 1 point, the softness is as low as 5.1 mm, the compression rate is only 7.4%, the rebound rate is only 2.4%, and it is not water-resistant; Comparative Example 7 first uses anhydrous ethanol for dehydration and then uses rapeseed oil and nano-zirconium dioxide for treatment. The crust leather is white, has a rapeseed oil smell, the leather body is relatively greasy, the antique grade is 2 points, the softness is 6.2 mm, the compression rate is 9.2%, the rebound rate is 2.9%, and the total organic carbon content of the alkali washing waste liquid is as high as 1316.2 mg / L; Comparative Example 8 first uses anhydrous ethanol for dehydration and then uses rapeseed oil, plant tannins and nano-zirconium dioxide for treatment. The crust leather is light brown, has the smell of tannin and rapeseed oil, the leather body is relatively greasy, the antique grade is 2 points, and the softness is 6.0 mm, a compression rate of 8.9%, and a rebound rate of 2.7%; in Example 1, dehydration is first performed with anhydrous ethanol, and then cashew nut shell oil and nano-zirconium dioxide are used for treatment. The crust leather has a natural cinnamon color and a rich nutty aroma. The leather body is dry and not greasy, with an antique grade of 5 points, a softness of up to 8.2 mm, a compression rate of up to 12.2%, a rebound rate of up to 4.1%, and the total organic carbon content of the alkali washing waste liquid is as low as 78.5 mg / L.

[0094] The results of the above examples and comparative examples demonstrate that crust leather produced by dehydration with anhydrous ethanol alone (Comparative Example 1) exhibits low softness, poor fullness, and poor water resistance. Crust leather produced by treatment with cashew nut shell liquid alone (Comparative Example 2) is extremely greasy and even impossible to dry. This is because the cashew nut shell liquid cannot penetrate the high-water content of pickled leather and accumulates only on the leather surface. Crust leather produced by treatment with nano-zirconium dioxide alone (Comparative Example 3) is almost in a raw state. These results demonstrate that separate treatments with anhydrous ethanol dehydration, cashew nut shell liquid, and nano-zirconium dioxide alone fail to produce crust leather with excellent softness and fullness.

[0095] The effect of treating undehydrated pickled leather with cashew nut shell liquid and nano zirconium dioxide (Comparative Example 4) is similar to that of treating with cashew nut shell liquid alone, which again shows that before cashew nut shell liquid treatment, the moisture content of the dehydrated leather must be controlled at a low content (4-12 wt%) so that the cashew nut shell liquid can fully infiltrate the collagen fibers; compared with the dehydrated leather, the softness of the leather obtained by treating the dehydrated leather with cashew nut shell liquid (Comparative Example 5) increased by 1.4 mm, the compression rate increased by 2.5%, and the rebound rate increased by 0.8%, but the leather body was slightly greasy and the total organic carbon content of the alkali washing wastewater was 435.6 mg / L, indicating that the use of cashew nut shell oil to treat dehydrated leather can indeed improve the softness and fullness of leather, but due to the limited binding ability of cashew nut shell oil with leather collagen fibers, cashew nut shell oil easily migrates in the collagen fibers, resulting in the leather being slightly greasy and not resistant to alkali washing; compared with the dehydrated leather, the softness (increase of 0 mm), compression rate (increase of 0.1%) and rebound rate (increase of 0%) of the leather obtained by treating the dehydrated leather (Comparative Example 6) were almost unchanged; while the use of cashew nut shell oil and nano zirconium dioxide to treat the dehydrated leather (Example 1) together, the softness of the leather obtained was increased by 3.1 compared with the dehydrated leather. mm, the compression rate increased by 4.9%, the rebound rate increased by 1.7%, the leather body was dry and not greasy, and the total organic carbon content of the alkali washing waste liquid was as low as 78.5 mg / L, indicating that the "cashew nut shell oil + nano zirconium dioxide" combination treatment of dehydrated leather can not only improve the softness and fullness of the leather, but also form a stable bond with the leather collagen fibers, ultimately resulting in a dry, non-greasy leather body and resistance to alkali washing. It should be noted that the increase in the softness of the crust leather in Example 1 (cashew nut shell liquid + nano-zirconium dioxide) is higher than the sum of the increases in the softness of the crust leather in Comparative Example 5 (cashew nut shell liquid) and Comparative Example 6 (nano-zirconium dioxide) (i.e., 3.1 mm>1.4 mm+0 mm); the increase in the compression rate of the crust leather in Example 1 is higher than the sum of the increases in the compression rates of the crust leather in Comparative Example 5 and Comparative Example 6 (i.e., 4.9%>2.5%+0.1%); and the increase in the resilience of the crust leather in Example 1 is higher than the sum of the increases in the resilience of the crust leather in Comparative Example 5 and Comparative Example 6 (i.e., 1.7%>0.8%+0%). It can be seen that the combination of "cashew nut shell liquid + nano zirconium dioxide" used in the present invention has a significant synergistic effect on improving the softness and fullness of the crust leather. This is mainly due to the fact that nano zirconium dioxide can catalyze the oxidation of unsaturated double bonds in cashew nut shell liquid to form covalent bonds with the amino groups of skin collagen, and the phenolic hydroxyl groups in cashew nut shell liquid can form hydrogen bonds with skin collagen. Under the synergistic effect of the two binding modes, the bonding strength of cashew nut shell liquid and skin collagen fibers is significantly enhanced, thereby improving the hydrophobic modification effect of cashew nut shell liquid on skin collagen fibers, and finally obtaining a soft and plump crust leather product.

[0096] Replacing the cashew nut shell liquid in Example 1 with rapeseed oil (Comparative Example 7) resulted in a crust leather that was less soft and full than the crust leather produced using the method of Example 1. The leather was relatively greasy, and the total organic carbon content of the alkali washing wastewater was as high as 1316.2 mg / L. This indicates that replacing the cashew nut shell liquid in the present invention with conventional unsaturated oils and fats cannot achieve the technical effects described in the present invention. This is because although nano-zirconium dioxide can catalyze the oxidation of unsaturated double bonds in conventional oils and fats to form covalent bonds with the amino groups of skin collagen, the lack of phenolic hydroxyl groups in conventional oils and fats prevents hydrogen bonding with skin collagen, thus failing to produce the synergistic effect of "covalent bonding + hydrogen bonding." This results in insufficient bonding strength between the natural oil and skin collagen fibers, resulting in the resulting crust leather being relatively greasy, not resistant to alkali washing, and not soft enough. In addition, the lack of rigid benzene rings in the molecular structure of conventional unsaturated oils and fats results in insufficient filling effect, resulting in poor fullness of the resulting crust leather. It can be seen that it is precisely based on the unique molecular structure characteristics of cashew nut shell liquid that the crust leather product of the present invention with high softness, good fullness, dryness and non-greasyness can be produced.

[0097] Replacing the cashew nut shell liquid in Example 1 with rapeseed oil and plant tannins (Comparative Example 8) resulted in a crust leather that was less soft and full than the crust leather produced using the method of Example 1, and the leather was also quite greasy. This demonstrates that even if the cashew nut shell liquid in the present invention is replaced with conventional unsaturated oils and plant tannins with phenolic hydroxyl groups, the technical effects of the present invention cannot be achieved. This is because, although nano-zirconium dioxide can catalyze the oxidation of unsaturated double bonds in conventional oils to form covalent bonds with amino groups in skin collagen, and the phenolic hydroxyl groups in plant tannins can form hydrogen bonds with skin collagen, the covalent and hydrogen bonding occurs between the "collagen-rapeseed oil" and "collagen-plant tannin" linkages, respectively, preventing the synergistic binding effect described in the present invention. It should be noted that it is precisely because of the unique molecular structure of cashew nut shell liquid and collagen that both hydrogen and hydrogen bonding occur, which promotes the synergistic binding effect between the cashew nut shell liquid and collagen, ultimately resulting in a crust leather product that exhibits excellent softness, fullness, and a dry, non-greasy feel.

[0098] Table 1 Test results

[0099] .

[0100] Example 2

[0101] The delimed leather was naturally immersed in anhydrous ethanol for dehydration based on the weight of the delimed leather to obtain a dehydrated leather blank with a moisture content of 4.8 wt%; 12 wt% of cashew nut shell liquid and 0.8 wt% of nano zirconium dioxide with a particle size of 20 nm were mixed and roll-coated on the flesh surface of the dehydrated leather blank for 30 min to obtain a hydrophobic leather blank; the hydrophobic leather blank was dried, moistened and softened according to conventional processes to obtain antique-style leather.

[0102] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 8.4 mm, the compression rate was 12.6%, the rebound rate was 4.4%, and the total organic carbon content of the alkaline washing wastewater was 91.3 mg / L.

[0103] Example 3

[0104] The softened bare leather was placed in anhydrous ethanol and mechanically rotated for dehydration to obtain a dehydrated leather blank with a moisture content of 12.0 wt%. 2 wt% of cashew nut shell liquid and 1.5 wt% of nano zirconium dioxide with a particle size of 50 nm were mixed and mechanically roller-coated on the flesh surface of the dehydrated leather blank for 5 minutes to obtain a hydrophobic leather blank. The hydrophobic leather blank was dried, moisturized and softened according to conventional processes to obtain antique-style leather.

[0105] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 7.7 mm, the compression rate was 11.8%, the rebound rate was 3.8%, and the total organic carbon content of the alkaline washing wastewater was 42.3 mg / L.

[0106] Example 4

[0107] The bare leather obtained by the pickling-deacidification process was placed in anhydrous ethanol for natural immersion and dehydration, and then mechanically rotated for dehydration to obtain a dehydrated leather blank with a moisture content of 6.4 wt%; 12 wt% of cashew nut shell liquid and 1.5 wt% of nano zirconium dioxide with a particle size of 20 nm were mixed, brushed and rolled on the flesh surface of the dehydrated leather blank. The mixing, brushing and rolling took 30 minutes to obtain a hydrophobic leather blank; the hydrophobic leather blank was dried, moistened and softened according to conventional processes to obtain antique style leather.

[0108] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 8.5 mm, the compression rate was 12.7%, the rebound rate was 4.6%, and the total organic carbon content of the alkaline washing waste liquid was 88.7 mg / L.

[0109] Example 5

[0110] Based on the weight of aluminum-tanned leather, the leather was naturally immersed in anhydrous ethanol for dehydration, and then mechanically rotated for dehydration to obtain a dehydrated leather blank with a moisture content of 11.6 wt%. 2 wt% of cashew nut shell liquid and 0.8 wt% of nano-zirconium dioxide with a particle size of 50 nm were mixed and applied to the flesh surface of the dehydrated leather blank by brushing and mechanical roller coating. The mixing, brushing and mechanical roller coating took 60 min to obtain a hydrophobic leather blank. The hydrophobic leather blank was dried, moisturized and softened according to conventional processes to obtain antique-style leather.

[0111] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 7.9 mm, the compression rate was 12.0%, the rebound rate was 3.9%, and the total organic carbon content of the alkaline washing wastewater was 40.1 mg / L.

[0112] Example 6

[0113] The zirconium-tanned leather was naturally immersed in anhydrous ethanol for dehydration, and then mechanically rotated for dehydration to obtain a dehydrated leather blank with a moisture content of 4.0 wt%. 7 wt% of cashew nut shell liquid and 0.2 wt% of nano-zirconium dioxide with a particle size of 30 nm were mixed and then rolled and mechanically rolled on the flesh surface of the dehydrated leather blank. The mixing, rolling and mechanical rolling took 30 minutes to obtain a hydrophobic leather blank. The hydrophobic leather blank was dried, moisturized and softened according to conventional processes to obtain antique-style leather.

[0114] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 8.3 mm, the compression rate was 12.4%, the rebound rate was 4.2%, and the total organic carbon content of the alkaline washing wastewater was 76.4 mg / L.

[0115] Example 7

[0116] Iron-tanned leather was naturally immersed in anhydrous ethanol for dehydration based on its weight to obtain a dehydrated leather blank with a moisture content of 11.2 wt%. 12 wt% of cashew nut shell liquid and 0.8 wt% of nano-zirconium dioxide with a particle size of 30 nm were mixed and brushed on the flesh surface of the dehydrated leather blank. The mixing and brushing process took 30 minutes to obtain a hydrophobic leather blank. The hydrophobic leather blank was dried, moisturized and softened according to conventional processes to obtain antique-style leather.

[0117] After sensory evaluation and instrumental measurement, the leather was yellow in color, had a strong nutty aroma, and the leather body was dry and not greasy. The antique grade was 5 points, the softness was 8.5 mm, the compression rate was 12.8%, the rebound rate was 4.7%, and the total organic carbon content of the alkaline washing waste liquid was 87.4 mg / L.

[0118] Example 8

[0119] Zeolite-tanned leather was placed in anhydrous ethanol and mechanically rotated for dehydration to obtain a dehydrated leather with a moisture content of 6.0 wt%. 7 wt% of cashew nut shell liquid and 0.2 wt% of nano-zirconium dioxide with a particle size of 20 nm were mixed and rolled onto the flesh surface of the dehydrated leather. The mixing and rolling process took 60 minutes to obtain a hydrophobic leather. The hydrophobic leather was then dried, moisturized, and softened according to conventional processes to obtain antique-style leather.

[0120] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 8.1 mm, the compression rate was 12.1%, the rebound rate was 4.0%, and the total organic carbon content of the alkaline washing wastewater was 78.2 mg / L.

[0121] Example 9

[0122] The leather tanned with multi-metal tanning agents was naturally immersed in anhydrous ethanol for dehydration based on its weight to obtain a dehydrated leather blank with a moisture content of 4.2 wt%. 2 wt% of cashew nut shell liquid and 1.5 wt% of nano-zirconium dioxide with a particle size of 50 nm were mixed and mechanically roller-coated on the flesh surface of the dehydrated leather blank for 5 minutes to obtain a hydrophobic leather blank. The hydrophobic leather blank was then dried, moisturized and softened according to conventional processes to obtain antique-style leather.

[0123] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 7.9 mm, the compression rate was 11.8%, the rebound rate was 3.8%, and the total organic carbon content of the alkaline washing wastewater was 40.7 mg / L.

[0124] Example 10

[0125] The vegetable tanned leather was naturally immersed in anhydrous ethanol for dehydration based on its weight to obtain a dehydrated leather blank with a moisture content of 6.1 wt%. 2 wt% of cashew nut shell liquid and 0.2 wt% of nano-zirconium dioxide with a particle size of 50 nm were mixed and brushed on the flesh surface of the dehydrated leather blank. The mixing and brushing process took 60 min to obtain a hydrophobic leather blank. The hydrophobic leather blank was then dried, moisturized and softened according to conventional processes to obtain antique-style leather.

[0126] After sensory evaluation and instrumental measurement, the leather was light brown in color, with both tannin extract and rich nutty aroma, and the leather body was dry and not greasy. The antique grade was 5 points, the softness was 7.6 mm, the compression rate was 11.5%, the rebound rate was 3.7%, and the total organic carbon content of the alkaline washing waste liquid was 43.4 mg / L.

[0127] Example 11

[0128] The aldehyde-tanned leather was placed in anhydrous ethanol and mechanically rotated for dehydration to obtain a dehydrated leather blank with a moisture content of 11.5 wt% based on the weight of the aldehyde-tanned leather. 7 wt% of cashew nut shell liquid and 1.5 wt% of nano-zirconium dioxide with a particle size of 30 nm were mixed and roll-coated on the flesh surface of the dehydrated leather blank for 30 minutes to obtain a hydrophobic leather blank. The hydrophobic leather blank was then dried, moisturized and softened according to conventional processes to obtain antique-style leather.

[0129] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 8.3 mm, the compression rate was 12.4%, the rebound rate was 4.2%, and the total organic carbon content of the alkaline washing wastewater was 79.3 mg / L.

[0130] Example 12

[0131] The active chlorine-tanned leather was naturally immersed in anhydrous ethanol for dehydration, obtaining a dehydrated leather with a moisture content of 4.7 wt%. 12 wt% of cashew nut shell liquid and 0.8 wt% of nano-zirconium dioxide with a particle size of 20 nm were mixed and mechanically roller-coated on the flesh surface of the dehydrated leather. The mixing and mechanical roller coating took 5 minutes to obtain a hydrophobic leather. The hydrophobic leather was then dried, moisturized, and softened according to conventional processes to obtain antique-style leather.

[0132] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 8.2 mm, the compression rate was 12.3%, the rebound rate was 4.0%, and the total organic carbon content of the alkaline washing waste liquid was 89.9 mg / L.

[0133] Example 13

[0134] Synthetic tanned leather was placed in anhydrous ethanol and mechanically rotated for dehydration to obtain a dehydrated leather with a moisture content of 11.4 wt%. 12 wt% of cashew nut shell liquid and 0.2 wt% of nano-zirconium dioxide with a particle size of 20 nm were mixed and applied to the flesh surface of the dehydrated leather by brushing and mechanical roller coating for 60 min to obtain a hydrophobic leather. The hydrophobic leather was then dried, moisturized and softened according to conventional processes to obtain antique-style leather.

[0135] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 7.9 mm, the compression rate was 12.1%, the rebound rate was 3.9%, and the total organic carbon content of the alkaline washing waste liquid was 39.7 mg / L.

[0136] Example 14

[0137] The polymer tanned leather was naturally immersed in anhydrous ethanol for dehydration based on its weight, and then mechanically rotated for dehydration to obtain a dehydrated leather blank with a moisture content of 6.1 wt%. 7 wt% of cashew nut shell liquid and 0.8 wt% of nano-zirconium dioxide with a particle size of 30 nm were mixed and applied by brushing and rolling on the flesh surface of the dehydrated leather blank for 30 min. The hydrophobic leather blank was then dried, moisturized and softened according to conventional processes to obtain antique-style leather.

[0138] After sensory evaluation and instrumental measurement, the leather was found to be natural cinnamon in color, with a strong nutty aroma and a dry and non-greasy body. The antique grade was 5 points, the softness was 8.0 mm, the compression rate was 12.2%, the rebound rate was 4.0%, and the total organic carbon content of the alkaline washing wastewater was 77.3 mg / L.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A short-process method for manufacturing antique-style leather without tanning agent, characterized in that: Using bare leather or wet white leather as raw material, first dehydrate it with anhydrous ethanol to obtain dehydrated leather blank, and then treat the dehydrated leather blank with cashew nut shell liquid and nano zirconium dioxide; wherein the moisture content of the bare hide or wet white leather after dehydration is 4-12 wt% based on the weight of the bare hide or wet white leather; Based on the weight of the bare leather or wet white leather, the added amount of the cashew nut shell liquid is 2-12 wt%, and the added amount of the nano zirconium dioxide is 0.2-1.5 wt%.

2. The tanning agent-free short-process manufacturing method for antique-style leather according to claim 1, characterized in that: The raw material of bare skin comprises any one of delimed bare skin, softened bare skin, pickled bare skin and bare skin obtained by pickling-depickling process.

3. The tanning agent-free short-process manufacturing method for antique-style leather according to claim 1, characterized in that: The wet white leather raw material is any one of leathers tanned using a non-chrome metal tanning agent or an organic tanning agent.

4. The tanning agent-free short-process manufacturing method for antique-style leather according to claim 1, characterized in that: The particle size of the nano zirconium dioxide is 20-50 nm.

5. The tanning agent-free short-process manufacturing method for antique style leather according to claim 1, characterized in that: The step of treating the dehydrated leather blank with cashew nut shell oil and nano zirconium dioxide is as follows: mixing the cashew nut shell oil and nano zirconium dioxide and applying the mixture on the flesh surface of the dehydrated leather blank.

6. The tanning agent-free short-process manufacturing method for antique style leather according to claim 1, characterized in that: The cashew nut shell liquid and nano zirconium dioxide are used to treat the dehydrated shell for 5-60 minutes.

7. The tanning agent-free short-process manufacturing method for antique-style leather according to claim 1, characterized in that: After the dehydrated leather blank is treated with cashew nut shell oil and nano zirconium dioxide, the method further comprises drying, rehydrating and softening the treated leather blank.

8. The tanning agent-free short-process manufacturing method for antique-style leather according to claim 3, characterized in that: The leather tanned using a non-chrome metal tanning agent includes any one of aluminum tanned leather, zirconium tanned leather, iron tanned leather, zeolite tanned leather and multi-metal tanning agent tanned leather.

9. The tanning agent-free short-process manufacturing method for antique-style leather according to claim 3, characterized in that: The leather tanned using an organic tanning agent includes any one of vegetable tanned leather, aldehyde tanned leather, active chlorine tanned leather, synthetic tanning agent tanned leather and polymer tanning agent tanned leather.

10. Antique style leather obtained by the tanning agent-free short-process manufacturing method according to any one of claims 1 to 9.

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