Preparation method of light-transmitting leather

Abstract

The invention relates to the technical field of leather manufacturing, in particular to a preparation method of light-transmitting leather. The preparation method provided by the invention comprises the following steps: after a chrome-free tanned leather blank is infiltrated in a transparent treatment solution, the free transparent treatment solution is squeezed out, and then drying is performed to obtain the light-transmitting leather, and the shrinkage temperature of the chrome-free tanned leather blank is 75-99 DEG C; the transparentizing treatment liquid is composed of an eutectic solvent and water, and the mass ratio of the eutectic solvent to the water is 1: (0.2-10). The light-transmitting leather obtained through the method is good in light transmission and excellent in softness, and the hand feeling of genuine leather is kept.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of leather manufacturing, in particular to a preparation method of light-transmitting leather. BACKGROUND

[0002] Animal fur can be obtained through the processes of soaking, liming, deliming, pickling, neutralization and filling, and various kinds of leather products can be prepared. At present, various kinds of leather, such as sofa leather, clothing leather, luggage leather and automobile cushion leather, are not transparent and light-transmitting because the air in the pores of the collagen fibers and the collagen fibers do not match the refractive index of the various materials and collagen fibers absorbed and combined in the leather after the leather is treated by the above processes, which causes refraction, scattering and reflection of light at the interfaces and leads to the non-transparency of the leather. With the increasing demand of consumers for personalized fashion products and the development of electronic product technology, people are more and more fond of adding dynamic light-emitting devices such as LED lights to shoes, clothes and luggage as fashion elements. At present, only some special purpose leathers, such as lampshade leather, shadow leather, parchment and drum skin, have certain light-transmitting properties. These leathers have light-transmitting properties, but are usually hard and brittle, and are not easy to bend. Some of them will produce irreversible marks after being bent, or even break. Obviously, these leathers cannot meet the needs of producing daily leather products. Although materials such as rubber, plastic and silicone can achieve light-transmitting properties, they have a strong plastic feel and are far from the comfortable and natural feel of leather, which greatly reduces the added value of the products. Therefore, the preparation of soft light-transmitting leather that has light-transmitting properties and can be bent can greatly improve the added value of leather.

[0003] The light-transmitting leather prepared by the method in the prior art has certain softness, but still has a strong plastic feel and lacks the feel of real leather. SUMMARY

[0004] Therefore, the present application provides a preparation method of light-transmitting leather, which has good light-transmitting properties and excellent softness, and maintains the feel of real leather.

[0005] The present application provides a preparation method of light-transmitting leather, which includes the following steps:

[0006] After the chrome-free tanned leather blank is soaked in a transparent treatment liquid, the free transparent treatment liquid is squeezed out, and then dried to obtain light-transmitting leather,

[0007] The shrinkage temperature of the chrome-free tanned leather blank is 75-99℃; the transparent treatment liquid is composed of a eutectic solvent and water, and the mass ratio of the eutectic solvent to water is 1:0.2-10.

[0008] Optionally, the eutectic solvent has a eutectic melting point lower than 20℃; the hydrogen bond donor of the eutectic solvent comprises at least one of ethylene glycol, glycerol, malonic acid, 2,2-dihydroxymethyl propionic acid, 2,2-dihydroxymethyl butyric acid, lactic acid, citric acid, oxalic acid, urea and sulfamic acid,

[0009] The hydrogen bond acceptor of the eutectic solvent comprises at least one of quaternary ammonium salt and choline chloride.

[0010] Optionally, the eutectic solvent is composed of choline chloride and lactic acid in a mass ratio of 139:112.5, or composed of choline chloride and glycerol in a mass ratio of 139:184, or composed of choline chloride and urea in a mass ratio of 139:120.

[0011] Optionally, the preparation method of the chrome-free tanning leather blank comprises the following steps:

[0012] (1) main tanning: the pickled raw hide is added into a rotating drum, water and salt are added, and the drum is rotated for 25-35 min, then the pH of the liquid in the drum is adjusted to 3.0-3.2, the first chrome-free tanning agent is added, and the drum is continuously rotated for 110-130 min, then the drum is stopped and the hide is left overnight, to obtain a preliminary tanned leather;

[0013] (2) re-tanning: the preliminary tanned leather is left to stand for 3-7 days, then is cut to a thickness of 1.5 mm or less, and is put into a rotating drum, water is added, and the drum is rotated for 8-12 min, then the pH of the liquid in the drum is adjusted to 5.5-5.8, the second chrome-free tanning agent is added, and the drum is rotated for 2-6 h, then formic acid is added, and the drum is continuously rotated for 18-22 min, then the drum is stopped and the leather is washed out, and is squeezed to obtain a re-tanned leather blank, which is a chrome-free tanned leather blank.

[0014] Optionally, taking 100 parts of the pickled raw hide as a unit, in step (1), the amount of water added is 65-75 parts, and the amount of salt added is 6-8 parts, and the salt is sodium chloride; the amount of the first chrome-free tanning agent added is 5-10 parts; the alkali neutralizer used for the alkali neutralization is at least one of sodium bicarbonate and sodium formate, and the amount of the alkali neutralizer is determined according to the pH of the solution in the drum, which is adjusted to 5.0-5.5; the amount of the second chrome-free tanning agent added is 2.5-3.5 parts; the amount of formic acid added is 0.4-0.6 parts; and in step (2), the amount of water added is 80-150 parts.

[0015] Optionally, the first and second chrome-free tanning agents are each independently at least one of oxazolidine tanning agent, carbamoyl sulfonate tanning agent, tricyanogen tanning agent, aldehyde tanning agent, epoxy synthetic tanning agent, sulfone synthetic tanning agent, zeolite tanning agent and metal tanning agent.

[0016] Optionally, after the re-tanning, the re-tanned leather is sequentially subjected to drying, re-humidification and softening, and the obtained leather after softening is used as a chrome-free tanned leather for infiltration.

[0017] Optionally, the raw hide for the pickled raw skin is goat skin, sheep skin, cow skin, cow skin second layer or pig skin.

[0018] Optionally, after the light-transmitting leather is obtained, the light-transmitting leather is subjected to a relaxing treatment, and then a surface is coated with an adhesive and a transparent finishing agent in sequence, and then dried to form a film.

[0019] Optionally, the transparent finishing agent is a water-based polyurethane emulsion, a casein emulsion, a wax emulsion or a feel agent.

[0020] The present application uses a transparent treatment liquid composed of a eutectic solvent and water to perform transparent treatment on a chrome-free tanned leather, wherein the eutectic solvent has good infiltration on collagen fibers, and the hydrogen bond effect improves the combination of the solvent and the collagen fibers, so that the refractive index of the eutectic solvent and the fibers are kept in synchronization, which is conducive to improving the transparency of the leather, and the hydrogen bond effect also better combines the eutectic solvent and the collagen fibers, avoiding the loss of the eutectic solvent. Using water to dilute the eutectic solvent not only saves cost, but also reduces the greasy feeling caused by the eutectic solvent on the surface of the leather, and is conducive to finishing. The light-transmitting leather obtained by the method has a light transmittance of 32.7-43.6%, and an average softness of 59.5-68.1 mm. The light-transmitting leather has excellent softness and real leather feel while having light transmission. BRIEF DESCRIPTION OF DRAWINGS

[0021] The above and other objects, features and advantages of the present application will become more apparent from the following description of preferred embodiments of the present application taken in conjunction with the accompanying drawings, in which:

[0022] Figure 1 A photo of the light-transmitting leather obtained in Example 1 irradiated by an LED lamp. DETAILED DESCRIPTION

[0023] The present application will be described in detail below through specific embodiments, and those skilled in the art can understand that the specific embodiments below are only for illustrative purposes, and do not limit the scope of the present application in any way. In addition, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If the specific treatment conditions and methods are not explicitly described in the following embodiments, the conditions and methods known in the art can be used for treatment.

[0024] The present application provides a preparation method of light-transmitting leather, comprising the following steps:

[0025] The chrome-free tanned leather blank is immersed in a transparent treatment liquid, free transparent treatment liquid is squeezed off, and then dried to obtain the light-transmitting leather,

[0026] The shrinkage temperature of the chrome-free tanned leather blank is 75-99 DEG C; the transparent treatment liquid is composed of a eutectic solvent and water, and the mass ratio of the eutectic solvent to water is 1:0.2-10.

[0027] The chrome-free tanned leather blank is used as raw material, the tanning agent and the collagen fiber in the leather maintain appropriate crosslinking degree, after being immersed in the transparent treatment liquid composed of the eutectic solvent and water, the hydrogen bond is used to improve the combination of the solvent and the collagen fiber, the refractive index of the eutectic solvent is synchronized with the fiber, the transparency of the leather is improved, the eutectic solvent and the collagen fiber are better combined through the hydrogen bond, the loss of the eutectic solvent is avoided, the use of water to dilute the eutectic solvent can save cost, reduce the greasy feeling caused by the eutectic solvent on the surface of the leather, and is beneficial to finishing.

[0028] In some embodiments of the present application, the preparation method of the chrome-free tanned leather blank comprises the following steps:

[0029] (1) main tanning: the pickled raw hide is added into a rotating drum, water and salt are added, and the rotating drum is rotated for 25-35 min, then the pH of the liquid in the rotating drum is adjusted to 3.0-3.2, the first chrome-free tanning agent is added, and the rotating drum is continuously rotated for 110-130 min, then the alkali is neutralized, and the rotating drum is stopped overnight to obtain the preliminary tanned leather;

[0030] (2) re-tanning: the preliminary tanned leather is aged for 3-7 days, then is cut to a thickness of 1.5 mm or less, and then is put into a rotating drum, water is added, and the rotating drum is rotated for 8-12 min, then the pH of the liquid in the rotating drum is adjusted to 5.5-5.8, the second chrome-free tanning agent is added, and the rotating drum is rotated for 2-6 h, then formic acid is added, and the rotating drum is continuously rotated for 18-22 min, then the rotating drum is washed out, and the water is squeezed out to obtain the re-tanned leather blank as the chrome-free tanned leather blank.

[0031] In some embodiments of the present application, the chrome-free tanned leather blank is prepared by the above method, the shrinkage temperature of the preliminary tanned leather obtained by the main tanning can reach 70-85 DEG C, the mechanical strength is good, and the binding rate of the tanning agent can be further improved after the re-tanning, the shrinkage temperature of the leather is increased by 5-10 DEG C, and the durability of the leather can be improved. The shrinkage temperature of the chrome-free tanned leather blank prepared by the above method is 75-95 DEG C, the crosslinking degree is moderate, the mechanical strength is good, and the light-transmitting leather with the texture of real leather can be obtained by combining with the subsequent transparent treatment liquid immersion step.

[0032] The source of the pickled pelt is not particularly limited in the present application; in some embodiments of the present application, the rawhide material of the pickled pelt is goat skin, sheep skin, cow skin, cow skin two layers or pig skin. The present application does not have special limitations on the specific preparation process of the pickled pelt, and the pelt obtained by using the pickling process of traditional leather processing can be used. The method of the present application does not change the traditional tanning process, and the operation is relatively simple.

[0033] In some embodiments of the present application, taking 100 parts of the mass of the pickled pelt as a basis, the amount of water added in step (1) is 65-75 parts, which can be 67 parts, 70 parts, 72 parts, etc.; the amount of salt added is 6-8 parts, which can be 6 parts, 7 parts and 8 parts, etc.; the salt is sodium chloride, which can be industrial salt; the amount of the first chromium-free tanning agent added is 5-10 parts, which can be 6 parts, 8 parts, 10 parts, etc.; the alkali extracting agent used for alkali extraction and neutralization is at least one of baking soda and sodium formate, and the amount of the alkali extracting agent is adjusted to the pH of the solution in the drum to 5.0-5.5, which can be 5.0, 5.2 and 5.5, etc.; the amount of the second chromium-free tanning agent added is 2.5-3.5 parts, which can be 3 parts; the amount of formic acid added is 0.4-0.6 parts, which can be 0.5 parts; the amount of water added in step (2) is 80-150 parts, which can be 100 parts, 120 parts, 150 parts, etc.

[0034] The present application does not have special limitations on the specific time of the drum overnight, and the conventional drum overnight time of the leather factory can be used, and in the examples of the present application, the specific time of the drum overnight is 12-14h.

[0035] The present application does not have special limitations on the rotation speed of the drum, the horseback aging, the water washing, the water squeezing and other operations, and the conventional parameters in the art can be used.

[0036] In the present application, after the horseback aging in the re-tanning, the leather is cut to a thickness of 1.5mm or less, which can be 1.0-1.4mm, 1.2-1.3mm, 1.0-1.2mm, etc.

[0037] In some embodiments of the present application, the first and second chromium-free tanning agents are each independently at least one of oxazolidine tanning agents, carbamoyl sulfonate tanning agents, tricyanogen tanning agents, aldehyde tanning agents, epoxy synthetic tanning agents, sulfone synthetic tanning agents, zeolite tanning agents and metal tanning agents, preferably oxazolidine tanning agents, carbamoyl sulfonate tanning agents or zirconium metal tanning agents. In embodiments of the present application, the oxazolidine tanning agent is LEATAN OT oxazolidine tanning agent produced by Qilu Lixing Chemical Co., Ltd., the zirconium metal tanning agent is PROSPTAN LMT zirconium metal tanning agent produced by Qilu Lixing Chemical Co., Ltd., and the carbamoyl sulfonate tanning agent is a tanning agent obtained according to the synthesis method of Example A1 in WO2012 / 016907. In the present application, the use of the above-mentioned types of tanning agents can obtain a moderate shrinkage temperature, moderate cross-linking degree and good mechanical strength, can better cooperate with the subsequent infiltration process of the transparentizing treatment solution, is conducive to improving the light transmittance of the leather, and can obtain light-transmitting leather with a true leather feel and better fullness.

[0038] In some embodiments of the present application, after the re-tanning, the re-tanned leather is sequentially subjected to drying, re-humidification and softening, and the obtained leather after softening is used as a chromium-free tanned leather for infiltration. In the present application, the drying, re-humidification and softening after re-tanning do not affect the transparency and shrinkage temperature of the leather, and the drying and re-humidification in the above-mentioned operations can further avoid damage to the fibers of the leather during the treatment process, thereby preventing the leather from being damaged, such as being broken or creased, and the softening can fully open and loosen the fibers, thereby restoring the softness of the leather. The present application does not have special limitations on the specific methods of the above-mentioned operations, and conventional drying, re-humidification and softening operations can be used. In embodiments of the present application, the degree of drying is 12.4-13.1% in terms of the moisture content of the leather; the softening is performed in a softening drum, and the softening time is 8-24h.

[0039] In some embodiments of the present application, the mass ratio of the eutectic solvent to water is 1:0.2-10, preferably 1:0.2-2, and more preferably 1:0.4-2, and can be 1:0.4, 1:1 and 1:1.9, etc.

[0040] In some embodiments of the present application, the eutectic solvent has a co-melting point lower than 20℃, so as to ensure that the eutectic solvent is in a liquid state at room temperature, thereby being able to infiltrate the leather; the hydrogen bond donor of the eutectic solvent includes at least one of ethylene glycol, glycerol, malonic acid, 2,2-dimethylmalonic acid, 2,2-dimethylbutyric acid, lactic acid, citric acid, oxalic acid, urea and sulfamic acid, and is preferably at least one of lactic acid, glycerol and urea; and the hydrogen bond acceptor of the eutectic solvent includes at least one of quaternary ammonium salt and choline chloride, and is preferably choline chloride.

[0041] In some embodiments of the present application, the eutectic solvent is composed of choline chloride and lactic acid at a mass ratio of 139:112.5, or composed of choline chloride and glycerol at a mass ratio of 139:184, or composed of choline chloride and urea at a mass ratio of 139:120. The present application does not have special limitations on the specific source of the lactic acid, and commercially available lactic acid can be used. In the examples of the present application, the lactic acid is JDLAY80 lactic acid produced by Henan Jindan Lactic Acid Technology Co., Ltd.

[0042] The present application does not have special limitations on the amount of the transparent treatment solution, and the chrome-free tanned leather blank can be completely immersed. The present application does not have special limitations on the specific conditions of the immersion, and the leather can be completely wetted without dry places. In the examples of the present application, the immersion is carried out by soaking the chrome-free tanned leather blank in the transparent treatment solution at room temperature, and the immersion time is 1-10 h, specifically 4 h, 5 h, 6 h, etc., preferably 4-6 h.

[0043] In the present application, after the chrome-free tanned leather blank is immersed in the transparent treatment solution, the transparent treatment solution is squeezed out, and then dried. The present application does not have special limitations on the method of squeezing out the transparent treatment solution, and the free (i.e. not adsorbed) transparent treatment solution can be squeezed out by using a conventional mechanical squeezing method. The present application does not have special limitations on the drying, and a conventional drying method can be used. In the examples of the present application, the drying is carried out at 40-50°C for 18-24 h.

[0044] In some embodiments of the present application, after the light-transmitting leather is obtained, the light-transmitting leather is further subjected to a stretching treatment, and then a glue and a transparent finishing agent are coated on the surface in sequence, and then dried to form a film. In the present application, the light-transmitting leather is further coated to further reduce the loss of the eutectic solvent, thereby more durably retaining the eutectic solvent and avoiding affecting the light transmittance.

[0045] The present application does not have special limitations on the specific operation of the stretching treatment, and a conventional stretching treatment can be used. In the examples of the present application, the stretching treatment is carried out by using a stretching machine, and the specific feeding speed is 2-5 m / min, and the oil pump pressure is 4.5-5.5 MPa. The present application does not have special limitations on the type of the glue, and a conventional transparent glue can be used, such as the glue commonly used in leather and shoe materials. In some embodiments of the present application, the transparent finishing agent is a water-based polyurethane emulsion, a casein emulsion, a wax emulsion, or a hand feel agent.

[0046] The technical solutions in the present application will be described clearly and completely in combination with the drawings and examples. The examples of the present application are only used as examples, and all other examples obtained by those skilled in the art without making creative efforts belong to the scope of protection of the present application.

[0047] The test method of shrinkage temperature in the embodiment is QB / T 2713-2005 Determination of Shrinkage Temperature of Leather-Physical and Mechanical Tests.

[0048] Example 1

[0049] Main tanning: 100 parts of goat skin immersed in acid naked skin was added to a rotating drum, 70 parts of water and 7 parts of industrial salt were added, and the rotating drum was rotated for 30 min. The pH of the liquid in the rotating drum was 3.1. 6 parts of oxazolidine tanning agent (LEATAN OT model oxazolidine tanning agent produced by Qihelihe Chemical Co., Ltd.) was added, and the rotating drum was continuously rotated for 120 min. Then, soda was used for alkaline neutralization, the pH was adjusted to 5.5, and the drum was stopped overnight (13 h) to obtain preliminary tanned leather. The shrinkage temperature of the preliminary tanned leather was tested to be 81℃.

[0050] Re-tanning: After the preliminary tanned leather was aged for 7 days, it was cut to a thickness of 1.0-1.4 mm and placed in a rotating drum. 100 parts of water was added, and the rotating drum was rotated for 10 min. The pH was measured to be 5.3. The pH of the liquid in the rotating drum was adjusted to 5.6 using soda. Then, 3 parts of oxazolidine tanning agent (LEATAN OT model oxazolidine tanning agent produced by Qihelihe Chemical Co., Ltd.) was added, and the rotating drum was rotated for 4 h. 0.5 parts of formic acid was added, and the rotating drum was rotated for 20 min. Then, the leather was washed out of the drum and squeezed to obtain re-tanned leather.

[0051] The re-tanned leather was dried in a vacuum dryer at 60℃ for 4 h, then sun-dried to a leather moisture content of 13.1%, then re-humidified, and then broken down in a breaking drum for 24 h to obtain chrome-free tanned leather. The shrinkage temperature of the chrome-free tanned leather was tested to be 88℃.

[0052] The chrome-free tanned leather was immersed in a transparent treatment liquid for 6 h, then squeezed to remove the transparent treatment liquid, and then dried at 50℃ for 18 h to obtain a light-transmitting leather; wherein the transparent treatment liquid was composed of 139 parts of choline chloride, 112.5 parts of lactic acid (solid content of 80%, JDLAY80 model lactic acid produced by Henan Jindan Lactic Acid Technology Co., Ltd.), and 100 parts of water.

[0053] The light-transmitting leather was stretched using a stretching machine at a feed speed of 2 m / min and an oil pump pressure of 4.5 MPa, then 1 part of adhesive JL250 produced by Dongguan Jili New Material Co., Ltd. was sprayed on the outer surface of the leather, and then naturally air-dried. Then, 5 parts of water-based polyurethane POLIPUR U-A120 produced by Qihelihe Chemical Co., Ltd. was sprayed on the outer surface of the leather, and then naturally air-dried. Then, the leather was further dried in a constant temperature oven at 60℃ to form a film, thereby obtaining a coated light-transmitting leather.

[0054] Example 2

[0055] Main tanning: 100 parts of rawhide of cowhide immersed in acid was added into a rotating drum, then 70 parts of water and 7 parts of industrial salt were added, and rotated for 30 min. The pH of the liquid in the rotating drum was tested to be 3.0. 10 parts of zirconium metal tanning agent (PROSPTAN LMT produced by Qihelihe Chemical Co., Ltd.) was added, and the rotation was continued for 120 min. Then soda was used for alkaline extraction and neutralization, and the pH was adjusted to 5.5. The drum was stopped overnight (12 h) to obtain the preliminary tanned leather. The shrinkage temperature of the tested preliminary tanned leather was 89℃.

[0056] Re-tanning: After the preliminary tanned leather was aged for 3 days, it was cut to a thickness of 1.2-1.3 mm and placed in a rotating drum. 120 parts of water was added, and the rotation was continued for 10 min. The pH was tested to be 5.5. Then 3 parts of zirconium metal tanning agent (PROSPTAN LMT produced by Qihelihe Chemical Co., Ltd.) was added, and the rotation was continued for 6 h. 0.5 parts of formic acid was added, and the rotation was continued for 20 min. Then the leather was washed out of the drum and squeezed to obtain the re-tanned leather.

[0057] The re-tanned leather was dried in a vacuum dryer at 60℃ for 3 h, then sun-dried to a leather moisture content of 12.6%, then re-humidified, and then softened in a softening drum for 12 h to obtain the chrome-free tanned leather blank. The shrinkage temperature of the chrome-free tanned leather blank was tested to be 99℃.

[0058] The chrome-free tanned leather blank was immersed in a transparent treatment liquid for 4 h, then the transparent treatment liquid was squeezed out, and the leather was dried at 45℃ for 24 h to obtain the transparent leather; wherein the transparent treatment liquid was composed of 139 parts of choline chloride, 184 parts of glycerol and 100 parts of water.

[0059] The transparent leather was stretched using a stretching machine at a feeding speed of 3 m / min and an oil pump pressure of 5 MPa, then 1 part of adhesive LF725 from Jiangsu Xinyi Synthetic New Material Co., Ltd. was sprayed on the outer surface of the leather, and then naturally air-dried. Then 8 parts of water-based polyurethane POLIPUR U-A 120 produced by Qihelihe Chemical Co., Ltd. was sprayed on the outer surface of the leather, and then naturally air-dried. Then the leather was further dried in a constant temperature oven at 50℃ to form a film, thereby obtaining the transparent leather with a coating.

[0060] Example 3

[0061] Main tanning: 100 parts of rawhide of pigskin immersed in acid was added into a rotating drum, then 70 parts of water and 7 parts of industrial salt were added, and rotated for 30 min. The pH of the liquid in the rotating drum was tested to be 3.1. 8 parts of carbamoyl sulfonate tanning agent (obtained by the synthetic method of Example A1 in the reference patent WO2012 / 016907) was added, and the rotation was continued for 120 min. Then soda was used for alkaline extraction and neutralization, and the pH was adjusted to 5.2. The drum was stopped overnight (14 h) to obtain the preliminary tanned leather. The shrinkage temperature of the tested preliminary tanned leather was 71℃.

[0062] Re-tanning: after the initial tanning leather was aged for 4 days, it was shaved to a thickness of 1.0-1.2 mm, put into a rotating drum, 150 parts of water was added, and rotated for 10 min, the pH was measured to be 5.0, the pH of the liquid in the rotating drum was adjusted to 5.5 using baking soda, then 3 parts of zirconium metal tanning agent (a tanning agent of PROSPTAN LMT model produced by Qihelihou Chemical Co., Ltd.) was added, rotated for 5 h, 0.5 parts of formic acid was added, rotated for 20 min, then washed out of the drum with water, and squeezed to obtain re-tanned leather,

[0063] The re-tanned leather was vacuum dried at 60℃ for 2 h, then sun dried until the moisture content of the leather was 12.4%, then re-humidified, and then broken down in a breaking drum for 24 h to obtain chrome-free tanned leather blanks. The shrinkage temperature of the chrome-free tanned leather blanks was tested to be 79℃.

[0064] The chrome-free tanned leather blanks were immersed in a transparentizing treatment liquid for 5 h, then squeezed to remove the transparentizing treatment liquid, and dried at 40℃ for 20 h to obtain light-transmitting leather; the transparentizing treatment liquid was composed of 139 parts of choline chloride, 120 parts of urea, and 500 parts of water.

[0065] The light-transmitting leather was stretched using a stretching machine at a feeding speed of 5 m / min and an oil pump pressure of 5.5 MPa, then 1 part of adhesive LF725 from Jiangsu Xinyi Synthetic New Material Co., Ltd. was sprayed on the outer surface of the light-transmitting leather, and naturally air-dried, then 4 parts of water-based polyurethane POLIPUR U-A 120 produced by Qihelihou Chemical Co., Ltd. was sprayed, and naturally air-dried, and then further baked in a constant temperature oven at 70℃ to form a film, thereby obtaining coated light-transmitting leather.

[0066] The light-transmitting leather and the coated light-transmitting leather obtained in Examples 1-3 were both touched by hand and had a real leather feel.

[0067] The light-transmitting leather and the coated light-transmitting leather obtained in Examples 1-3 were tested for light transmittance using method B spectrophotometer method in GB / T 2410-2008 "Determination of Light Transmittance and Haze of Transparent Plastics", the average softness was tested using a leather softness instrument, and the shrinkage temperature of the light-transmitting leather was tested, and the results are shown in Table 1.

[0068] Table 1 Performance test of light-transmitting leather and coated light-transmitting leather obtained in Examples 1-3

[0069]

[0070] As can be seen from Table 1, the light-transmitting leather obtained by the preparation method provided by the present application not only has a real leather feel, but also has excellent light-transmitting property and softness.

[0071] In the examples, the LED soft screen (maximum power is 5V*2A=10W (in the case of white light), that is, the white light in the figure is 10W power, and the light of other colors is lower than 10W) is used to irradiate the light-transmitting leather obtained in Examples 1-3, and obvious light can be seen on the other side, that is, the light-transmitting leather obtained by the present application can also transmit the light of the weaker LED lamp. Figure 1 The transmission of the LED lamp irradiating the light-transmitting leather obtained in Example 1 of the present application is shown, and the light-transmitting leather obtained in Examples 2-3 also has similar effects.

[0072] Although the preferred embodiments of the present application have been shown and described, it is contemplated that those skilled in the art can design various modifications to the present application within the spirit and scope of the appended claims.

Claims

1. A method for preparing translucent leather, comprising the following steps: After immersing the chrome-free tanned leather blank in a transparentizing solution, the free transparentizing solution is squeezed off, and then dried to obtain translucent leather. in, The shrinkage temperature of the chromium-free tanned leather blank is 75-99℃; the transparent treatment liquid is composed of a eutectic solvent and water, and the mass ratio of the eutectic solvent to water is 1:0.2-10.

2. The preparation method according to claim 1, characterized in that, The eutectic solvent has a melting point below 20°C; the hydrogen bond donor of the eutectic solvent includes at least one selected from ethylene glycol, glycerol, malonic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, lactic acid, citric acid, oxalic acid, urea, and aminosulfonic acid. The hydrogen bond acceptors of the eutectic solvent include at least one of quaternary ammonium salts and choline chloride.

3. The preparation method according to claim 2, characterized in that, The eutectic solvent is composed of choline chloride and lactic acid in a mass ratio of 139:112.5, or choline chloride and glycerol in a mass ratio of 139:184, or choline chloride and urea in a mass ratio of 139:

120.

4. The preparation method according to claim 1, characterized in that, The preparation method of the chromium-free tanned leather blank includes the following steps: (1) Main tanning: Add the pickled naked hide to the drum, add water and salt, rotate for 25-35 minutes, then adjust the pH of the liquid in the drum to 3.0-3.2, add the first chromium-free tanning agent, continue to rotate for 110-130 minutes, then remove the alkali to neutralize, stop the drum overnight, and obtain the initial tanned leather; (2) Retanning: After the primary tanned leather is aged for 3-7 days, it is shaved to a thickness of less than 1.5 mm, then placed in a drum, water is added, and the drum is rotated for 8-12 minutes. The pH of the liquid in the drum is adjusted to 5.5-5.8, then a second chromium-free tanning agent is added, and the drum is rotated for 2-6 hours. Then formic acid is added, and the drum is rotated for another 18-22 minutes. The leather is then washed with water and squeezed to obtain a retanned leather blank, which is used as a chromium-free tanned leather blank.

5. The preparation method according to claim 4, characterized in that, taking 100 parts by weight of the pickled hide as an example, in step (1), the amount of water added is 65-75 parts, the amount of salt added is 6-8 parts, and the salt is sodium chloride; the amount of the first chromium-free tanning agent added is 5-10 parts; the alkali-refining agent used for alkali neutralization is at least one of sodium bicarbonate and sodium formate, and the amount of the alkali-refining agent is adjusted to adjust the pH of the solution in the drum to 5.0-5.5; the amount of the second chromium-free tanning agent added is 2.5-3.5 parts; the amount of formic acid added is 0.4-0.6 parts; and the amount of water added in step (2) is 80-150 parts.

6. The preparation method according to claim 4, characterized in that, The first chromium-free tanning agent and the second chromium-free tanning agent are each independently at least one of the following: oxazolidine tanning agents, carbamoyl sulfonate tanning agents, cyanuric chloride tanning agents, aldehyde tanning agents, epoxy synthetic tanning agents, sulfone synthetic tanning agents, zeolite tanning agents, and metal tanning agents.

7. The preparation method according to claim 4, characterized in that, After retanning, the process further includes drying, remoistening, and softening the retanned leather blank in sequence, and then impregnating the softened leather blank as a chromium-free tanned leather blank.

8. The preparation method according to claim 4, characterized in that, The raw materials for the acid-treated raw hides are goatskin, sheepskin, cowhide, cowhide split, or pigskin.

9. The preparation method according to claim 1, characterized in that, after obtaining the translucent leather, the method further includes stretching the translucent leather, coating the surface with an adhesive and a transparent finishing agent in sequence, and then drying it to form a film.

10. The preparation method according to claim 9, characterized in that, The transparent coating agent is a water-based polyurethane emulsion, casein emulsion, wax emulsion, or hand feel agent.

Images