Method for preparing an environmentally friendly transparent conductive leather

Abstract

The application discloses a preparation method of environment-friendly transparent conductive leather, comprising the following steps: soaking the bare skin after deliming and softening in an acid or alkali aqueous solution at 15-35 DEG C for 1-14 days; placing the obtained skin in a rotating drum, adding 100%-500% of the weight of the oil tanning agent, and starting the rotating drum to tan for 2-48 h at 15-35 DEG C; placing the obtained skin in a bleaching solution, and standing for 10-30 min; taking out the obtained skin, placing it in a rotating drum, adding 150%-500% of the weight of the water-retaining agent, and rotating for 1-72 h, and then drying the skin on a board at 40-60 DEG C for 6-72 h, with the water content being controlled to be 20%-30%; mixing a transparent conductive material with a solvent or an adhesive to prepare a conductive solution with a mass fraction of 2%-20%; and adding the prepared conductive solution to the obtained transparent leather, and drying the leather on a board at 40-60 DEG C for 3-6 h. The transparent conductive leather prepared by the method has good light transmittance, rubbing resistance, tensile property, electrical property and environmental friendliness, and has a wide application prospect in the fields of flexible display screens, transparent optical elements and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing an environmentally friendly transparent conductive leather, in particular to a transparent conductive leather, a transparent optical element, a transparent medical material, a flexible electronic display device and a method for preparing the same. BACKGROUND

[0002] Leather is a natural bio-based material composed of peptide chains, collagen, collagen fibrils and collagen fibers in turn, and has the characteristics of natural flexibility, durability and biodegradability, so it has a wide range of applications in clothing, luggage and automotive interiors. However, traditional leather is opaque, which limits its application in flexible displays, transparent medical materials and wearable flexible electronic devices. There are two reasons why traditional leather is opaque. First, the refractive index of the leather collagen fiber structure and the refractive index of the air in the leather pores differ greatly in the internal structure of the leather. Second, because the tanning process in leather processing mostly uses vegetable tanning, chrome tanning or aluminum tanning, which makes it appear the color of the tanning agent.

[0003] Among the existing methods for producing transparent leather, one method uses ion liquid soaking of chrome tanned leather to prepare transparent leather. The final product inevitably has a blue color after chrome tanning treatment, and the light transmittance is relatively low. Transparent leather can also be prepared by treating the dehydrated and softened raw hide with multi-functional active substances or polyols. Although the product produced by this method has high light transmittance and no color, its durability is poor because it has not been tanned. Transparent leather can also be prepared using the principle of matching refractive indices, but by polymerizing high molecular weight polymers in situ within the raw hide, the original skeleton of the raw hide is replaced, losing its biodegradable characteristics.

[0004] Moreover, the existing transparent leather lacks exploration in the field of conductivity, limiting its application in smart flexible electronic devices, touch screens, flexible circuit boards and other fields in smart wearable technology. In addition, transparent conductive leather can also be used to create more innovative and unique designs. By adding conductive functions, more diversified lighting effects, display functions, etc. can be achieved on transparent leather, adding more value and appeal to the product.

[0005] Therefore, it is very important to develop a colorless, high-transmittance and environmentally friendly transparent conductive leather production method to improve its quality and application range. SUMMARY

[0006] The purpose of the present application is to provide a method for preparing an environmentally friendly transparent conductive leather, which solves one or more of the above-mentioned problems in the prior art.

[0007] In one aspect, the present application provides a method for preparing an environmentally friendly transparent conductive leather, comprising the following steps:

[0008] Step 1. Swelling: The delimed and softened rawhide is soaked in an acid or base aqueous solution at 15-35 °C for 1-14 days;

[0009] Step 2. Oil tanning: The rawhide obtained in step 1 is weighed and placed in a rotating drum, and an oil tanning agent is added at 100-500% of the weight of the rawhide, and the drum is started, and the tanning is carried out at 15-35 °C for 2-48 h, so that the oil tanning agent is fully filled in the pores of the rawhide;

[0010] Step 3. Bleaching: The rawhide obtained in step 2 is placed in a bleaching solution and soaked for 10-30 min;

[0011] Step 4. Water retention treatment and drying: The rawhide obtained in step 3 is taken out and placed in a rotating drum, and a water retention agent is added at 150-500% of the weight of the rawhide, and the drum is rotated for 1-72 h, and then the rawhide is dried on a stretching board at 40-60 °C for 6-72 h, and the water content is controlled at 20-30%;

[0012] Step 5. Preparation of transparent conductive solution: A transparent conductive material is mixed with a solvent or adhesive to prepare a conductive solution with a mass fraction of 2-20%, and the mixture is uniformly mixed to obtain stable conductive properties;

[0013] Step 6. Conductive treatment: The conductive solution prepared in step 5 is added to the transparent rawhide obtained in step 4, and the mixture is dried on a stretching board at 40-60 °C for 3-6 h.

[0014] In some embodiments, the rawhide after deliming and softening in step 1 is selected from one of the following: cow head leather, cow two-layer leather, sheepskin, goat skin, or pigskin.

[0015] In some embodiments, the acid in step 1 is selected from one of the following: sulfuric acid, nitric acid, or hydrochloric acid, and the base is selected from one of the following: sodium hydroxide, potassium hydroxide, or calcium hydroxide.

[0016] In some embodiments, the oil tanning agent in step 2 is selected from one or more of the following: fish oil, lanolin, castor oil, olive oil, rapeseed oil, or linseed oil.

[0017] In some embodiments, the bleaching solution in step 3 is selected from one of the following: sodium peroxide, hydrogen peroxide, sodium hypochlorite, sodium chlorite, or oxalic acid.

[0018] In some embodiments, the water retention agent in step 4 is selected from one or more of the following: propylene glycol, sorbitol, polyethylene glycol, glycerol, sodium hyaluronate, urea, or trehalose.

[0019] In some embodiments, the rotating speed of the drum in steps 2 and 4 is 80-150 r / min.

[0020] In some embodiments, the transparent conductive material in step 5 is selected from any one or mixture of indium tin oxide (ITO), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), silver nanowires (AgNWs), copper oxide (Cu2O), and the solvent or adhesive is one or more of water, ethanol, isopropanol, tetrahydrofuran, 1,2-dimethoxyethane (DME), epoxy resin, acrylate resin, or polyurethane.

[0021] In some embodiments, the conductive solution in step 6 is added by one or more of spraying, printing, suction filtration, or impregnation.

[0022] In another aspect, the present application provides a transparent conductive leather prepared by the above method.

[0023] Advantages of the present application:

[0024] The present application selects dehydrated and softened raw hide as raw material, and develops an environmentally friendly preparation process of transparent conductive leather. Through the steps of swelling, bleaching, drum tanning, etc., a transparent leather with excellent light transmittance can be obtained. Using drum tanning can make the oil tanning agent and water retaining agent fully fill in the swollen raw hide fibers, significantly enhance the bonding force between the reaction raw materials and the raw hide, and form a more tough skeleton, so that the transparent leather has strong friction resistance and tensile resistance. At the same time, the transparent conductive material is added to make it have good electrical properties. The raw materials used have relatively small environmental impact during production and processing, and the final product can be decomposed by microorganisms in the natural environment, which can reduce damage to the environment and ecosystem, and meet the current environmental protection standards and sustainable development requirements.

[0025] The present application selects different oil tanning agents, bleaching agents, water retaining agents, and transparent conductive materials, and uses drum tanning to prepare a transparent leather with high light transmittance, friction resistance, tensile resistance, excellent conductivity, and environmental friendliness, which can be used for flexible display screens. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The photo and UV-Vis-NIR spectrum of the transparent conductive leather prepared in Example 1 of the present application;

[0027] Figure 2 The scanning electron microscope images of the surface and cross section of the transparent conductive leather prepared in Example 1 of the present application;

[0028] Figure 3 The surface scanning electron microscope images of the transparent conductive leather prepared in Example 1 of the present application after bending 500 times and rubbing 500 times;

[0029] Figure 4 A tensile stress-strain curve of the transparent conductive leather prepared in Example 1 of the present application;

[0030] Figure 5 A resistance change graph of the transparent conductive leather prepared in Example 1 of the present application in a room temperature environment. DETAILED DESCRIPTION

[0031] The present application will be further described in conjunction with examples. The following examples are only used to more clearly illustrate the performance of the present application, and cannot be limited to the following examples.

[0032] Example 1:

[0033] In this example, we select the deashed and softened sheepskin as raw material, and fish oil is selected as oil tanning agent to prepare transparent leather.

[0034] First, the deashed and softened sheepskin is cut to a specific size, washed with pure water, and ready for use.

[0035] Dissolve hydrochloric acid in water to prepare a 6% mass fraction hydrochloric acid solution, mix it with the raw skin so that it is immersed in the raw skin, and stand for 5 days of immersion. After the reaction is completed, the excess reaction solution is poured out, the skin is picked up with tweezers, the excess hydrochloric acid on the surface is washed off with pure water, and dried.

[0036] After the acid swelling of the raw skin, it is placed in a drum, 200% of fish oil by mass is added, the rotation speed is set to 120 r / min, and tanning is carried out at 30℃ for 3 h. After the reaction, the excess reaction solution is poured out, the leather is picked up with tweezers, and the excess fish oil on the surface is washed off with pure water and dried.

[0037] Prepare a 15% mass fraction sodium hypochlorite solution, add the above treated leather, and stand for 20 min of immersion. After the reaction, the excess reaction solution is poured out, the leather is picked up with tweezers, the excess bleaching agent on the surface is washed off with pure water, and dried.

[0038] Dissolve sorbitol in water to prepare a 10% mass fraction water-retaining agent solution, mix it with the above treated leather, and place it in a drum, the amount is 180% of the weight of the leather, the rotation speed is set to 100 r / min, and tanning is carried out at 30℃ for 1 h. After the reaction is completed, the excess reaction solution is poured out, the leather is picked up with tweezers, the excess water-retaining agent on the surface is washed off with pure water, and dried.

[0039] The transparent leather obtained after the above steps is dried on a stretching board at 45℃ for 12 h, and the water content is controlled at 20%-30%.

[0040] The silver nanowire powder was added to a mixed solution of ethanol and water, and stirred using a magnetic stirrer until a uniformly dispersed state was achieved. The silver nanowires were diluted to a mass fraction of 5% in an aqueous solution by adding an appropriate amount of purified water. Ultrasonic treatment was used to disperse them.

[0041] The silver nanowire aqueous solution with a mass fraction of 5% prepared in the above step was added dropwise uniformly to ensure that the entire transparent leather was covered and a uniform film was formed, and then subjected to suction filtration. The leather was dried on a tenter at 40°C for 4 h to accelerate the curing process.

[0042] Example 1 was tested:

[0043] From Figure 1 it can be seen that the transparent conductive leather prepared in Example 1 has a high light transmittance, and analysis by ultraviolet-visible near-infrared spectrogram shows that the light transmittance in the visible light region can reach 75% or more.

[0044] From Figure 2 it can be seen that after drum tanning, the oil tanning agent is well combined with the leather, and the oil tanning agent is tightly combined with the collagen fiber bundles, and subsequent use of a water retention agent to fill the inside makes the surface smooth and has excellent stability.

[0045] The transparent conductive leather was placed on a friction tester, the pressure of the friction tester was set to 50 kPa, the grit number of the sandpaper was 1000, and the number of rubs was 500. By comparing the scanning electron microscope images before and after friction, it can be seen that the transparent conductive leather only has a slight surface damage, as shown in Figure 3 . This proves that the transparent conductive leather prepared by the method has strong wear resistance.

[0046] The transparent conductive leather was placed on a mechanical tester for tensile testing, and the stress-strain curve was obtained, as shown in Figure 4 . Analysis shows that the maximum stress it can withstand can reach 8 MPa, which proves that the transparent conductive leather prepared by the method has good tensile properties.

[0047] Ten batches of transparent conductive leather were prepared by the same method, and their resistances were tested, as shown in Figure 5 . Analysis shows that the resistance of each batch is below 500 ohms, which proves that the transparent conductive leather prepared by the method has good electrical properties.

[0048] Example 2:

[0049] In this example, we selected pigskin after deliming and softening as the raw material, and castor oil and rapeseed oil as the oil tanning agent to prepare transparent leather.

[0050] First, the pigskin after deliming and softening was cut to a specific size and washed with purified water for use.

[0051] Sulfuric acid was dissolved in water to prepare a 3% sulfuric acid solution by mass, which was mixed with the raw hide so that it was immersed in the solution. The solution was left to stand for 7 days. After the reaction was completed, the excess solution was poured out, the hide was picked up with tweezers, and the excess sulfuric acid on the surface was washed off with pure water. The hide was dried and weighed.

[0052] The acid-swollen raw hide was placed in a rotating drum, and 230% of the mass of the raw hide of a mixed oil tannage of castor oil and rapeseed oil was added at a ratio of 1:2. The rotation speed was set to 80 r / min, and the tanning was performed at 25°C for 5 h. After the reaction, the excess solution was poured out, the leather was picked up with tweezers, and the excess oil tannage on the surface was washed off with pure water. The leather was dried.

[0053] A 20% oxalic acid solution by mass was prepared, and the above-processed leather was added and left to stand for 15 min. After the reaction, the excess solution was poured out, the leather was picked up with tweezers, and the excess bleaching solution on the surface was washed off with pure water. The leather was dried.

[0054] Polyethylene glycol was dissolved in water to prepare a 10% water-retaining agent solution by mass, which was mixed with the above-processed leather and placed in a rotating drum at a dosage of 200% of the mass of the leather. The rotation speed was set to 120 r / min, and the tanning was performed at 30°C for 2 h. After the reaction was completed, the excess solution was poured out, the leather was picked up with tweezers, and the excess water-retaining agent on the surface was washed off with pure water. The leather was dried.

[0055] The transparent leather obtained after the above steps was dried on a stretching board at 50°C for 8 h, and the water content was controlled to be 20%-30%.

[0056] Indium oxide and tin oxide powders were mixed uniformly at a ratio of 1:2, and the mixed powders were added to isopropyl alcohol to prepare a 5% indium tin oxide coating material by mass. The powders in the solvent were mixed and dispersed sufficiently using a shaking ball mill until a uniform coating solution was obtained.

[0057] The 5% indium tin oxide coating material by mass was dropped onto the center of the transparent leather, and a spin coater was started at a speed of 1000 RPM to uniformly distribute the coating solution on the surface of the transparent leather. The leather was dried on a stretching board at 45°C for 3 h to accelerate the curing process.

[0058] Example 3:

[0059] In this example, dehydrated and softened cow head leather was selected as the raw material, and rapeseed oil was used as the oil tannage to prepare transparent leather.

[0060] First, the dehydrated and softened cow head leather was cut to a specific size and washed with pure water.

[0061] Potassium hydroxide was dissolved in water to prepare a 5% potassium hydroxide solution, which was mixed with the raw hide so that the solution covered the hide. The hide was left to soak for 12 days. After the reaction was complete, the excess solution was poured off, the hide was picked up with tweezers, and the excess solution was washed off with purified water. The hide was then dried and weighed.

[0062] The alkali-swollen raw hide was placed in a rotating drum, and 200% of the mass of the hide was added as rapeseed oil. The rotation speed was set to 150 r / min, and the tanning was carried out at 30°C for 8 h. After the reaction, the excess solution was poured off, the leather was picked up with tweezers, and the excess oil tanning agent was washed off with purified water. The leather was then dried.

[0063] A 10% hydrogen peroxide solution was prepared, and the above-treated leather was added to the solution. The solution was left to soak for 10 min. After the reaction, the excess solution was poured off, the leather was picked up with tweezers, and the excess bleaching solution was washed off with purified water. The leather was then dried.

[0064] Trehalose was dissolved in water to prepare a 15% water-retaining agent solution, which was mixed with the above-treated leather and placed in a rotating drum. The amount of the solution was 180% of the mass of the leather, the rotation speed was set to 100 r / min, and the tanning was carried out at 35°C for 3 h. After the reaction, the excess solution was poured off, the leather was picked up with tweezers, and the excess water-retaining agent was washed off with purified water. The leather was then dried.

[0065] The transparent leather obtained after the above steps was dried on a stretching board at 45°C for 10 h, and the water content was controlled to be 20%-30%.

[0066] A water solution of polystyrene sulfonate and 3,4-ethylenedioxythiophene monomers was mixed, and the pH value was adjusted to 3. The mixture was mixed with potassium permanganate under a nitrogen atmosphere and was ultrasonically treated for 10 min. The ultrasonically treated reaction solution was reacted at 25°C for 10 h to obtain a PEDOT:PSS polymer. The polymer was dispersed in isopropyl alcohol to prepare a 2% PEDOT:PSS coating.

[0067] The transparent leather was sprayed with the 2% PEDOT:PSS coating at a distance of 10 cm from the transparent leather. The coating was uniformly sprayed on the surface of the transparent leather at a distance of 10 cm from the transparent leather, and the spraying speed and angle were kept consistent. The leather was dried on a stretching board at 40°C for 5 h to accelerate the curing process.

[0068] Example 4:

[0069] In this example, deashed and softened cow split leather was selected as the raw material, and olive oil and lanolin were selected as the oil tanning agent to prepare transparent leather.

[0070] First, the deashed and softened cow split leather was cut to a specific size, and was washed with purified water.

[0071] Dissolve calcium hydroxide in water to prepare a 6% calcium hydroxide solution by mass, mix it with the raw hide, and make it submerge the raw hide. Let it stand for 10 days. After the reaction is completed, pour out the excess reaction solution, pick up the hide with tweezers, wash off the excess alkali solution on the surface with pure water, dry and weigh.

[0072] Put the alkali-swollen raw hide in a drum, add 250% of olive oil and lanolin mixed tanning agent by mass, with a mass ratio of 3:2, set the rotation speed to 100 r / min, and tan at 25°C for 12 h. After the reaction, pour out the excess reaction solution, pick up the leather with tweezers, and wash off the excess oil tanning agent on the surface with pure water, and dry.

[0073] Prepare a 8% sodium chlorite solution by mass, add the above treated leather, and stand for 10 min. After the reaction, pour out the excess reaction solution, pick up the leather with tweezers, wash off the excess bleaching solution on the surface with pure water, and dry.

[0074] Dissolve polyethylene glycol and glycerol in water to prepare a 20% water-retaining agent solution by mass, with a mass ratio of 1:1, mix it with the leather treated above, and put it in a drum, with a dosage of 300% of the leather weight, set the rotation speed to 120 r / min, and tan at 30°C for 5 h. After the reaction is completed, pour out the excess reaction solution, pick up the leather with tweezers, wash off the excess water-retaining agent on the surface with pure water, and dry.

[0075] Dry the transparent leather obtained after the above steps on a stretching board at 55°C for 10 h, and control the water content to 20%-30%.

[0076] Dissolve copper sulfate pentahydrate in deionized water, add a mixed solution of glucose, sodium hydroxide, and PVP, adjust the pH to 1, then add a sodium hypophosphite solution, and after the reaction, separate the product by high-speed centrifugation, wash it with deionized water and anhydrous ethanol, and dry it in a vacuum drying oven for 12 h to obtain copper nanoparticles. Perform oxidation treatment on the copper nanoparticles to form copper oxides. Disperse the copper oxides in tetrahydrofuran to prepare a 3% copper oxide coating by mass.

[0077] Place the transparent leather on a printing table, pour the above-mentioned 3% copper oxide coating by mass into the silk screen, evenly scrape the coating over the silk screen with a scraper, and transfer it to the surface of the transparent leather through the image openings on the screen. Dry on a stretching board at 50°C for 3 h to accelerate the curing process.

[0078] Therefore, the transparent leather prepared by the present application selects the softened raw hide as raw material, and the oil tanning agent is fully combined with the fiber bundle of the raw hide through drum tanning, the oil tanning agent can obviously improve the transparency of the leather, the tanning method also retains the mechanical strength of the leather, enhances the durability, the water retention agent combined with the transparent leather makes the leather have excellent friction resistance, tensile resistance and excellent water retention. At the same time, the addition of transparent conductive material makes it have good electrical properties, which can widen its application in the fields of flexible display screen, transparent optical element and the like. The raw materials and processing materials have less influence on the environment in the processing process, and the transparent leather produced can be decomposed by microorganisms in the natural environment, and has the characteristics of environmental friendliness.

[0079] The above description of disclosed embodiments enables one skilled in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an environmentally friendly transparent conductive leather, characterized in that, Includes the following steps: Step 1. Expansion: Immerse the delimed and softened bare hides in an acid or alkaline aqueous solution at 15-35℃ for 1-14 days; Step 2. Oil Tanning: Weigh the hide obtained in Step 1, place it in a drum, add 100%-500% of its weight of oil tanning agent, start the drum, and tan at 15-35 ℃ for 2-48 h; Step 3. Bleaching and decolorization: Place the leather obtained in step 2 in bleaching solution and let it stand and soak for 10-30 minutes; Step 4. Water retention and drying: Take out the leather obtained in step 3, place it in a drum, add 150%-500% of its weight of water retention agent, rotate for 1-72 hours, and then stretch and dry at 40-60 ℃ for 6-72 hours, with the moisture content controlled at 20%-30%, to obtain transparent leather. Step 5. Preparation of transparent conductive solution: Mix the transparent conductive material with a solvent or adhesive to prepare a conductive solution with a mass fraction of 2%-20%; Step 6. Conductive treatment: Apply the conductive solution prepared in step 5 to the transparent leather obtained in step 4, and dry it on a stretcher at 40-60℃ for 3-6 hours.

2. The preparation method according to claim 1, characterized in that: The de-ashed and softened bare hide in step 1 is selected from one of the following: bovine top layer hide, bovine split hide, sheepskin, goatskin, or pigskin.

3. The preparation method according to claim 1, characterized in that: The acid in step 1 is selected from sulfuric acid, nitric acid or hydrochloric acid, and the base is selected from sodium hydroxide, potassium hydroxide or calcium hydroxide.

4. The preparation method according to claim 1, characterized in that: The tanning agent in step 2 is selected from one or more of fish oil, lanolin, castor oil, olive oil, rapeseed oil, or flaxseed oil.

5. The preparation method according to claim 1, characterized in that: The bleaching solution in step 3 is selected from one of sodium peroxide, hydrogen peroxide, sodium hypochlorite, sodium chlorite, or oxalic acid.

6. The preparation method according to claim 1, characterized in that: The water-retaining agent in step 4 is selected from one or more of propylene glycol, sorbitol, polyethylene glycol, glycerin, sodium hyaluronate, urea, or trehalose.

7. The preparation method according to claim 1, characterized in that: In steps 2 and 4, the rotational speed of the drum is 80-150 r / min.

8. The preparation method according to claim 1, characterized in that: In step 5, the transparent conductive material is selected from any one of indium tin oxide (ITO), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), silver nanowires (AgNWs), cuprous oxide (Cu2O), or a mixture thereof. The solvent is one or more of water, ethanol, isopropanol, tetrahydrofuran, or 1,2-dimethoxyethane (DME). The adhesive is one or more of epoxy resin or acrylate resin.

9. The preparation method according to claim 1, characterized in that: The conductive solution applied in step 6 is selected from one or more of spraying, printing, filtration, or immersion.

10. An environmentally friendly transparent conductive leather obtained by the preparation method according to any one of claims 1-9.

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