Preparation method of conductive leather, conductive leather and its application and finishing method

Abstract

The present application relates to a method for preparing conductive leather, conductive leather, and its application and finishing methods, and more particularly to a method for preparing conductive leather, conductive leather, and its application and finishing methods that can be applied to electronic products such as flexible or wearable devices. The conductive leather preparation method includes grinding the leather, a primary tanning process in which a conductive material and leather are drum-tanned together, and a secondary tanning process in which the leather obtained above is drum-tanned together with ingredients such as organic raw materials. The conductive leather obtained by this preparation method not only has basic conductivity but also has high wear resistance, thereby ensuring its durability and preventing a decrease in its sensory ability.

Description

Technical Field

[0001] The present application relates to a method for preparing conductive leather, conductive leather, and its application and finishing method, and in particular to a method for preparing conductive leather that can be applied to electronic products such as flexible or wearable devices, conductive leather, and its application and finishing method. Background Art

[0002] Leather, a unique material composed of tightly wound collagen fibers in three dimensions, has a wide range of applications due to its durability and flexibility. Key applications include the production of leather clothing, leather goods, footwear, furniture, gloves, as well as car seats and steering wheels. Currently, due to the unique properties of leather fibers, they are expected to be used in various electronic products such as flexible and wearable devices to better capture, sense, or detect external force signals.

[0003] In this application process, the leather itself needs to be modified. Since leather fibers themselves are not conductive, they need to be modified into leather products with conductivity by adding conductive components. For example, the conductive components can be attached to the surface of the leather or penetrate into the interior of the leather through surface coating, impregnation, filtration or in-situ growth.

[0004] In the existing preparation methods of conductive leather, the resulting conductive leather performs poorly in terms of overall wear resistance and is more likely to exhibit poor conductivity after friction, resulting in poor durability and poor perception. This limits its application in electronic products such as flexible or wearable devices. Summary of the Invention

[0005] The purpose of this application is to provide a method for preparing conductive leather, conductive leather, and its application and coating method. The conductive leather obtained by the preparation method has basic conductivity and high wear resistance, thereby ensuring its durability and avoiding a decrease in its perception ability.

[0006] The first solution provided in this application is: a method for preparing conductive leather, the preparation method comprising the following steps:

[0007] 1) Grinding: Place the leather on a leather grinding machine to polish it, removing any damaged areas on the upper and lower surfaces of the leather. At the same time, use a dust collector to remove any debris or hair from the leather surface.

[0008] 2) Preliminary tanning: placing the leather obtained in step 1) in a drum, adding the conductive material and starting the drum to preliminarily tannage and fill the pores of the leather with the conductive material. The preliminarily tanning and filling time is 1 hour to 3 hours.

[0009] 3) Secondary tanning: adding the organic raw material, penetrant, softener, and deodorizer to the drum of step 2) in a certain volume ratio, tanning at 0°C to 10°C for 1 hour to 2 hours, then adding a catalyst solution at a temperature of 0°C to 10°C to the drum, and continuing tanning for 3 hours to 6 hours to carry out a polymerization reaction; after the polymerization reaction is completed, adding a flame retardant to the drum, and continuing tanning for 1 hour to 3 hours; then, washing, ultrasonicating, drying, vibrating, and ironing the leather after the secondary tanning are completed to obtain a conductive leather with a smooth surface.

[0010] Optionally, the leather in step 1) is one or more of animal leather or plant leather that has been chrome tanned or vegetable tanned.

[0011] Optionally, the conductive material in step 2) is one or more of metal and metal oxide nanomaterials, non-metallic nanoconductive materials, conductive carbon-based materials, and conductive ink.

[0012] Optionally, the rotation speed of the drum in step 2) and step 3) is 80 r / min to 150 r / min.

[0013] Optionally, the organic raw materials in step 3) include one or more of pyrrole and its derivatives, aniline and its derivatives, thiophene and its derivatives, phenylene and its derivatives, and acetylene and its derivatives.

[0014] Optionally, the catalyst solution in step 3) includes one or more of a strong reducing / oxidizing agent, persulfate, organic acid or inorganic acid.

[0015] Optionally, the temperature of the ironing roller in step 3) is 60° C. to 90° C., the pressure is 6 MPa, and the roller speed is 5 m / min to 9 m / min.

[0016] The present application also provides a second solution, namely, conductive leather prepared by any of the aforementioned preparation methods.

[0017] The present application also provides a third solution, namely, the application of the conductive leather described above, wherein the conductive leather is applied to electronic products of flexible or wearable devices.

[0018] The present application also provides a fourth solution, namely the aforementioned conductive leather coating method, comprising the following steps:

[0019] 4) Finishing: The conductive leather obtained in step 3) is placed on a roller coater or a spray coater and is primed, mid-coated, and top-coated with conductive paint.

[0020] Optionally, after the primer, mid-coat and top-coat in step 4), the coating must be dried and placed in air at a temperature of 20±5°C and a relative humidity of 63% to 67% overnight.

[0021] Optionally, the conductive coating in step 4) includes one or more conductive components selected from graphene and conductive silver paste, and auxiliary components.

[0022] Optionally, the conductive coating in step 4) comprises a conductive component and an auxiliary component in a weight ratio of (1.5-2.5):1.

[0023] Optionally, in the conductive coating used for the primer in step 4), the auxiliary components include, by weight, 8 to 25 parts of pigment paste, 20 to 40 parts of soft filler, 10 to 24 parts of soft polyacrylic resin, 2 to 8 parts of polyacrylic resin, 12 to 24 parts of soft polyurethane, 0 to 20 parts of leveling agent, and 3 to 9 parts of feel agent.

[0024] Optionally, in the conductive coating used in the mid-coat in step 4), the auxiliary components include, by weight, 10 to 15 parts of pigment paste, 5 to 15 parts of softener, 16 to 24 parts of soft acrylic resin, 12 to 24 parts of soft polyurethane, 2 to 8 parts of medium-soft polyurethane, 6 to 15 parts of matting agent, 0.5 to 1.5 parts of feel agent, and 12 to 20 parts of water.

[0025] Optionally, in the conductive coating used for the top coating in step 4), the auxiliary components include, by weight, 0.1 to 3 parts of pigment paste, 10 to 20 parts of soft top coating acrylic resin, 40 to 60 parts of matting resin / high gloss resin, 2 to 8 parts of feel agent, 1 to 5 parts of thickener, 9 to 15 parts of cross-linking agent, and 0 to 5 parts of water.

[0026] Optionally, the roller coating speed of the roller coater in step 4) is 3 m / min to 9 m / min, and the coating amount is 5 g / sf to 12 g / sf.

[0027] Optionally, the drying temperature in step 4) is 60°C to 120°C.

[0028] The present application is directed to a method for preparing conductive leather, which includes the steps of grinding, primary tanning, and secondary tanning. During the primary tanning, conductive materials are added to facilitate their filling into the leather fiber network. During the secondary tanning, organic raw materials, penetrants, and other ingredients are added to facilitate the conductive materials already filled into the network to form a conductive polymer with the conductive materials, thereby tightly entangled with the leather fiber network. This not only allows the production of conductive leather with relatively uniform and excellent conductive properties, but also because the tanning process significantly enhances the bonding strength between the conductive polymer and the leather, forming a more stable conductive path, which makes the conductive leather have stronger friction resistance.

[0029] The present invention also adjusts the coating method, selects different conductive coatings, prepares a conductive coating with a reasonable ratio, and selects different coating steps to obtain a conductive leather product with a beautiful surface and high wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A photograph of the polypyrrole conductive leather prepared in Example 1 of the present application (left) and a scanning electron microscope image of the conductive leather (right);

[0031] Figure 2 A photograph of the coated conductive leather prepared in Example 1 of the present application (left) and a scanning electron microscope image of the coated conductive leather (right);

[0032] Figure 3 This is a data graph of multi-site planar equidistant resistance of the polypyrrole conductive leather (black) and the coated conductive leather (red) prepared in Example 1 of the present application;

[0033] Figure 4 Graph showing the change in planar equidistant resistance at multiple locations of the polypyrrole conductive leather (black) and the coated conductive leather (red) prepared in Example 1 of the present application after being rubbed 1000 times with 300-grit sandpaper at a pressure of 50 kPa;

[0034] Figure 5 The figures show scanning electron microscope images of the conductive leather prepared in Example 1 before (a) and after (b) friction;

[0035] Figure 6 This is a data graph of the multi-site planar equidistant resistance of different conductive leathers obtained by the method of directly immersing the leather filled with conductive material in the organic raw material (blue) and directly drum tanning the leather with the conductive polymer (red) prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0036] Embodiment 1:

[0037] In this embodiment, pyrrole polymer material is selected as the reaction raw material, and ferric chloride and p-toluenesulfonic acid solution are selected as catalysts to prepare conductive leather.

[0038] 1) Leather sanding: First, cut the top layer of chrome-tanned cowhide into specific sizes. Use a sanding machine to sand the upper and lower surfaces of the leather. Use 400-grit sandpaper for the upper surface and 200-grit sandpaper for the lower surface. Use a dust collector to remove dust and clean.

[0039] 2) Preliminary Tanning: Dissolve single-walled carbon nanotubes in NMP (N-methylpyrrolidone) to prepare a 3% SWNT-NMP dispersion. Place this dispersion and the leather in a rotating drum at a speed of 80–150 rpm for 1–3 hours. After the reaction is complete, discard the excess reaction solution, pick up the leather with tweezers, rinse with water to remove any excess carbon nanotubes, and sonicate for 2 hours.

[0040] 3) Secondary tanning: prepare 200 mL of pyrrole monomer and ethanol solution in a volume ratio of 1:10, add 4 mL of penetrant, 5 mL of softener and 6 mL of deodorant into a rotary drum, place the filled leather into the drum, set the speed to 80 r / min~150 r / min, and tan for 1 h~2 h; prepare a 0.3 mol / L ferric chloride / p-toluenesulfonic acid solution, cool it to 0℃~10℃ in an ice bath, pour the ferric chloride / p-toluenesulfonic acid solution into a 5 L drum, then place the leather tanned with pyrrole monomer into the drum, set the speed to 80 r / min~150 r / min, tan for 3 h~6 h to carry out polymerization reaction. After the polymerization is complete, add 10 mL of flame retardant into the drum and continue tanning for 1 h~3 h.

[0041] After the reaction, the excess reaction solution was poured off, the leather was picked up with tweezers, and the excess polypyrrole on the surface was rinsed with pure water. Then, it was placed in an ultrasonic machine for 2 hours, and finally ironed on a roller ironing machine to obtain the conductive leather of Example 1. The temperature of the ironing machine was set to 60°C~90°C, the pressure was 6 MPa, and the roller speed was 5 m / min~9 m / min.

[0042] The resistance of the conductive leather prepared after this step is 15Ω~70Ω. Figure 3 、 Figure 4 、 Figure 6 As shown, Figure 6 Adopt the method of embodiment 1 with the longest tanning time and the slowest rotation speed, Figure 3 Adopt the method with the shortest tanning time and the fastest speed in Example 1, Figure 4 The tanning time is medium and the speed is medium in Example 1. Regardless of the method, the friction resistance of the conductive leather obtained is relatively stable. Figure 4 As shown in the figure, its resistance does not change much after multiple frictions.

[0043] In addition, the conductive leather of the first embodiment can also be decorated on its surface through the following finishing steps.

[0044] 4) Finishing: The conductive leather obtained in step (3) is placed on a roller coater or a spray coater and different conductive coatings are used for primer coating, mid-coating and top coating.

[0045] Primer: Prepare auxiliary ingredients by weight: 23.2 parts pigment paste, 29.1 parts soft filler, 18.6 parts soft acrylic resin, 4.6 parts polyacrylic filler, 18.6 parts soft polyurethane, and 5.8 parts feel agent. Set the shaker speed to 800 r / min to fully dissolve and disperse. Then, mix the prepared auxiliary ingredients with graphene conductive material (conductive component) in a 1:2 weight ratio in an ultrasonic machine to obtain the conductive primer. Apply the primer to the leather with a roller coater at a speed of 5 m / min and a coating weight of 10 g / sf. The leather is then dried in a 60°C oven and placed in standard air at 20°C and 65% relative humidity for 12 hours.

[0046] Middle coat: Auxiliary ingredients are prepared by weight: 11.5 parts pigment paste, 10.3 parts softener, 22.7 parts soft acrylic resin, 20.6 parts soft polyurethane, 6.2 parts medium-soft polyurethane, 8.2 parts matting agent, 1 part feel agent, and 15.5 parts water. Set the oscillator speed to 800 r / min to fully dissolve and disperse them. Subsequently, the prepared auxiliary ingredients and graphene conductive material (conductive component) are placed in an ultrasonic machine and mixed in a weight ratio of 1:2 to obtain the conductive coating for the middle coat. The conductive coating for the middle coat is roller-coated on the leather, setting the roller coater conveyor speed to 5m / min and the coating amount to 5g / sf. The leather after roller coating is then placed in a 60°C oven to dry, removed and placed in standard air at a temperature of 20°C and a relative humidity of 65% for 12 hours.

[0047] Top coating: Auxiliary ingredients are prepared by weight: 1.35 parts pigment paste, 13.5 parts soft top coating acrylic resin, 50.6 parts matting agent, 5.6 parts feel agent, 2.8 parts thickener, 11.2 parts crosslinking agent, and 2.8 parts water. The oscillator speed is set to 800 r / min to fully dissolve and disperse them. The prepared auxiliary ingredients are then mixed with graphene conductive material (conductive component) in an ultrasonic machine at a weight ratio of 1:2 to obtain the top coating conductive coating. The top coating conductive coating is roller-coated onto the leather, setting the roller coater speed to 5m / min and the coating amount to 5g / sf. The roller-coated leather is then dried in an 80°C oven and placed in standard air at 20°C and 65% relative humidity for 12 hours.

[0048] The resistance of the conductive leather prepared after this step is 40Ω~200Ω.

[0049] Example 1 was tested:

[0050] from Figure 1It can be seen that the conductive leather prepared in Example 1 has the characteristics of micro-nanoscale fibers and fiber clusters and multi-level deformation. The conductive polymer material after tanning penetrates the micro-nano porous structure inside the leather and is tightly interwoven with the collagen fiber bundles to form a dense polypyrrole film, constructing an effective 3D conductive network and giving the leather conductivity.

[0051] Figure 2 The photograph and SEM images of the conductive leather after coating are shown.

[0052] from Figure 3 It can be seen that the equidistant interface resistance of the leather electrode at multiple sites after drum tanning polymerization has better stability, and the conductive leather resistance after coating also has excellent stability.

[0053] from Figure 4 It can be seen that the conductive leather obtained by tanning polymerization is placed on a friction tester, the pressure of the friction tester is set to 50 kPa, the mesh size of the sandpaper is 300, the number of frictions is 1000, and the resistance changes of the leather grain and hair surface are recorded every 200 times. Through analysis, it can be concluded that the resistance of the leather grain surface increases by 2%, 14%, 35%, 52% and 69% after friction for 200 times, 400 times, 600 times, 800 times and 1000 times, respectively; the resistance of the leather hair surface increases by 7%, 15%, 28%, 18% and 25% after friction for 200 times, 400 times, 600 times, 800 times and 1000 times, respectively.

[0054] Figure 5 The scanning electron microscope images of the conductive leather of Example 1 before (a) and after (b) friction are shown. Figure 5 (b) It can be seen that after 1000 frictions, the fibers on the leather surface are slightly broken, but the polymer conductive material (polypyrrole) is still wrapped on the surface of the leather fibers without obvious shedding, and the resistance between the two surfaces of the leather does not change significantly. This proves that the conductive leather prepared by this method has strong wear resistance.

[0055] Figure 6 This is a data graph of the multi-site planar equidistant resistance of the polypyrrole conductive leather prepared in Example 1 of the present application (conductive material and organic raw material are tanned separately, black), the leather filled with conductive material is directly immersed in the organic raw material (blue), and the leather is directly drum tanned with the conductive polymer (red). Figure 6It can be seen that the conductive leather prepared by the method of the present application, i.e., tanning the conductive material and the organic raw material in two steps, thereby enabling the conductive polymer to better and more tightly combine with the leather fiber network, can obtain conductive leather with low surface resistance and stability. As can be seen from the other two methods shown in the figure, the surface resistance of the conductive leather obtained by directly impregnating the leather filled with conductive material into the organic raw material (impregnation polymerization) is large and uneven, and this method does not use drum tanning polymerization. The other method (red) uses drum tanning polymerization, and the surface resistance of the conductive leather obtained is also small and uniform, but there is a certain gap in conductivity compared to the method of the present application.

[0056] Table 1 below shows the test results of various physical properties of the conductive leather obtained in Example 1 before and after coating.

[0057] Table 1

[0058]

[0059] In addition, in Examples 2 and 3, the aforementioned three steps are the same as in Example 1, except that the weight ratio of the conductive component to the auxiliary component in the conductive coating in step 4) is changed. The electrical properties of the coated conductive leathers obtained in Examples 1 to 3 are tested, as shown in Table 2 below.

[0060] Table 2

[0061]

[0062] From the above Figure 4 、 Figure 5 As can be seen from Table 1, the conductive leather obtained in this application has excellent tear resistance, tension resistance and wear resistance, and is fully capable of being used in scenarios of smart materials such as automotive smart cockpits, robot tactile sensing, VR human-computer interaction, and wearable electronic devices.

[0063] Therefore, the conductive leather prepared by the present invention uses a conductive polymer as the conductive material, and performs in-situ polymerization on the fiber bundles of the leather through drum tanning. The inventors found that the use of conductive polymers, such as polypyrrole and its derivatives, can significantly enhance its bonding with the leather and form a stable conductive path. At the same time, the inventors selected a conductive polymer material in combination with a leather coating material and used a traditional leather coating method for coating, so that the leather has excellent friction resistance, tear resistance, friction color fastness and adhesive layer adhesion fastness while still having more excellent conductive properties.

[0064] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing conductive leather, characterized in that: The preparation method comprises the following steps: 1) Grinding: Place the leather on a leather grinding machine to polish it, removing any damaged areas on the upper and lower surfaces. At the same time, use a dust collector to remove any debris or hair from the leather surface. 2) Preliminary tanning: placing the leather obtained in step 1) in a rotating drum, adding a conductive material, and starting the drum to preliminarily tannage and fill the conductive material into the pores of the leather. The preliminarily tanning and filling time is 1 hour to 3 hours. The conductive material is one or more of metal and metal oxide nanomaterials, non-metallic nanoconductive materials, conductive carbon-based materials, and conductive inks. 3) Secondary tanning: adding organic raw materials, penetrants, softeners, and deodorizers in a certain volume ratio to the drum of step 2), tanning at 0°C~10°C for 1h~2h, then adding a catalyst solution at a temperature of 0°C~10°C to the drum, and continuing tanning for 3h~6h to carry out polymerization reaction; after the polymerization reaction is completed, adding a flame retardant to the drum, and continuing tanning for 1h~3h; then, washing, ultrasonicating, drying, vibrating, and ironing the front of the leather after the secondary tanning is completed to obtain conductive leather with a smooth surface; the organic raw materials include one or more of pyrrole and its derivatives, aniline and its derivatives, thiophene and its derivatives, and acetylene and its derivatives.

2. The preparation method according to claim 1, characterized in that The leather in step 1) is one or more of animal leather or plant leather after chrome tanning or vegetable tanning.

3. The preparation method according to claim 1, characterized in that The rotation speed of the drum in step 2) and step 3) is 80 r / min to 150 r / min.

4. The preparation method according to claim 1, characterized in that The catalyst solution in step 3) includes a strong oxidant.

5. The preparation method according to claim 1, characterized in that The catalyst solution in step 3) includes peroxysulfate.

6. The preparation method according to claim 1, characterized in that The temperature of the ironing roller in step 3) is 60° C. to 90° C., the pressure is 6 MPa, and the roller speed is 5 m / min to 9 m / min.

7. Conductive leather prepared by the preparation method according to any one of claims 1 to 6.

8. The use of the conductive leather according to claim 7, characterized in that: The conductive leather is applied to electronic products of flexible or wearable devices.

9. The conductive leather finishing method according to claim 7, characterized in that: The following steps are included: 4) Finishing: Place the conductive leather obtained in step 3) on a roller coater or sprayer and use conductive paint for primer coating, mid-coating, and top coating.

10. The coating method according to claim 9, characterized in that: After the primer, mid-coat and top-coat described in step 4), they must be dried and placed in air at a temperature of 20±5°C and a relative humidity of 63%~67% overnight.

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