Conductive leather based on TGIC / multi-walled carbon nanotube chrome-free tanning agent and preparation method

Abstract

The invention discloses conductive leather based on a TGIC (triglycidyl isocyanurate) / multi-walled carbon nanotube chrome-free tanning agent. The conductive leather comprises a multi-walled carbon nanotube, gamma-glycidyl ether oxypropyl trimethoxy silane, triglycidyl isocyanurate and triethylamine, the preparation method comprises the following steps: performing amination modification on multi-walled carbon nanotubes through KH550, and uniformly dispersing the multi-walled carbon nanotubes under the action of a silane coupling agent; an epoxy group of triglycidyl isocyanurate and an amino group on the surface of the aminated carbon tube are subjected to a ring-opening cross-linking reaction, and a three-dimensional covalent network structure is constructed; and carrying out ethanol precipitation purification and drying treatment to obtain the chrome-free tanning agent. The traditional chromium salt is completely replaced, and the conductivity of the obtained leather is greater than 10 <-4 > S / cm; the mechanical property of the material is excellent, and the tensile strength exceeds 15 MPa; the material has excellent damp-heat resistance stability, and the structure is still stable after being treated at 100 DEG C for 24 hours; the production process is green and environment-friendly, and the cost is reduced by 40% compared with a traditional method. The method is especially suitable for manufacturing intelligent wearable equipment and flexible electronic sensors.

Description

Technical Field

[0001] The invention belongs to the technical field of leather tanning, and particularly relates to conductive leather based on a TGIC / multi-walled carbon nanotube chrome-free tanning agent and a preparation method thereof. Background Art

[0002] Currently, in the field of leather tanning, traditional chrome tanning agents have long dominated due to their excellent tanning effects. However, chrome tanning has serious shortcomings: 1) Hexavalent chromium compounds are recognized as strong carcinogens, and their environmental toxicity has led to strict restrictions on the use of chrome tanning agents in developed countries such as Europe and the United States; 2) the tanning process produces chromium-containing wastewater (Cr 6 ⁺Concentrations as high as 200-500mg / L are expensive to treat. To address this issue, existing technologies primarily utilize two alternatives: aldehyde tanning agents (such as glutaraldehyde) and plant tannins. However, these chrome-free tanning agents have significant drawbacks: ① Although aldehyde tanning agents can increase the shrinkage temperature (Ts≈85°C), the finished leather lacks functionality (conductivity >10¹²Ω / sq); ② Plant tannins have weak binding to collagen fibers (binding rate <60%) and have no antibacterial properties (inhibition zone diameter for E. coli = 0mm).

[0003] Multi-walled carbon nanotubes (MWCNTs) have intrinsic properties (conductivity 10 4 -10 5 While MWCNTs (with a high surface area of ​​100 nm and a tensile strength of 63 GPa) are considered ideal functional fillers, their direct application faces technical bottlenecks: 1) the surface inertness of pristine MWCNTs (contact angle >140°) results in insufficient interfacial bonding strength with collagen fibers (peel strength <2 N / cm); 2) they tend to aggregate in polar media (absolute zeta potential <20 mV), making it difficult to form a stable dispersion. Existing improved methods (such as acid oxidation) can introduce -COOH groups, but these methods disrupt the sp² structure of the carbon nanotubes (increasing the ID / IG ratio to 1.25), resulting in a decrease in electrical conductivity by over 30%. Summary of the Invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the present invention aims to provide a conductive leather based on TGIC / multi-walled carbon nanotube chrome-free tanning agent and a preparation method thereof, which solves the problems of the existing chrome-free tanning agent with single function, lack of antibacterial property and conductivity, and insufficient binding force with collagen fibers. The conductivity of the obtained leather is greater than 10 -4 The material boasts excellent mechanical properties, with a tensile strength exceeding 15 MPa. It also boasts exceptional moisture and heat stability, maintaining structural stability even after treatment at 100°C for 24 hours. The production process is environmentally friendly, reducing costs by 40% compared to traditional methods. It is particularly suitable for the manufacture of smart wearable devices and flexible electronic sensors. It features chromium-free, environmentally friendly tanning, high conductivity, high antibacterial properties, and a green, environmentally friendly, and universally applicable process.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] The conductive leather based on TGIC / aminated multi-walled carbon nanotube chrome-free tanning agent is composed of raw materials in the following weight ratio, including the following components:

[0007] 1-3g of multi-walled carbon nanotubes; 0.2-2.4g of γ-glycidyloxypropyltrimethoxysilane; 0.5-3.6g of triglycidyl isocyanurate; 0.54-12.48g of water; and 0.02-0.24g of triethylamine.

[0008] The preparation method of conductive leather based on TGIC / aminated multi-walled carbon nanotube chrome-free tanning agent comprises the following steps:

[0009] Step 1, preparation of amination multi-walled carbon nanotube solution:

[0010] 1-3 g of multi-walled carbon nanotubes and 0.2-2.4 g of γ-glycidyloxypropyltrimethoxysilane (KH550) were mixed to obtain a mixture, 0.5-8.24 g of water was added, the pH of the solution was adjusted to 2.5-3.1 with HCl, and the mixture was reacted at 35°C-55°C for 1-2 hours. After the reaction, the mixture was cooled to room temperature, the pH was adjusted to 6.3-6.8 with 0.01-0.12 g of triethylamine, and the mixture was stirred for 10-30 minutes to obtain an amino-modified multi-walled carbon nanotube solution.

[0011] Step 2, TGIC cross-linking reaction:

[0012] The amination-modified multi-walled carbon nanotube solution obtained in step 1 is mixed with 0.5-3.6 g of triglycidyl isocyanurate (TGIC), 0.5-4.24 g of water and 0.01-0.12 g of triethylamine catalyst are added, and the mixture is reacted at 55°C-85°C for 3 h-6 h to obtain a tanning agent solution;

[0013] Step 3, solid powder preparation:

[0014] The tanning agent solution in step 2 was cooled to room temperature, and ethanol in an amount 2 to 3 times the volume of the tanning agent solution was added to precipitate. The precipitate was washed after filtration, dried under vacuum at 50°C to 60°C, and crushed through a 200-mesh sieve to obtain a gray-black solid powder.

[0015] In step 1:

[0016] The reaction stirring speed is 500~800r / min;

[0017] pH adjustment was performed using 10% HCl solution;

[0018] After cooling, the solution temperature is controlled at 20℃~25℃.

[0019] In step 2:

[0020] The reaction is stirred at a speed of 600-1000 r / min;

[0021] The molar ratio of -NH2 functional groups of aminated multi-walled carbon nanotubes to epoxy groups of TGIC is 1:0.5~1:1.2;

[0022] The triethylamine addition rate is 1~2mL / min.

[0023] In step 3:

[0024] The addition rate of ethanol precipitation was 5-10 mL / min, and the vacuum drying pressure was ≤ 0.1 MPa;

[0025] Ethanol: purity ≥99.5%;

[0026] The vacuum drying time is 12~24h.

[0027] The mass ratio of the multi-walled carbon nanotubes to gamma-glycidyloxypropyltrimethoxysilane is 1:0.2 to 1:0.8.

[0028] The beneficial effects of the present invention are:

[0029] The present invention is based on the chemical crosslinking of amino-modified multi-walled carbon nanotubes (NH2-MWCNT) and triglycidyl isocyanurate (TGIC). It uses a green process to construct a multifunctional chromium-free conductive leather tanning agent with the following significant advantages:

[0030] 1) Chrome-free, environmentally friendly and highly efficient tanning: It completely replaces traditional hexavalent chromium tanning agents and eliminates the risk of heavy metal pollution. The epoxy groups of TGIC covalently crosslink with the carboxyl groups of collagen fibers and the -NH2 of amino carbon nanotubes. The shrinkage temperature of the leather after tanning is ≥84°C, far exceeding that of traditional plant tannins or aldehyde tanning agents.

[0031] 2) Conductivity: Carbon nanotubes form a continuous conductive network with a conductivity of 1.8×10⁻³ S / cm, which is suitable for electromagnetic shielding and flexible sensing;

[0032] 3) Antibacterial properties: The physical puncture effect of the amino-treated carbon tubes and the active groups loaded on the surface synergistically inactivate more than 93% of Staphylococcus aureus and Escherichia coli;

[0033] 4) Mechanical enhancement: The three-dimensional cross-linked network increases the tensile strength of leather by ≥45%.

[0034] 5) High dispersibility and stability: The amino modification of KH550 significantly improves the dispersibility of carbon nanotubes in the aqueous system. The TGIC cross-linking network fixes the carbon nanotube spacing to ≤100 nm, preventing nanofiller agglomeration or migration during the tanning process.

[0035] 6) Green process and universal applicability: The entire process is water-based, without organic solvents and toxic by-products; the tanning agent solid powder has a moisture content of ≤3%, can be stored for a long time, and is compatible with existing leather production lines.

[0036] The core innovation of this invention lies in the synergistic effect of amino modification and TGIC cross-linking, overcoming the technical bottlenecks of the limited functionality of chrome-free tanning agents and the difficulty in dispersing nanofillers. The -NH2 on the surface of the amino-modified carbon nanotubes reacts with the epoxy groups of TGIC to form β-hydroxylamine bonds, which then cross-link with the carboxyl groups of collagen fibers, creating a "collagen-TGIC-MWCNT" ternary supramolecular network that combines high binding strength, electrical conductivity, and environmental stability. Furthermore, an ethanol precipitation purification process (2-3 times the volume) ensures the purity of the tanning agent powder (impurity content <0.5%), and vacuum drying (50°C-60°C) preserves the integrity of the nanostructure. Conductive leather can be integrated with flexible circuits for real-time monitoring of human movement or ambient temperature and humidity. Its antibacterial properties extend the lifespan of medical protective products, promoting the upgrading of smart wearable devices and high-end leather products. This technology provides innovative solutions for smart leather, flexible electronics, and sustainable fashion, driving the leather industry's transition towards greener, more high-end products, and offering significant ecological benefits and market competitiveness.

[0037] The tanning agent of this invention chemically crosslinks the epoxy groups of triglycidyl isocyanurate (TGIC) with the surface amino groups of amino-modified multi-walled carbon nanotubes, forming a three-dimensional covalent network. The carbon nanotubes are also amino-modified with a silane coupling agent (KH550) to enhance their dispersibility and interfacial bonding. The preparation process includes: 1) amino modification of the multi-walled carbon nanotubes; 2) ring-opening crosslinking reaction between TGIC and the amino-modified carbon nanotubes; and 3) purification by ethanol precipitation and drying. The resulting tanning agent completely replaces traditional chromium salts, imparting leather with excellent electrical conductivity, high mechanical strength, and moisture-heat stability. By leveraging the multifunctional properties of TGIC and the synergistic effect of the conductivity of the amino-modified carbon nanotubes, this invention addresses the issues of chrome-free tanning agents with limited functionality and poor nanofiller dispersibility. Furthermore, the process is environmentally friendly and the raw material cost is low, making it suitable for high-end applications such as smart wearable leather and flexible electronic sensors.

[0038] This invention modifies MWCNTs through amination, crosslinking their surface amino groups with the epoxy groups of triglycidyl isocyanurate (TGIC). This creates a supramolecular network structure that combines high reactivity, antibacterial properties, electrical conductivity, and strong binding capacity. This provides an innovative solution for the production of multifunctional chrome-free leather. This invention expands the single tanning function of traditional tanning agents to include composite properties such as electrical conductivity, antibacterial properties, and high strength. This provides an innovative solution for high-end leather applications such as smart wearables and medical protective products, and promotes the green transformation of the industry.

[0039] The leather obtained by the present invention has a conductivity greater than 10 -4The material boasts excellent mechanical properties, with a tensile strength exceeding 15 MPa. It also boasts exceptional heat and humidity stability, maintaining structural stability even after treatment at 100°C for 24 hours. The production process is environmentally friendly, reducing costs by 40% compared to traditional methods. It is particularly suitable for the manufacture of smart wearable devices and flexible electronic sensors. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below with reference to specific embodiments.

[0041] Example 1

[0042] The conductive leather based on TGIC / aminated multi-walled carbon nanotube chrome-free tanning agent is composed of raw materials in the following weight ratio, including the following components:

[0043] Multi-walled carbon nanotubes (MWCNTs) 3g; γ-glycidyloxypropyltrimethoxysilane (KH550) 2.4g; triglycidyl isocyanurate (TGIC) 3.6g; water 12.48g; triethylamine 0.24g.

[0044] The method for preparing a conductive leather reference document based on a TGIC / aminated multi-walled carbon nanotube chrome-free tanning agent comprises the following steps:

[0045] Step 1, preparation of amination multi-walled carbon nanotube solution:

[0046] 3 g of multi-walled carbon nanotubes (MWCNTs) and 2.4 g of γ-glycidyloxypropyltrimethoxysilane (KH550) were mixed, 6.24 g of water (20% of the total mass) was added, the pH of the solution was adjusted to 3.1 with HCl, and the mixture was reacted at 55°C for 2 h. After the reaction, the mixture was cooled to room temperature, the pH was adjusted to 6.8 with 0.12 g of triethylamine, and the mixture was stirred for 30 minutes to obtain an amino-modified multi-walled carbon nanotube solution.

[0047] The reaction stirring speed is 800r / min;

[0048] pH adjustment was performed using 10% HCl solution;

[0049] After cooling, the solution temperature was controlled at 25°C;

[0050] Step 2, TGIC cross-linking reaction:

[0051] The amination multi-walled carbon nanotube solution obtained in step 1 was mixed with triglycidyl isocyanurate (TGIC) at a molar ratio of 1:1.2, 6.24 g of water and 0.12 g of triethylamine catalyst were added, and the mixture was reacted at 85° C. for 6 h to obtain a tanning agent solution;

[0052] The stirring speed of the reaction system was 1000 r / min;

[0053] The molar ratio of -NH2 functional groups of aminated MWCNTs to epoxy groups of TGIC was 1:1.2;

[0054] The triethylamine addition rate was 2 mL / min.

[0055] Step 3, solid powder preparation:

[0056] The tanning agent solution in step 2 was cooled to room temperature, and ethanol in an amount 3 times the volume of the tanning agent solution was added to precipitate, the precipitate was washed after filtration, dried under vacuum at 60°C, and crushed through a 200 mesh sieve to obtain a gray-black solid powder;

[0057] The addition rate of ethanol precipitation was 10 mL / min, and the vacuum drying pressure was 0.1 MPa;

[0058] Ethanol: purity 99.8%;

[0059] The vacuum drying time is 24h.

[0060] Example 2

[0061] The conductive leather based on TGIC / aminated multi-walled carbon nanotube chrome-free tanning agent is composed of raw materials in the following weight ratio, including the following components:

[0062] Multi-walled carbon nanotubes (MWCNTs) 1g; γ-glycidyloxypropyltrimethoxysilane (KH550) 0.2g; triglycidyl isocyanurate (TGIC) 0.5g; water 0.54g; triethylamine 0.02g.

[0063] The preparation method of conductive leather based on TGIC / aminated multi-walled carbon nanotube chrome-free tanning agent comprises the following steps:

[0064] Step 1, preparation of amination multi-walled carbon nanotube solution:

[0065] 1 g of multi-walled carbon nanotubes (MWCNTs) and 0.2 g of γ-glycidyloxypropyltrimethoxysilane (KH550) were mixed, 0.27 g of water was added, the pH of the solution was adjusted to 2.5 with HCl, and the mixture was reacted at 35°C for 1 h. After the reaction, the mixture was cooled to room temperature, the pH was adjusted to 6.3 with 0.01 g of triethylamine, and the mixture was stirred for 10 minutes to obtain an amino-modified multi-walled carbon nanotube solution.

[0066] The reaction stirring speed is 500r / min;

[0067] pH adjustment was performed using 10% HCl solution;

[0068] After cooling, the solution temperature was controlled at 20°C;

[0069] Step 2, TGIC cross-linking reaction:

[0070] The amination multi-walled carbon nanotube solution obtained in step 1 was mixed with triglycidyl isocyanurate (TGIC) at a molar ratio of 1:0.5, 0.27 g of water and 0.01 g of triethylamine catalyst were added, and the mixture was reacted at 55° C. for 3 h to obtain a tanning agent solution;

[0071] The stirring speed of the reaction system was 600 r / min;

[0072] The molar ratio of -NH2 functional groups of aminated multi-walled carbon nanotubes to epoxy groups of TGIC was strictly controlled at 1:0.5;

[0073] The triethylamine addition rate was 1 mL / min;

[0074] Step 3, solid powder preparation:

[0075] The reaction solution in step 2 was cooled to room temperature, and ethanol twice its volume was added to precipitate, the precipitate was filtered and washed, dried under vacuum at 50°C, and pulverized through a 200-mesh sieve to obtain a gray-black solid powder;

[0076] The addition rate of ethanol precipitation was 5 mL / min, and the vacuum drying pressure was 0.1 MPa;

[0077] Ethanol: purity 99.5%;

[0078] The vacuum drying time is 12 h.

[0079] Example 3

[0080] The conductive leather based on TGIC / aminated multi-walled carbon nanotube chrome-free tanning agent is composed of raw materials in the following weight ratio, including the following components:

[0081] Multi-walled carbon nanotubes (MWCNTs) 2g; γ-glycidyloxypropyltrimethoxysilane (KH550) 1.2g; triglycidyl isocyanurate (TGIC) 2.4g; water 6.24g; triethylamine 0.12g.

[0082] The preparation method of conductive leather based on TGIC / aminated multi-walled carbon nanotube chrome-free tanning agent comprises the following steps:

[0083] Step 1, preparation of amination multi-walled carbon nanotube solution:

[0084] 2 g of multi-walled carbon nanotubes (MWCNTs) and 1.2 g of γ-glycidyloxypropyltrimethoxysilane (KH550) were mixed, 3.12 g of water was added, the pH of the solution was adjusted to 2.8 with HCl, and the reaction was carried out at 45°C for 1.5 h. After the reaction, the solution was cooled to room temperature, the pH was adjusted to 6.5 with 0.06 g of triethylamine, and stirred for 20 minutes to obtain an amino-modified multi-walled carbon nanotube solution.

[0085] The reaction stirring speed was 650 r / min;

[0086] pH adjustment was performed using 10% HCl solution;

[0087] After cooling, the solution temperature was controlled at 22.5°C;

[0088] Step 2, TGIC cross-linking reaction:

[0089] The solution obtained in step 1 was mixed with triglycidyl isocyanurate (TGIC) at a molar ratio of 1:0.85 between amino multi-walled carbon nanotubes and TGIC, 3.12 g of water and 0.06 g of triethylamine catalyst were added, and the mixture was reacted at 70° C. for 4.5 h to obtain a tanning agent solution;

[0090] The stirring speed of the reaction system was 8000 r / min;

[0091] The molar ratio of -NH2 functional groups of amino-modified multi-walled carbon nanotubes to epoxy groups of TGIC was strictly controlled at 1:0.85;

[0092] The triethylamine addition rate was 1.5 mL / min;

[0093] Step 3, solid powder preparation:

[0094] The reaction solution in step 2 was cooled to room temperature, and ethanol (2.5 times its volume) was added to precipitate. The precipitate was filtered, washed, vacuum-dried at 55°C, and crushed through a 200-mesh sieve to obtain a gray-black solid powder.

[0095] The addition rate of ethanol precipitation was 7.5 mL / min, and the vacuum drying pressure was 0.1 MPa;

[0096] Ethanol: purity 99.6%;

[0097] The vacuum drying time is 18 h.

[0098] ‌Application Effect‌:

[0099] Tanned sheepskin leather (8% usage): shrinkage temperature 84°C, antibacterial rate 93%, tensile strength increased by 45%.

[0100] The technical effects are compared in the following table:

[0101]

Claims

1. Conductive leather based on TGIC / multi-walled carbon nanotube chrome-free tanning agent, composed of the following raw materials in the following weight ratio, characterized in that: Includes the following components: 1-3g multi-walled carbon nanotubes; 0.2-2.4g γ-glycidyloxypropyltrimethoxysilane; 0.5-3.6g triglycidyl isocyanurate; 1-12.48g water; 0.02-0.24g triethylamine.

2. A method for preparing conductive leather based on TGIC / multi-walled carbon nanotube chrome-free tanning agent, characterized in that: The following steps are involved: Step 1, preparation of amination multi-walled carbon nanotube solution: 1-3 g of multi-walled carbon nanotubes and 0.2-2.4 g of γ-glycidyloxypropyltrimethoxysilane are mixed to obtain a mixture, 0.5-8.24 g of water is added, the pH of the solution is adjusted to 2.5-3.1 with HCl, and the mixture is reacted at 35° C.-55° C. for 1-2 hours; after the reaction, the mixture is cooled to room temperature, the pH is adjusted to 6.3-6.8 with 0.01-0.12 g of triethylamine, and the mixture is stirred for 10-30 minutes to obtain an amino-modified multi-walled carbon nanotube solution; Step 2, TGIC cross-linking reaction: The amination multi-walled carbon nanotube solution obtained in step 1 was mixed with 0.5-3.6 g of triglycidyl isocyanurate, 0.5-4.24 g of water and 0.01-0.12 g of triethylamine catalyst were added, and the mixture was reacted at 55° C.-85° C. for 3 h-6 h to obtain a tanning agent solution; Step 3, solid powder preparation: The tanning agent solution in step 2 was cooled to room temperature, and ethanol in an amount 2 to 3 times the volume of the tanning agent solution was added to precipitate. The precipitate was washed after filtration, dried under vacuum at 50°C to 60°C, and crushed through a 200-mesh sieve to obtain a gray-black solid powder.

3. The method for preparing conductive leather based on TGIC / multi-walled carbon nanotube chrome-free tanning agent according to claim 1, characterized in that: In step 1: The reaction stirring speed is 500~800r / min; pH adjustment was performed using 10% HCl solution; After cooling, the solution temperature is controlled at 20℃~25℃.

4. The method for preparing conductive leather based on TGIC / multi-walled carbon nanotube chrome-free tanning agent according to claim 1, characterized in that: In step 2: The reaction is stirred at a speed of 600-1000 r / min; The molar ratio of -NH2 functional groups of aminated multi-walled carbon nanotubes to epoxy groups of TGIC is 1:0.5~1:1.2; The triethylamine addition rate is 1~2mL / min.

5. The method for preparing conductive leather based on TGIC / multi-walled carbon nanotube chrome-free tanning agent according to claim 1, characterized in that: In step 3: The addition rate of ethanol precipitation was 5-10 mL / min, and the vacuum drying pressure was ≤0.1 MPa; Ethanol: purity ≥99.5%; The vacuum drying time is 12~24h.

6. The method for preparing conductive leather based on TGIC / multi-walled carbon nanotube chrome-free tanning agent according to claim 2, characterized in that: The mass ratio of the multi-walled carbon nanotubes to gamma-glycidyloxypropyltrimethoxysilane is 1:0.2 to 1:0.8.

Images