Preparation method and application of LST-GO-Fe composite functional chrome-free tanning agent

Abstract

The invention relates to a preparation method and application of an LST-GO-Fe composite functional chrome-free tanning agent, and the LST-GO-Fe composite functional chrome-free tanning agent comprises the following components by weight: triglycidyl isocyanurate, a solvent, sodium lignin sulfonate LS, ethanol, graphene oxide, ferric sulfate and a catalyst. The preparation method comprises the following steps: S1, dissolving triglycidyl isocyanurate in water, and heating to obtain a uniform triglycidyl isocyanurate TGIC solution; s2, sodium lignin sulfonate LS is added into a triglycidyl isocyanurate TGIC solution, and a reaction mixed solution is obtained; s3, adding graphene oxide and ferric sulfate into the reaction mixed solution obtained in the step S2 to obtain a reaction mixed solution; and S4, cooling the reaction mixed solution in the step S3 to room temperature, adding ethanol, precipitating a product, filtering, washing, precipitating, and carrying out vacuum drying to obtain the LST-GO-Fe composite chrome-free tanning agent. The obtained tanning agent is green, environmentally friendly and low in cost, leather is endowed with excellent shrinkage temperature, mechanical strength and washing resistance, and tanning strengthening, photo-thermal management and electromagnetic shielding synergism are achieved.

Description

Technical Field

[0001] This invention belongs to the field of leather tanning agent preparation technology, specifically relating to the preparation method and application of LST-GO-Fe composite functional chromium-free tanning agent. Background Technology

[0002] In recent years, with the increasing severity of global environmental problems, the development of eco-friendly and resource-saving new materials has become a strategic priority for industrial development in various countries. Data from the United Nations Environment Programme (UNEP) shows that the leather manufacturing industry discharges over 500,000 tons of chromium-containing wastewater annually, of which approximately 15% is chromium. 3+ In the natural environment, it transforms into highly toxic Cr. 6+ This causes irreversible damage to soil and water bodies. As a cutting-edge topic in the utilization of biomass resources, how to efficiently utilize renewable resources and reduce environmental pollution has become an important direction for promoting sustainable development. Especially in the leather manufacturing industry, although traditional chrome tanning has long occupied more than 85% of the market share due to its high tanning efficiency and excellent leather performance, the chromium pollution problem generated during its use is becoming increasingly prominent. Cr in chrome tanning agents... 3+ Under certain conditions, it can be oxidized into highly toxic Cr. 6+ Chromium-containing substances (WHO Group 1 carcinogens) not only cause serious harm to the ecological environment, but may also accumulate in the human body through the food chain, inducing diseases such as skin ulcers and respiratory cancers. Therefore, developing efficient and environmentally friendly chromium-free tanning agents has become a strategic goal that the leather industry urgently needs to address.

[0003] Sodium lignosulfonate (LS) is a byproduct of the papermaking industry, with a global annual production exceeding 50 million tons. Rich in sulfonic acid and hydroxyl groups, it is naturally renewable and highly biodegradable, possessing the potential to cross-link with collagen molecules. Theoretical studies indicate that its sulfonic acid groups can bind to collagen amino groups via electrostatic interactions, while its hydroxyl groups can form a hydrogen bond network. However, LS molecules suffer from significant steric hindrance and embedded reactive sites, resulting in insufficient cross-linking efficiency when directly used for tanning. This leads to a tanning shrinkage temperature (Ts) of only 65-72℃ (far lower than the >95℃ of chrome-tanned leather). Due to the low reactivity of LS, its direct use in tanning fails to achieve ideal tanning results, limiting its application in practical production.

[0004] On the other hand, triglycidyl isocyanate (TGIC), as a highly active crosslinking agent, has attracted widespread attention due to its rich epoxy groups, achieving a reactivity of 98%. The epoxy groups of TGIC can undergo efficient crosslinking reactions with functional groups such as amino and hydroxyl groups, a characteristic that gives it great potential in the field of material modification. However, its small molecule nature leads to easy tanning agent loss and poor washability of the finished leather. Nevertheless, the application of TGIC in leather tanning has not been fully studied, especially its synergistic effect with biomass raw materials (such as LS), which is still in its early stages.

[0005] In the research and development of environmentally friendly tanning agents, biomass-synthetic synergistic systems have attracted much attention. While existing research has confirmed that the LS-TGIC complex (LST) can raise temperature saturation (Ts) to above 80°C, bottlenecks remain, including functional limitations: it lacks value-added properties such as photothermal conversion and electromagnetic shielding, making it difficult to meet the needs of smart leather. Inspired by the "Trojan horse" strategy, the use of metal ions (Fe...)... 3+ The integration of graphene oxide (GO) with nanocarriers to penetrate deep into the collagen layer has become a breakthrough approach. Graphene oxide (GO) has excellent photothermal conversion capabilities (solar energy absorption rate >80%) and an ultra-large specific surface area (>500 m² / g), but its application in tanning is limited by poor dispersion stability and weak binding force with collagen.

[0006] In summary, given the pollution risks of traditional chrome tanning and the functional limitations of existing chrome-free tanning agents, there is an urgent need to develop a novel biomass-based multifunctional tanning agent. Through innovative integration, LST's biomass-based framework can provide reactive sites and ecological safety; GO's photothermal conversion network can endow it with solar energy management functions; Fe... 3+ The "Trojan Horse" tanning center can achieve deep and uniform cross-linking through carrier mounting. Some iron ions form nanoscale magnetic particles in the three-dimensional network. These magnetic particles can undergo hysteresis loss under the action of an alternating magnetic field, converting electromagnetic energy into heat energy. The two-dimensional sheet structure of graphene oxide can also produce multiple reflections and scatterings of electromagnetic waves, further enhancing the electromagnetic shielding effect. Constructing the LST-GO-Fe ternary system is expected to simultaneously achieve tanning strengthening, photothermal management, and electromagnetic shielding, promoting the green and intelligent transformation and upgrading of leather manufacturing, and providing technical support for the development of environmentally friendly new materials. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing and applying an LST-GO-Fe composite functional chromium-free tanning agent. This tanning agent achieves chemical cross-linking between the epoxy groups of TGIC and the sulfonic acid and hydroxyl groups of LS, forming a stable three-dimensional network structure, significantly improving the tanning effect, and further introducing GO and Fe. 3+ By constructing an LST-GO-Fe ternary system, it is expected to simultaneously achieve tanning strengthening, photothermal management, and electromagnetic shielding.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A chromium-free LST-GO-Fe composite tanning agent, by weight ratio, comprises the following components: 4-24g of triglycidyl isocyanurate, 75-200g of solvent, 5-16g of sodium lignosulfonate, 300-800g of ethanol, 0.02-0.08g of graphene oxide, 0.2-0.8g of ferric sulfate, and 0.05-0.64g of catalyst.

[0010] The solvent is replaced with water; the ethanol is replaced with methanol.

[0011] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0012] Step S1: Dissolve 4-24g of triglycidyl isocyanurate in 75-200g of water and heat to 50℃~80℃ to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0013] Step S2: Add 5-16g of sodium lignosulfonate LS and 0.05-0.64g of catalyst to the triglycidyl isocyanurate TGIC solution from step S1, heat and stir at 50℃~80℃ for 3h~5h to obtain a reaction mixture.

[0014] Step S3: Add 0.02-0.08g of graphene oxide and 0.2-0.8g of ferric sulfate to the reaction mixture in step S2, heat and stir at 50℃~80℃ for 1h~3h to obtain the reaction mixture;

[0015] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 300-800g of ethanol to precipitate the product, filter and wash the precipitate, and vacuum dry it at 40℃~70℃ to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0016] In step S1, the water is replaced with deionized water.

[0017] In step S2, the mass ratio of sodium lignosulfonate LS to triglycidyl isocyanate TGIC is 0.8 to 1:5.

[0018] In step S2, the catalyst is tetramethylethylenediamine or triethylamine, and the amount used is 1% to 4% of the mass of sodium lignosulfonate LS; 5-16g of sodium lignosulfonate LS is added to the heated triglycidyl isocyanurate solution, and the heating temperature is kept constant for 4h to 6h.

[0019] In step S3, the carbon content of the graphene oxide (GO) is 50%–80%.

[0020] In step S4, ethanol is used to wash the precipitate, with a mass ratio of ethanol to water of 4:1.

[0021] In step S4, the vacuum drying time is 12h to 24h.

[0022] In step S4, the ethanol is replaced by methanol or propanol.

[0023] The application of the LST-GO-Fe composite chromium-free tanning agent in leather tanning.

[0024] Step 1: Prepare a solution by mixing 8% to 15% of the weight of the acid leather with LST-GO-Fe composite chromium-free tanning agent at a liquid ratio of 1.0 to obtain the tanning liquor;

[0025] Step 2: Adjust the pH of the tanning solution to 2-5, and react with the pickled bare hides at 30℃-50℃ for 4-6 hours;

[0026] Step 3: After tanning, the shrinkage temperature of the leather is 81℃~87℃, and the thickness increase rate is 20%~50%.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) Fundamentally eliminates chromium pollution, exhibiting outstanding environmental friendliness.

[0029] This invention completely eliminates toxic chromium salts, using sodium lignosulfonate (LS), a biomass derivative, as its core framework. This eliminates Fe at the source. 3+ To the highly toxic Cr 6+ The transformation mitigates the risks and solves the water and soil pollution problems caused by traditional chrome tanning processes, meeting the stringent requirements of green chemistry and sustainable development.

[0030] 2) Excellent tanning performance, reaching or approaching the level of traditional chrome tanning:

[0031] A stable LST three-dimensional network matrix is ​​formed through efficient cross-linking of the epoxy groups of triglycidyl isocyanate (TGIC) with the sulfonic acid and hydroxyl groups of LS. This matrix can form dense multiple forces (such as electrostatic attraction and hydrogen bonding) with collagen fibers, resulting in a stable shrinkage temperature (Ts) of 83.8℃ for the tanned leather, with a preferred embodiment reaching 84.5℃. This is significantly higher than that of ordinary commercial chrome-free tanned leather, such as TWS tanned leather (76.3℃) and F-90 tanned leather (81.6℃), and is close to the level of traditional chrome-tanned leather (>95℃). Simultaneously, the thickness increase of the raw leather can reach 20%-50%. Mechanically, the tensile strength and tear strength of the tanned leather can reach 14.2 MPa and 63.7 N / mm, respectively, far exceeding the requirements for garment leather (tear strength ≥18 N / mm, tensile strength ≥6.5 MPa) (QB1872-93). This is due to the skeletal effect of GO and Fe... 3+ The synergistic effect of these properties not only enhances thermal stability and mechanical properties, but also results in a high elongation at break of 76.3%, demonstrating excellent flexibility.

[0032] 3) Innovatively introducing the "Trojan Horse" strategy to achieve deep and efficient tanning:

[0033] The core innovation of this invention lies in the construction of an LST-GO-Fe ternary synergistic system. In this system, graphene oxide (GO) is bonded to the LST matrix, serving as a nanocarrier; Fe... 3+ The compound tanning agent is effectively loaded onto the carrier through coordination. During the tanning process, this compound tanning agent acts like a "Trojan horse," utilizing the excellent permeability of the GO-LST carrier to precisely deliver Fe³⁺ to the internal layers of collagen fibers, thus solving the bottlenecks of insufficient penetration depth and uneven distribution of free iron ions. 3+ The collagen fibers are firmly coordinated with carboxyl groups and other groups inside, achieving deep and uniform cross-linking at the molecular level. This is the key to obtaining high shrinkage temperature and excellent washability.

[0034] 4) It endows leather with high added value and multi-functionality, achieving multiple benefits from a single treatment:

[0035] This invention successfully integrates the tanning function with intelligent functions such as photothermal management and electromagnetic shielding, breaking through the limitation of the single function of traditional tanning agents.

[0036] Highly efficient photothermal conversion performance: GO itself possesses excellent near-infrared light absorption capabilities. In the LST-GO-Fe system, GO and Fe... 3+The synergistic effect further enhances the photothermal conversion efficiency. Leather treated with the tanning agent of this invention can achieve rapid and controllable heating under simulated sunlight irradiation, which is of great significance for the development of leather products with intelligent thermal management functions (such as dehumidification and heat preservation).

[0037] Significant electromagnetic shielding (EMI) effectiveness: In a three-dimensional network structure, Fe... 3+ It can partially form nanoscale magnetic particles, while the two-dimensional layered structure of GO can construct a conductive network. The two work synergistically, through the combined effects of magnetic and electrical losses, giving the resulting leather products excellent electromagnetic shielding performance, making their application possible in fields such as electronic equipment protection and special clothing. The electromagnetic shielding effectiveness in the 8.2-12.4 GHz range can reach 36.2 dB, meeting the target standard of ≥20 dB for commercial EMI shielding materials (shielding more than 99% of incident electromagnetic waves).

[0038] 5) The preparation process is simple and controllable, the raw material cost is low, and it is easy to industrialize:

[0039] The preparation method is a classic solution reaction and precipitation purification process, with mild reaction conditions (temperature 50-80℃), a short process, and no need for complex equipment. The main raw material, LS, is papermaking waste, which is inexpensive and readily available, achieving high-value utilization of waste; TGIC, GO, etc., are all commercially available common chemicals. Therefore, this invention combines technological advancement with economic feasibility, possessing enormous potential for large-scale industrial production.

[0040] This invention provides a method for preparing a multifunctional chromium-free tanning agent, LST-GO-Fe, by chemically crosslinking the hydroxyl groups of sodium lignosulfonate with the epoxy groups of triglycidyl isocyanate to form a three-dimensional LST network framework, and further introducing GO and Fe. 3+ Graphene oxide (GO) and Fe2(SO4)3 were in-situ reduced and self-assembled under acidic conditions to generate GO-Fe nanocomposites, thus constructing an LST-GO-Fe ternary system and preparing a crude product mixture. After precipitation and vacuum drying, LST-GO-Fe chromium-free tanning agent solid powder was obtained. Using triglycidyl isocyanate (TGIC), sodium lignosulfonate (LS), graphene oxide (GO), and Fe2(SO4)3 as raw materials, a chromium-free tanning agent was prepared. The preparation method is simple, and the prepared chromium-free tanning agent can be applied to tanning experiments. Leather tanned with this agent exhibits high shrinkage temperature, physical and mechanical properties, and photothermal conversion performance.

[0041] This invention prepares an LST matrix by crosslinking the epoxy groups of TGIC with the sulfonic acid / hydroxyl groups of LS, then introduces Fe2(SO4)3 and GO, and forms a three-dimensional network structure through in-situ reduction self-assembly; Fe 3+Through a "Trojan horse" effect, the GO-LST carrier is loaded and penetrates deep into the collagen fiber layer, simultaneously exerting tanning enhancement and photothermal catalysis. GO provides a photothermal conversion framework and improves mechanical stability. In the formed three-dimensional network structure, ferric sulfate and graphene oxide work synergistically to endow the tanning agent with unique electromagnetic shielding function. The crude product of the LST-GO-Fe complex is precipitated, washed, and dried to obtain a solid powder of chromium-free tanning agent. The resulting tanning agent is environmentally friendly, low in cost, and imparts excellent shrinkage temperature, mechanical strength, and wash resistance to leather, while achieving synergistic effects of tanning enhancement, photothermal management (PTM), and electromagnetic shielding. This invention provides a method to solve the problems of pollution from traditional chromium tanning and the limited functionality of chromium-free tanning agents, which can promote the green and sustainable development of the leather industry.

[0042] Sodium lignosulfonate (LS), a byproduct of the papermaking industry, is rich in sulfonic acid and hydroxyl groups, possessing natural renewability and biodegradability. Its phenolic hydroxyl groups provide reaction sites for epoxy modification, but steric hindrance during direct tanning results in a collagen fiber binding rate of <40%. Graphene oxide (GO) has an ultra-high specific surface area and broad-spectrum absorption characteristics, but it is prone to aggregation and has weak affinity for collagen; while Fe³⁺ can form coordination bonds with collagen carboxyl groups, its free ion penetration depth is insufficient. By constructing a “LST-GO-Fe” ternary system, the bottleneck of single-component applications can be overcome.

[0043] Therefore, the novel chromium-free tanning agent proposed in this invention not only solves the chromium pollution problem in the leather industry but also imparts enhanced properties to the raw leather, thereby promoting the green and sustainable development of the leather industry. This invention not only successfully provides a high-performance, chromium-free alternative but also, through a unique structural design, endows leather with unprecedented intelligent functions, powerfully driving the transformation and upgrading of the leather industry towards green, high-end, and intelligent directions. Attached Figure Description

[0044] Figure 1 This is a temperature rise curve for LST-GO-Fe tanning of different strengths according to the present invention. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to specific examples. To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the specific embodiments will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0046] Example 1

[0047] A chromium-free LST-GO-Fe composite tanning agent, comprising the following components in the following weight ratio: 4g triglycidyl isocyanurate, 75g solvent, 5g sodium lignosulfonate, 300g ethanol, 0.02g graphene oxide, 0.2g ferric sulfate, and 0.05g catalyst.

[0048] After tanning, the shrinkage temperature of the leather is 81℃, the thickening rate is 30%, and the tensile strength and tear strength of the tanned leather can reach 11.2 MPa and 53.6 N / mm, respectively, with an elongation at break of 70.2%.

[0049] Example 2

[0050] A chromium-free LST-GO-Fe composite tanning agent, comprising the following components in the following weight ratio: 14g of triglycidyl isocyanurate, 137.5g of solvent, 11.5g of sodium lignosulfonate (LS1), 550g of ethanol, 0.05g of graphene oxide, 0.5g of ferric sulfate, and 0.345g of catalyst.

[0051] After tanning, the shrinkage temperature of the leather is 84℃, the thickening rate is 50%, and the tensile strength and tear strength of the tanned leather can reach 9.3MPa and 44.78N / mm, respectively, with an elongation at break of 80.5%.

[0052] Example 3

[0053] A chromium-free LST-GO-Fe composite tanning agent, comprising the following components in the following weight ratio: 24g triglycidyl isocyanurate, 200g solvent, 16g sodium lignosulfonate (LS1), 800g ethanol, 0.08g graphene oxide, 0.8g ferric sulfate, and 0.64g catalyst.

[0054] After tanning, the shrinkage temperature of the leather is 87℃, the thickening rate is 20%, and the tensile strength and tear strength of the tanned leather can reach 15.6 MPa and 43.6 N / mm, respectively, with an elongation at break of 55.7%.

[0055] Example 4

[0056] A chromium-free LST-GO-Fe composite tanning agent, comprising the following components in the following weight ratio: 9.6g of triglycidyl isocyanurate, 120g of solvent, 12g of sodium lignosulfonate (LS1), 480g of ethanol, 0.05g of graphene oxide, 0.6g of ferric sulfate, and 0.2g of catalyst.

[0057] After tanning, the shrinkage temperature of the leather is 84.5℃, the thickening rate is 50%, and the tensile strength and tear strength of the tanned leather can reach 14.2 MPa and 63.7 N / mm, respectively, with an elongation at break of 76.3%.

[0058] Example 5

[0059] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0060] Step S1: Dissolve 13g of triglycidyl isocyanurate in 75g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 50°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0061] Step S2: Take 9g of LS and 0.1g of tetramethylethylenediamine and disperse them in a triglycidyl isocyanurate TGIC solution. Under mechanical stirring, keep the temperature at 50°C and stir for 3 hours to form a reaction mixture.

[0062] Step S3: Add 0.05g of graphene oxide and 0.5g of ferric sulfate to the reaction mixture obtained in step S2, heat and stir at 50°C for 3 hours to obtain a reaction mixture; the carbon content of the graphene oxide (GO) is 50%.

[0063] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 300g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate. After filtration, vacuum dry at 70°C for 12h to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0064] Example 6

[0065] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0066] Step S1: Dissolve 4g of triglycidyl isocyanurate in 90g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 60°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0067] Step S2: Take 5g LS and 0.12g triethylamine and disperse them in a triglycidyl isocyanurate TGIC solution. Under mechanical stirring, keep the temperature at 60°C and stir for 5 hours to form a reaction mixture.

[0068] Step S3: Add 0.06g of graphene oxide and 0.8g of ferric sulfate to the reaction mixture from step S2, heat at 60°C and stir for 1 hour to obtain a reaction mixture; the carbon content of the graphene oxide (GO) is 60%.

[0069] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 360g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate. After filtration, vacuum dry at 70°C for 14h to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0070] Example 7

[0071] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0072] Step S1: Dissolve 16g of triglycidyl isocyanurate in 100g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 60°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0073] Step S2: Take 13g LS and 0.4g tetramethylethylenediamine and disperse them in a triglycidyl isocyanate TGIC solution. Under mechanical stirring, keep the temperature at 60°C and stir for 4 hours to form a reaction mixture.

[0074] Step S3: Add 0.02g of graphene oxide and 0.2g of ferric sulfate to the reaction mixture from step S2, heat at 60°C and stir for 2 hours to obtain a reaction mixture; the graphene oxide (GO) has a carbon content of 70%.

[0075] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 400g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate, filter, and vacuum dry at 40°C to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0076] Example 8

[0077] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0078] Step S1: Dissolve 15g of triglycidyl isocyanurate in 125g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 75°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0079] Step S2: Take 16g LS and 0.64g triethylamine and disperse them in a triglycidyl isocyanurate TGIC solution. Under mechanical stirring, keep the temperature at 75°C and stir for 5 hours to form a reaction mixture.

[0080] Step S3: Add 0.07g of graphene oxide and 0.3g of ferric sulfate to the reaction mixture from step S2, heat at 75°C and stir for 3 hours to obtain a reaction mixture; the graphene oxide (GO) has a carbon content of 80%.

[0081] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 500g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate. After filtration, vacuum dry at 70°C for 13h to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0082] Example 9

[0083] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0084] Step S1: Dissolve 12g of triglycidyl isocyanurate in 137.5g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 55°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0085] Step S2: Take 8g LS and 0.3g tetramethylethylenediamine and disperse them in a triglycidyl isocyanurate TGIC solution. Under mechanical stirring, keep the temperature at 55°C and stir for 3 hours to form a reaction mixture.

[0086] Step S3: Add 0.05g of graphene oxide and 0.4g of ferric sulfate to the reaction mixture from step S2, heat at 55°C and stir for 1 hour to obtain a reaction mixture; the carbon content of the graphene oxide (GO) is 50%.

[0087] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 400g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate. After filtration, vacuum dry at 65°C for 18h to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0088] Example 10

[0089] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0090] Step S1: Dissolve 7g of triglycidyl isocyanurate in 90g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 70°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0091] Step S2: Take 8g LS and 0.5g triethylamine and disperse them in a triglycidyl isocyanurate TGIC solution. Under mechanical stirring, keep the temperature at 70°C and stir for 4 hours to form a reaction mixture.

[0092] Step S3: Add 0.03g of graphene oxide and 0.5g of ferric sulfate to the reaction mixture from step S2, heat at 70°C and stir for 2 hours to obtain a reaction mixture; the carbon content of the graphene oxide (GO) is 70%.

[0093] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 360g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate. After filtration, vacuum dry at 50°C for 14h to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0094] Example 11

[0095] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0096] Step S1: Dissolve 10g of triglycidyl isocyanurate in 200g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 80°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0097] Step S2: Take 12g LS and 0.6g tetramethylethylenediamine and disperse them in a triglycidyl isocyanate TGIC solution. Under mechanical stirring, keep the temperature at 80°C and stir for 3 hours to form a reaction mixture.

[0098] Step S3: Add 0.05g of graphene oxide and 0.2g of ferric sulfate to the reaction mixture from step S2, heat at 80°C and stir for 3 hours to obtain a reaction mixture; the carbon content of the graphene oxide (GO) is 60%.

[0099] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 800g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate. After filtration, vacuum dry at 40°C for 24h to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0100] Example 12

[0101] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0102] Step S1: Dissolve 8g of triglycidyl isocyanurate in 150g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 50°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0103] Step S2: Take 6g LS and 0.09g tetramethylethylenediamine and disperse them in a triglycidyl isocyanurate TGIC solution. Under mechanical stirring, keep the temperature at 50°C and stir for 3 hours to form a reaction mixture.

[0104] Step S3: Add 0.06g of graphene oxide and 0.8g of ferric sulfate to the reaction mixture from step S2, heat at 50°C and stir for 3 hours to obtain a reaction mixture; the carbon content of the graphene oxide (GO) is 80%.

[0105] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 600g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate. After filtration, vacuum dry at 60°C for 16h to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0106] Example 13

[0107] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0108] Step S1: Dissolve 10g of triglycidyl isocyanurate in 80g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 55°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0109] Step S2: Take 12g LS and 0.3g triethylamine and disperse them in a triglycidyl isocyanate triglycidyl ester TGIC solution. Under mechanical stirring, keep the temperature at 55℃ and stir for 4 hours to form a reaction mixture.

[0110] Step S3: Add 0.05g of graphene oxide and 0.3g of ferric sulfate to the reaction mixture from step S2, heat at 55°C and stir for 2 hours to obtain a reaction mixture; the graphene oxide (GO) has a carbon content of 50%.

[0111] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 320g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate, filter, and vacuum dry at 65°C for 20h to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0112] Example 14

[0113] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0114] Step S1: Dissolve 24g of triglycidyl isocyanurate in 180g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 80°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0115] Step S2: Take 16g LS and 0.45g tetramethylethylenediamine and disperse them in a triglycidyl isocyanurate TGIC solution. Under mechanical stirring, keep the temperature at 80°C and stir for 5 hours to form a reaction mixture.

[0116] Step S3: Add 0.05g of graphene oxide and 0.6g of ferric sulfate to the reaction mixture from step S2, heat at 80°C and stir for 1-3 hours to obtain a reaction mixture; the graphene oxide (GO) has a carbon content of 50%.

[0117] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 720g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate, filter, and vacuum dry at 70°C for 15h to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0118] Example 15

[0119] A method for preparing an LST-GO-Fe composite chromium-free tanning agent includes the following steps:

[0120] Step S1: Dissolve 23g of triglycidyl isocyanurate in 160g of water, pour the solution into a three-necked flask, place the three-necked flask in an oil bath, and heat to 60°C to obtain a homogeneous triglycidyl isocyanurate TGIC solution.

[0121] Step S2: Take 15g LS and 0.4g tetramethylethylenediamine dispersed triglycidyl isocyanate TGIC solution, heat and stir at 60℃ for 4h under mechanical stirring to form a reaction mixture;

[0122] Step S3: Add 0.08g of graphene oxide and 0.2g of ferric sulfate to the reaction mixture from step S2, heat at 60°C and stir for 1 hour to obtain a reaction mixture; the carbon content of the graphene oxide (GO) is 60%.

[0123] Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 640g of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate. After filtration, vacuum dry at 60°C for 23h to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

[0124] Application effect

[0125] When the LST-GO-Fe composite chromium-free tanning agent obtained in Example 4 was used for sheepskin tanning, the shrinkage temperature of the raw leather reached 84.5℃, the thickness increase rate was 50%, and there was no chromium emission.

[0126] Leveraging the natural renewability of LS and the high reactivity of TGIC, efficient resource utilization is achieved; the biomass-based framework of LST provides reactive sites and ecological safety; the photothermal conversion network of GO can provide solar energy management functions; Fe 3+ The "Trojan Horse" tanning center can achieve deep and uniform cross-linking through carrier loading, constructing an LST-GO-Fe ternary system. It is expected to simultaneously achieve tanning strengthening, photothermal management and electromagnetic shielding, promoting the green and intelligent transformation and upgrading of leather manufacturing, and providing technical support for the development of environmentally friendly new materials.

[0127] See Figure 1 , Figure 1 The graph shows the photothermal response curves of LST-GO-Fe tanned leather under different solar radiation intensities. The horizontal axis represents time (in seconds, ranging from 0 to 360 s), divided into two stages: "180 s with light on" and "180 s with light off". The vertical axis represents the temperature of the tanned leather (in degrees Celsius, ranging from 20 to 100 degrees Celsius). The four different curves in the graph correspond to different solar radiation intensities: the light blue dashed line represents 600 W / m², the dark blue solid line represents 1000 W / m², the pink dashed line represents 1400 W / m², and the red solid line represents 1800 W / m². Within 0-180 seconds of the illumination period, the tanning temperature under different conditions continuously increased with time. The higher the radiation intensity, the faster the temperature rise and the higher the peak temperature. At 180 seconds, the temperature corresponding to 1800 W / m² reached 93℃, 1400 W / m² reached 74℃, 1000 W / m² reached 57℃, and 600 W / m² reached 47℃. During the illumination-off period from 180 to 360 seconds, the temperature under each condition gradually decreased. The higher the initial temperature (the higher the radiation intensity), the faster the rate of temperature decrease. By 360 seconds, the temperature had mostly dropped back to around 40℃. This curve clearly demonstrates the excellent photothermal response capability of LST-GO-Fe tanning, confirming its photothermal management function and providing data support for the green and intelligent application of materials.

[0128] Terminology Explanation: LS stands for sodium lignosulfonate, TGIC stands for triglycidyl isocyanurate, LST stands for the complex of LS grafted with TGIC, GO stands for graphene oxide, Fe2(SO4)3 stands for ferric sulfate, and LST-GO-Fe stands for a multifunctional chromium-free tanning agent.

[0129] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An LST-GO-Fe composite chromium-free tanning agent, characterized in that, The formula, by weight, includes the following components: 4-24g triglycidyl isocyanurate, 75-200g solvent, 5-16g sodium lignosulfonate, 300-800g ethanol, 0.02-0.08g graphene oxide, 0.2-0.8g ferric sulfate, and 0.05-0.64g catalyst.

2. The LST-GO-Fe composite chromium-free tanning agent according to claim 1, characterized in that, The solvent is water; the ethanol is replaced by methanol; and the catalyst is tetramethylethylenediamine or triethylamine.

3. A method for preparing an LST-GO-Fe composite chromium-free tanning agent, characterized in that, Includes the following steps: Step S1: Dissolve 4-24g of triglycidyl isocyanurate in 75-200g of water and heat to 50℃~80℃ to obtain a homogeneous triglycidyl isocyanurate TGIC solution. Step S2: Add 5-16g of sodium lignosulfonate LS and 0.05-0.64g of catalyst to the triglycidyl isocyanurate TGIC solution from step S1, heat and stir at 50℃~80℃ for 3h~5h to obtain a reaction mixture. Step S3: Add 0.02-0.08g of graphene oxide and 0.2-0.8g of ferric sulfate to the reaction mixture in step S2, heat and stir at 50℃~80℃ for 1h~3h to obtain the reaction mixture; Step S4: Cool the reaction mixture prepared in step S3 to room temperature, add 300-800g of ethanol to precipitate the product, filter and wash the precipitate, and vacuum dry it at 40℃~70℃ to obtain solid powder LST-GO-Fe composite chromium-free tanning agent.

4. The preparation method of the LST-GO-Fe composite chromium-free tanning agent according to claim 3, characterized in that, In step S1, the solvent is deionized water or water.

5. The preparation method of the LST-GO-Fe composite chromium-free tanning agent according to claim 3, characterized in that, In step S2, the mass ratio of sodium lignosulfonate (LS) to triglycidyl isocyanate (TGIC) is 0.8–1.

5.

6. The method for preparing an LST-GO-Fe composite chromium-free tanning agent according to claim 5, characterized in that, The catalyst is tetramethylethylenediamine or triethylamine, and the amount used is 1% to 4% of the mass of sodium lignosulfonate (LS).

7. The preparation method of the LST-GO-Fe composite chromium-free tanning agent according to claim 3, characterized in that, In step S3, the carbon content of the graphene oxide (GO) is 50% to 80%.

8. The method for preparing an LST-GO-Fe composite chromium-free tanning agent according to claim 3, characterized in that, In step S4, ethanol is used to wash the precipitate, with a mass ratio of ethanol to water of 4:

1.

9. The preparation method according to claim 3, characterized in that, In step S4, the vacuum drying time is 12h to 24h.

10. The application of the LST-GO-Fe composite chromium-free tanning agent according to claim 1 in leather tanning.

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