Sodium lignin sulfonate-TGIC (triglycidyl isocyanurate) composite chrome-free tanning agent as well as preparation method and application thereof

Abstract

The invention discloses a sodium lignin sulfonate-TGIC composite functional chrome-free tanning agent as well as a preparation method and application thereof. The sodium lignin sulfonate-TGIC composite functional chrome-free tanning agent comprises the following components: triglycidyl isocyanurate, an organic solvent, a sodium lignin sulfonate LS solution and ethanol, the preparation method comprises the following steps: S1, dissolving triglycidyl isocyanurate in an organic solvent or water, and heating to obtain a uniform triglycidyl isocyanurate TGIC solution; s2, adding a sodium lignin sulfonate LS solution into the triglycidyl isocyanurate TGIC solution in the step S1, heating and stirring for reaction to obtain a reaction mixed solution; s3, cooling the reaction mixed solution prepared in the step S2 to room temperature, adding ethanol, precipitating a product, filtering, washing, precipitating, and performing vacuum drying to obtain a solid powdery LST chrome-free tanning agent for leather tanning; the combining capacity of the tanning agent and leather collagen fibers is remarkably improved; the prepared LST tanning agent is environmentally friendly, low in cost and capable of replacing a traditional chrome tanning agent.

Description

Technical Field

[0001] The invention belongs to the technical field of leather chemical preparation, and specifically relates to a sodium lignin sulfonate-TGIC composite chrome-free tanning agent, a preparation method and application thereof. Background Art

[0002] In recent years, as global environmental problems have become increasingly severe, the development of eco-friendly and resource-saving new materials has become a strategic focus of industrial development in various countries. 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 field of leather manufacturing, although the traditional chrome tanning method has long dominated due to its high tanning efficiency and excellent leather performance, the chromium pollution problem generated during its use has become increasingly prominent. Cr³⁺ in chrome tanning agents can be oxidized to highly toxic Cr under certain conditions. 6 ⁺, not only does it cause serious harm to the ecological environment, but it may also pose a threat to human health through the food chain. Therefore, the development of efficient and environmentally friendly chrome-free tanning agents has become a strategic goal that the leather industry urgently needs to solve.

[0003] Sodium lignin sulfonate (LS) is a by-product of the papermaking industry. It is rich in active groups such as sulfonic acid and hydroxyl groups. It is naturally renewable and biodegradable, but its reactivity is insufficient when used directly in tanning. Triglycidyl isocyanurate (TGIC) contains highly active epoxy groups and can be efficiently cross-linked with amino, hydroxyl and other groups. In the research and development of environmentally friendly tanning agents, the utilization of biomass resources has attracted much attention. Sodium lignin sulfonate (LS), as a by-product of the papermaking industry, is regarded as a potential environmentally friendly tanning agent raw material because of its natural renewable and biodegradable characteristics. LS molecules contain abundant active groups such as sulfonic acid and hydroxyl groups, and have the potential to undergo cross-linking reactions with collagen molecules. However, due to the low reactivity of LS, it is difficult to achieve the ideal tanning effect when it is directly used in tanning, which limits its application in actual production.

[0004] On the other hand, triglycidyl isocyanurate (TGIC), as a highly active crosslinking agent, has attracted widespread attention due to its rich epoxy groups in its molecules. The epoxy groups of TGIC can undergo efficient crosslinking reactions with functional groups such as amino and hydroxyl groups, and this property makes it show great potential in the field of material modification. However, the application of TGIC in leather tanning has not been fully studied, especially in the synergistic effect with biomass raw materials (such as LS), which is still in its infancy.

[0005] In summary, in view of the environmental pollution problems of traditional chrome tanning and the limitations of existing chrome-free tanning agents, the development of an efficient and environmentally friendly tanning agent based on biomass resources has important practical significance and broad application prospects. By innovatively combining the advantages of LS and TGIC, it is expected to achieve the green transformation of leather manufacturing process and provide technical support for the development of environmentally friendly new materials. Summary of the invention

[0006] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a sodium lignin sulfonate-TGIC composite functional chrome-free tanning agent, a preparation method and an application thereof. The tanning agent forms a stable three-dimensional network structure by chemically cross-linking the epoxy group of TGIC with the sulfonic acid group and hydroxyl group of LS, thereby significantly improving the tanning effect.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A sodium lignin sulfonate-TGIC composite chrome-free tanning agent, characterized in that it comprises the following components in the following weight ratio: 3-20 g of triglycidyl isocyanurate, 50-100 ml of an organic solvent, 5-18 g of a sodium lignin sulfonate LS solution, 300-600 ml of ethanol, and 0.05-0.72 g of a catalyst.

[0009] The organic solvent is replaced by water; the ethanol is replaced by methanol.

[0010] A method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent comprises the following steps:

[0011] Step S1: dissolving 3-20 g of triglycidyl isocyanurate in 50-100 ml of an organic solvent or water at a heating temperature of 50° C. to 80° C. to obtain a uniform triglycidyl isocyanurate TGIC solution;

[0012] Step S2: adding 5-18 g of sodium lignin sulfonate LS solution to the triglycidyl isocyanurate TGIC solution of step S1, heating at 50° C. to 80° C. and stirring for reaction for 3 h to 8 h to obtain a reaction mixture;

[0013] Step S3: Cool the reaction mixture prepared in step S2 to room temperature, add 300-600 ml of ethanol or methanol to precipitate the product, filter and wash the precipitate, and vacuum dry it at 40°C to 70°C to obtain a solid powdery LST chrome-free tanning agent, i.e., triglycidyl isocyanurate modified sodium lignin sulfonate organic chrome-free tanning agent.

[0014] In step S1, the organic solvent is dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

[0015] In step S1, the heating temperature is 60°C to 80°C.

[0016] In step S2, sodium lignin sulfonate LS and a catalyst are dispersed in dimethyl sulfoxide or water to obtain a sodium lignin sulfonate LS solution.

[0017] The catalyst is tetramethylethylenediamine or triethylamine, and the amount used is 1% to 4% of the mass of sodium lignin sulfonate LS; in step S2, 5 to 18 g of sodium lignin sulfonate LS solution is added to the heated triglycidyl isocyanurate solution, and the heating temperature is kept unchanged for 4 to 6 hours.

[0018] In step S3, ethanol is used to wash the precipitate, and the volume ratio of ethanol to the reaction mixture is 3:1.

[0019] In step S3, the vacuum drying time is 12 h to 24 h, and the drying temperature is 40-60° C. to obtain a solid powdery LST chrome-free tanning agent.

[0020] In step S3, the ethanol is replaced by methanol or propanol.

[0021] The molecular weight of the sodium lignin sulfonate is 200-800.

[0022] The application of the sodium lignin sulfonate-TGIC composite chrome-free tanning agent LST in leather tanning.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The invention discloses a method for preparing an organic chrome-free tanning agent of sodium lignin sulfonate modified by triglycidyl isocyanurate, wherein the hydroxyl group of sodium lignin sulfonate is chemically cross-linked with the epoxy group of triglycidyl isocyanurate to prepare a crude product mixture. After precipitation and vacuum drying, a solid powder of an organic chrome-free tanning agent of sodium lignin sulfonate modified by triglycidyl isocyanurate is prepared. With triglycidyl isocyanurate (TGIC) and sodium lignin sulfonate (LS) as raw materials, the preparation of an organic chrome-free tanning agent is realized, the preparation method is simple, the prepared organic chrome-free tanning agent can be applied to tanning experiments, and the crust leather tanned by the tanning agent has a higher shrinkage temperature, physical and mechanical properties and water washing resistance. Therefore, the novel organic chrome-free tanning agent proposed by the invention can not only solve the chromium pollution problem in the leather industry, but also reduce the use of mildew inhibitors in the leather industry. In this way, the green and sustainable development of the leather industry is promoted.

[0025] Sodium lignin sulfonate (LS), a by-product of the papermaking industry, is rich in sulfonic acid groups and hydroxyl groups. It is naturally renewable, low-cost and environmentally friendly. However, it has a weak binding force with collagen fibers when used directly for tanning. The hydroxyl groups in its structure make it possible to undergo epoxidation modification.

[0026] The invention applies triglycidyl isocyanurate modified sodium lignin sulfonate organic chrome-free tanning agent to tanning, which reduces the harm of chrome tanning agent to human beings and the environment and can also give the crust leather a higher shrinkage temperature, physical and mechanical properties and water washing resistance.

[0027] The invention makes full use of the natural renewability of sodium lignin sulfonate, the reactivity of sulfonic acid group and hydroxyl group, and the high reaction efficiency of epoxy group of TGIC, and significantly improves the binding ability of tanning agent and leather collagen fiber. The prepared LST tanning agent is green, environmentally friendly, low-cost, and can replace traditional chrome tanning agent.

[0028] The invention combines sodium lignin sulfonate LS with triglycidyl isocyanurate TGIC to prepare an LST chrome-free tanning agent with both environmental protection and functionality, thereby solving the problem of insufficient performance of traditional chrome-free tanning agents. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with specific examples. To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the specific embodiments are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0030] Example 1

[0031] A sodium lignin sulfonate-TGIC composite chrome-free tanning agent LST, comprising the following components according to the following weight ratio: 3g of triglycidyl isocyanurate, 50ml of an organic solvent, 5g of a sodium lignin sulfonate LS solution, 300ml of ethanol, and 0.05g of a catalyst;

[0032] The organic solvent is replaced by water; the ethanol is replaced by methanol.

[0033] Example 2

[0034] A sodium lignin sulfonate-TGIC composite chrome-free tanning agent LST, comprising the following components according to the following weight ratio: 11.5 g of triglycidyl isocyanurate, 75 ml of an organic solvent, 11.5 g of a sodium lignin sulfonate LS solution, 450 ml of ethanol, and 0.385 g of a catalyst;

[0035] The organic solvent is replaced by water; the ethanol is replaced by methanol.

[0036] Example 3

[0037] A sodium lignin sulfonate-TGIC composite chrome-free tanning agent LST, comprising the following components according to the following weight ratio: 20g of triglycidyl isocyanurate, 100ml of an organic solvent, 18g of sodium lignin sulfonate LS solution, 600ml of ethanol, and 0.72g of a catalyst;

[0038] The organic solvent is replaced by water; the ethanol is replaced by methanol.

[0039] Example 4

[0040] A sodium lignin sulfonate-TGIC composite chrome-free tanning agent LST, comprising the following components according to the following weight ratio: 6.6g of triglycidyl isocyanurate, 55ml of an organic solvent, 10g of a sodium lignin sulfonate LS solution, 500ml of ethanol, and 0.1g of a catalyst;

[0041] The organic solvent is replaced by water; the ethanol is replaced by methanol.

[0042] Example 5

[0043] A method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent comprises the following steps:

[0044] Step S1, dissolving 13.3 g of triglycidyl isocyanurate in 60 ml of water, pouring the mixture into a three-necked flask, and heating the three-necked flask in an oil bath at 65° C. to obtain a uniform triglycidyl isocyanurate TGIC solution;

[0045] Step S2, taking 10g LS (sulfonation degree 1.2mmol / g) and 0.25g tetramethylethylenediamine and dispersing them into 100mL water to obtain a sodium lignin sulfonate LS solution, pouring the obtained sodium lignin sulfonate LS solution into a constant pressure dropping funnel, and slowly dropping the sodium lignin sulfonate LS solution in the constant pressure dropping funnel into a three-necked flask under mechanical stirring, reacting for 6h to form a reaction mixture;

[0046] Step S3, cooling the reaction mixture prepared in step S2 to room temperature, adding 500 ml of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate, filtering, and vacuum drying at 50° C. to obtain triglycidyl isocyanurate-modified sodium lignin sulfonate organic chrome-free tanning agent LST, that is, solid powdered LST chrome-free tanning agent.

[0047] Example 6

[0048] A method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent comprises the following steps:

[0049] Step S1, dissolving 8 g of triglycidyl isocyanurate in 70 ml of water, pouring the mixture into a three-necked flask, and heating the three-necked flask in an oil bath at 65° C. to obtain a uniform triglycidyl isocyanurate TGIC solution;

[0050] Step S2, taking 12g LS (sulfonation degree 1.2mmol / g) and 0.42g tetramethylethylenediamine and dispersing them into 80mL water to obtain a sodium lignin sulfonate LS solution, pouring the obtained sodium lignin sulfonate LS solution into a constant pressure dropping funnel, and slowly dropping the sodium lignin sulfonate LS solution in the constant pressure dropping funnel into a three-necked flask under mechanical stirring, reacting for 7h to form a reaction mixture;

[0051] Step S3, cooling the reaction mixture prepared in step S2 to room temperature, adding 500 ml of ethanol and methanol to precipitate the product and remove unreacted triglycidyl isocyanurate, filtering, and vacuum drying at 60° C. to obtain triglycidyl isocyanurate-modified sodium lignin sulfonate organic chrome-free tanning agent LST, that is, solid powdered LST chrome-free tanning agent.

[0052] Example 7

[0053] A method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent comprises the following steps:

[0054] Step S1, dissolving 5.7 g of triglycidyl isocyanurate in 80 ml of water, pouring the mixture into a three-necked flask, and heating the three-necked flask in an oil bath at 65° C. to obtain a uniform triglycidyl isocyanurate TGIC solution;

[0055] Step S2, taking 9g LS (sulfonation degree 1.2mmol / g) and 0.36g triethylamine and dispersing them into 90mL water to obtain a sodium lignin sulfonate LS solution, pouring the obtained sodium lignin sulfonate LS solution into a constant pressure dropping funnel, and slowly dropping the sodium lignin sulfonate LS solution in the constant pressure dropping funnel into a three-necked flask under mechanical stirring, reacting for 8h to form a reaction mixture;

[0056] Step S3, cooling the reaction mixture prepared in step S2 to room temperature, adding 500 ml of propanol to precipitate the product and remove unreacted triglycidyl isocyanurate, filtering, and vacuum drying at 55° C. to obtain triglycidyl isocyanurate-modified sodium lignin sulfonate organic chrome-free tanning agent LST, that is, solid powdered LST chrome-free tanning agent.

[0057] Example 8

[0058] A method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent comprises the following steps:

[0059] Step S1, dissolving 8.3 g of triglycidyl isocyanurate in 100 ml of water, pouring the mixture into a three-necked flask, and heating the three-necked flask in an oil bath at 65° C. to obtain a uniform triglycidyl isocyanurate TGIC solution;

[0060] Step S2, taking 13g LS (sulfonation degree 1.2mmol / g) and 0.52g triethylamine and dispersing them into 60mL water to obtain a sodium lignin sulfonate LS solution, pouring the obtained sodium lignin sulfonate LS solution into a constant pressure dropping funnel, and slowly dropping the sodium lignin sulfonate LS solution in the constant pressure dropping funnel into a three-necked flask under mechanical stirring, reacting for 4h to form a reaction mixture;

[0061] Step S3, cooling the reaction mixture prepared in step S2 to room temperature, adding 500 ml of propanol to precipitate the product and remove unreacted triglycidyl isocyanurate, filtering, and vacuum drying at 40° C. to obtain triglycidyl isocyanurate modified sodium lignin sulfonate organic chrome-free tanning agent LST, that is, solid powdered LST chrome-free tanning agent.

[0062] Example 9

[0063] A method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent comprises the following steps:

[0064] Step S1, dissolving 3 g of triglycidyl isocyanurate in 50 ml of an organic solvent, pouring the mixture into a three-necked flask, and heating the three-necked flask in an oil bath at 65° C. to obtain a uniform triglycidyl isocyanurate TGIC solution;

[0065] Step S2, taking 5g LS (sulfonation degree 1.2mmol / g) and 0.05g triethylamine and dispersing them into 50mL water to obtain a sodium lignin sulfonate LS solution, pouring the obtained sodium lignin sulfonate LS solution into a constant pressure dropping funnel, and slowly dropping the sodium lignin sulfonate LS solution in the constant pressure dropping funnel into a three-necked flask under mechanical stirring, maintaining heating and stirring at 50°C for 8h to form a reaction mixture;

[0066] Step S3, cooling the reaction mixture prepared in step S2 to room temperature, adding 500 ml of ethanol to precipitate the product and remove unreacted triglycidyl isocyanurate, filtering, and vacuum drying at 40° C. to obtain triglycidyl isocyanurate modified sodium lignin sulfonate organic chrome-free tanning agent LST, i.e., solid powdered LST chrome-free tanning agent.

[0067] In step S1, the organic solvent is dimethyl sulfoxide (DMSO).

[0068] In step S2, sodium lignin sulfonate LS and a catalyst are dispersed in dimethyl sulfoxide DMSO to obtain a sodium lignin sulfonate LS solution.

[0069] The catalyst is triethylamine, and the amount used is 1% of the mass of sodium lignin sulfonate LS.

[0070] In step S3, ethanol is used to wash the precipitate, and the volume ratio of ethanol to the reaction mixture is 3:1.

[0071] In step S3, the vacuum drying time is 12 hours to obtain a solid powdery LST chrome-free tanning agent.

[0072] The molecular weight of the sodium lignin sulfonate is 400.

[0073] Example 10

[0074] A method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent comprises the following steps:

[0075] Step S1, dissolving 11.5 g of triglycidyl isocyanurate in 55 ml of an organic solvent, pouring the mixture into a three-necked flask, and heating the three-necked flask in an oil bath at 65° C. to obtain a uniform triglycidyl isocyanurate TGIC solution;

[0076] Step S2, taking 11.5g of sodium lignin sulfonate LS solution (sulfonation degree 1.2mmol / g) and 0.23g of catalyst and dispersing them into 45mL of water to obtain sodium lignin sulfonate LS solution, pouring the sodium lignin sulfonate LS solution into a constant pressure dropping funnel, and slowly dropping the sodium lignin sulfonate LS solution in the constant pressure dropping funnel into a three-necked flask under mechanical stirring conditions, reacting for 6h to form a reaction mixture;

[0077] Step S3, cooling the reaction mixture prepared in step S2 to room temperature, adding 500 ml of methanol to precipitate the product and remove unreacted triglycidyl isocyanurate, filtering, and vacuum drying at 50° C. to obtain triglycidyl isocyanurate-modified sodium lignin sulfonate organic chrome-free tanning agent LST, that is, solid powdered LST chrome-free tanning agent.

[0078] In step S1, the organic solvent is N,N-dimethylformamide (DMF).

[0079] In step S2, sodium lignin sulfonate LS and a catalyst are dispersed in N,N-dimethylformamide DMF to obtain a sodium lignin sulfonate LS solution.

[0080] The catalyst is tetramethylethylenediamine, and the amount used is 2% of the mass of sodium lignin sulfonate LS; in step S2, the obtained sodium lignin sulfonate LS solution is added to the heated triglycidyl isocyanurate solution, and the heating temperature is kept unchanged for 6.5 hours.

[0081] In step S3, methanol is used to wash the precipitate, and the volume ratio of methanol to the reaction mixture is 3:1.

[0082] In step S3, the vacuum drying time is 18 hours and the drying temperature is 55° C. to obtain a solid powdery LST chrome-free tanning agent.

[0083] The molecular weight of the sodium lignin sulfonate is 500.

[0084] Embodiment 11

[0085] A method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent comprises the following steps:

[0086] Step S1, dissolving 20 g of triglycidyl isocyanurate in 45 ml of water, pouring the mixture into a three-necked flask, and heating the three-necked flask in an oil bath at 80° C. to obtain a uniform triglycidyl isocyanurate TGIC solution;

[0087] Step S2, taking 18g of sodium lignin sulfonate LS solution (sulfonation degree 1.2mmol / g) and 0.72g of catalyst and dispersing them into 55mL of water to obtain sodium lignin sulfonate LS solution, pouring the obtained sodium lignin sulfonate LS solution into a constant pressure dropping funnel, and slowly dropping the sodium lignin sulfonate LS solution in the constant pressure dropping funnel into a three-necked flask under mechanical stirring, reacting at 80°C for 8h to form a reaction mixture;

[0088] Step S3, cooling the reaction mixture prepared in step S2 to room temperature, adding 500 ml of propanol, precipitating the product and removing unreacted triglycidyl isocyanurate, filtering, and vacuum drying at 70° C. to obtain triglycidyl isocyanurate-modified sodium lignin sulfonate organic chrome-free tanning agent LST, that is, solid powdered LST chrome-free tanning agent.

[0089] In step S2, sodium lignin sulfonate LS and a catalyst are dispersed in water to obtain a sodium lignin sulfonate LS solution.

[0090] The catalyst is tetramethylethylenediamine, and the amount used is 4% of the mass of sodium lignin sulfonate LS.

[0091] In step S3, ethanol is used to wash the precipitate, and the volume ratio of ethanol to the reaction mixture is 3:1.

[0092] In step S3, the vacuum drying time is 24 hours and the drying temperature is 70° C. to obtain a solid powdery LST chrome-free tanning agent.

[0093] The molecular weight of the sodium lignin sulfonate is 600.

[0094] Example 12

[0095] A method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent comprises the following steps:

[0096] Step S1, dissolving 18 g of triglycidyl isocyanurate in 50 ml of water, pouring the mixture into a three-necked flask, and heating the three-necked flask in an oil bath at 75° C. to obtain a uniform triglycidyl isocyanurate TGIC solution;

[0097] Step S2, taking 17g of sodium lignin sulfonate LS solution (sulfonation degree 1.2mmol / g) and 0.51g of catalyst and dispersing them into 50mL of water to obtain sodium lignin sulfonate LS solution, pouring the obtained sodium lignin sulfonate LS solution into a constant pressure dropping funnel, and slowly dropping the sodium lignin sulfonate LS solution in the constant pressure dropping funnel into a three-necked flask under mechanical stirring, reacting at 78°C for 7h to form a reaction mixture;

[0098] Step S3, cooling the reaction mixture prepared in step S2 to room temperature, adding 500 ml of propanol, precipitating the product and removing unreacted triglycidyl isocyanurate, filtering, and vacuum drying at 60° C. to obtain triglycidyl isocyanurate-modified sodium lignin sulfonate organic chrome-free tanning agent LST, that is, solid powdered LST chrome-free tanning agent.

[0099] The catalyst is triethylamine, and the amount used is 3% of the mass of sodium lignin sulfonate LS; in step S2, the obtained sodium lignin sulfonate LS solution is added to the heated triglycidyl isocyanurate solution, and the heating temperature is kept unchanged for 8 hours.

[0100] In step S3, the vacuum drying time is 23 hours and the drying temperature is 55° C. to obtain a solid powdery LST chrome-free tanning agent.

[0101] The molecular weight of the sodium lignin sulfonate is 600.

[0102] Application Effect

[0103] The LST tanning agent obtained in Example 5 was used for sheepskin tanning, and the shrinkage temperature of the crust leather reached 84°C, the tensile strength was 25 MPa, the water washing resistance was good (the thickening rate after 5 water washings was ≤3%), and there was no chromium emission.

[0104] By utilizing the natural renewability of LS and the high reactivity of TGIC, efficient resource utilization can be achieved; the three-dimensional cross-linked structure enhances the binding force between tanning agent and collagen and improves leather performance; the preparation process is simple and suitable for industrial production, promoting the green transformation of the leather industry.

[0105] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A sodium lignin sulfonate-TGIC composite chrome-free tanning agent, characterized in that: The following components are included according to the following weight ratio: 3-20 g of triglycidyl isocyanurate, 50-100 ml of an organic solvent, 5-18 g of a sodium lignin sulfonate LS solution, 300-600 ml of ethanol, and 0.05-0.72 g of a catalyst.

2. The sodium lignin sulfonate-TGIC composite chrome-free tanning agent LST according to claim 1, characterized in that: The organic solvent is replaced by water; the ethanol is replaced by methanol.

3. A method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent, characterized in that: The following steps are involved: Step S1: dissolving 3-20 g of triglycidyl isocyanurate in 50-100 ml of an organic solvent or water, and heating to 50° C. to 80° C. to obtain a uniform triglycidyl isocyanurate TGIC solution; Step S2: adding 5-18 g of sodium lignin sulfonate LS solution to the triglycidyl isocyanurate TGIC solution of step S1, heating at 50° C. to 80° C. and stirring for reaction for 3 h to 8 h to obtain a reaction mixture; Step S3: Cool the reaction mixture prepared in step S2 to room temperature, add 300-600 ml of ethanol to precipitate the product, filter and wash the precipitate, and vacuum dry it at 40° C. to 70° C. to obtain a solid powdered LST chrome-free tanning agent.

4. The method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent according to claim 3, characterized in that: In step S1, the organic solvent is dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

5. The method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent according to claim 3, characterized in that: In step S2, the molecular weight of the sodium lignin sulfonate LS is 200-800, and the degree of sulfonation is 1.2-2.5 mmol / g.

6. The method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent according to claim 3, characterized in that: In step S2, the mass ratio of sodium lignin sulfonate LS to triglycidyl isocyanurate TGIC is 0.75-1:75; sodium lignin sulfonate LS and 0.05-0.72g of catalyst are dispersed in 50-100ml of dimethyl sulfoxide or 50-100ml of water to obtain a sodium lignin sulfonate LS solution.

7. The method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent according to claim 6, characterized in that: The catalyst is tetramethylethylenediamine or triethylamine, and the amount used is 1% to 4% of the mass of sodium lignin sulfonate LS; in step S2, 5 to 18 g of sodium lignin sulfonate LS solution is added to the heated triglycidyl isocyanurate solution, and the heating temperature is kept unchanged for 4 to 6 hours.

8. The method for preparing a sodium lignin sulfonate-TGIC composite chrome-free tanning agent according to claim 3, characterized in that: In step S3, ethanol is used to wash the precipitate, and the volume ratio of ethanol to the reaction mixture is 3:

1.

9. The preparation method according to claim 3, characterized in that: The vacuum drying time in step S3 is 12 h to 24 h.

10. Use of the sodium lignin sulfonate-TGIC composite chrome-free tanning agent LST according to claim 1 in leather tanning.