Preparation method of leather tanning agent based on modified concave-convex rod crystals

Abstract

The present invention discloses a preparation method of a leather tanning agent based on modified convexobar crystals, specifically: γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, and deionized water are sequentially added to a convexobar crystal solution, stirred to obtain a mixed solution; hydrochloric acid is added to the obtained mixed solution to adjust the pH to 4-6, and then freeze-dried to obtain a solid powder, which is a leather tanning agent modified by convexobar crystals. The present invention stably combines the epoxy groups on the convexobar crystals modified with KH-560 through the amino groups in chitosan, and the free epoxy groups exert a tanning effect and cross-link with collagen fibers, thereby greatly improving the shrinkage temperature of the leather. In addition, the present invention proposes a "gradient feeding in-situ one-step preparation strategy" to modify the convexobar crystals, which is environmentally friendly and simple, and realizes the sustainable development of chrome-free tanning technology.

Description

Technical Field

[0001] The invention belongs to the technical field of leather tanning agent preparation, and particularly relates to a preparation method of a leather tanning agent based on modified concave-convex rod crystals. Background Art

[0002] Attapulgite is a natural one-dimensional porous nanomaterial. Due to its unique crystal structure, it possesses advantages such as large specific surface area, strong adsorption properties, high chemical stability, and strong ion exchangeability. Due to its unique pore structure and these physical and chemical properties, it has broad applications and research in many diverse fields, including soil remediation and transformation, water pollution treatment, catalysis, and functional carriers. However, leather tanned using attapulgite has extremely poor blending properties. The main reasons are its poor dispersibility, easy agglomeration, which makes it difficult to penetrate, and its lack of flexibility. Therefore, it requires certain treatments to be better suited for tanning. Modification of attapulgite aims to improve its dispersion properties in polymers or enhance its various properties. Secondly, due to its large specific surface area, attapulgite is prone to agglomeration in solvents, and its surface contains a large number of polar hydroxyl groups, resulting in poor affinity with non-polar organic polymers. Therefore, modifying the surface of the attapulgite can improve the compatibility of the attapulgite with other materials, which is also beneficial to improving the dispersibility and stability of the attapulgite in the polymer system, so as to obtain a nano-composite material with excellent performance.

[0003] Chitosan has suitable water solubility, surface charge properties, and functional groups suitable for setting up the system. Although scholars in other fields have used chitosan to modify attapulgite, their methods and processes are not suitable for the leather industry. For example, Peng Yonggang et al. used chitosan to graft and modify attapulgite to obtain an adsorption material. The process system is relatively complex, which limits its application in actual production. At the same time, the bonding in its reaction mechanism is relatively unstable, and the reagent dialdehyde used in the experiment is relatively limited in fields such as leather making, which is contrary to the clean production concept in leather technology. Therefore, the modification method is not suitable for leather tanning technology. Therefore, it is of great significance to explore a method for modifying attapulgite in the leather tanning field that is simple to operate and has good tanning effects. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of a leather tanning agent based on modified convexo-convexo rod crystals, thereby improving the surface activity of the convexo-convexo rod crystals and enhancing the tanning performance of the convexo-convexo rod crystals.

[0005] The technical solution adopted by the present invention is a method for preparing a leather tanning agent based on modified convexo-convex rod crystals, which is specifically implemented according to the following steps:

[0006] Step 1, adding γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, and deionized water to the convexo-convexo-rod crystal solution in sequence, stirring, and obtaining a mixed solution;

[0007] Step 2: adding hydrochloric acid to the mixed solution obtained in step 1 to adjust the pH to 4-6, and then freeze-drying the mixture to obtain a solid powder which is a leather tanning agent modified with convexo-convex rod crystals.

[0008] The present invention is also characterized in that:

[0009] In step 1, the stirring temperature is 60-80° C., the stirring time is 1.5-3.5 h, and the stirring rate is 300-500 r / min.

[0010] In step 1, the mass concentration of the convexo-rod crystal solution is 15-30 g / L.

[0011] In step 1, the mass ratio of γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, deionized water, and convexo-rod crystal solution is 1-3:1-3:0.1-0.4:50-60:200-300.

[0012] In step 2, the freeze-drying temperature is -40 to -10°C, and the freeze-drying time is 8 to 12 hours.

[0013] The beneficial effects of the present invention are:

[0014] (1) The present invention utilizes γ-glycidyl ether propyl trimethoxysilane (KH-560) to modify the convex rod crystals, thereby solving the problem of unstable dispersion of convex rods in aqueous solution, and facilitating the penetration of the convex rod crystals into the collagen fiber structure, playing a filling role and improving its tanning effect. At the same time, the surface of the convex rod crystals has a large number of silanol groups, which can undergo dehydration condensation with the silanol groups generated after the hydrolysis of KH-560 and cross-link together, grafting the active functional groups on the other side of KH-560 onto the surface of the convex rod crystals, greatly improving the surface activity of the convex rod crystals, and providing more active binding sites for the subsequent combination of the convex rod crystals with chitosan, and the combination between the chitosan-modified convex rod composite tanning agent and the leather collagen fibers;

[0015] (2) The present invention stably combines the amino groups in chitosan with the epoxy groups on the KH-560 modified concave-convex rod crystals, wherein the free epoxy groups play a tanning role and cross-link with the collagen fibers, thereby greatly increasing the shrinkage temperature of the leather;

[0016] (3) By gradient addition, the in-situ one-step modification of the convex-concave rod crystals was achieved to obtain a new organic-inorganic combined tanning agent. No traditional chrome tanning reagents were used in the preparation process, which continued the sustainable development concept of chrome-free tanning technology. The experimental operation is simple and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a graph of shrinkage temperature of leather tanned with a tanning agent modified with concavo-convex rod crystals of the present invention;

[0018] Figure 2 The infrared spectra of γ-glycidyl ether propyl trimethoxysilane (KH-560), concave-convex rod crystals, and modified concave-convex rod crystals;

[0019] Figure 3 These are infrared spectra of chitosan, modified convexo-convexo rod crystals, and chitosan-modified convexo-convexo rod crystals;

[0020] Figure 4 This is an SEM image of a cross section of leather tanned with the chitosan-modified attapulgite rod crystal tanning agent of the present invention (I);

[0021] Figure 5 This is the SEM picture (2) of the cross section of leather after tanning with the chitosan-modified attapulgite rod crystal tanning agent of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] The preparation method of the leather tanning agent based on the modification of convexo-convex rod crystals of the present invention is specifically implemented according to the following steps:

[0024] Step 1, adding γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, and deionized water in sequence to a convexo-concave rod crystal solution with a mass concentration of 15-30 g / L, stirring to obtain a mixed solution;

[0025] The stirring temperature is 60-80°C, the stirring time is 1.5-3.5h, and the stirring rate is 300-500r / min;

[0026] The mass ratio of γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, deionized water, and convexo-rod crystal solution is 1-3:1-3:0.1-0.4:50-60:200-300;

[0027] Step 2, adding hydrochloric acid to the mixed solution obtained in step 1 to adjust the pH to 4-6, and then freeze-drying to obtain a solid powder which is a leather tanning agent modified with convexo-convex rod crystals;

[0028] The freeze-drying temperature is -40 to -10°C, and the freeze-drying time is 8 to 12 hours.

[0029] There are two main reasons why the present invention introduces chitosan tanning molecules into the modified convexo-convex rod crystals: first, chitosan is a precursor of a tanning agent with good performance, and its combination with the modified convexo-convex rod crystals can improve the tanning performance; second, chitosan contains amino groups, which can combine with the epoxy groups on the modified convexo-convex rod crystals to improve the properties of the modified convexo-convex rod crystals in the leather making process.

[0030] Example 1

[0031] The preparation method of the leather tanning agent based on the modification of convexo-convex rod crystals of the present invention is specifically implemented according to the following steps:

[0032] Step 1, adding γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, and deionized water in sequence to a convexo-concave rod crystal solution with a mass concentration of 15 g / L, stirring to obtain a mixed solution;

[0033] The stirring temperature was 60°C, the stirring time was 1.5 h, and the stirring rate was 300 r / min;

[0034] The mass ratio of γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, deionized water, and convexo-rod crystal solution is 1:1:0.1:50:200;

[0035] Step 2: Use 0.2M hydrochloric acid to adjust the pH of the solution after the reaction in step 1 to 4, and then freeze-dry it. The freeze-drying temperature is -40°C and the freeze-drying time is 8 hours. The obtained solid powder is the leather tanning agent modified with convexo-convex rod crystals.

[0036] Example 2

[0037] The preparation method of the leather tanning agent based on the modification of convexo-convex rod crystals of the present invention is specifically implemented according to the following steps:

[0038] Step 1, adding γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, and deionized water in sequence to a convexo-concave rod crystal solution with a mass concentration of 20 g / L, stirring to obtain a mixed solution;

[0039] The stirring temperature was 70 °C, the stirring time was 2 h, and the stirring rate was 400 r / min;

[0040] The mass ratio of γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, deionized water, and convexo-rod crystal solution is 2:1:0.2:55:240;

[0041] Step 2, adding 0.2M hydrochloric acid to the mixed solution obtained in step 1 to adjust the pH to 5, and then freeze-drying to obtain a solid powder which is a leather tanning agent modified with convexo-convex rod crystals;

[0042] The freeze-drying temperature was -20°C and the freeze-drying time was 10 h.

[0043] Example 3

[0044] The preparation method of the leather tanning agent based on the modification of convexo-convex rod crystals of the present invention is specifically implemented according to the following steps:

[0045] Step 1, adding γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, and deionized water in sequence to a 30 g / L convexo-rod crystal solution, stirring to obtain a mixed solution;

[0046] The stirring temperature was 80°C, the stirring time was 3.5 h, and the stirring rate was 500 r / min;

[0047] The mass ratio of γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, deionized water, and convexo-rod crystal solution is 3:3:0.4:60:300;

[0048] Step 2, adding 0.2M hydrochloric acid to the mixed solution obtained in step 1 to adjust the pH to 6, and then freeze-drying to obtain a solid powder which is a leather tanning agent modified with convexo-convex rod crystals;

[0049] The freeze-drying temperature was -10°C and the freeze-drying time was 12 h.

[0050] During the leather production process, shrinkage temperature (Ts) is a key physical parameter reflecting the wet-heat stability of finished leather. The change in shrinkage temperature before and after tanning serves as a primary indicator for evaluating the effectiveness of tanning agents. Studies have shown that the degree of penetration of tanning agent molecules into the collagen fiber structure and the degree of multi-point cross-linking between tanning agent molecules and collagen fibers are key factors influencing leather shrinkage temperature. Figure 1 The shrinkage temperature of the leather tanned with the leather tanning agent modified with the attapulgite rod crystals of the present invention shows that the maximum shrinkage temperature of the leather reaches about 80°C, and the minimum shrinkage temperature is about 77.5°C, which indicates that the overall degree of bonding between the tanning agent in the leather tanned with the chitosan-modified attapulgite and the collagen fibers is good.

[0051] Figure 2 The infrared spectra of γ-glycidyl ether propyl trimethoxysilane (KH-560), convexoamyl crystal (ATP), and modified convexoamyl crystal are shown in Figure 1. -1 3375cm -1 、1650cm -1 There are vibration peaks of hydroxyl groups at 3560 cm -1 The peak at 3375cm corresponds to the stretching vibration peak of the hydroxyl group of crystal water in the concave-convex rod crystal, while the peak at 3375cm -1The peak at 1650cm corresponds to the stretching vibration peak of zeolite water in the concave-convex rod crystal and the hydroxyl group of water adsorbed on the surface. -1 The peak at 2934 cm corresponds to the antisymmetric stretching vibration absorption peak of zeolite water and surface adsorbed water hydroxyl groups. In addition, the infrared spectrum of KH560-ATP is different from that of unmodified ATP. -1 、2860cm -1 There is an absorption peak at 910 cm -1 The absorption peak of epoxy group appeared at , which indicated that the silane coupling agent KH-560 was successfully modified on the surface of concave-convex rod crystal.

[0052] Figure 3 The infrared spectra of chitosan, modified convexo-rod crystals, and chitosan-modified convexo-rod crystals are shown in Figure 2. -1 to 1550cm -1 The stretching vibration double peak of the amide group in chitosan is at 2935cm, and the chitosan-modified concave-convex rod crystal disappears in this range compared with the single chitosan, while the chitosan-modified concave-convex rod crystal has a double peak at 2935cm -1 and 2890cm -1 The interval is the double absorption peak of methylene stretching vibration. Chitosan has only one methylene stretching vibration single peak here, but after being branched with modified attapulgite, an obvious double peak appears. The chitosan-modified attapulgite crystal has a larger peak at 910 cm-1 than that of chitosan. -1 The characteristic peak of the epoxy group of KH-560 appears at , so it can be judged that there is basically no chitosan single molecule in the composite tanning agent solution. From this, it can be judged that the branching effect of chitosan and the modified concave-convex rod crystal is good and the reaction is complete.

[0053] Figure 4 and Figure 5 This is the SEM picture of the leather cross-section after tanning with chitosan-modified embossing crystal tanning agent. From high magnification to low magnification, it can be seen that a large number of chitosan-modified embossing crystal tanning agent molecules have penetrated into the leather fibers, which also reflects that the introduction of chitosan improves and enhances the tanning properties of embossing crystal molecules.

Claims

1. A method for preparing a leather tanning agent based on modified convexo-convex rod crystals, characterized in that: Please follow the steps below to implement: Step 1, adding γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, and deionized water to the convexo-convexo-rod crystal solution in sequence, stirring, and obtaining a mixed solution; In the step 1, the stirring temperature is 60-80°C, the stirring time is 1.5-3.5h, and the stirring rate is 300-500 r / min; The mass ratio of γ-glycidyl ether propyl trimethoxysilane, chitosan, triethylamine, deionized water, and convexo-rod crystal solution is 1-3:1-3:0.1-0.4:50-60:200-300; Step 2, adding hydrochloric acid to the mixed solution obtained in step 1 to adjust the pH to 4-6, and then freeze-drying to obtain a solid powder which is a leather tanning agent modified with convexo-convex rod crystals; The amino groups in chitosan are stably combined with the epoxy groups on the KH-560 modified concave-convex rod crystals, where the free epoxy groups play a tanning role and cross-link with the collagen fibers, thereby greatly increasing the shrinkage temperature of the leather.

2. The method for preparing a leather tanning agent based on modified convexo-convex rod crystals according to claim 1, characterized in that: In the step 1, the mass concentration of the convexo-rod crystal solution is 15-30 g / L.

3. The method for preparing a leather tanning agent based on modified convexo-convex rod crystals according to claim 1, characterized in that: In step 2, the freeze-drying temperature is -40 to -10°C, and the freeze-drying time is 8 to 12 hours.

Images