Flexible gelatin-based leather adhesive and preparation method thereof

Abstract

The invention discloses a preparation method of a flexible gelatin-based leather adhesive, which specifically comprises the following steps: adding gelatin into deionized water, fully stirring and dissolving, then adding an initiator ammonium persulfate, stirring and reacting, and initiating the gelatin to generate free radicals to obtain a gelatin-initiated mixed solution; and adding allyl glycidyl ether and tannin into the gelatin-initiated mixed solution, and carrying out a stirring reaction, so as to obtain the flexible gelatin-based leather adhesive. According to the method disclosed by the invention, epoxy groups of allyl glycidyl ether are grafted on gelatin molecules to form a cross-linked network structure, and the epoxy groups can remarkably improve the mechanical property, tensile property and thermal stability of the material and endow the adhesive with excellent bonding strength and mechanical flexibility; through hydrogen bond crosslinking of tannin and gelatin, a crosslinking network is more stable, and the bonding strength of the gelatin-based adhesive is further improved through double interlocking of free radical polymerization and hydrogen bond crosslinking.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesive preparation, and in particular relates to a preparation method of a flexible gelatin-based leather adhesive, and also relates to the flexible gelatin-based leather adhesive. Background Art

[0002] Gelatin is a non-toxic and biodegradable biomass resource, a partial hydrolysis product of collagen, and is essentially a protein. Gelatin offers advantages such as low cost, abundant raw materials, safety, and environmental friendliness. Its environmental and pollution-free nature is irreplaceable by synthetic adhesives. However, gelatin has a certain viscosity and a brittle film-forming property, making it suitable for use on rigid materials like wood but unsuitable for flexible materials like leather.

[0003] To expand the application range of gelatin and enhance its practicality, it can be modified through physical (blending, fillers) and chemical cross-linking methods. Physical modification of gelatin can effectively prevent the infiltration of exogenous toxic and harmful chemicals. However, its disadvantage is that it is difficult to obtain a uniform cross-linked product, which affects the adhesion effect. Compared with physical modification, chemical cross-linking is the most effective method for improving gelatin adhesives. Because gelatin protein chains contain a large number of active groups, they can react with cross-linkers (aldehyde compounds, epoxy compounds, and amide compounds) to form new chemical bonds, thereby forming a stable cross-linked network structure. However, chemical cross-linking introduces a large amount of organic solvents, which has an adverse impact on the environment. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a flexible gelatin-based leather adhesive, thereby solving the problems of low adhesion and poor tortuosity of existing leather adhesives.

[0005] Another object of the present invention is to provide the above-mentioned gelatin-based leather adhesive having flexibility.

[0006] The technical solution adopted by the present invention is a method for preparing a flexible gelatin-based leather adhesive, which is specifically implemented according to the following steps: Step 1, initiation of gelatin free radicals; Step 2, preparing a gelatin-allyl glycidyl ether / tannin adhesive; Allyl glycidyl ether and tannin are added to the gelatin initiation mixture prepared in step 1, and stirred to react to obtain a gelatin-allyl glycidyl ether / tannin adhesive, which is a flexible gelatin-based leather adhesive.

[0007] The present invention is also characterized in that: In step 1, gelatin is added to deionized water and fully stirred to dissolve, and then an initiator, ammonium persulfate, is added and stirred to react to induce the gelatin to generate free radicals, thereby obtaining a gelatin-initiated mixed solution.

[0008] The mass ratio of gelatin, ammonium persulfate, and deionized water is 1-2:0.1-0.2:10-15. The dissolution time is 15-20 minutes. The reaction time is 15-30 minutes, and the reaction temperature is 50-60°C.

[0009] In step 2, the mass ratio of allyl glycidyl ether, tannin, and gelatin initiator mixture is 0.8-0.9:0.1-0.2:1-2.2.

[0010] In step 2, the reaction temperature is 60-80°C and the reaction time is 5-8h.

[0011] Another technical solution adopted by the present invention is a gelatin-based leather adhesive prepared by a method for preparing a flexible gelatin-based leather adhesive.

[0012] The present invention has the following beneficial effects: The method grafts epoxy groups of allyl glycidyl ether onto gelatin molecules, forming a cross-linked network structure. The epoxy groups significantly enhance the material's mechanical properties, tensile strength, and thermal stability, imparting excellent bonding strength and mechanical flexibility to the adhesive. Tannin molecules, containing two phenyl rings and a polyphenol structure, exhibit excellent dispersibility and reactivity. The hydrogen-bonded crosslinking between tannin and gelatin further stabilizes the cross-linked network. The dual interlocking of free radical polymerization and hydrogen-bonding further enhances the bond strength of the gelatin-based adhesive. Furthermore, the method utilizes water as a solvent, making it environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Graph showing the bonding strength of the adhesives prepared in Examples 1-4 of the present invention to leather. DETAILED DESCRIPTION

[0014] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] The preparation method of the flexible gelatin-based leather adhesive of the present invention is specifically implemented according to the following steps: Step 1, initiation of gelatin free radicals; Add gelatin into deionized water, stir thoroughly to dissolve, then add initiator ammonium persulfate and stir to react, initiating gelatin to generate free radicals to obtain a gelatin initiation mixture; The mass ratio of gelatin, ammonium persulfate and deionized water is 1-2:0.1-0.2:10-15, the dissolution time is 15-20 minutes, the reaction time is 15-30 minutes, and the reaction temperature is 50-60°C. Step 2, preparing a gelatin-allyl glycidyl ether / tannin adhesive; Adding allyl glycidyl ether and tannin to the gelatin initiation mixture prepared in step 1, stirring and reacting, to obtain a gelatin-allyl glycidyl ether / / tannin adhesive, which is a flexible gelatin-based leather adhesive; The mass ratio of allyl glycidyl ether, tannin, and gelatin initiator mixture is 0.8-0.9:0.1-0.2:1-2.2; the reaction temperature is 60-80°C, and the reaction time is 5-8h; The method of the present invention uses ammonium persulfate as an initiator to initiate free radical polymerization of gelatin and allyl glycidyl ether, while simultaneously cross-linking the gelatin and tannins through hydrogen bonds to prepare a gelatin-based adhesive. This gelatin-based adhesive exhibits excellent mechanical properties, with a maximum bond strength of 1.96 MPa for leather and a bond strength of 1.86 MPa after 100 bends. Furthermore, the method avoids the use of formaldehyde, is environmentally friendly, and has potential for industrial production.

[0016] Example 1 The preparation method of the flexible gelatin-based leather adhesive of the present invention is specifically implemented according to the following steps: Step 1, initiation of gelatin free radicals; Under magnetic stirring, add 1.5 g of gelatin and 10 mL of deionized water to a 50 mL single-necked flask, adjust the temperature to 60°C, and stir for 20 min to fully dissolve the gelatin at a stirring rate of 220 rpm; then add 100 mg of ammonium persulfate and stir for 15 min at a stirring rate of 220 rpm.

[0017] Step 2, preparation of gelatin-allyl glycidyl ether / tannin adhesive Add 0.9 mL of allyl glycidyl ether and 100 mg of tannin to the solution in step 1 and react at 80 °C for 5 h with a stirring rate of 260 rpm to obtain gelatin-allyl glycidyl ether / tannin adhesive.

[0018] Example 2 The preparation method of the flexible gelatin-based leather adhesive of the present invention is specifically implemented according to the following steps: Step 1, initiation of gelatin free radicals Under magnetic stirring, add 2 g of gelatin and 10 mL of deionized water to a 50 mL single-necked flask, adjust the temperature to 60°C, and stir for 20 min to fully dissolve the gelatin at a stirring rate of 220 rpm. Then, add 100 mg of ammonium persulfate and stir for 15 min at a stirring rate of 220 rpm.

[0019] Step 2, preparation of gelatin-allyl glycidyl ether / tannin adhesive Add 0.9 mL of allyl glycidyl ether and 150 mg of tannin to the solution in step 1 and react at 80 °C for 6 h with a stirring rate of 260 rpm to obtain gelatin-allyl glycidyl ether / tannin adhesive.

[0020] Example 3 The preparation method of the flexible gelatin-based leather adhesive of the present invention is specifically implemented according to the following steps: Step 1, initiation of gelatin free radicals Under magnetic stirring, add 1.5 g of gelatin and 10 mL of deionized water to a 50 mL single-necked flask, adjust the temperature to 60°C, and stir for 20 min to fully dissolve the gelatin at a stirring rate of 220 rpm. Then, add 100 mg of ammonium persulfate and stir for 20 min at a stirring rate of 220 rpm.

[0021] Step 2, preparation of gelatin-allyl glycidyl ether / tannin adhesive Add 0.9 mL of allyl glycidyl ether and 180 mg of tannin to the solution in step 1 and react at 80 °C for 6 h with a stirring rate of 260 rpm to obtain gelatin-allyl glycidyl ether / tannin adhesive.

[0022] Example 4 The preparation method of the flexible gelatin-based leather adhesive of the present invention is specifically implemented according to the following steps: Step 1, initiation of gelatin free radicals Under magnetic stirring, add 2 g of gelatin and 10 mL of deionized water to a 50 mL single-necked flask, adjust the temperature to 60°C, and stir for 20 min to fully dissolve the gelatin at a stirring rate of 220 rpm. Then, add 100 mg of ammonium persulfate and stir for 30 min at a stirring rate of 220 rpm.

[0023] Step 2, preparation of gelatin-allyl glycidyl ether / tannin adhesive Add 0.9 mL of allyl glycidyl ether and 200 mg of tannin to the solution in step 1 and react at 80 °C for 8 h with a stirring rate of 260 rpm to obtain gelatin-allyl glycidyl ether / tannin adhesive; Example 5 Detection method The adhesives prepared by the methods of Examples 1 to 4 were used as experimental samples, and the shear strength of leather was tested according to GB / T 7124-2008.

[0024] Figure 1The adhesive strengths of the adhesives prepared in Examples 1-4 to leather and their bond strengths after 100 bends are shown. The gelatin-allyl glycidyl ether / tannin adhesive had a maximum bond strength of 1.96 MPa, and the bond strength at the joint after 100 bends was 1.86 MPa, effectively addressing the brittleness of gelatin adhesives after curing.

[0025] Example 6 The preparation method of the flexible gelatin-based leather adhesive of the present invention is specifically implemented according to the following steps: Step 1, initiation of gelatin free radicals; Add gelatin into deionized water, stir thoroughly to dissolve, then add initiator ammonium persulfate and stir to react, initiating gelatin to generate free radicals to obtain a gelatin initiation mixture; The mass ratio of gelatin, ammonium persulfate and deionized water is 2:0.2:10, the dissolution time is 15 minutes, the reaction time is 15 minutes, and the reaction temperature is 50°C. Step 2, preparing a gelatin-allyl glycidyl ether / tannin adhesive; Adding allyl glycidyl ether and tannin to the gelatin initiation mixture prepared in step 1, stirring and reacting, to obtain a gelatin-allyl glycidyl ether / tannin adhesive, which is a flexible gelatin-based leather adhesive; The mass ratio of allyl glycidyl ether, tannin and gelatin initiator mixture is 0.8:0.1:1; the reaction temperature is 60℃ and the reaction time is 5h.

[0026] Example 7 The preparation method of the flexible gelatin-based leather adhesive of the present invention is specifically implemented according to the following steps: Step 1, initiation of gelatin free radicals; Add gelatin into deionized water, stir thoroughly to dissolve, then add initiator ammonium persulfate and stir to react, initiating gelatin to generate free radicals to obtain a gelatin initiation mixture; The mass ratio of gelatin, ammonium persulfate and deionized water is 1.5:0.2:12, the dissolution time is 18 minutes, the reaction time is 20 minutes, and the reaction temperature is 55°C. Step 2, preparing a gelatin-allyl glycidyl ether / tannin adhesive; Adding allyl glycidyl ether and tannin to the gelatin initiation mixture prepared in step 1, stirring and reacting, to obtain a gelatin-allyl glycidyl ether / tannin adhesive, which is a flexible gelatin-based leather adhesive; The mass ratio of allyl glycidyl ether, tannin and gelatin initiator mixture is 0.9:0.1:2; the reaction temperature is 75℃ and the reaction time is 6h.

[0027] Example 8 The preparation method of the flexible gelatin-based leather adhesive of the present invention is specifically implemented according to the following steps: Step 1, initiation of gelatin free radicals; Add gelatin into deionized water, stir thoroughly to dissolve, then add initiator ammonium persulfate and stir to react, initiating gelatin to generate free radicals to obtain a gelatin initiation mixture; The mass ratio of gelatin, ammonium persulfate and deionized water is 2:0.2:15, the dissolution time is 15 minutes, the reaction time is 30 minutes, and the reaction temperature is 60°C. Step 2, preparing a gelatin-allyl glycidyl ether / tannin adhesive; Adding allyl glycidyl ether and tannin to the gelatin initiation mixture prepared in step 1, stirring and reacting, to obtain a gelatin-allyl glycidyl ether / tannin adhesive, which is a flexible gelatin-based leather adhesive; The mass ratio of allyl glycidyl ether, tannin and gelatin initiator mixture is 0.9: 0.2: 2.2; the reaction temperature is 80°C and the reaction time is 8h.

[0028] The gelatin-based adhesive prepared by the present invention has a flexible property of being resistant to bending, overcomes the disadvantage of the gelatin-based adhesive being brittle, and expands the application range of the gelatin-based adhesive; and the preparation process is simple and the cost is low.

Claims

1. A method for preparing a flexible gelatin-based leather adhesive, characterized in that: Please follow the steps below to implement it: Step 1, initiation of gelatin free radicals; Step 2, preparing a gelatin-allyl glycidyl ether / tannin adhesive; Allyl glycidyl ether and tannin are added to the gelatin initiation mixture prepared in step 1, and stirred to react to obtain a gelatin-allyl glycidyl ether / / tannin adhesive, which is a flexible gelatin-based leather adhesive.

2. The method for preparing a flexible gelatin-based leather adhesive according to claim 1, wherein In the step 1, gelatin is added to deionized water, fully stirred to dissolve, and then an initiator, ammonium persulfate, is added to react with stirring to induce the gelatin to generate free radicals, thereby obtaining a gelatin initiation mixture.

3. The method for preparing a flexible gelatin-based leather adhesive according to claim 2, wherein: The mass ratio of gelatin, ammonium persulfate and deionized water is 1-2:0.1-0.2:10-15.

4. The method for preparing a flexible gelatin-based leather adhesive according to claim 2, wherein: The dissolution time is 15-20 minutes.

5. The method for preparing a flexible gelatin-based leather adhesive according to claim 2, wherein: The reaction time is 15-30 min, and the reaction temperature is 50-60°C.

6. The method for preparing a flexible gelatin-based leather adhesive according to claim 1, wherein: In the step 2, the mass ratio of allyl glycidyl ether, tannin, and gelatin initiator mixture is 0.8-0.9:0.1-0.2:1-2.

2.

7. The method for preparing a flexible gelatin-based leather adhesive according to claim 1, wherein: In the step 2, the reaction temperature is 60-80° C., and the reaction time is 5-8 hours.

8. The gelatin-based leather adhesive prepared by the method for preparing the flexible gelatin-based leather adhesive as claimed in claim 1.

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