PREPARATION METHOD OF PLANT BIOMASS-BASED ACTIVE TANNING AGENT

Abstract

Disclosed is a preparation method of a plant biomass-based active tanning agent. Under a low-temperature reaction condition, cyanuric chloride and a plant biomass compound are used to synthesize an environment-friendly plant biomass-based active tanning agent through a nucleophilic substitution reaction. The active tanning agent obtained in the present disclosure appears as a white or light brown emulsion at room temperature, and has substantial active groups such as hydroxyl groups, carboxyl groups and ester groups introduced into its structure, thus endowing leathers with desirable hydrothermal stability and physical properties and having a desirable synergistic effect with metal tanning agents. Meanwhile, health and environment risks caused by hexavalent chromium and free formaldehyde in leathers are avoided.

Claims

1. A method for preparing a plant biomass-based active tanning agent, comprising: weighing a predetermined amount of cyanuric trichloride and distilled water into a reaction flask, and adding dropwise an appropriate amount of an emulsifier for uniform dispersion under a low-temperature reaction condition; subsequently, adding dropwise an aqueous plant biomass compound solution, wherein a molar ratio of cyanuric trichloride to the plant biomass compound in the aqueous plant biomass compound solution is within a range of (1.0-3.0):1; simultaneously, adding dropwise an alkali solution to control a reaction pH to be within a range of 4.0-8.0; after adding dropwise, conducting a reaction for 4-8 h; then leaving reactants to stand overnight at a low temperature to obtain a white or light brown emulsion of the plant biomass-based active tanning agent.

2. The method according to claim 1, wherein the emulsifier is one or a mixture of at least two selected from the group consisting of polyoxyethylene octylphenol ether-10, polyoxyethylene sorbitan monooleate, sorbitan fatty acid ester and fatty alcohol polyoxyethylene ether.

3. The method according to claim 1, wherein the plant biomass compound is one selected from the group consisting of gallic acid, ellagic acid, aloneaic acid, catechin, proanthocyanidins and tannic acid.

4. The method according to claim 1, wherein the low-temperature reaction condition is one selected from the group consisting of low-temperature mechanical stirring, low-temperature ultrasonic treatment and low-temperature microwave irradiation.

5. The method according to claim 1, wherein a temperature for the low-temperature reaction condition is 0? C., 3? C. or 5? C.

6. A plant biomass-based active tanning agent prepared by the method according to claim 1.

7. Use of the plant biomass-based active tanning agent according to claim 6 in leather making, wherein carboxyl groups and hydroxyl groups are introduced into a molecular structure of the plant biomass-based active tanning agent, promoting coordination crosslinking between collagen and a non-chromium metal ion to produce a desirable synergistic tanning effect.

8. The method according to claim 4, wherein a temperature for the low-temperature reaction condition is 0? C., 3? C. or 5? C.

9. A plant biomass-based active tanning agent prepared by the method according to claim 2.

10. A plant biomass-based active tanning agent prepared by the method according to claim 3.

11. A plant biomass-based active tanning agent prepared by the method according to claim 4.

12. A plant biomass-based active tanning agent prepared by the method according to claim 5.

13. Use of the plant biomass-based active tanning agent according to claim 9 in leather making, wherein carboxyl groups and hydroxyl groups are introduced into a molecular structure of the plant biomass-based active tanning agent, promoting coordination crosslinking between collagen and a non-chromium metal ion to produce a desirable synergistic tanning effect.

14. Use of the plant biomass-based active tanning agent according to claim 10 in leather making, wherein carboxyl groups and hydroxyl groups are introduced into a molecular structure of the plant biomass-based active tanning agent, promoting coordination crosslinking between collagen and a non-chromium metal ion to produce a desirable synergistic tanning effect.

15. Use of the plant biomass-based active tanning agent according to claim 11 in leather making, wherein carboxyl groups and hydroxyl groups are introduced into a molecular structure of the plant biomass-based active tanning agent, promoting coordination crosslinking between collagen and a non-chromium metal ion to produce a desirable synergistic tanning effect.

16. Use of the plant biomass-based active tanning agent according to claim 12 in leather making, wherein carboxyl groups and hydroxyl groups are introduced into a molecular structure of the plant biomass-based active tanning agent, promoting coordination crosslinking between collagen and a non-chromium metal ion to produce a desirable synergistic tanning effect.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 shows an infrared absorption spectrum analysis graph of a plant biomass-based active tanning agent in Example 1, where a plant biomass used is gallic acid;

[0018] FIG. 2 shows a mass spectrum analysis graph of a plant biomass-based active tanning agent in Example 1, where a plant biomass used is gallic acid.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Example 1

[0019] 0.1 mol of cyanuric chloride was weighed accurately into a reaction flask charged with an appropriate amount of distilled water, an appropriate amount of an emulsifier was added dropwise, and a reaction temperature was controlled at 3?C; a 0.1 mol alkaline solution of gallic acid was added dropwise, an alkali solution was added dropwise simultaneously to control a reaction pH of 6.5, and then a reaction was conducted for 6.0 h under mechanical stirring; the reactants were left to stand overnight at a low temperature to obtain a white emulsion, namely a plant biomass-based active tanning agent.

[0020] FIG. 1 shows an infrared absorption spectrum analysis graph of the plant biomass-based active tanning agent in Example 1. It is seen from FIG. 1 that the stretching vibration absorption peak of CCl is represented at 794 cm.sup.?1, the stretching vibration absorption peaks of triazine ring or benzene ring are represented at 1400 cm.sup.?1, 1468 cm.sup.?1 and 1564 cm.sup.?1, the stretching vibration absorption peak of CO in carboxyl structure is represented at 1704 cm.sup.?1, the stretching vibration absorption peaks of OH are represented at 2923-3215 cm.sup.?1, and the absorption peak of COC(ether bond) also appears at 1204 cm.sup.?1, indicating a successful nucleophilic substitution reaction of gallic acid with cyanuric chloride.

[0021] FIG. 2 shows a mass spectrum analysis graph of the plant biomass-based active tanning agent in Example 1. It is seen from FIG. 2 that the molecular weight of the tanning agent measured on a mass spectrometer (m/z: 338.9) is consistent with the accurate molecular weight thereof according to the chemical structural formula (C10H4Cl2N3O5Na). This further demonstrates that the plant biomass-based active tanning agent was successfully synthesized by the method of the present disclosure.

Example 2

[0022] 0.3 mol of cyanuric chloride was weighed accurately into a reaction flask charged with an appropriate amount of distilled water, an appropriate amount of an emulsifier was added dropwise, and a reaction temperature was controlled at 5? C.; a 0.1 mol alkaline solution of ellagic acid was added dropwise, an alkali solution was added dropwise simultaneously to control a reaction pH of 7.0, and then a reaction was conducted for 4.0 h under ultrasonic treatment; the reactants were left to stand overnight at a low temperature to obtain a light brown emulsion, namely a plant biomass-based active tanning agent.

Example 3

[0023] 0.2 mol of cyanuric chloride was weighed accurately into a reaction flask charged with an appropriate amount of distilled water, an appropriate amount of an emulsifier was added dropwise, and a reaction temperature was controlled at 0? C.; a 0.1 mol alkaline solution of tannic acid was added dropwise, an alkali solution was added dropwise simultaneously to control a reaction pH of 6.0, and then a reaction was conducted for 5.0 h under microwave irradiation; the reactants were left to stand overnight at a low temperature to obtain a light brown emulsion, namely a plant biomass-based active tanning agent.

Test Example 1: Particle Size Testing

[0024] A droplet of each emulsion obtained after reaction in Examples 1 to 3 was diluted to a concentration of 0.1 g/L with deionized water, and filtered through a 0.45 ?m filter head to be injected into a sample cell. The hydrodynamic radius (Rh) and polydispersity index (PDI) of the plant biomass-based active tanning agent were determined at 25? C. on a nanoparticle size analyzer. The specific results are shown in Table 1.

[0025] Table 1 The average particle size, particle size distribution and polydispersity index of plant biomass-based active tanning agents in Examples 1 to 3.

TABLE-US-00001 TABLE 1 Plant biomass- based active Average Particle size tanning agent particle size PDI distribution Example 1 about 95 nm 0.4 about 76 nm Example 2 about 110 nm 0.5 about 25 nm about 112 nm Example 3 about 409 nm 0.6 about 74 nm about 454 nm

[0026] It is seen from Table 1 that for the plant biomass-based active tanning agent prepared in Example 1, the average particle size and hydrodynamic radius (Rh) are about 95 nm and about 76 nm, respectively, only one peak appears, and the PDI is about 0.4, falling within the moderate dispersion range; for the plant biomass-based active tanning agents prepared in Examples 2 and 3, the average particle sizes increase to about 110 nm and about 409 nm, respectively, two peaks appear, and the corresponding hydrodynamic radiuses (Rh) are about 25 nm and about 112 nm (PDI: 0.5), about 74 nm and about 454 nm (PDI: 0.6), respectively. Thus, it may be seen that the particle sizes of the plant biomass-based active tanning agents prepared in Examples 1 to 3 in aqueous solutions are all less than or equal to 500 nm, indicating a desirable permeability and dispersion stability during tanning for leathers.

Test Example 2: Tanning Performance Testing

[0027] The bated pelts were tanned directly with the plant biomass-based active tanning agents prepared in Examples 1 to 3 without pickling. The specific tanning process was as follows: the materials used during tanning were based on the weight of a limed hide, the liquor ratio (water weight/hide weight) was controlled at 0.7, and the temperature in drum was room temperature (25? C.); a bated hide was treated with 10% of plant biomass-based active tanning agent directly; after running for 2 h, during which the plant biomass-based active tanning agent was completely penetrated into leather, 50% of hot water (water temperature: 60? C.) was added in twice, and the drum was run at 40? C. for 2 h and at 45? C. for 4 h, respectively, so as to promote the binding of the plant biomass-based active tanning agent to collagen; finally, the hide was left to stand overnight, washed with water for 30 min next day, then taken out of the drum and horse-stacked.

[0028] Shrinkage temperature testing: the shrinkage temperatures (Ts) of the bated hide and the leathers tanned with the plant biomass-based active tanning agents were measured on a shrinkage temperature tester. Specifically, a sample (10 mm?60 mm) was suspended vertically in distilled water and heated at a heating rate of 2? C./min, and the temperature at which the sample shrank was recorded as Ts of the crust leather. Specific results are shown in Table 2.

[0029] Table 2 The shrinkage temperature of leathers tanned with the plant biomass-based active tanning agents in Examples 1 to 3.

TABLE-US-00002 TABLE 2 Sample Bated hide Example 1 Example 2 Example 3 Shrinkage 58 77 74 78 temperature/? C.

[0030] It is seen from Table 2 that by applying the plant biomass-based active tanning agents in Examples 1 to 3 to leather tanning, the crust leathers obtained have shrinkage temperatures up to 74-78? C., which are significantly higher than that of the bated hide (about 58? C.), indicating that the plant biomass-based active tanning agents may endow the leathers with desirable hydrothermal stability.

[0031] The description above is merely the preferred embodiments of the present disclosure. It should be noted that a person of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure, and such improvements and modifications should be deemed as falling within the protection scope of the present disclosure.