Gallic acid-based diphenol-free tanning agent, preparation method and application thereof

Abstract

The present application relates to tanning agent, provide a kind of gallic acid-based no bisphenol tanning agent, preparation method and application, including the following steps: polyglycerol, p-sulfobenzoic acid, gallic acid, solvent, concentrated sulfuric acid are mixed and reacted;The solution obtained after reaction is dried to obtain finished product.The present application of a kind of leather tanning agent, preparation method and application, it can overcome the color of vegetable tanned leather, and avoid phenol-formaldehyde resin polymer tanning agent produces bisphenol A and other bisphenol substances.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tanning agents, in particular to a gallotannin-based diphenol-free tanning agent, a preparation method and applications. BACKGROUND

[0002] Plant tannin is a polyphenol compound contained in the plant body which can make raw hide into leather. Plant tannin is also called tannin in forest chemistry, and is also called plant polyphenol. The skin, stem, leaf and fruit of the plant rich in tannin and having utilization value are called plant tanning material. The extractive obtained by extracting tannin from plant tanning material with water is called plant tanning liquid. The solid obtained by further processing the plant tanning liquid is called plant tanning agent or tannin extract.

[0003] Tannin extract is divided into hydrolytic tannin extract and condensed tannin extract. Due to the difference in the structure of tannin, their tanning properties also have great difference. Generally, the hydrolytic tannin extract contains more organic acid, has low solution pH, small molecules, weak astringency, good light resistance, firmness and thickness of the finished leather, but poor enzyme resistance and aging resistance. The condensed tannin extract contains less organic acid, has high solution pH, and the molecules are easy to polymerize, so it has strong astringency, good enzyme resistance and aging resistance of the finished leather, but poor light resistance, firmness and thickness of the finished leather.

[0004] Tannin extract is difficult to meet the requirements of light, thin and soft of light leather products due to its large molecular weight, too strong astringency, poor permeability and deep color.

[0005] Plant tanned leather generally has the color of tannin extract, and the color is different according to the color of the tannin extract used. When the plant tanned leather is dyed, the dyeing must consider the bottom color of the leather.

[0006] The leather tanned by phenolic resin tanning agent is soft, full, has high tanning coefficient and high tensile strength, and the shrinkage temperature is as high as 82℃. This kind of tanning agent can be used alone or combined with plant tanning agent to tan heavy leather, and can also be used as a retanning agent and filler of chrome leather.

[0007] The traditional phenolic resin tanning agent is prepared by polymerization reaction of sulfonated phenol and formaldehyde. The reaction will have residues and generation of formaldehyde, phenol, bisphenol A, bisphenol S and bisphenol F. The restriction proposal of the European Union on bisphenol substances mentioned in the “EU will list bisphenol substances in REACH Appendix 17 limited substance list” published by Hangmei Testing and Inspection contains bisphenol F, and the proposal suggests that the total concentration of all bisphenol substances in the mixture and article should be less than 10 mg / kg. The fashion clothing brand H&M group will implement more stringent restriction requirements in the next two years, and the limit of bisphenol A will be less than 1 mg / kg, and the total amount of bisphenol S and bisphenol F will not exceed 200 mg / kg. Therefore, how to effectively avoid the total content of bisphenol S and bisphenol F exceeding the standard in leather products will be a great challenge for tannery enterprises. SUMMARY

[0008] The present application aims to provide a gallus acid-based non-bisphenol tanning agent, a preparation method and an application, which can overcome the color of vegetable tanned leather and avoid the generation of bisphenol A and other bisphenols in phenolic resin polymer tanning agents.

[0009] The embodiment of the present application is implemented by the following technical scheme: the preparation method of the gallus acid-based non-bisphenol tanning agent of the present application comprises the following steps: adding polyglycerol, p-sulfobenzoic acid, gallus acid, a solvent, concentrated sulfuric acid into a reaction container; controlling the temperature at 95-100 DEG C for 7-8 h of heat preservation esterification reaction. After the reaction is completed, spray drying is performed to obtain a white powder product, and the solvent is recovered. The synthesis principle is shown in the chemical reaction formula as follows, wherein m and n are positive integers, and m+n = 7, 8, 9, 10.

[0010]

[0011] Further, the molar ratio of polyglycerol, p-sulfobenzoic acid and gallus acid is 1:(3.6-4.8):(5.4-7.2), and the solvent is used in an amount of 0.5-1.0 times the total mass of polyglycerol, p-sulfobenzoic acid and gallus acid. The amount of concentrated sulfuric acid is 15% of the total mass of p-sulfobenzoic acid and gallus acid. Gallus acid, also known as 3,4,5-trihydroxybenzoic acid, is a kind of polyphenolic organic compound. There are three phenolic hydroxyl groups in the structure of gallus acid, which is easy to form complexation with collagen. The gallus acid molecule alone does not have tanning properties due to its small molecular weight, and needs to be combined into a polymer with a certain molecular weight to have tanning properties. The carboxyl group on the gallus acid molecule is an active group, which is easy to esterify with alcohol and can be connected to the high molecular polymer chain segment with hydroxyl group, thereby giving the high molecular compound certain tanning properties. The present application utilizes the esterification reaction of polyglycerol with gallus acid and p-sulfobenzoic acid to connect the gallus acid to the polyglycerol chain segment, thereby providing a binding site for the tanning agent, and the sulfonic acid group provides hydrophilicity to improve the permeability of the tanning agent and further increase the binding performance of the tanning agent and the skin collagen. The polymer does not have any harmful polyphenolic substance residue and generation, and meets the requirements of the European Union related regulations on synthetic tanning agents.

[0012] Further, the polyglycerol is one of heptaglycerol, octaglycerol, nonaglycerol and decaglycerol.

[0013] Further, the solvent is one of dipropylene glycol dimethyl ether or methyl isobutyl ketone.

[0014] The present application also provides a leather tanning agent prepared by the above method, and application of the leather tanning agent to light color leather tanning.

[0015] The technical scheme of the embodiment of the present application has at least the following advantages and beneficial effects: the leather tanning agent, the preparation method and the application of the present application, (1) a polymer containing phenolic hydroxyl groups is prepared by selecting gallic acid, and the phenolic hydroxyl groups are combined with skin collagen to impart tannability; (2) the synthetic tanning agent does not generate bisphenol A, bisphenol S and bisphenol F, and the leather tanned by the synthetic tanning agent does not contain bisphenol substances and is pollution-free to the environment; (3) the polymer tanning agent with the gallic acid structure overcomes the color problem of vegetable tanned leather and is suitable for tanning light-colored leather. DETAILED DESCRIPTION

[0016] Embodiment 1

[0017] 107.20g (0.20mol) of heptaglycerol, 145.57g (0.72mol) of p-sulfobenzoic acid, 183.6g (1.08mol) of gallic acid, 218.18g of solvent dipropylene glycol dimethyl ether, 49.38g of concentrated sulfuric acid, and 7h of incubation were added to a reaction container, and the mixture was stirred and incubated at a temperature of 95℃. The solution was subjected to spray drying to remove the solvent to obtain a white powder product, and the solvent was recovered.

[0018] Embodiment 2

[0019] 107.20g (0.20mol) of heptaglycerol, 145.57g (0.72mol) of p-sulfobenzoic acid, 183.6g (1.08mol) of gallic acid, 218.18g of solvent dipropylene glycol dimethyl ether, 49.38g of concentrated sulfuric acid, and 7h of incubation were added to a reaction container, and the mixture was stirred and incubated at a temperature of 95℃. The solution was subjected to spray drying to remove the solvent to obtain a white powder product, and the solvent was recovered.

[0020] Embodiment 3

[0021] 107.20g (0.20mol) of heptaglycerol, 145.57g (0.72mol) of p-sulfobenzoic acid, 183.6g (1.08mol) of gallic acid, 218.18g of solvent dipropylene glycol dimethyl ether, 49.38g of concentrated sulfuric acid, and 7h of incubation were added to a reaction container, and the mixture was stirred and incubated at a temperature of 95℃. The solution was subjected to spray drying to remove the solvent to obtain a white powder product, and the solvent was recovered.

[0022] Embodiment 4

[0023] Into the reaction vessel, 107.20 g (0.20 mol) decaglycerol, 194.09 g (0.96 mol) p-sulfobenzoic acid, 244.80 g (1.44 mol) gallic acid were added, 546.09 g of solvent methyl isobutyl ketone was added, the temperature was raised to 100°C, 65.83 g of concentrated sulfuric acid was added and mixed with stirring, and the reaction was kept at temperature for 8 h. The solution was spray dried to remove the solvent to obtain a white powdery product, and the solvent was recovered.

[0024] Test Example 1

[0025] After using the product, the content of bisphenols and formaldehyde in the leather was determined, and the fastness to yellowing was detected.

[0026] The detection method is as follows:

[0027] The detection method of bisphenol A, bisphenol S and bisphenol F is according to the standard ISO 11936:2023.

[0028] The content of formaldehyde is determined according to GB / T 19941-2005 "Chemical test of leather and fur-determination of formaldehyde content";

[0029] The detection and evaluation of fastness to yellowing: the test conditions of fastness to yellowing are UV, 50°C and 6h. The evaluation of discoloration uses a gray sample card (GB 250-1995, 5 best, 1 worst).

[0030] Test Example 2

[0031] Application test of sheep skin main tanning

[0032] Sheep skin was main tanned by using Examples 1-4 and mimosa bark extract (Mimosa ME from South Africa). The tanning process is as follows: sheep skin (pH 3.2-3.4), after weighing, the weight was increased by 100%; deacidification (sodium bicarbonate 1.2%) for 60 min, pH 5.0-5.2; pretreatment (sodium sulfate 10%) for 60 min; main tanning (tanning agent dosage 15%) for 2d, tanning penetration; fatliquoring (Neopristol EWK) for 5h; fixation (formic acid 0.3%) for 60 min, pH 3.4-3.6; drumming and stacking for 2d; rinsing, washing, and hanging drying.

[0033] Product inspection: the quality of the leather after main tanning was evaluated by sensory performance, the shrinkage temperature and physical properties of the leather after main tanning were determined, and the results are shown in Table 1.

[0034] Table 1 Test results of Test Example 2

[0035]

[0036] Test Example 3

[0037] Application in chrome leather retanning test

[0038] The purchased yellow wet leather was applied in chrome leather retanning filling with examples 1-4 and Lanxess OS, and the operation process is shown in Table 2, then the tanned leather was detected for bisphenol content, formaldehyde content and yellowing resistance, wherein the detection method is as follows:

[0039] Bisphenol A, bisphenol S and bisphenol F detection method: according to standard ISO 11936:2023 test.

[0040] Formaldehyde content: refer to GB / T19941-2005 Leather and fur chemical test determination of formaldehyde content;

[0041] Yellowing resistance detection and evaluation: yellowing resistance test conditions: UV, 50℃, 6h. Evaluation of discoloration with gray sample card (GB 250-1995, 5 best, 1 worst).

[0042] The bisphenol content, formaldehyde content and yellowing resistance detection results are shown in Table 3.

[0043] The yellow wet leather in Table 2 is from Zhejiang Tongtianxing Group Co., Ltd., the degreasing agent DOC, interstitial remover TJ-A180, rewetting protective agent BSP, chrome tanning agent TJ-T125, high-efficiency neutralizing agent TJ-R819 and fatting agent F-9668 are all from Sichuan Tingjiang New Material Co., Ltd., other chemicals are from Kelong Reagent Co., Ltd., and the dosages of all chemicals are calculated based on the weight percentage of blue wet leather.

[0044] Table 2 Product application process for chrome leather

[0045]

[0046] Table 3 Product application test results for chrome leather

[0047]

[0048] The above is only the preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a bisphenol-free tanning agent based on gallic acid, characterized in that, The process includes the following steps: mixing and reacting polyglycerol, p-sulfobenzoic acid, gallic acid, solvent, and concentrated sulfuric acid; drying the resulting solution to obtain the final product. The molar ratio of polyglycerol, p-sulfobenzoic acid, and gallic acid is 1:(3.6-4.8):(5.4-7.2). The amount of solvent used is 0.5-1.0 times the total mass of polyglycerol, p-sulfobenzoic acid, and gallic acid; The amount of concentrated sulfuric acid used is 15% of the total mass of p-sulfobenzoic acid and gallic acid; The temperature for the mixed reaction is 95-100℃, and the reaction time is 7-8 hours.

2. The method for preparing a bisphenol-free tanning agent based on gallic acid according to claim 1, characterized in that, Polyglycerol is one of heptaglycerol, octaglycerol, nonaglycerol, or decaglycerol.

3. The method for preparing a bisphenol-free tanning agent based on gallic acid according to claim 1, characterized in that, The solvent is either dipropylene glycol dimethyl ether or methyl isobutyl ketone.

4. A leather tanning agent prepared by the method for preparing a gallic acid-based bisphenol-free tanning agent according to any one of claims 1-3.

5. The use of the leather tanning agent according to claim 4 in the tanning of light-colored leather.

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