CN113215332B

CN113215332B - Method for improving antibacterial performance of chrome-free tanned white wet leather

Info

Publication number: CN113215332B
Application number: CN202110403980.XA
Authority: CN
Inventors: 温会涛; 李银生; 陈永榜; 牛泽; 但卫华; 孙辉永
Original assignee: XINGYE LEATHER TECHNOLOGY CO LTD
Current assignee: XINGYE LEATHER TECHNOLOGY CO LTD
Priority date: 2021-04-15
Filing date: 2021-04-15
Publication date: 2022-04-26
Anticipated expiration: 2041-04-15
Also published as: CN113215332A

Abstract

The invention discloses a method for improving the antibacterial performance of chrome-free tanned wet white leather, which is suitable for various wet white leather tanning systems and at least comprises a tanning process, and the method comprises the following steps: the method comprises the following steps: controlling the pH value of bath liquid in the tanning procedure to be 2.5-3.5, adding 2-4% of cyclodextrin polyaldehyde derivative, reacting for 2-6h, adjusting the pH value to be 4.0-6.0, and continuing to react for 4-8 h; step two: regulating the pH value of the bath liquid to 4.0-6.0, adding 0.01-0.05% of micromolecular substance (antibacterial agent) into the bath liquid, continuing to react for 4-8h, and taking out the leather to obtain the white wet leather with the antibacterial function.

Description

Method for improving antibacterial performance of chrome-free tanned white wet leather

Technical Field

The invention relates to the technical field of leather production, in particular to a method for improving the antibacterial performance of chrome-free tanned wet-white leather.

Background

Tanning is a physical and chemical process for converting rawhide into leather through a tanning agent, the tanned leather is called wet leather, belongs to an important leather product, can be subsequently processed according to the requirements of customers, and can also be used as a leather commodity. The wet blue leather tanned by the chrome tanning agent has high thermal shrinkage temperature, soft leather body, plump hand feeling, certain antibacterial performance and storage resistance, and is the most main tanning method in the shoe upper leather production. However, the use of the chrome tanning agent brings certain chromium pollution to the environment, particularly hexavalent chromium has strong toxicity, and is pressed by great ecological environmental protection and consumption concept transformation. Therefore, chrome-free tanned wet-white leather is the fundamental approach to solving this problem.

The improved chrome-free tanning technology can enable the tanning effect to reach a level which is comparable to chrome tanning, but the antibacterial performance is poor and the leather is not durable to store. The reason is that most heterotrophic bacteria are best suitable for growth, the pH value is 6.5-7.5, the pH value of the chromium-free tanned wet-white leather is neutral to alkalescent, a very suitable living environment is created for bacteria because no chromium exists, and meanwhile, due to the fact that production is arranged according to orders in production, the tanned wet-white leather can be best stored for 1-3 months, and obviously, the requirements are difficult to meet due to the fact that the chromium-free tanned wet-white leather is produced. Therefore, the poor antibacterial performance has been the biggest obstacle to the application of chrome-free tanning technology.

The mildew-proof antibacterial performance of leather is mainly realized by adding an antibacterial agent at the later stage of tanning. In the case of chrome-tanned wet blue leather, this requirement can be met by the addition of an antimicrobial agent. However, for chrome-free tanned wet-white leather, the antibacterial requirement cannot be met only by adding the antibacterial agent, and even if the added antibacterial agent is higher, the wet-white leather cannot be completely prevented from mildewing and rotting. The reason for this may be: firstly, the antibacterial agent is not firmly combined with the leather and is easy to run off or volatilize; secondly, the existing antibacterial agent is matched with a chrome tanning system and is not matched with different chrome tanning systems.

Disclosure of Invention

The embodiment of the application provides a method for improving the antibacterial performance of the chrome-free tanned wet-white leather, solves the technical problems that bacteria are easy to breed and the chrome-free tanned wet-white leather in the prior art cannot be stored for a long time, and realizes the preparation of the chrome-free tanned wet-white leather which is suitable for industrial production and can be stored for a long time.

The embodiment of the application provides a method for improving the antibacterial performance of chrome-free tanned wet white leather, which is suitable for various wet white leather tanning systems and at least comprises a tanning process, wherein the percentage value is the percentage of the weight of the initially input hide, and the specific steps are as follows:

step A: controlling the pH value of bath liquid in the tanning procedure to be 2.5-3.5, adding 2-4% of cyclodextrin polyaldehyde derivative, and reacting for 2-6 h;

and B: regulating the pH value of the bath liquid to 4.0-6.0, adding 0.01-0.05% of micromolecular substances into the bath liquid, continuing to react for 4-8h, and then taking out the leather to obtain the white wet leather with the antibacterial function.

Further, the cyclodextrin polyaldehyde derivative is selected from at least one of mono-6-aldehyde-cyclodextrin, bis-6-aldehyde-cyclodextrin, tri-6-aldehyde-cyclodextrin and poly-6-aldehyde-cyclodextrin.

Further, the preparation method of the cyclodextrin polyaldehyde derivative comprises the following steps:

step (1): dissolving 1mmol of cyclodextrin in 5-15mL of dimethyl sulfoxide to obtain a solution A;

step (2): dissolving 1.2mmol of o-iodoacyl benzoic acid in 5-15mL of dimethyl sulfoxide to obtain a solution B;

and (3): dropwise adding the solution B into the solution A, and reacting for 24 hours to obtain a solution C;

and (4): filtering the solution C, dripping the filtrate into 200-500ml of acetone, and stirring for 2h at 4 ℃;

and (5): and (4) centrifuging by using a refrigerated centrifuge, dissolving the filter residue by using deionized water, filtering, and freeze-drying the filtrate to obtain the cyclodextrin polyaldehyde derivative.

and (4): dropwise adding the solution B into the solution C;

and (5): repeating the step (4) for N times to obtain a mixed solution, wherein N is more than or equal to 0 and less than or equal to 5;

and (6): filtering the mixed solution, dripping the filtrate into 200-500ml of acetone, and stirring for 2h at 4 ℃;

and (7): and (4) centrifuging by using a refrigerated centrifuge in the step (6), dissolving the filter residue by using deionized water, filtering, and freeze-drying the filtrate to obtain the cyclodextrin polyaldehyde derivative.

Further, the cyclodextrin is selected from any one of alpha-cyclodextrin, beta-cyclodextrin and gamma-cyclodextrin.

Further, the cyclodextrin is beta-cyclodextrin.

Further, the concentration of the small molecule substance is 4-20 mg/L;

the micromolecule substance is aromatic substance containing benzene ring or naphthalene structure, and is selected from any one of benzene sulfonamides, isothiazolinone, benzothiazole and fluoroquinolone antibacterial agents.

Further, the small molecular substance is at least one selected from 2-octyl-4-isothiazolin-3-ketone, 2-thiocyanomethylthio benzothiazole, 4-isopropyl tropolone, ciprofloxacin hydrochloride and tea polyphenol.

Further, the method also comprises the following steps: putting the white wet leather with the antibacterial function into the bath liquid, adjusting the pH value to 4.0-6.0, adding 0.01-0.05% of micromolecular substances, continuing to react for 4-8h, and taking out of the drum. This step is directed to wet white leather that has not been produced in time and has deteriorated antimicrobial properties, and this type of wet white leather is treated to impart antimicrobial properties again.

One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

1. according to the method, the cyclodextrin polyaldehyde derivative is introduced during tanning, a cyclodextrin cavity in the cyclodextrin polyaldehyde derivative is introduced into leather collagen fibers under the tanning effect, and then a small molecular substance (such as ciprofloxacin hydrochloride) is included in the cyclodextrin cavity, so that the antibacterial chromium-free tanned wet-white leather with a slow release effect can be prepared, the antibacterial effect can reach at least more than 3 months, and the production requirement is met. Meanwhile, when the antibacterial effect of the wet white leather is poor, the wet white leather can be placed into the antibacterial solution for inclusion again, so that the antibacterial time is prolonged.

2. The small molecular substances used in the application are immobilized on the wet white leather through inclusion, and the using amount is small. Specifically, taking ciprofloxacin hydrochloride as an antibacterial agent for example, the addition amount of the conventional antibacterial agent is 0.1-0.3% of the weight of the wet-white leather, while the solution concentration of the antibacterial agent during inclusion is about 4-20mg/L (added after chrome tanning, when the bath ratio is calculated as 2.5 (raw hide: water 1: 2.5), and is reduced to 0.01-0.05% of the weight of the wet-white leather), and the dosage of the antibacterial agent is greatly reduced.

3. The polyaldehyde cyclodextrin has a multi-point crosslinking effect on collagen fibers of leather, so that the heat resistance of chrome-free tanned wet-white leather is improved, and the thermal denaturation temperature Td is also improved by (2-5) DEG C.

Drawings

FIG. 1 is the antibacterial performance against E.coli after 3 months of storage (first row from the top are examples 1-5, second row are comparative examples 1A-5A, third row are comparative examples 1B-5B);

FIG. 2 is a graph showing the antibacterial performance against Staphylococcus aureus after 3 months of storage (first row from the top are examples 1-5, second row are comparative examples 1A-5A, and third row are comparative examples 1B-5B).

Detailed Description

For a better understanding of the above technical solution, it will be described in detail with reference to the description and the specific embodiments, wherein the percentage values are percentages by weight of the hides, calculated as 1kg by weight of the hides charged, 250% of water being 2.5kg by weight of water; the polyaldehyde in the cyclodextrin polyaldehyde derivative can be polyaldehyde such as monoaldehyde, dialdehyde, trialdehyde and the like or a mixture thereof.

Example 1

A method for improving the antibacterial performance of chrome-free tanned white wet leather comprises the following steps:

the method comprises the following steps: preparation of the cyclodextrin polyaldehyde derivative MACD:

step (1): dissolving 1mmol of cyclodextrin in 10mL of dimethyl sulfoxide to obtain a solution A (recorded as 1 part of solution A);

step (2): dissolving 1.2mmol of o-iodoxybenzoic acid in 12mL of dimethyl sulfoxide to obtain a solution B (recorded as 1 part of solution B);

and (4): dropwise adding the solution B into the solution C;

and (5): repeating the step (4) for 1 time to obtain a mixed solution; [ the mixture solution at this time contained 1 part of solution A and 3 parts of solution B ]

Step two: washing with water

Putting the raw hide into a rotary drum, adding 250% of water, adjusting the temperature to 25 ℃, rotating for 10min, and discharging liquid;

step three: pickling

Adding 30% water (25 deg.C) and 7% salt into the rotary drum, rotating for 10min, adding 1% formic acid (85%) diluted with 10 times of room temperature water (25 deg.C) from the drum shaft of the rotary drum, rotating for 30min, adding sulfuric acid (more than or equal to 98%) diluted with 10 times of room temperature water (25 deg.C), adjusting pH to 2.5-3.0, and rotating for 90 min.

Step four: tanning

(1) Adding 4% zirconium-aluminum-titanium multi-metal complex powder and 1% sodium formate into the rotary drum, controlling pH to 2.5-3.0, adding 4% zirconium-aluminum-titanium multi-metal complex powder, and rotating for 180 min;

(2) a cyclodextrin modification treatment process: controlling the pH value to be 2.5-3.5, adding 4% of cyclodextrin polyaldehyde derivative MACD, and reacting for 120 min;

(3) diluting 2.0% baking soda with 15 times warm water (25 deg.C), adding baking soda at intervals of 20min for 6-8 times after dissolving to final pH of 3.8-4.0, rotating for 120min, and adding 150% hot water (40 deg.C);

(4) an antibacterial treatment process: adjusting the pH value to 4.0, adding 0.02% ciprofloxacin hydrochloride, and continuing to react for 240 min;

(5) and continuing rotating for 30min, and draining water and discharging from the drum.

Example 2

step (2): dissolving 1.2mmol of o-iodoxybenzoic acid in 15mL of dimethyl sulfoxide to obtain a solution B (recorded as 1 part of solution B);

and (3): dropwise adding the solution B into the solution A, and reacting for 24 hours to obtain a solution C; [ solution C at this time contains 1 part of solution A and 1 part of solution B ]

Step two: washing with water

step three: pickling

Adding 100% water (25 deg.C) and 7% salt into the rotary drum, rotating for 10min, adding 1% formic acid (85%) diluted with 10 times of room temperature water (25 deg.C) from the drum shaft of the rotary drum, rotating for 30min, adding 1% sulfuric acid (more than or equal to 98%) diluted with 10 times of room temperature water (25 deg.C), adjusting pH to 3.0, and rotating for 90 min.

Step four: tanning

(1) A cyclodextrin modification treatment process: controlling the pH of the bath solution to 3.0, adding 4% of cyclodextrin polyaldehyde derivative MACD, and reacting for 120 min;

(2) adding 4% aldehyde tanning agent (TWS tanning agent produced by Tanjiang chemical industry) and 3% sodium formate into the rotary drum, controlling pH to 4.5, and rotating for 150 min;

(3) an antibacterial treatment process: adjusting pH to 4.5, adding 0.03% ciprofloxacin hydrochloride, and rotating for 120 min;

(4) adding 2.0% sodium sulfate, diluting with 15 times of warm water (25 deg.C) to dissolve 5.0% sodium bicarbonate, adding at intervals of 20min for 6-8 times to obtain final pH of 6.5, and rotating for 180 min;

(5) 250% hot water (25 ℃) is added into the rotary drum, and the drum is drained after 30min of rotation.

Example 3

step (1): dissolving 1mmol of cyclodextrin in 15mL of dimethyl sulfoxide to obtain a solution A (recorded as 1 part of solution A);

step (2): dissolving 1.2mmol of o-iodoxybenzoic acid in 8mL of dimethyl sulfoxide to obtain a solution B (recorded as 1 part of solution B);

and (4): dropwise adding the solution B into the solution C;

and (5): repeating the step (4) for 2 times to obtain a mixed solution; at this time, the mixed solution contains 1 part of solution A and 4 parts of solution B;

Step two: washing with water

step three: pickling

Adding 30% water (25 deg.C) and 7% salt into the rotary drum, rotating for 10min, adding 0.5% formic acid (85%) diluted with 10 times of room temperature water (25 deg.C) from the drum shaft of the rotary drum, rotating for 30min, adding 1.0% sulfuric acid (more than or equal to 98%) diluted with 10 times of room temperature water (25 deg.C), adjusting pH to 3.5-3.8, and rotating for 90 min.

Step four: tanning

(1) A cyclodextrin modification treatment process: controlling the pH value to be 3.0, adding 4% of cyclodextrin polyaldehyde derivative MACD, and reacting for 120 min;

(2) adding 15% bayberry extract and 10% sodium sulfate into the rotary drum, controlling pH to 4.0-4.5, rotating for 120min, adding 1.5% of dispersible tannin (tannin extract ISG, Langsheng), 1.5% of grease (Dawile FL-71), 0.1% of auxiliary agent (Dawilatoo DCA, Dawile chemical engineering) and rotating for 30min, adding 15% bayberry extract and rotating for 360min, and adding 50% water (35 deg.C);

(3) an antibacterial treatment process: adjusting pH to 4.5, adding 0.02% ciprofloxacin hydrochloride, and rotating for 120 min;

(4) adding 0.5% sodium bicarbonate diluted with 10 times of warm water at 35 deg.C into the rotary drum, controlling pH to 3.0-3.5, and reacting for 120 min;

(5) 250% water (25 ℃) is added into the rotary drum, the reaction is carried out for 30min, and the drum is drained.

Example 4

step (1): dissolving 1mmol of cyclodextrin in 5mL of dimethyl sulfoxide to obtain a solution A (recorded as 1 part of solution A);

step (2): dissolving 1.2mmol of o-iodoxybenzoic acid in 5mL of dimethyl sulfoxide to obtain a solution B (recorded as 1 part of solution B);

and (4): dropwise adding the solution B into the solution C;

and (5): repeating the step (4) for 4 times to obtain a mixed solution; [ at this time, the mixed solution contained 1 part of solution A and 6 parts of solution B ];

Step two: washing with water

Putting the raw hide into a rotary drum, adding 250% water (25 deg.C), controlling pH to 7.0, rotating for 10min, and discharging liquid;

step three: tanning

(1) Adding 30% water (30 deg.C) into the drum, adding 5.0% synthetic tanning agent F-90, rotating for 30min, adding 5.0% synthetic tanning agent F-90, controlling pH to 5.5, and rotating for 120 min;

(2) adding 30% water (38 deg.C) into the rotary drum, rotating for 120min, adding 30% water (42 deg.C), rotating for 120min, adding 30% water (45 deg.C), adding 1.0% formic acid diluted with 10 times of room temperature water (25 deg.C), controlling pH to 3.5, and rotating for 30 min;

(3) a cyclodextrin modification treatment process: controlling the pH of the bath solution to 3.5, adding 4% of cyclodextrin polyaldehyde derivative MACD, and reacting for 120 min;

(4) adding 1.0% sodium bicarbonate diluted with 15 times of room temperature water (25 deg.C) into the rotary drum, controlling pH to 3.8-4.2, and rotating for 120 min;

(5) an antibacterial treatment process: adjusting pH to 4.0, adding 0.04% ciprofloxacin hydrochloride, and rotating for 300 min;

(6) rotating for 30min, draining water, and discharging from the drum.

Example 5

step (1): dissolving 1mmol of cyclodextrin in 8mL of dimethyl sulfoxide to obtain a solution A (recorded as 1 part of solution A);

step (2): dissolving 1.2mmol of o-iodoxybenzoic acid in 7mL of dimethyl sulfoxide to obtain a solution B (recorded as 1 part of solution B);

and (4): dropwise adding the solution B into the solution C;

Step two: washing with water

Putting the raw hide into a rotary drum, adding 250% water (25 deg.C), rotating for 10min, and discharging liquid;

step three: pickling

Adding 30% water (25 deg.C) into the rotary drum, adding 7% salt, rotating for 10min, adding 0.5% formic acid (85%) diluted with 10 times of room temperature water from the drum shaft of the rotary drum, rotating for 30min, adding 1% sulfuric acid (more than or equal to 98%) diluted with 10 times of room temperature water, adjusting pH to 2.5-3.0, and rotating for 90 min.

Step four: tanning

(2) adding 15% bayberry tannin extract and 10% sodium sulfate into the rotary drum, controlling pH to 4.0-4.5, and rotating for 120 min; adding dispersive tannin (tannin essence ISG, Langsheng) 1.5%, oil (Dawile FL-71) 1.5%, auxiliary agent (Dawilatou DCA, Dawile chemical engineering) 0.1%, rotating for 30min, adding 15% bayberry extract, rotating for 360min, adding formic acid diluted with 15 times room temperature water (25 deg.C) at intervals and rotating for 30 min.

(3) Adding 4% zirconium-aluminum-titanium multi-metal complex powder and 1% sodium formate into the rotary drum, controlling pH to 2.5-3.0, adding 4% zirconium-aluminum-titanium multi-metal complex powder, and rotating for 180 min;

(4) diluting and dissolving 2.0% sodium bicarbonate with 15 times of warm water (25 deg.C), adding at intervals of 20min for 6-8 times to obtain final pH of 3.8-4.0, and rotating for 180 min;

(5) an antibacterial treatment process: adjusting the pH value to 4.0, adding 0.05% ciprofloxacin hydrochloride, and continuing to react for 120 min;

(6) adding 150% water into the drum, rotating at 40 deg.C for 30min, and draining.

Comparative example 1A

Comparative example 1A is the same as example 1 except that comparative example 1A lacks the cyclodextrin modification treatment procedure for preparing the cyclodextrin polyaldehyde derivative MACD.

Comparative example 1B

Comparative example 1B is the same as example 1 except that comparative example 1B lacks the steps of preparing the cyclodextrin polyaldehyde derivative MACD, the cyclodextrin modification treatment step, and the antibacterial treatment step.

Comparative example 2A

Comparative example 2A is the same as example 2 except that comparative example 2A lacks the cyclodextrin modification treatment procedure for preparing the cyclodextrin polyaldehyde derivative MACD.

Comparative example 2B

Comparative example 2B is the same as example 2 except that comparative example 2B lacks the steps of preparing the cyclodextrin polyaldehyde derivative MACD, the cyclodextrin modification treatment step, and the antibacterial treatment step.

Comparative example 3A

Comparative example 3A is the same as example 3 except that comparative example 3A lacks the cyclodextrin polyaldehyde derivative MACD, cyclodextrin modification treatment procedure.

Comparative example 3B

Comparative example 3B is the same as example 3 except that comparative example 3B lacks the steps of preparing the cyclodextrin polyaldehyde derivative MACD, the cyclodextrin modification treatment step, and the antibacterial treatment step.

Comparative example 4A

Comparative example 4A is the same as example 4 except that comparative example 4A lacks the cyclodextrin modification treatment procedure for preparing the cyclodextrin polyaldehyde derivative MACD.

Comparative example 4B

Comparative example 4B is the same as example 4 except that comparative example 4B lacks the steps of preparing the cyclodextrin polyaldehyde derivative MACD, the cyclodextrin modification treatment step, and the antibacterial treatment step.

Comparative example 5A

Comparative example 5A is the same as example 5 except that comparative example 5A lacks the cyclodextrin modification treatment procedure for preparing the cyclodextrin polyaldehyde derivative MACD.

Comparative example 5B

Comparative example 5B is the same as example 5 except that comparative example 5B lacks the steps of preparing the cyclodextrin polyaldehyde derivative MACD, the cyclodextrin modification treatment step, and the antibacterial treatment step.

Experimental methods

First, antibacterial experiment

200mg of each of the wet white leathers of examples 1 to 5, comparative examples 1A to 5A and comparative examples 1B to 5B was ground and sterilized by irradiation for use. Under aseptic conditions, Escherichia coli or Staphylococcus aureus in logarithmic growth phase is scraped off by using an inoculating loop, transferred into a conical flask with glass beads containing 100ml of physiological saline, scattered and counted on a blood counting chamber to prepare bacterial suspension with bacterial concentration of 1-2 × 107 cfu/ml. Respectively sucking 4ml of the bacterial suspension, adding the bacterial suspension into a 36ml conical flask filled with physiological saline, adding a sample to be detected, sealing, and then placing on a constant-temperature cradle at 37 ℃ for oscillation for 3h, wherein the oscillation speed is 100 r/min. Each group of samples was taken 0.5ml separately and added to the test with 4.5ml of physiological saline and shaken well. And repeating the dilution operation for 2 times, taking 0.1ml of diluted bacterial liquid, uniformly coating the diluted bacterial liquid in a culture dish filled with a solid beef peptone culture medium, culturing at 37 ℃ for 24 hours, counting viable bacteria, selecting a proper gradient, and detecting the antibacterial effect.

The antibacterial properties against E.coli and Staphylococcus aureus were examined after storing examples 1 to 5 and comparative examples 1A to 5A, which were obtained as described above, for 3 months, respectively. Comparative examples 1B to 5B had no antibacterial effect, and the antibacterial effect was 1 day after the test. The test results are shown in FIGS. 1 and 2, from which it can be seen that comparative examples 1B to 5B had no antibacterial effect, comparative examples 1A to 5A using ciprofloxacin hydrochloride as an antibacterial agent had a certain antibacterial effect, examples 1 to 5 using cyclodextrin treatment and inclusion of ciprofloxacin hydrochloride were excellent in antibacterial property, and colonies of Escherichia coli and Staphylococcus aureus were almost not survived. Compared with comparative examples 1A-5A, examples 1-5 all had better antibacterial effects and can meet the storage requirements of leather production on wet leather.

Secondly, detecting heat resistance

The thermal properties of various wet and white leathers were measured using a differential scanning calorimeter. Weighing 3-5mg of sample, and under the protection of 60ml/min nitrogen, the heating rate is 10K/min, and the testing temperature range is 20-120 ℃. The control sample was a blank aluminum crucible. The results of the measurements are shown in Table 1 below.

	Thermal denaturation temperature Td
		Example 1	84.5
Comparative example 1A	79.9
		Example 1-comparative example 1A	4.6
Example 2	77.5
		Comparative example 2A	75.0
Example 2-comparative example 2A	2.5
		Example 3	76.3
Comparative example 3A	74.3
		Example 3-comparative example 3A	3.4
Example 4	76.3
		Comparative example 4A	73.1
Example 4-comparative example 4A	3.2
		Example 5	86.1
Comparative example 5A	81.0
		Example 5-comparative example 5A	5.1

TABLE 1

As can be seen from Table 1, the thermal denaturation temperatures Td of examples 1 to 5 were all improved and the heat-resistant properties were better as compared with those of comparative examples 1A to 5A, which is consistent with the purpose of tanning leather.

The above description is only an embodiment utilizing the technical content of the present disclosure, and any modification and variation made by those skilled in the art can be covered by the claims of the present disclosure, and not limited to the embodiments disclosed.

Claims

1. A method for improving the antibacterial performance of chrome-free tanned wet white leather is suitable for various wet white leather tanning systems and at least comprises a tanning process, and is characterized by comprising the following specific steps:

and B: adjusting the pH value of the bath liquid to 4.0-6.0, adding 0.01-0.05% of micromolecular substances into the bath liquid, continuing to react for 4-8h, and then taking out the bath liquid to obtain the white wet leather with the antibacterial function;

the concentration of the micromolecular substance is 4-20 mg/L;

2. The method for improving the antibacterial performance of chrome-free tanned white wet leather according to claim 1, wherein the cyclodextrin polyaldehyde derivative is at least one selected from the group consisting of mono-6-aldehyde-cyclodextrin, bis-6-aldehyde-cyclodextrin and poly-6-aldehyde-cyclodextrin.

3. The method for improving the antibacterial performance of chrome-free tanned wet white leather according to claim 1, wherein the preparation method of the cyclodextrin polyaldehyde derivative comprises the following steps:

4. The method for improving the antibacterial performance of chrome-free tanned wet white leather according to claim 1, wherein the preparation method of the cyclodextrin polyaldehyde derivative comprises the following steps:

step (1): dissolving 1mmol of cyclodextrin in 5-15mL of dimethyl sulfoxide to obtain 1 part of solution A;

step (2): dissolving 1.2mmol of o-iodoacyl benzoic acid in 5-15mL of dimethyl sulfoxide to obtain 1 part of solution B;

and (3): dropwise adding 1 part of the solution B into 1 part of the solution A, and reacting for 24 hours to obtain a solution C;

and (4): dropwise adding 1 part of the solution B into the solution C;

and (5): repeating the step (4) for N times to obtain a mixed solution, wherein the mixed solution contains (N +2) parts of solution B and 1 part of solution A, and N is more than or equal to 0 and less than or equal to 5;

5. The method for improving the antibacterial performance of chrome-free tanned white wet leather according to claim 3, wherein the cyclodextrin is selected from any one of alpha-cyclodextrin, beta-cyclodextrin and gamma-cyclodextrin.

6. The method for improving the antibacterial performance of chrome-free tanned wet white leather according to claim 5, wherein the cyclodextrin is β -cyclodextrin.