Preparation method of chrome-free tanned upper leather

Abstract

The present invention discloses a preparation method of chrome-free tanned upper leather, comprising the following steps: Step 1: Re-wetting Add the prepared aqueous solution of sodium chloride and sodium bicarbonate into a drum machine, and then put in the raw hide, and rotate for 10 - 30 min; Step 2: Water washing Immerse the re-wetted raw hide in pure water and wash for 10 - 30 min; Step 3: Tanning Add water, a catalyst, and a modified tanning agent into the drum machine, and run the drum machine for tanning for 200 - 360 min; Step 4: Alkali raising Add sodium bicarbonate into the drum machine, adjust the pH to 8.0, raise the temperature to 35 °C, rotate for 4 h, stand for 5 - 20 h, and dry to obtain the upper leather; The modified tanning agent is formed by the reaction of starch, trimethylolethane triglycidyl ether, tetramethylethylenediamine, N-(2-hydroxyethyl)guanidine, and epoxypropionic acid. The purpose of the present invention is to provide a preparation method of chrome-free tanned upper leather.

Description

Technical Field

[0001] The present invention relates to the field of leather processing, and more specifically to a method for preparing chrome-free tanned upper leather. Background Art

[0002] When leather is being produced and processed, it often needs to be tanned. The physical and chemical process of turning raw hide into leather through a tanning agent is called tanning. Tanning is an important process in leather making and fur processing. Using different tanning agents to tan leather results in different tanning methods. For example, the most commonly used chromium tanning agent for light leather is called the chrome tanning method.

[0003] However, in the chrome tanning process, heavy metal tanning agents containing chromium are often used, which can cause significant pollution. In the prior art, there are tanning agents with other metal ions used to replace the use of chromium tanning agents, but there are few reports on tanning with metal-free tanning agents. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for preparing chrome-free tanned upper leather.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A method for preparing chrome-free tanned upper leather,

[0007] comprising the following steps:

[0008] Step 1: Rehydration

[0009] Add the prepared aqueous solution of sodium chloride and sodium bicarbonate into a drum machine, and then put in the raw hide, and rotate for 10 - 30 min;

[0010] Step 2: Water washing

[0011] Immerse the rehydrated raw hide in pure water and wash for 10 - 30 min;

[0012] Step 3: Tanning

[0013] Add water, a catalyst, and a modified tanning agent into a drum machine, and run the drum machine for tanning for 200 - 360 min;

[0014] Step 4: Alkaliation

[0015] Add sodium bicarbonate into a drum machine, adjust the pH to 8.0, raise the temperature to 35 °C, rotate for 4 h, stand for 5 - 20 h, and dry to obtain the upper leather;

[0016] The modified tanning agent is formed by the reaction of starch, trimethylolethane triglycidyl ether, tetramethylethylenediamine, N-(2-hydroxyethyl)guanidine, and epoxypropionic acid.

[0017] As a further improvement of the present invention,

[0018] The preparation method of the modified tanning agent is as follows:

[0019] Step A: Dissolve N-(2-hydroxyethyl)guanidine and epoxypropionic acid in water, add sulfuric acid, and react for 30-120 minutes. After drying, a modifier is obtained;

[0020] Step B: Dissolve starch in a solvent, then add tetramethylethylenediamine. After complete dissolution, add trimethylolethane triglycidyl ether and the modifier, and reflux and react at 60°C for 5 hours to obtain a purified and dried modified tanning agent.

[0021] As a further improvement of the present invention,

[0022] In the first step, the mass ratio of water, sodium chloride, and sodium bicarbonate is 200:7:2.

[0023] As a further improvement of the present invention,

[0024] In the third step, the catalyst is hexamethylenetetramine.

[0025] As a further improvement of the present invention,

[0026] In the third step, the mass ratio of water, catalyst, and modified tanning agent is 100:0.5:3-10.

[0027] As a further improvement of the present invention,

[0028] The starch is soluble corn starch.

[0029] As a further improvement of the present invention,

[0030] The mass ratio of starch, trimethylolethane triglycidyl ether, and modifier is 10-20:30-50:5-10.

[0031] As a further improvement of the present invention,

[0032] The solvent is dimethyl sulfoxide.

[0033] In the present invention, a self-made modified tanning agent is mainly used to tan leather. The modified tanning agent is first obtained by the esterification reaction of N-(2-hydroxyethyl)guanidine and epoxypropionic acid under acid catalysis to obtain a lipid compound containing guanidine bonds and epoxy groups. Then, the hydroxyl groups on starch can react with the lipid compound and trimethylolethane triglycidyl ether under the catalysis of a catalyst to finally produce the modified tanning agent. The leather after using the modified tanning agent does not contain any metal ions but has an effect similar to that of chrome tanning agents. Specific embodiments

[0034] Example 1:

[0035] Synthesis of tanning agents:

[0036] Step A: dissolving 100 parts by mass of N-(2-hydroxyethyl)guanidine and 90 parts by mass of epoxypropionic acid in 500 parts by mass of water, adding 5 parts of concentrated sulfuric acid after the solvent is completely dissolved, reacting for 30 to 120 minutes, filtering and naturally drying to obtain a modifier;

[0037] Step B: Take 17g of soluble corn starch and dissolve it in 50mL of dimethyl sulfoxide, then add 0.05mL of tetramethylethylenediamine, and after the solvent is completely decomposed, a mixed solution is obtained for use, 45g of trimethylolethane triglycidyl ether and 5g of modifier are dissolved in 50mL of dimethyl sulfoxide, and then the mixed solution is added thereto, refluxed at 60°C for 5h, cooled to room temperature, dialyzed with a dialysis bag with a molecular weight of 500, and then added 300mL of anhydrous ethanol to wash out the solid, and vacuum dried at 40°C for 24h to obtain the purified and dried modified tanning agent.

[0038] Shoe leather upper tanning:

[0039] The steps include:

[0040] Step 1: Rewetting

[0041] Add the prepared sodium chloride and sodium bicarbonate aqueous solution into the drum machine, then put in the bare skin and rotate for 30 minutes;

[0042] In the step 1, the mass ratio of water, sodium chloride and sodium bicarbonate is 200:7:2

[0043] Step 2: Wash

[0044] Immerse the rewetted bare skin in pure water and wash for 30 minutes;

[0045] Step 3: Tanning

[0046] Add water, hexamethylenetetramine and modified tanning agent into a drum machine, and run the drum machine for tanning for 300 minutes;

[0047] In the step 3, the mass ratio of water, hexamethylenetetramine and modified tanning agent is 100:0.5:5.

[0048] Step 4: Alkali Extraction

[0049] Sodium bicarbonate was added to a drum machine, the pH was adjusted to 8.0, the temperature was raised to 35° C., the drum machine was rotated for 4 hours, the drum machine was allowed to stand for 10 hours, and the upper leather was obtained by drying.

[0050] Comparative Example 1:

[0051] Shoe leather upper tanning:

[0052] It includes the following steps:

[0053] Step 1: Moistening back

[0054] Add the prepared aqueous solution of sodium chloride and sodium bicarbonate into the drum machine, then put in the raw hide, and rotate for 30 min;

[0055] In Step 1, the mass ratio of water, sodium chloride, and sodium bicarbonate is 200∶7∶2

[0056] Step 2: Washing with water

[0057] Immerse the moistened-back raw hide into pure water and wash for 30 min;

[0058] Step 3: Tanning

[0059] Add water, hexamethylenetetramine, and commercially available chrome tanning agent into the drum machine, and run the drum machine for tanning for 300 min;

[0060] In Step 3, the mass ratio of water, hexamethylenetetramine, and commercially available chrome tanning agent is 100∶0.5∶5.

[0061] Step 4: Raising the alkalinity

[0062] Add sodium bicarbonate into the drum machine, adjust the pH to 8.0, raise the temperature to 35 °C, rotate for 4 h, stand for 10 h, and dry to obtain the upper leather.

[0063] Comparative Example 2:

[0064] Tanning of shoe upper leather:

[0065] It includes the following steps:

[0066] Step 1: Moistening back

[0067] Add the prepared aqueous solution of sodium chloride and sodium bicarbonate into the drum machine, then put in the raw hide, and rotate for 30 min;

[0068] In Step 1, the mass ratio of water, sodium chloride, and sodium bicarbonate is 200∶7∶2

[0069] Step 2: Washing with water

[0070] Immerse the moistened-back raw hide into pure water and wash for 30 min;

[0071] Step 3: Tanning

[0072] Add water, hexamethylenetetramine, and soluble corn starch into the drum machine, and run the drum machine for tanning for 300 min;

[0073] In Step 3, the mass ratio of water, hexamethylenetetramine, and modified tanning agent is 100∶0.5∶5.

[0074] Step 4: Alkali Extraction

[0075] Sodium bicarbonate was added to a drum machine, the pH was adjusted to 8.0, the temperature was raised to 35° C., the drum machine was rotated for 4 hours, the drum machine was allowed to stand for 10 hours, and the upper leather was obtained by drying.

[0076] Comparative Example 3:

[0077] Synthesis of tanning agents:

[0078] Take 17g of soluble corn starch and dissolve it in 50mL of dimethyl sulfoxide, then add 0.05mL of tetramethylethylenediamine, and after the solvent is completely decomposed, a mixed solution is obtained for use, 45g of trihydroxymethylethane triglycidyl ether is dissolved in 50mL of dimethyl sulfoxide, and then the mixed solution is added thereto, refluxed at 60°C for 5h, cooled to room temperature, dialyzed with a dialysis bag with a molecular weight of 500, and then added 300mL of anhydrous ethanol, washed out the solid, and vacuum dried at 40°C for 24h to obtain the purified and dried modified tanning agent.

[0079] Shoe leather upper tanning:

[0080] The steps include:

[0081] Step 1: Rewetting

[0082] Add the prepared sodium chloride and sodium bicarbonate aqueous solution into the drum machine, then put in the bare skin and rotate for 30 minutes;

[0083] In the step 1, the mass ratio of water, sodium chloride and sodium bicarbonate is 200:7:2

[0084] Step 2: Wash

[0085] Immerse the rewetted bare skin in pure water and wash for 30 minutes;

[0086] Step 3: Tanning

[0087] Add water, hexamethylenetetramine and modified tanning agent into a drum machine, and run the drum machine for tanning for 300 minutes;

[0088] In the step 3, the mass ratio of water, hexamethylenetetramine and modified tanning agent is 100:0.5:5.

[0089] Step 4: Alkali Extraction

[0090] Sodium bicarbonate was added to a drum machine, the pH was adjusted to 8.0, the temperature was raised to 35° C., the drum machine was rotated for 4 hours, the drum machine was allowed to stand for 10 hours, and the upper leather was obtained by drying.

[0091] In the embodiments and comparative examples, the bare skin is selected from sheep bare skin.

[0092] Ingredients:

[0093] Raw materials Manufacturer Sodium chloride Shanghai Jinjinle Industry Co., Ltd. Sodium bicarbonate Shanghai Jinjinle Industry Co., Ltd. Hexamethylenetetramine Shanghai Jinjinle Industry Co., Ltd. Soluble corn starch Shanghai Macklin Biochemical Co., Ltd. Trimethylolpropane triglycidyl ether Shanghai Jinjinle Industry Co., Ltd. Tetramethylethylenediamine Shanghai Jinjinle Industry Co., Ltd. N-(2-Hydroxyethyl)guanidine Shanghai Enno Biotechnology Co., Ltd. Epoxypropionic acid Shanghai Jinjinle Industry Co., Ltd. Dimethyl sulfoxide Shandong Rongsheng New Materials Co., Ltd. Commercially available chrome tanning agent Shenyang Elepux Chemical Co., Ltd. Sheep bare skin Hebei Dongming Leather Co., Ltd.

[0094] Test:

[0095] For the mechanical property test, refer to QB-T 2710-2005;

[0096] For the thickness measurement of leather, refer to QB / T2709-2005, and calculate the thickening rate;

[0097] For the softness measurement, use the PW-T300 leather softness tester of Bowit Instrument (Shanghai) Co., Ltd. For the leather shrinkage temperature measurement, refer to QB / T2713-2005.

[0098]

[0099] In the present invention, a self-made modified tanning agent is mainly used to tan leather. The modified tanning agent is first obtained by the esterification reaction of N-(2-hydroxyethyl)guanidine and epoxypropionic acid under acid catalysis to obtain a lipid compound containing guanidine bonds and epoxy groups. Then, the hydroxyl groups on starch can react with the lipid compound and trimethylolethane triglycidyl ether under the catalysis of a catalyst to finally produce the modified tanning agent. The leather after using the modified tanning agent does not contain any metal ions but has an effect similar to that of chromium tanning agent.

[0100] It can be seen from the comparison between Example 1 and Comparative Example 1 that Comparative Example 1 uses a commercially available chromium tanning agent, and its effect is very ideal. Although the leather tanned in Example 1 has a certain gap with Comparative Example 1, it is already very close.

[0101] In Example 2, corn starch is directly used, and no reaction occurs during the tanning process. Therefore, the leather hardly changes, showing the characteristics of high tensile strength and high tear strength. However, its elongation at break is low, the thickening is less, the softness is poor, and the shrinkage temperature is also low.

[0102] Comparing Example 1 with Comparative Example 3, in the modified tanning agent prepared in Comparative Example 3, no lipid compound synthesized by adding N-(2-hydroxyethyl)guanidine and epoxypropionic acid is added, so the guanidine bond is missing. Therefore, the tanning effect is greatly reduced.

[0103] The above is only the preferred implementation mode of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing chrome-free tanned shoe upper leather, characterized in that: The steps include: Step 1: Rewetting Add the prepared sodium chloride and sodium bicarbonate aqueous solution into the drum machine, then put in the bare skin and rotate for 10-30 minutes; Step 2: Wash Immerse the rewetted bare skin in pure water and wash for 10 to 30 minutes; Step 3: Tanning Add water, catalyst and modified tanning agent into the drum machine and run the drum machine for tanning for 200-360 minutes; Step 4: Alkali Extraction Sodium bicarbonate is added to a drum machine, the pH is adjusted to 8.0, the temperature is raised to 35°C, the drum machine is rotated for 4 hours, the drum machine is allowed to stand for 5 to 20 hours, and the upper leather is dried; Preparation method of the modified tanning agent: Step A: dissolving N-(2-hydroxyethyl)guanidine and epoxypropionic acid in water, adding sulfuric acid, reacting for 30-120 minutes, and drying to obtain a modifier; Step B: dissolve starch in a solvent, then add tetramethylethylenediamine, and after the solvent is completely dissolved, add trimethylolethane triglycidyl ether and a modifier, reflux at 60° C. for 5 hours, and purify and dry to obtain a modified tanning agent.

2. The method for preparing chrome-free tanned shoe upper leather according to claim 1, characterized in that: In the step 1, the mass ratio of water, sodium chloride and sodium bicarbonate is 200:7:

2.

3. The method for preparing chrome-free tanned shoe upper leather according to claim 1, characterized in that: In the step 3, the catalyst is hexamethylenetetramine.

4. The method for preparing chrome-free tanned shoe upper leather according to claim 1, characterized in that: In the step 3, the mass ratio of water, catalyst and modified tanning agent is 100:0.5:3~10.

5. The method for preparing chrome-free tanned shoe upper leather according to claim 1, characterized in that: The starch is soluble corn starch.

6. The method for preparing chrome-free tanned shoe upper leather according to claim 1, characterized in that: The mass ratio of the starch, trimethylolethane triglycidyl ether and the modifier is 10-20:30-50:5-10.

7. The method for preparing chrome-free tanned shoe upper leather according to claim 1, characterized in that: The solvent is dimethyl sulfoxide.

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