Chrome-free tanning method for greenfin pufferfish leather and obtained fish leather

Abstract

The present invention provides a chrome-free tanning method for green fin puffer fish leather and the obtained fish leather, belonging to the technical field of aquatic products. The chrome-free tanning method for green fin puffer fish leather provided by the present invention comprises the following steps: batching and weighing the fresh green fin puffer fish skin, putting it into a rotary drum for soaking, degreasing, liming, deliming, pickling, neutralization, and further comprising the steps of rewetting and retanning, wherein the retanning step is performed by a chrome-free tanning method. The green fin puffer fish leather provided by the present invention is thin and soft, breathable and comfortable, and the softness of the green fin puffer fish leather can reach 5.7-6.5mm after being rubbed soft; the flesh surface is soft and comfortable, and the scale surface has velvety scales which are very distinctive, and can be used as climbing gloves, etc., and is breathable and waterproof. Moreover, the green fin puffer fish leather provided by the present invention is a fish leather tanned by a chrome-free process, does not contain harmful substances, is environmentally friendly, and has related properties such as high bursting strength and shrinkage temperature comparable to chrome-free tanned cowhide.

Description

Technical Field

[0001] The invention belongs to the technical field of aquatic products, and in particular relates to a chrome-free tanning method for greenfin pufferfish leather and the obtained fish leather. Background Art

[0002] Greenfin pufferfish (Thamnaconus septentrionalis; Günther 1874) belongs to the order Tetraodontiformes, family Aluteridae, genus Thamnaconus. It is high in protein and low in fat, rich in a variety of essential amino acids, and nutritious. It is an economical marine fish and is deeply loved by people. It is distributed in the Bohai Sea, Yellow Sea, and East China Sea areas of my country. The East China Sea was once the main sea area for fishing greenfin pufferfish in my country. Because the skin of greenfin pufferfish is easy to peel off, has a hard texture, and is not edible, it is often peeled off and eaten, so it is commonly known as skinned fish, rubber fish, etc. In recent years, breakthroughs have been made in the artificial breeding and breeding technology of greenfin pufferfish. Cage breeding has been carried out in coastal areas of my country, and the scale of the industry is getting bigger and bigger. It is estimated that the annual output of greenfin pufferfish farming is expected to reach more than 1 million tons. The fish skin accounts for about 6% to 7% of the fish weight. 1 million tons of fish can produce about 60,000 to 70,000 tons of fish skin. How to make use of so many greenfin pufferfish skin resources that are treated as waste is an important issue.

[0003] Chrome tanning is the most commonly used tanning method in the leather processing process. Chrome tanning is simple to operate, and the finished leather obtained by chrome tanning has high moisture and heat resistance and physical and chemical properties. However, the process will produce chromium-containing wastewater that is difficult to treat, and may produce hexavalent chromium that is toxic to the human body. With the improvement of people's environmental awareness and the change of production mode, it is particularly important to adopt a more environmentally friendly and cleaner way to process leather. Chrome-free tanning technology mainly includes non-chrome metal tanning technology, aldehyde tanning technology and vegetable tanning technology. The use of chrome-free tanning method to prepare greenfin pufferfish leather can not only solve the hexavalent chromium that may be produced during the processing of fish leather from the source, but also solve the problem of recycling greenfin pufferfish skin resources. However, there are currently no reports on the use of chrome-free tanning technology to prepare greenfin pufferfish leather at home and abroad. Summary of the invention

[0004] The invention provides a chrome-free tanning method for greenfin pufferfish leather and the obtained fish leather. The greenfin pufferfish leather is prepared by the chrome-free tanning method, which can not only solve the hexavalent chromium that may be generated in the processing of the fish leather from the source, but also solve the problem of recycling the greenfin pufferfish skin resources.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a chrome-free tanning method for greenfin puffer fish leather. The fresh greenfin puffer fish leather is batched and weighed, and then put into a rotary drum for soaking, degreasing, liming, deliming, pickling, and neutralization. The method also includes the steps of rewetting and retanning, wherein the retanning step is carried out by a chrome-free tanning method.

[0006] Preferably, in the soaking and degreasing steps, 300% to 500% water, 0.1% to 0.3% degreasing agent OC, and 0.3% soda ash are added to the drum, and the drum is rotated at a temperature of 25 to 30° C. for 60 to 120 minutes, and the liquid is drained after stopping for 20 minutes;

[0007] In the liming step, 50% to 200% water, 0.4% to 0.6% NaHS, 0.6% to 0.9% Na2S and 1% to 1.5% lime are added to the drum in two portions, and the drum is rotated at a temperature of 20 to 25°C for 60 to 120 minutes, and the liquid is drained after stopping for 10 minutes;

[0008] In the deashing step, 100% to 200% of water, 1% to 3% of deashing agent DEL, 0.1% to 0.3% of sodium pyrosulfite, and 0.1% to 0.3% of degreasing agent OC are added to the drum, and the drum is rotated at a temperature of 20 to 25° C. for 60 to 120 minutes, and the liquid is discharged after stopping for 10 minutes.

[0009] Preferably, in the pickling step, 50% to 100% water is added to the drum, the temperature is adjusted to 18 to 20° C., 10% to 20% NaCl is added, and after rotating for 10 minutes, 0.5% to 1.0% of formic acid diluted by a volume ratio of 1:10 and 0.5% to 1.0% of concentrated sulfuric acid diluted by a volume ratio of 1:10 are added twice, and after rotating for another 90 to 120 minutes, 1% to 2.0% of a 50% glutaraldehyde aqueous solution is added, and after rotating for 60 to 120 minutes, the drum is stopped overnight and rotated for another 30 minutes the next day;

[0010] In the neutralization step, 100% to 200% water is added, 0.3% NaHCO3 is added twice, the temperature is raised to 35 to 40°C, the mixture is rotated for 120 to 240 minutes, and the liquid is drained and washed with water; the fish skin is then placed in a 4°C refrigerator for refrigeration and allowed to stand for 48 to 72 hours.

[0011] Preferably, in the retanning step, 100% to 200% of water is added to the drum, the temperature is adjusted to 25 to 30°C, 1% to 3% of synthetic tanning agent is added, the drum is rotated for 30 to 60 minutes, and then 0.5% to 1% of formic acid is added twice, the drum is rotated for 30 to 60 minutes and then the liquid is drained.

[0012] Preferably, after the retanning step, the steps of filling and fatliquoring are further included, wherein in the filling and dyeing step, 1% to 2% natural quebracho tannin, 1% to 3% wattle bark tannin, 1% to 2% disperse tannin and 0.1% to 0.2% dye are added to the drum, and after rotating for 60 to 120 minutes, 1% to 2% wattle bark tannin, 1% to 2% tara tannin, 1% to 2% disperse tannin and 1% to 2% sulfonated fatliquoring agent are added, and after rotating for 60 to 240 minutes, the drum is stopped overnight, and rotated for 20 to 30 minutes the next day, 100 to 200% water is added, the temperature is raised to 40 to 45°C, 0.5 to 1.0% oxalic acid is added, and after rotating for 15 to 30 minutes, 1% to 2% formic acid is added twice, the liquid is drained, and the drum is washed with water.

[0013] Preferably, in the fatliquor step, 200% to 400% water and 2% to 4% protein filler are added to the drum, which is rotated for 10 to 20 minutes, and 2.0% to 3.0% synthetic fatliquor, 2.0% to 3.0% neat's foot oil fatliquor and 1.0% to 2.0% sulfonated fatliquor are added, and the drum is rotated for 60 to 120 minutes at a temperature of 50° C. to 55° C.; then 0.5% to 1.0% formic acid is added twice, each time rotating for 15 to 20 minutes, the liquid is drained, the drum is washed with water, and the drum is dried and finished.

[0014] Preferably, after the soaking and degreasing steps, the liming step, the deliming step and the rewetting step, a washing and weighing step is also included, that is, the fish skin treated in each step is fully washed with water and then weighed, and the required chemical materials are measured according to the weight of the fish skin at each corresponding stage.

[0015] The present invention also provides a greenfin pufferfish leather, which is prepared by the chrome-free tanning method described in any one of the above technical solutions.

[0016] Preferably, the greenfin pufferfish leather has a thickness of 0.55-0.63 mm and a tensile strength of 9.07-12.81 N / mm 2 , the elongation at break is 23.25-27.43%.

[0017] Preferably, the greenfin pufferfish leather does not contain hexavalent chromium, has a shrinkage temperature of 78.5-80.2°C, a burst strength of 229.52-248.48 N / mm, and a softness of 5.7-6.5 mm.

[0018] Compared with the prior art, the advantages and positive effects of the present invention are:

[0019] 1. In the production of the greenfin puffer fish leather provided by the present invention, the raw material leather is convenient to source, and the fish skin of the greenfin puffer fish is easy to peel, simple to operate, easy to transport, and has a small risk of exposure to related personnel (anthrax, glanders, mad cow disease, foot-and-mouth disease, brucellosis, etc.). It is easy to process and treat, and can be made into various shapes and colors to meet the needs of different occasions;

[0020] 2. The green-fin pufferfish leather provided by the present invention is thin and soft, breathable and comfortable. After being rubbed and softened, the softness of the green-fin pufferfish leather can reach 5.7-6.5mm; the flesh surface is soft and comfortable, and the scale surface has velvety scales which are very distinctive. It can be used to make climbing gloves, etc., and is breathable and waterproof;

[0021] 3. The greenfin pufferfish leather provided by the present invention is fish leather tanned by a chrome-free process. The material is environmentally friendly and sustainable, does not contain harmful substances, is environmentally friendly, and has relevant properties such as high bursting strength and shrinkage temperature that are comparable to chrome-free tanned cowhide. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the leather scales of the greenfin pufferfish;

[0023] Figure 2 This is a schematic diagram of the leather scales of the greenfin pufferfish;

[0024] Figure 3 This is a schematic diagram of the leather scales of the greenfin pufferfish;

[0025] Figure 4 The present invention provides a process flow chart of greenfin pufferfish leather according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] like Figure 4 As shown, the preparation process is as follows:

[0029] Batching and weighing: remove the flesh of the greenfin pufferfish skin, tear off the meat membrane, batch it according to the size of the sheet, and then wash it thoroughly with water. Weigh the fresh skin, and the required chemical materials are calculated based on the weight of the fresh skin. Then put the fresh skin into a rotating drum for soaking and degreasing.

[0030] Soaking and degreasing: add 300% water, 0.1% degreasing agent OC, and 0.3% soda ash into the drum, the temperature is 25-30℃, rotate for 60min, stop for 20min, and drain;

[0031] Washing and weighing: the fresh greenfin puffer fish skin after soaking and defatting is fully washed with water, the required chemical material is calculated based on the weight of the fish skin at this stage, and then the greenfin puffer fish skin is put into a rotary drum for liming treatment;

[0032] Liming: add 50% water to the drum, add 0.4% NaHS, add 0.6% Na2S and 1% lime twice, the temperature is 20-25℃, rotate for 60min, stop for 10min, and drain;

[0033] Washing and weighing: After the limed skin is fully washed, it is weighed, and the required chemical materials are calculated based on the weight of the gray skin. Then the gray skin is placed in a rotary drum for deliming.

[0034] Deashing: add 100% water, 1% deashing agent DEL, 0.1% sodium pyrosulfite, 0.1% degreasing agent OC into the drum, the temperature is 20-25℃, rotate for 60-120min, stop for 10min, and drain;

[0035] Washing and weighing: the delimed fresh green-finned pufferfish skin is fully washed with water, and then weighed after washing. The required chemical material is calculated based on the weight of the fish skin at this stage, and then the fish skin is placed in a rotary drum for acid treatment;

[0036] Acid soaking: add 50% water to the drum, adjust the temperature to 18-20°C, add 10% NaCl, rotate for 10 minutes, add 0.5% formic acid diluted 1:10 by volume and 0.5% concentrated sulfuric acid diluted 1:10 by volume in two portions, rotate for 90 minutes, add 1% 50% glutaraldehyde aqueous solution, rotate for 60 minutes, stop the drum overnight, and rotate for 30 minutes the next day.

[0037] Neutralization: add 100% water, add 0.3% NaHCO3 twice, heat to 35-40℃, rotate for 120min, drain and wash with water.

[0038] Let stand: Refrigerate the fish skin at 4°C for 48 to 72 hours.

[0039] Rewetting: put the fish skin after standing into a drum, add 100% water into the drum, adjust the temperature to 35-40°C, add 0.1% degreasing agent OC, 0.2% oxalic acid, 0.1% formic acid, 1% synthetic fatliquor, rotate for 40-60 minutes, and drain;

[0040] Washing and weighing: the re-moistened fish skin is fully washed with water, and then weighed. The required chemical materials are calculated based on the weight of the fish skin at this stage. Then the fish skin is placed in a rotary drum for retanning, filling and fat-liquoring.

[0041] Retanning: put the washed and weighed fish skin into a drum, add 100% water into the drum, adjust the temperature to 25-30°C, add 1% synthetic tanning agent, rotate for 30 minutes, add 0.5% formic acid twice, rotate for 30 minutes, and drain;

[0042] Dyeing: add 1% natural quebracho tannin, 1% wattle bark tannin, 1% dispersed tannin, and 0.1% dye to the drum, rotate for 60 minutes, then add 1% wattle bark tannin, 1% tara tannin, 1% dispersed tannin, and 1% sulfonated fatliquor, rotate for 60 minutes, stop the drum overnight, rotate for 20-30 minutes the next day, add 100% water, heat to 40-45°C, add 0.5% oxalic acid, rotate for 15-30 minutes, then add 1% formic acid twice, drain and wash;

[0043] Fat-liquoring: Put the washed leather into a drum, add 200% water and 2% protein filler into the drum, rotate for 10-20 minutes, add 2.0% synthetic fat-liquor, 2.0% neatsfoot oil fat-liquor, 1.0% sulfonated fat-liquor, adjust the drum temperature to 50-55°C, rotate for 60 minutes; then add 0.5% formic acid twice, rotate for 15 minutes each time, drain, wash with water, and take out of the drum; dry and finish. The schematic diagram of the scale surface of the prepared greenfin pufferfish leather is as follows Figure 1 shown.

[0044] Example 2

[0045] Batching and weighing: remove the flesh of the greenfin pufferfish skin, tear off the meat membrane, batch it according to the size of the sheet, and then wash it thoroughly with water. Weigh the fresh skin, and the required chemical materials are calculated based on the weight of the fresh skin. Then put the fresh skin into a rotating drum for soaking and degreasing.

[0046] Soaking and degreasing: add 400% water, 0.2% degreasing agent OC, and 0.3% soda ash into the drum, the temperature is 25-30℃, rotate for 100min, stop for 20min, and drain;

[0047] Washing and weighing: the fresh greenfin puffer fish skin after soaking and defatting is fully washed with water, the required chemical material is calculated based on the weight of the fish skin at this stage, and then the greenfin puffer fish skin is put into a rotary drum for liming treatment;

[0048] Liming: add 120% water to the drum, add 0.5% NaHS, add 0.8% Na2S and 1.2% lime twice, the temperature is 22℃, rotate for 100min, stop for 10min, and drain;

[0049] Washing and weighing: After the limed skin is fully washed, it is weighed, and the required chemical materials are calculated based on the weight of the gray skin. Then the gray skin is placed in a rotary drum for deliming.

[0050] Deashing: add 150% water, 2% deashing agent DEL, 0.2% sodium pyrosulfite, 0.2% degreasing agent OC into the drum, the temperature is 22℃, rotate for 100min, stop for 10min, and drain;

[0051] Washing and weighing: the de-ashed fresh green-finned puffer fish skin is fully washed with water, and then weighed after washing. The required chemical material is calculated based on the weight of the fish skin at this stage, and then the fish skin is placed in a rotary drum for acid treatment;

[0052] Acid soaking: add 80% water to the drum, adjust the temperature to 18-20°C, 15% NaCl, rotate for 10 minutes, add 0.8% formic acid diluted 1:10 by volume twice, 0.8% concentrated sulfuric acid diluted 1:10 by volume, rotate for 100 minutes, add 1.5% 50% glutaraldehyde aqueous solution, rotate for 100 minutes, stop the drum overnight, and rotate for 30 minutes the next day.

[0053] Neutralization: add 150% water, add 0.3% NaHCO3 twice, heat to 35-40℃, rotate for 180min, drain and wash with water.

[0054] Let stand: Refrigerate the fish skin at 4°C for 48 to 72 hours.

[0055] Rewetting: put the fish skin after standing into a drum, add 150% water into the drum, adjust the temperature to 35-40°C, add 0.2% degreasing agent OC, 0.4% oxalic acid, 0.2% formic acid, 1.5% synthetic fatliquor, rotate for 50 minutes, and drain;

[0056] Washing and weighing: the re-moistened fish skin is fully washed with water, and then weighed. The required chemical materials are calculated based on the weight of the fish skin at this stage. Then the fish skin is placed in a rotary drum for retanning, filling and fat-liquoring.

[0057] Retanning: put the washed and weighed fish skin into a drum, add 150% water into the drum, adjust the temperature to 25-30°C, add 2% synthetic tanning agent, rotate for 45 minutes, add 0.8% formic acid twice, rotate for 50 minutes, and drain;

[0058] Dyeing: add 1.5% natural quebracho tannin, 1.5% wattle bark tannin, 1.5% dispersed tannin, and 0.15% dye to the drum, rotate for 100 minutes, then add 1.5% wattle bark tannin, 1.5% tara tannin, 1.5% dispersed tannin, and 1.5% sulfonated fatliquor, rotate for 180 minutes, stop the drum overnight, rotate for 20-30 minutes the next day, add 150% water, heat to 40-45°C, add 0.8% oxalic acid, rotate for 15-30 minutes, then add 1.5% formic acid twice, drain and wash;

[0059] Fat-liquoring: Put the washed leather into the drum, add 300% water and 3% protein filler into the drum, rotate for 10-20 minutes, add 2.5% synthetic fat-liquor, 2.5% neatsfoot oil fat-liquor, 1.5% sulfonated fat-liquor, adjust the drum temperature to 50-55°C, rotate for 100 minutes; then add 0.8% formic acid twice, rotate for 15-20 minutes each time, drain, wash with water, and take out of the drum; dry and finish. The schematic diagram of the scale surface of the prepared greenfin pufferfish leather is as follows: Figure 2 shown.

[0060] Example 3

[0061] Batching and weighing: remove the flesh of the greenfin pufferfish skin, tear off the meat membrane, batch it according to the size of the sheet, and then wash it thoroughly with water. Weigh the fresh skin, and the required chemical materials are calculated based on the weight of the fresh skin. Then put the fresh skin into a rotating drum for soaking and degreasing.

[0062] Soaking and degreasing: add 500% water, 0.3% degreasing agent OC, and 0.3% soda ash into the drum, the temperature is 25-30℃, rotate for 120min, stop for 20min, and drain;

[0063] Washing and weighing: the fresh greenfin puffer fish skin after soaking and defatting is fully washed with water, the required chemical material is calculated based on the weight of the fish skin at this stage, and then the greenfin puffer fish skin is put into a rotary drum for liming treatment;

[0064] Liming: add 200% water to the drum, add 0.6% NaHS, add 0.9% Na2S and 1.5% lime twice, the temperature is 20-25℃, rotate for 120min, stop for 10min, and drain;

[0065] Washing and weighing: After the limed skin is fully washed, it is weighed, and the required chemical materials are calculated based on the weight of the gray skin. Then the gray skin is placed in a rotary drum for deliming.

[0066] Deashing: add 200% water, 3% deashing agent DEL, 0.3% sodium pyrosulfite, 0.3% degreasing agent OC into the drum, the temperature is 20-25℃, rotate for 120min, stop for 10min, and drain;

[0067] Washing and weighing: the de-ashed fresh green-finned puffer fish skin is fully washed with water, and then weighed after washing. The required chemical material is calculated based on the weight of the fish skin at this stage, and then the fish skin is placed in a rotary drum for acid treatment;

[0068] Acid soaking: add 100% water to the drum, adjust the temperature to 18-20°C, 20% NaCl, rotate for 10 minutes, add 1.0% formic acid diluted 1:10 by volume twice, add 1.0% concentrated sulfuric acid diluted 1:10 by volume, rotate for 90-120 minutes, add 2.0% 50% glutaraldehyde aqueous solution, rotate for 120 minutes, stop the drum overnight, and rotate for 30 minutes the next day.

[0069] Neutralization: add 200% water, add 0.3% NaHCO3 twice, heat to 35-40℃, rotate for 240min, drain and wash with water.

[0070] Let stand: Refrigerate the fish skin at 4°C for 48 to 72 hours.

[0071] Rewetting: put the fish skin after standing in a drum, add 200% water into the drum, adjust the temperature to 35-40°C, add 0.3% degreasing agent OC, 0.5% oxalic acid, 0.3% formic acid, 2% synthetic fatliquor, rotate for 40-60 minutes, and drain;

[0072] Washing and weighing: the re-moistened fish skin is fully washed with water, and then weighed. The required chemical materials are calculated based on the weight of the fish skin at this stage. Then the fish skin is placed in a rotary drum for retanning, filling and fat-liquoring.

[0073] Retanning: put the washed and weighed fish skin into a drum, add 200% water into the drum, adjust the temperature to 25-30°C, add 3% synthetic tanning agent, rotate for 30-60 minutes, add 1% formic acid twice, rotate for 60 minutes, and drain;

[0074] Dyeing: add 2% natural quebracho extract, 3% wattle bark extract, 2% disperse tannin, 0.2% dye to the drum, rotate for 120 minutes, add 2% wattle bark extract, 2% tara extract, 2% disperse tannin, 2% sulfonated fatliquor, rotate for 240 minutes, stop the drum overnight, rotate for 20-30 minutes the next day, add 200% water, heat to 40-45°C, add 1.0% oxalic acid, rotate for 15-30 minutes, add 2% formic acid twice, drain and wash;

[0075] Fat-liquoring: Put the washed leather into a drum, add 400% water and 4% protein filler into the drum, rotate for 10-20 minutes, add 3.0% synthetic fat-liquor, 3.0% neatsfoot oil fat-liquor, 2.0% sulfonated fat-liquor, adjust the drum temperature to 50-55°C, rotate for 120 minutes; then add 1.0% formic acid twice, rotate for 15-20 minutes each time, drain, wash with water, and take out of the drum; dry and finish. The schematic diagram of the scale surface of the prepared greenfin pufferfish leather is as follows: Figure 3 shown.

[0076] Performance Testing

[0077] The shrinkage temperature, physical properties and effects of the fish leather obtained in Examples 1-3 are summarized as shown in Table 1 below. The test methods for each index are as follows:

[0078] Shrinkage temperature: QB / T 2713-2005; Thickness: QB / T 2709-2005; Tensile strength: QB / T2710-2018; Elongation at break: QB / T 2710-2018; Burst strength: QB / T 2712-2005; Softness: The instrument used is GT-303 leather softness tester, which complies with the instrument settings in ISO 17235:2015 and IULTCS.IUP / 36 standards, so the foreign standard ISO 17235:2015 is adopted.

[0079] Table 1

[0080]

[0081] Combined with the data in the table, it can be seen that the green fin puffer fish leather provided by the present invention is thin and soft, breathable and comfortable. After being rubbed and softened, the softness of the green fin puffer fish leather can reach 5.7-6.5mm; the flesh surface is soft and comfortable, and the scale surface has velvety scales, which are very distinctive. It can be used to make rock climbing gloves, etc., and is breathable and waterproof. Moreover, the green fin puffer fish leather provided by the present invention is fish leather tanned by a chrome-free process, does not contain harmful substances, is environmentally friendly, and has related properties such as high bursting strength and shrinkage temperature that are comparable to chrome-free tanned cowhide.

Claims

1. A chrome-free tanning method for greenfin pufferfish leather, characterized in that: The greenfin puffer fish skin is batched and weighed, and then put into a rotary drum for soaking, degreasing, liming, deliming, pickling, and neutralization, and further comprising the steps of rewetting and retanning, wherein the retanning step is performed by a chrome-free tanning method; In the soaking and degreasing steps, 300%~500% water, 0.1%~0.3% degreasing agent OC, and 0.3% soda ash are added to the drum, and the drum is rotated at a temperature of 25~30℃ for 60~120min, and the liquid is drained after stopping for 20min; In the liming step, 50% to 200% water, 0.4% to 0.6% NaHS, 0.6% to 0.9% Na2S and 1% to 1.5% lime are added to the drum in two portions, and the drum is rotated at a temperature of 20 to 25°C for 60 to 120 minutes, and the liquid is drained after stopping for 10 minutes; In the deashing step, 100%~200% water, 1%~3% deashing agent DEL, 0.1%~0.3% sodium pyrosulfite, and 0.1%~0.3% degreasing agent OC need to be added to the drum, and the drum should be rotated at a temperature of 20~25℃ for 60~120min, and the liquid should be drained after stopping for 10min; In the pickling step, 50% to 100% water is added to the drum, and after adjusting the temperature to 18 to 20°C, 10% to 20% NaCl is added. After rotating for 10 minutes, 0.5% to 1.0% of formic acid diluted by a volume ratio of 1:10 and 0.5% to 1.0% of concentrated sulfuric acid diluted by a volume ratio of 1:10 are added twice. After rotating for another 90 to 120 minutes, 1% to 2.0% of a 50% glutaraldehyde aqueous solution is added. After rotating for 60 to 120 minutes, the drum is stopped overnight and rotated for another 30 minutes the next day. In the neutralization step, 100% to 200% water is added, 0.3% NaHCO3 is added twice, the temperature is raised to 35-40°C, the mixture is rotated for 120-240 minutes, and the liquid is drained and washed with water; the fish skin is then placed in a 4°C refrigerator and left to stand for 48-72 hours; In the retanning step, 100% to 200% water is added to the drum, the temperature is adjusted to 25 to 30°C, 1% to 3% synthetic tanning agent is added, the drum is rotated for 30 to 60 minutes, and then 0.5% to 1% formic acid is added twice, the drum is rotated for 30 to 60 minutes, and then the liquid is drained; After the retanning step, the method further comprises the steps of filling and dyeing and fatliquoring, wherein in the filling and dyeing step, 1% to 2% natural quebracho tannin, 1% to 3% wattle bark tannin, 1% to 2% dispersed tannin, and 0.1% to 0.2% dye are added to the drum, and after rotating for 60 to 120 minutes, 1% to 2% wattle bark tannin, 1% to 2% tara tannin, 1% to 2% dispersed tannin, and 1% to 2% sulfonated fatliquoring agent are added, and after rotating for 60 to 240 minutes, the drum is stopped overnight, and the drum is rotated for 20 to 30 minutes the next day, 100 to 200% water is added, the temperature is raised to 40 to 45 degrees Celsius, 0.5 to 1.0% oxalic acid is added, and after rotating for 15 to 30 minutes, 1% to 2% formic acid is added twice, and the drum is drained and washed with water; In the fatliquor step, 200%~400% water and 2%~4% protein filler are added to the drum, which is rotated for 10min~20min, and 2.0%~3.0% synthetic fatliquor, 2.0%~3.0% neat's foot oil fatliquor and 1.0%~2.0% sulfonated fatliquor are added. The drum is rotated at a temperature of 50℃~55℃ for 60min~120min. Then, 0.5%~1.0% formic acid is added twice, each time rotating for 15min~20min, the liquid is drained, the drum is washed with water, and the drum is dried and finished.

2. The chrome-free tanning method according to claim 1, characterized in that: After the soaking and degreasing steps, the liming step, the deliming step and the rewetting step, the method further comprises the steps of washing and weighing, that is, the fish skin treated in each step is fully washed with water and then weighed, and the required chemical materials are calculated based on the weight of the fish skin at each corresponding stage.

3. Greenfin pufferfish leather, characterized in that: The chrome-free tanning method according to claim 1 or 2 is used for preparing the tanning product.

4. The greenfin pufferfish leather according to claim 3, characterized in that: The green fin pufferfish leather has a thickness of 0.55-0.63 mm and a tensile strength of 9.07-12.81 N / mm 2 , the elongation at break is 23.25-27.43%.

5. The greenfin pufferfish leather according to claim 3, characterized in that: The greenfin pufferfish leather does not contain hexavalent chromium, has a shrinkage temperature of 78.5-80.2° C., a burst strength of 229.52-248.48 N / mm, and a softness of 5.7-6.5 mm.

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