A process for solving the frost formation on leather under high temperature conditions

Abstract

The present application relates to the technical field of leather making process, and particularly relates to a process for solving the problem of white frost of leather under high temperature conditions. The water soaking process stage includes fur weighing, fur feeding, water washing, pre-water soaking, mechanical fleshing, and main water soaking; the liming process stage includes liming, unhairing, water washing, mechanical fleshing, and cutting; the deliming process stage includes weighing, fur feeding, water washing, pre-deliming, main deliming, and softening; the desulfurization process stage includes desulfurization: adding water with a product mass ratio of 180-220% and a temperature of 30-35 DEG C in a rotating drum, rotating for 15 min, draining water, and repeating twice; sulfur content measurement: liquid detection: dropping 5% dilute sulfuric acid, liquid turbidity, repeating desulfurization for treatment, and if the liquid is clear and does not become turbid, it is qualified; acid soaking and chrome tanning process stage: acid soaking, chrome tanning, alkali extraction, water washing, drum discharging, horse mounting, and standing; the problem of sulfur frost of leather under high temperature conditions is solved, and the pathogenic factor of white frost, i.e. sulfur, is effectively eliminated.

Description

Technical Field

[0001] This invention relates to the field of leather manufacturing technology, and in particular to a process for solving the problem of white bloom forming on leather under high temperature conditions. Background Technology

[0002] Leather products are high-end consumer goods in people's lives. White spots on leather are a common defect in leather products. Once white spots appear in leather products, they directly affect the quality and grade of the leather products. In the sales process, customers often return or claim compensation because of this white spot problem, which seriously affects the image and reputation of the manufacturer and causes huge economic losses to the manufacturer.

[0003] Currently, there are two types of white frost on leather recognized in the industry: one is salt frost, which is prone to occur under humid conditions; the other is oil frost, which is prone to occur under low temperature conditions. These two types of white frost are relatively easy to solve, with mature solutions and related invention patent applications. The patent application for salt frost is CN 114231670A; the patent application for oil frost is CN105624344 A. The solutions for salt frost and oil frost will not be elaborated here.

[0004] In their production practice, the inventors discovered a new type of white frost on leather that is neither salt frost nor oil frost. This white frost is produced during the high-temperature shaping process in the post-processing of leather or when leather products are used under high-temperature conditions. For example, it can occur when leather is left to stand after ironing; after high-temperature shaping of finished leather shoes; and when genuine leather car seats are exposed to high temperatures under the scorching sun. This type of white frost is very difficult to resolve, as methods used to resolve oil frost and salt frost are ineffective. Scientific analysis revealed that this white frost is a sulfur-containing leather exudate, which we named sulfur frost, containing a sulfur content of 97.36%. Because elemental sulfur is chemically stable at room temperature, insoluble in water, and has a melting point of 112.8℃, if the temperature exceeds this melting point, elemental sulfur within the leather fibers will migrate to the leather surface, forming sulfur frost. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a process for preventing white blooms from forming on leather under high-temperature conditions. This process effectively avoids the formation of white blooms on leather during the high-temperature setting process in the finishing stage or when leather products are used under high-temperature conditions.

[0006] To address the aforementioned technical problems, the solution adopted by this invention is as follows:

[0007] A process for solving the problem of white bloom formation on leather under high-temperature conditions, characterized by comprising the following steps in sequence:

[0008] I. Immersion Process Stage:

[0009] Step 1, Weighing the fur: Determine the mass percentage of water and reagents to be used in subsequent processing steps based on the quality of the fur;

[0010] Step 2, Putting the pelts in: Put the weighed pelts into the rotating drum;

[0011] Step 3, water washing: Add water (130%-160% of the weight of the fur added in Step 2) and 0.12%-0.16% degreasing agent to the drum; rotate for 10 minutes, stop for 50 minutes, repeat the rotation and stop process twice, and then drain the water.

[0012] Step 4, Pre-soaking: Add water (130%-160% of the fur weight added in Step 2) at a temperature of 25℃-30℃, 0.12%-0.16% degreasing agent, 0.12%-0.16% rehumidifier, 0.12%-0.16% bactericide, and 0.2%-0.3% soda ash to the drum; rotate for 10 minutes, stop for 50 minutes, repeat the rotation and stop cycle twice, then drain; test: pH 6.5-6.9; Baume degree 4.2; temperature 27.7-27.9℃; remove from drum;

[0013] Step 5, Mechanical de-fleshing: Use a de-fleshing machine to remove the fat from the surface of the fur and then put it back into the drum;

[0014] Step 6, Main Soaking: Add water (130%-160% of the fur weight added in Step 2) at a temperature of 25℃-30℃, 0.05-0.10% degreasing agent, 0.3%-0.5% rehumidifier, 0.12-0.16% bactericide, 0.5-0.8% soda ash, and 0.5%-0.6% soaking aid to the drum and rotate for 30 minutes; check the pH value to be 10-10.2; add soaking enzyme (0.2% of the fur weight added in Step 2), rotate for 180 minutes, rotate for 5 minutes, stop for 55 minutes, repeat the rotation and stop 14 times; check the pH value to be 9.0-9.4; Baume degree to be 3.2-3.4; temperature to be 27.7-28.1℃, then drain the water;

[0015] II. Lime Impregnation Process Stage

[0016] Step 7, Lime Soaking and Hair Removal: Add water (60%-80% of the weight of the fur added in Step 2) at a temperature of 25℃-30℃, 1.0-1.8% liming agent, and 1.5-2.0% lime powder to the drum and rotate for 90 minutes; add 0. Add 4-0.6% sodium hydrosulfide and 0.6-0.9% sodium sulfide, rotate for 15 minutes, stop for 45 minutes, repeat twice; add 0.3-0.6% soaking agent, 0.8-1.5% lime powder and 0.3-0.6% sodium sulfide, rotate for 10 minutes, stop for 50 minutes, repeat twice; add 0.2-0.3% sodium sulfide, 0.1-0.2% protease and 0.9-1.2% lime powder (based on the weight of fur added in step 2), rotate for 5 minutes, stop for 55 minutes, repeat four times; add water at 70-90% of the weight of fur added in step 2 and a temperature of 25-28℃, rotate for 3 minutes, stop for 57 minutes, repeat 14 times; test: pH value > 12; temperature: 27℃; then drain.

[0017] Step 8, water washing: Add water to the drum at a temperature of 25-28°C, which is 150-200% of the mass of water added in step 2. Rotate for 10 minutes, then drain the water and remove the drum.

[0018] Step 9, Mechanical degreasing: Use a degreasing machine to remove excess fat from the inside of the gray skin to obtain gray skin;

[0019] Step 10, Slicing: Cut the grey leather into first-layer grey leather and second-layer grey leather of specified thickness, and process the first-layer grey leather and second-layer grey leather separately;

[0020] III. Ash Removal Process Stage

[0021] Step 11, Weighing: Weigh the cut top layer of skin and use this weight as a basis to determine the percentage of water and reagents to be used in subsequent process steps;

[0022] Step 12, Putting the Skin: Put the weighed first-layer ash skin into the rotating drum;

[0023] Step 13, Water washing: Add water at a temperature of 28-30°C to the drum at a mass ratio of 150-200% of the first-layer ash described in Step 12, rotate for 10 minutes, and then drain the water;

[0024] Step 14, Pre-de-ashing: Add water (100-150% of the weight of the first-layer ash as stated in Step 12) at a temperature of 20-35℃, 0.1%-0.2% degreasing agent, 0.1%-0.2% masking agent, and 0.5%-0.6% ammonium sulfate to the drum, rotate for 20 minutes, and check the pH value to 9.5-9.8; then drain the water.

[0025] Step 15, Main De-ashing and Softening: Add water (50%-70% of the mass of the top-grain ash leather mentioned in Step 12) at a temperature of 28-30℃, 0.1-0.2% montmorillonite, and 1.0-1.5% ammonium sulfate to the drum and rotate for 30 minutes; check the pH value to be 7.8-8.0; then add water (90-110% of the mass of the top-grain leather mentioned in Step 12) at a temperature of 25-35℃, 0.2%-0.3% softening enzyme, and 0.2%-0.3% degreasing agent, rotate for 30 minutes, check the skin incision line with phenolphthalein, drain the water, wash with water, and then drain again;

[0026] IV. Desulfurization process stages:

[0027] Step 16, Desulfurization: Add water to the drum at a temperature of 30-35℃, which is 180-220% of the mass of the first-layer ash product mentioned in Step 12. Rotate for 15 minutes, then drain the water. Repeat twice.

[0028] Step 17, Sulfur content test: Add water at 20-30℃, which is 50-70% of the mass of the first layer of ash weighed in Step 12, to the drum. Rotate for 15 minutes and take a sample for testing: Take an appropriate amount of liquid in a colorless mineral water bottle and add 5% dilute sulfuric acid. If the liquid becomes cloudy and a light milky white solution appears, repeat Step 16 for processing. If the liquid is clear and does not become cloudy, it is qualified.

[0029] V. Pickling and Chrome Tanning Process Stages:

[0030] Step 18, Acid Immersion: After measuring the sulfur content, add water (60-70% by weight of the first-layer grey leather product mentioned in Step 12, at a temperature of 18-25℃), 7%-8% by weight of salt, and 0.1-0.2% by weight of acid immersion aid to the drum, and rotate for 10 minutes; check the Baume degree: 7.5-7.6; add 0.5%-0.6% formic acid diluted at 1:20, and rotate for 20 minutes; add 1.2%-1.4% sulfuric acid diluted at 1:20 in three equal portions, rotating for 10 minutes, 10 minutes, and 40 minutes respectively; check the pH value (2.8-3.0), and check the penetration of the cut; check the penetration of the cut.

[0031] Step 19, Chrome Tanning: Add 3.5%-4.5% chrome powder (based on the weight of the top-grain grey leather in Step 12) to the drum and rotate for 30 minutes; add 1%-1.5% tanning aid (based on the weight of the top-grain leather in Step 12) and rotate for 30 minutes; add 3.5%-4.0% chrome powder (based on the weight of the top-grain grey leather in Step 12) and rotate for 60 minutes; check the penetration of the cut and test; pH value 2.5-2.7;

[0032] Step 20, Alkali Extraction: Add water (30%-40% of the mass ratio of the first-layer ash used in Step 12) and 0.4%-0.5% alkali extracting agent to the drum and rotate for 240 minutes; check the pH value to be 3.5-3.6; temperature: 28-30℃; add hot water (70-80% of the mass ratio of the first-layer ash used in Step 12) and 75-80℃ and rotate for 180 minutes; add 0.4%-0.5% baking soda (diluted with water at a 1:20 mass ratio) and add it in three equal portions over three rotations, rotating for 20 minutes, 20 minutes, and 30 minutes respectively, checking the pH value to be 3.8-4.0; temperature: 40℃-42℃, then drain the water.

[0033] Step 21, water washing and drum removal: Add water to the drum at a mass ratio of 150%-200% of the water drained in Step 20 and a temperature of 25-28℃, rotate for 10 minutes, and then pour the water out of the drum.

[0034] Step 22: Install the horse and let it stand still.

[0035] The beneficial effects of the present invention using the above technical solution are: it solves the problem of white bloom forming on leather under high temperature conditions. The solution is to add "desulfurization" and "sulfur content detection" processes during the blue leather processing stage, effectively eliminating sulfur, the pathogenic factor that causes white bloom. An additional desulfurization process is added in the later stages of deliming, and the sulfur content is then tested.

[0036] The present invention adopts the following preferred embodiment:

[0037] In step 6, the rotation is carried out overnight, rotating for 5 minutes and stopping for 55 minutes, and the rotation and stopping are repeated 14 times; in step 7, the rotation is carried out overnight, rotating for 3 minutes and stopping for 57 minutes, and the rotation and stopping are repeated 14 times.

[0038] In step 18, the penetration of the incision is checked by using litmus reagent to detect whether the acid has penetrated and whether the inside and outside of the incision are consistent. If they are inconsistent, the rotation time is increased.

[0039] The grey leather is sliced ​​into top-layer grey leather of the specified thickness using a splitting machine, with an allowable error of less than 0.2 mm. Detailed Implementation

[0040] The present invention will be described in detail below through specific embodiments, which can be used to solve practical technical problems and achieve technical effects. The process can be fully understood and implemented. It is necessary to point out that the embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential improvements and adjustments based on the above content of the present invention or directly apply the key steps and concepts of the present invention to existing processes. Any solution to the problem of sulfur bloom in leather during the blue leather stage and the use of ion-state desulfurization technology are within the scope of protection of this patent.

[0041] Unless otherwise specified, the methods of adding water, reagents, etc., used in the embodiments are methods well known to those skilled in the art, and the reagents and products used are all commercially available on the market. Example 1:

[0042] This embodiment provides a blue leather processing method for cowhide shoe uppers that includes "desulfurization" and "sulfur content determination" steps. It includes the following steps:

[0043] I. Immersion Process Stage

[0044] Step 1: Weigh 5000kg of fur for 180 pieces. Use this 5000kg fur weight as a baseline to determine the mass percentage of water and reagents used in subsequent processing steps. (For simplicity, the percentages based on this 5000kg value will not be repeated in subsequent steps 2-10.)

[0045] Step 2, Feeding the pelts: Feed the weighed pelts one by one into the rotating drum.

[0046] Step 3, water washing: Add 150% water at 28°C and 0.15% degreasing agent (commercial source: Eusapon® OE, BASF) to the drum, rotate for 10 minutes, stop for 50 minutes, repeat the rotation and stop process twice, and drain the water.

[0047] Step 4, Pre-soaking: Add 120% water at 28°C, 0.15% degreasing agent (BASF Eusapon® OE), 0.15% rehumidifier (BASF Eusapon® W), 0.15% bactericide (BASF Mollescal® BAC), and 0.25% soda ash to the drum; rotate for 10 minutes, stop for 50 minutes, and repeat the rotation and stop cycle twice; check the pH value: 6.7; Baume degree: 4.2; temperature: 27.7°C; drain the water and remove the drum.

[0048] Step 5, Mechanical de-fleshing: Use a de-fleshing machine to remove the fat from the inside of the fur and reload it into the drum.

[0049] Step 6, Main Immersion: Add 120% water at 25°C, 0.05% degreasing agent (BASF Eusapon® OE), 0.35% rehumidifier (BASF Eusapon® W), 0.15% bactericide (BASF Mollescal® BAC), 0.6% soda ash, and 0.5% immersion aid (BASF Mollescal® HW) to the drum. Rotate for 30 minutes and check the pH value to be 10. Add 0.2% immersion enzyme (BASF Basozym® S20) and rotate for 180 minutes. Rotate overnight, rotating for 5 minutes and stopping for 55 minutes. Repeat the rotation and stopping process 14 times. Check the pH value to be 8.7, Baume degree to be 3.2, and temperature to be 26°C. Drain the water.

[0050] II. Lime impregnation and hair removal process stages

[0051] Step 7, Lime Impregnation and Hair Removal: Add 70% water at 25°C, 1.2% liming agent (BASF Mollescal® AB), and 1.5% lime powder to the drum and rotate for 90 minutes; add 0.6% sodium hydrosulfide and 0.8% sodium sulfide, rotate for 15 minutes, stop for 45 minutes, and repeat the rotation and stop process twice; add 0.3% liming agent (BASF Mollescal® AB), 0.9% lime powder, and 0.4% sodium sulfide, rotate for 10 minutes, stop for 50 minutes, and repeat the rotation and stop process twice; add 0.2% sodium sulfide, 0.1% protease (BASF Basozym® L10), and 0.9% lime powder, rotate for 5 minutes, stop for 55 minutes, and repeat the rotation and stop process four times; add 80% water at 28°C, rotate overnight, rotate for 3 minutes, stop for 57 minutes, and repeat the rotation and stop process 14 times; test: pH value 12; temperature 27°C, drain the water.

[0052] Step 8, water washing: Add 25℃, 150% water to the drum, rotate for 10 minutes, drain the water, and remove the drum.

[0053] Step 9, Mechanical de-meating: Use a de-meating machine to remove excess fat from the inside of the skin.

[0054] Step 10, Slicing: Use a slicer to slice the grey leather into a first-layer grey leather with a thickness of 2.0 mm to 2.2 mm. However, there are no special requirements for the thickness of the second-layer grey leather. The thickness of the second-layer grey leather can be arbitrarily formed to meet the thickness index of the first-layer leather. The second-layer grey leather is processed separately and is not included in the following process.

[0055] III. Deashing and softening process stages

[0056] Step 11, Weighing: Weigh the sliced ​​top-layer grey leather to 3100 kg. Use this weight as a benchmark to determine the percentage of water and reagents to be used in subsequent processing steps. (For simplicity, the percentages based on this 3100 kg value will not be repeated in subsequent steps.)

[0057] Step 12, Loading the hull: Place the weighed first-layer hull into the rotating drum. (The second layer of hull is sold directly or processed separately.)

[0058] Step 13, Water washing: Add 30℃, 150% water to the drum, rotate for 10 minutes, and drain.

[0059] Step 14, Pre-de-ashing: Add 100% water at 30°C, 0.1% degreasing agent (BASF Eusapon® OE), 0.1% scavenging agent (BASF Decaltall® Pic S), and 0.5% ammonium sulfate to the drum, rotate for 20 minutes, check the pH value to be 9.5, and drain the water.

[0060] Step 15, Main Deashing and Softening: Add 30°C, 50% water, 0.2% sclerosing agent (BASF Decaltall® Pic S), and 1.2% ammonium sulfate to the drum and rotate for 30 minutes. The pH value is measured to be 7.8. Add 30°C, 100% water, 0.2% softening enzyme (BASF Basozym® B10), and 0.2% degreasing agent (BASF Eusapon® OE) and rotate for 30 minutes. The pH value is measured to be 7.8. A line of red skin is detected by phenolphthalein reagent. Drain the water, wash with water, and drain again.

[0061] IV. Desulfurization Process Stage

[0062] Step 16, Desulfurization: Add 200% water at 33℃ into the drum, rotate for 15 minutes, drain; repeat twice, wash with running water for 10 minutes, drain.

[0063] Step 17, Measure sulfur content: Add 20℃, 50% water to the drum and rotate for 15 minutes. Take a sample for testing: Take an appropriate amount of liquid in a colorless mineral water bottle and add dilute sulfuric acid (1:20). If the liquid becomes cloudy and a light milky white solution appears, repeat step 16 for processing. If the liquid is clear and does not become cloudy, it is qualified and can be drained.

[0064] V. Pickling and Chrome Tanning Stages

[0065] Step 18, Acid Immersion: Add 60% water at 18°C, 7% salt, and 0.1% acid immersion aid (BASF Mollescal® FUN) to the drum and rotate for 10 minutes; check the Baumé degree: 7.5; add 0.5% formic acid (diluted 1:20 with water), rotate for 20 minutes, then add 1.2% sulfuric acid (diluted 1:20 with water) in three equal portions, rotating for 10 minutes, 10 minutes, and 40 minutes respectively. Check the pH value: 2.8, and thoroughly inspect the cut.

[0066] Step 19, Chrome Tanning: Add 3.5% chrome powder (Lanxess Tankrom AB) to the drum and rotate for 30 minutes; add 1% tanning aid (BASF Implenal® DC liq.) and rotate for 30 minutes; add 3.5% chrome powder (Lanxess Tankrom AB) and rotate for 60 minutes; check the penetration of the cut; test the pH value to be 2.5.

[0067] Step 20, Alkali Extraction: Add 30% water at 60℃ and 0.4% alkali extractant (BASF Neutrigan® MOS) to the drum and rotate for 240 min; the pH value is measured to be 3.5; at 30℃, add 80% hot water at 75℃ and rotate for 180 min; 0.4% baking soda (diluted with water at 1:20) is divided into three equal portions and added in three separate additions, with each addition rotating for 20 min, 20 min, and 30 min; the pH value is measured to be 3.8; at 40℃, drain the water.

[0068] Step 21, water washing and drum removal: Add 25℃, 150% water to the drum, rotate for 10 minutes, and remove the drum skin.

[0069] Step 22: Install the horse and let it stand still.

[0070] One week later, take the blue leather prepared in this example, mark it, and perform the following operations: squeeze out water → evenly cut → weigh → retanning and dyeing (black) with fat addition → squeeze out water → vacuum drying → hang to dry → high temperature drying → let stand.

[0071] A week later, it was found that the surface of the blue leather used to make the leather blanks was clean after high-temperature treatment, and there was no white frost. Example 2:

[0072] This embodiment provides a process for producing blue leather for cowhide car seat cushions that includes "desulfurization" and "sulfur content determination" steps. It includes the following steps:

[0073] I. Immersion Process Stage

[0074] Step 1: Weigh 200 pelts (5500kg). Use this 5500kg pelt weight as a baseline to determine the percentage of water and reagents used in subsequent processing steps (the percentage of this 5500kg value will not be repeated in subsequent steps 2-10 for simplification).

[0075] Step 2, Feeding the pelts: Feed the weighed pelts one by one into the rotating drum.

[0076] Step 3, water washing: Add 150% water at 28°C and 0.15% degreasing agent (Eusapon® OE from BASF) to the drum, rotate for 10 minutes, stop for 50 minutes, repeat the rotation and stop process twice, and then drain the water.

[0077] Step 4, Pre-soaking: Add 120% water at 28°C, 0.15% Eusapon® OE (degreasing agent, BASF), 0.15% rehumidifier (BASF Eusapon® W), 0.15% bactericide (BASF Mollescal® BAC), and 0.25% soda ash to the drum; rotate for 10 minutes, stop for 50 minutes, repeat the rotation and stop cycle twice; check the pH value to be 2.5; Baumé degree to be 4.2; temperature to be 27.7°C, drain the water, and remove the drum.

[0078] Step 5, Mechanical de-fleshing: Use a de-fleshing machine to remove the fat from the surface of the fur and reload it into the drum.

[0079] Step 6, Main Immersion: Add 120% water at 28°C, 0.05% Eusapon® OE (degreasing agent, BASF), 0.35% rehumidifier (BASF Eusapon® W), 0.15% bactericide (BASF Mollescal® BAC), 0.5% immersion aid (BASF Mollescal® HW), and 0.8% soda ash to the drum. Rotate for 60 minutes and check the pH value to be 10. Add 0.25% immersion enzyme (BASF Basozym® S20) and rotate for 240 minutes. Rotate overnight, rotating for 5 minutes and stopping for 55 minutes, repeating this cycle 14 times. Check the pH value to be 9.0, Baume degree 3.2, and temperature 29°C. Drain the water.

[0080] II. Lime impregnation and hair removal process stages

[0081] Step 7, Lime Impregnation and Hair Removal: Add 70% water at 28℃, 1.2% liming aid (BASF Mollescal® AB), and 2.0% lime powder to the drum and rotate for 90 minutes; add 0.6% sodium hydrosulfide and 0.8% sodium sulfide, rotate for 15 minutes, stop for 45 minutes, and repeat the rotation and stop process twice; add 0.3% liming aid (BASF Mollescal® AB), 0.9% lime powder, and 0.4% sodium sulfide, rotate for 15 minutes, stop for 45 minutes, and repeat the rotation and stop process twice; add 0.2% sodium sulfide, 0.1% protease (BASF Basozym® L10), and 1.2% lime powder, rotate for 5 minutes, stop for 55 minutes, and repeat the rotation and stop process 4 times; add 80% water at 28℃, rotate overnight, rotate for 3 minutes, stop for 57 minutes, and repeat the rotation and stop process 14 times; check the pH value > 12 and the temperature 28℃, drain the water, and remove the drum.

[0082] Step 8, water washing: Add 25℃, 150% water to the drum, rotate for 10 minutes, and drain.

[0083] Step 9, Mechanical de-meating: Use a de-meating machine to remove excess fat from the inside of the skin.

[0084] Step 10, Peeling: Use a peeling machine to peel the grey leather into a first-layer grey leather with a thickness of 1.8 mm to 2.0 mm. However, there are no special requirements for the thickness of the second-layer grey leather. The thickness of the second-layer grey leather can be arbitrarily formed to meet the thickness index of the first-layer leather. The second-layer grey leather is processed separately and is not included in the following process.

[0085] III. Deashing and softening process stages

[0086] Step 11, Weighing: Weigh the sliced ​​top-layer grey leather to 3200 kg. Use this weight as a benchmark to determine the percentage of water and reagents to be used in subsequent processing steps. (For simplicity, the percentages based on this 3200 kg value will not be repeated in subsequent steps 12-21.)

[0087] Step 12, Loading the hull: Place the weighed first-layer hull into the rotating drum. (The second layer of hull is sold directly or processed separately.)

[0088] Step 13, Water washing: Add 30℃, 120% water to the drum, rotate for 10 minutes, and drain.

[0089] Step 14, Pre-de-ashing: Add 100% water at 30°C, 0.1% degreasing agent (BASF Eusapon® OE), 0.1% scavenging agent (BASF Decaltall® Pic S), and 0.5% ammonium sulfate to the drum, rotate for 20 minutes, check the pH value to be 9.5, and drain the water.

[0090] Step 15, Main Deashing and Softening: Add 30°C, 50% water, 0.2% saturant (BASF Decaltall® Pic S), and 1.2% ammonium sulfate to the drum and rotate for 30 minutes; the pH value is measured to be 7.8; add 30°C, 100% water, 0.2% softening enzyme (BASF Basozym® B10), and 0.2% degreasing agent (BASF Eusapon® OE), and rotate for 30 minutes; the pH value is measured to be 7.8, and a line of red is detected on the skin incision with phenolphthalein reagent; drain the water, wash with water, and drain again.

[0091] IV. Desulfurization Process Stage

[0092] Step 16, Desulfurization: Add 200% water at 33℃ into the drum, rotate for 15 minutes, drain, and repeat twice; wash with running water for 10 minutes, then drain.

[0093] Step 17, Measure sulfur content: Add 20℃, 50% water to the drum, rotate for 15 minutes, and take a sample for testing: Take an appropriate amount of liquid in a colorless mineral water bottle and add dilute sulfuric acid (1:20). If the liquid becomes cloudy and a light milky white solution appears, repeat step 16 for processing. If the liquid is clear and does not become cloudy, it is qualified and can be drained.

[0094] V. Pickling and Chrome Tanning Stages

[0095] Step 18, Acid Immersion: Add 60% water at 18°C, 7% salt, and 0.1% acid immersion aid (BASF Mollescal® FUN) to the drum and rotate for 10 minutes. Check the Baumé degree to be 7.5. Add 0.5% formic acid (1:20 diluted with water) and rotate for 20 minutes. Add 1.2% sulfuric acid (1:20 diluted with water) in three portions, rotating for 10 minutes, 10 minutes, and 40 minutes respectively each time. Check the pH value to be 2.8 and ensure the incision is thoroughly inspected.

[0096] Step 19, Chrome Tanning: Add 3.5% chrome powder (Lanxess Tankrom AB) to the drum and rotate for 30 minutes; add 1% tanning aid (BASF Implenal® DC liq.) and rotate for 30 minutes; add 3.5% chrome powder (Lanxess Tankrom AB) and rotate for 60 minutes; check the penetration of the cut, and the pH value is 2.5.

[0097] Step 20, Alkali Extraction: Add 30% water at 60°C and 0.4% alkali extractant (BASF Neutrigan® MOS) to the drum and rotate for 240 min; pH 3.5, temperature 30°C, add 80% hot water at 75°C and rotate for 180 min; 0.4% baking soda (diluted 1:20 with water) is divided into three equal portions and added in three batches, rotating for 20 min, 20 min, and 30 min respectively each time; check pH 3.8; temperature: 40°C, drain.

[0098] Step 21, water washing and drum removal: Add 25℃, 150% water to the drum, rotate for 10 minutes, and remove the drum skin.

[0099] Step 22: Install the horse and let it stand still.

[0100] One week later, take the blue leather prepared in this example, mark it, and perform the following operations: squeeze out water → evenly cut → weigh → retanning and dyeing (black) with fat addition → squeeze out water → vacuum drying → hang to dry → high temperature drying → let stand.

[0101] A week later, it was found that the leather blanks made from the blue leather were clean and free of white frost after being treated at high temperature. Example 3:

[0102] This embodiment provides a process for producing blue leather for cowhide sofas that includes "desulfurization" and "sulfur content determination" steps. It includes the following steps:

[0103] I. Immersion Process Stage

[0104] Step 1: Weigh 160 pieces of fur (4800 kg). Use this 4800 kg fur weight as a baseline to determine the percentage of water and reagents used in subsequent processing steps. (In subsequent steps 2-10, the percentage of water and reagents based on this 4800 kg weight will not be repeated in order to simplify the expression.)

[0105] Step 2, Feeding the pelts: Feed the weighed pelts one by one into the rotating drum.

[0106] Step 3, water washing: Add 150% water at 29°C and 0.15% degreaser (BASF Eusapon® OE) to the drum, rotate for 10 minutes, stop for 50 minutes, repeat the rotation and stop process twice, and drain the water.

[0107] Step 4, Pre-soaking: Add 120% water at 29°C, 0.15% degreasing agent (BASF Eusapon® OE), 0.15% rehumidifier (BASF Eusapon® W), 0.15% bactericide (BASF Mollescal® BAC), and 0.25% soda ash to the drum; rotate for 10 minutes, stop for 50 minutes, and repeat the rotation and stop process twice; check the pH value (6.7), Baume degree (4.2), and temperature (27.7°C), drain the water, and remove the drum.

[0108] Step 5, Mechanical de-fleshing: Use a de-fleshing machine to remove the fat from the surface of the fur and reload it into the drum.

[0109] Step 6, Main Immersion: Add 120% water at 30°C, 0.05% degreasing agent (BASF Eusapon® OE), 0.35% rehumidifier (BASF Eusapon® W), 0.15% bactericide (BASF Mollescal® BAC), 0.5% immersion aid (BASF Mollescal® HW), and 0.8% soda ash to the drum. Rotate for 30 minutes and check the pH value to be 10. Add 0.3% immersion enzyme (BASF Basozym® S20) and rotate for 240 minutes. Rotate overnight, rotating for 5 minutes and stopping for 55 minutes. Repeat the rotation and stopping process 14 times. Check the pH value to be 9.3 and the Baume degree to be 3.2. Drain at 29°C.

[0110] II. Lime impregnation and hair removal process stages

[0111] Step 7, Lime Impregnation and Hair Removal: Add 70% water at 30℃, 1.5% liming aid (BASF Mollescal® AB), and 2.0% lime powder to the drum and rotate for 90 minutes; add 0.6% sodium hydrosulfide and 0.8% sodium sulfide, rotate for 15 minutes, stop for 45 minutes, and repeat the rotation and stop process twice; add 0.4% liming aid (BASF Mollescal® AB), 1.5% lime powder, and 0.4% sodium sulfide, rotate for 10 minutes, stop for 50 minutes, and repeat the rotation and stop process twice; add 0.2% sodium sulfide, 0.2% protease (BASF Basozym® L10), and 1.0% lime powder, rotate for 5 minutes, stop for 55 minutes, and repeat the rotation and stop process 4 times; add 80% water at 28℃. Due to operational issues such as shift work, overnight rotation is required, rotating for 3 minutes, stopping for 57 minutes, and repeating the rotation and stop process 14 times. The pH value should be >12, the temperature 30℃, and the water should be drained.

[0112] Step 8, water washing: Add 28℃, 150% water to the drum, rotate for 10 minutes, drain the water, and remove the drum.

[0113] Step 9, Mechanical de-meating: Use a de-meating machine to remove excess fat from the inside of the skin.

[0114] Step 10, Peeling: Use a peeling machine to peel the grey leather into a first-layer grey leather with a thickness of 1.6 mm to 1.8 mm and a second-layer grey leather with no thickness limit; the second-layer grey leather is sold directly or processed separately, and the second-layer grey leather is not included in the processing of the following processes.

[0115] III. Deashing and softening process stages

[0116] Step 11, Weighing: Weigh the sliced ​​top layer of grey leather: 2800kg. Based on this weight, determine the percentage of water and reagents used in subsequent process steps (for simplicity, the percentage of this 2800kg value will not be repeated in subsequent steps 12-21).

[0117] Step 12, Loading the hull: Place the weighed first-layer hull into the rotating drum. (The second layer of hull is sold directly or processed separately.)

[0118] Step 13, Water washing: Add 30℃, 120% water to the drum, rotate for 10 minutes and drain.

[0119] Step 14, Pre-de-ashing: Add 100% water at 30°C, 0.1% degreasing agent (BASF Eusapon® OE), 0.1% scavenging agent (BASF Decaltall® Pic S), and 0.5% ammonium chloride to the drum, rotate for 20 minutes, check the pH value to 9.0, and drain the water.

[0120] Step 15, Main Deashing and Softening: Add 30°C, 50% water, 0.2% sizing agent (BASF Decaltall® Pic S), and 1.2% ammonium chloride to the drum and rotate for 30 minutes; the pH value is measured to be 7.8; add 30°C, 100% water, 0.2% softening enzyme (BASF Basozym® B10), and 0.2% degreasing agent (BASF Eusapon® OE) and rotate for 30 minutes; the pH value is measured to be 7.3, and phenolphthalein reagent is used to test if the skin incision is completely transparent. Drain the water, wash with water, and drain again.

[0121] IV. Desulfurization Process Stage

[0122] Step 16, Desulfurization: Add 200% water at 33℃ into the drum, rotate for 15 minutes, drain, repeat twice, wash with running water for 10 minutes, and drain.

[0123] Step 17, Measure sulfur content: Add 20℃, 50% water to the drum and rotate for 15 minutes. Take a sample for testing: Take an appropriate amount of liquid in a colorless mineral water bottle and add dilute sulfuric acid (1:20). If the liquid becomes cloudy and a light milky white solution appears, repeat step 16 for processing. If the liquid is clear and does not become cloudy, it is qualified and can be drained.

[0124] V. Pickling and Chrome Tanning Stages

[0125] Step 18, Acid Immersion: Add 60% water (18°C), 7% salt, and 0.1% acid immersion aid (BASF Mollescal® FUN) to the drum and rotate for 10 minutes; (Check: Baumé degree: 7.5); add 0.5% formic acid (1:20 diluted with water) and rotate for 20 minutes; divide 1.2% sulfuric acid (1:20 diluted with water) into three equal portions and add them in three separate additions, rotating for 10 minutes, 10 minutes, and 40 minutes respectively. (Check: pH: 2.8, verified by cutting a slit with litmus paper).

[0126] Step 19, Chrome Tanning: Add 3.5% chrome powder (Lanxess Tankrom AB) to the drum and rotate for 30 minutes; add 1% tanning aid (BASF Implenal® DC liq.) and rotate for 30 minutes; add 3.5% chrome powder (Lanxess Tankrom AB) and rotate for 60 minutes; check the penetration of the cut; test the pH value to 2.5.

[0127] Step 20, Alkali Extraction: Add 30% water at 60°C and 0.4% alkali extractant (BASF Neutrigan® MOS) to the drum and rotate for 240 minutes; check the pH value to be 3.5; at 30°C, add 80% hot water at 75°C and rotate for 180 minutes; divide 0.4% baking soda (1:20 diluted with water) into three equal portions and add them in three separate additions, rotating for 20 minutes, 20 minutes, and 30 minutes respectively, checking the pH value to be 3.8, and the temperature to be 40°C, then drain the water.

[0128] Step 21, water washing and drum removal: Add 25℃, 150% water to the drum, rotate for 10 minutes, and remove the drum skin.

[0129] Step 22: Install the horse and let it stand still.

[0130] One week later, take the blue leather prepared in this example, mark it, and perform the following operations: squeeze out water → evenly cut → weigh → retanning and dyeing (black) with fat addition → squeeze out water → vacuum drying → hang to dry → high temperature drying → let stand.

[0131] A week later, it was found that the surface of the blue leather used to make the leather blanks was clean after high-temperature treatment, and there was no white frost.

[0132] Comparative example:

[0133] This invention provides a comparative example of a normal blue leather processing method for cowhide shoe uppers. It includes the following steps:

[0134] I. Immersion Process Stage

[0135] Step 1, Weighing: Weigh 5000kg of fur for 180 pieces. Use this 5000kg fur weight as a baseline to determine the weight percentage of water and reagents used in subsequent processing steps. The ratios of water or other added components such as degreasing agents mentioned in the following steps are all mass ratios based on this 5000kg weight.

[0136] Step 2, Feeding the pelts: Feed the weighed pelts one by one into the rotating drum.

[0137] Step 3, water washing: Add 150% water at 28°C and 0.15% degreasing agent (BASF Eusapon® OE) to the drum, rotate for 10 minutes, stop for 50 minutes, repeat the rotation and stop process twice, and drain the water.

[0138] Step 4, Pre-soaking: Add 120% water at 28°C, 0.15% degreasing agent (BASF Eusapon® OE), 0.15% rehumidifier (BASF Eusapon® W), 0.15% bactericide (BASF Mollescal® BAC), and 0.25% soda ash to the drum. Rotate for 10 minutes, stop for 50 minutes, and repeat the rotation and stop cycle twice. The pH value should be 6.7; Baumé degree 4.2; temperature 27.7°C. Drain the water and remove the drum.

[0139] Step 5, Mechanical de-fleshing: Use a de-fleshing machine to remove the fat from the inside of the fur and reload it into the drum.

[0140] Step 6, Main Immersion: Add 120% water at 25°C, 0.05% degreasing agent (BASF Eusapon® OE), 0.35% rehumidifier (BASF usapon® W), 0.15% bactericide (BASF Mollescal® BAC), 0.5% immersion aid (BASF Mollescal® HW), and 0.6% soda ash to the drum. Rotate for 30 minutes and check the pH: 10. Add 0.2% immersion enzyme (BASF Basozym® S20) and rotate for 180 minutes. Rotate overnight, rotating for 5 minutes and stopping for 55 minutes. Repeat the rotation and stopping process 14 times. Check the pH: 8.7; Baume degree: 3.2; temperature: 26°C. Drain.

[0141] II. Lime impregnation and hair removal process stages

[0142] Step 7, Lime Impregnation and Hair Removal: Add 70% water at 25°C, 1.2% liming agent (BASF Mollescal® AB), and 1.5% lime powder to the drum and rotate for 90 minutes; add 0.6% sodium hydrosulfide and 0.8% sodium sulfide, rotate for 15 minutes, stop for 45 minutes, and repeat the rotation and stop process twice; add 0.3% liming agent (BASF Mollescal® AB), 0.9% lime powder, and 0.4% sodium sulfide, rotate for 10 minutes, stop for 50 minutes, and repeat the rotation and stop process twice; add 0.2% sodium sulfide, 0.1% protease (BASF asozym® L10), and 0.9% lime powder, rotate for 5 minutes, stop for 55 minutes, and repeat the rotation and stop process four times; add 80% water at 28°C, rotate overnight, rotate for 3 minutes, stop for 57 minutes, and repeat the rotation and stop process 14 times; check the pH value > 12; maintain the temperature at 27°C, and drain the water.

[0143] Step 8, water washing: Add 25℃, 150% water to the drum and rotate for 10 minutes to drain.

[0144] Step 9, Mechanical de-meating: Use a de-meating machine to remove excess fat from the inside of the skin.

[0145] Step 10, Peeling: Use a peeling machine to peel the grey leather into a first-layer grey leather with a thickness of 2.0 mm to 2.2 mm and a second-layer grey leather with no thickness limit; the second-layer grey leather is sold directly or processed separately, and the second-layer grey leather is not included in the processing of the following processes.

[0146] III. Deashing and Softening Stage

[0147] Step 11, Weighing: Weigh the sliced ​​top layer of grey leather to 3100kg. Use this weight as a benchmark to determine the percentage of water and reagents to be used in subsequent process steps.

[0148] Step 12, Putting the hull: Put the weighed first-layer hull into the rotating drum. (The second layer of hull is sold directly or processed separately).

[0149] Step 13, Water washing: Add 30℃, 120% water to the drum, rotate for 10 minutes and drain.

[0150] Step 14, Pre-de-ashing: Add 100% water at 30°C, 0.1% degreasing agent (BASF Eusapon® OE), 0.1% scavenging agent (BASF Decaltall® Pic S), and 0.5% ammonium sulfate to the drum, rotate for 20 minutes; check the pH value to be 9.5; drain the water.

[0151] Step 15, Main Deashing and Softening: Add 50% water at 30°C, 0.2% sizing agent (BASF Decaltall® Pic S), and 1.2% ammonium sulfate to the drum and rotate for 30 minutes. The pH value is measured to be 7.8. Add 100% water at 30°C, 0.2% softening enzyme (BASF Basozym® B10), and 0.2% degreasing agent (BASF Eusapon® OE), rotate for 30 minutes, and the pH value is measured to be 7.8. Phenolphthalein reagent is used to detect a single red line on the skin incision. Drain the water.

[0152] Step 16, Water Wash: Add 20℃, 120% water to the drum, rotate for 10 minutes, drain the water; check the pH value to 7.6, and observe whether the liquid is clear.

[0153] IV. Pickling and Chrome Tanning Stages

[0154] Step 17, Acid Immersion: Add 60% water at 18°C, 7% salt, and 0.1% acid immersion aid (BASF Mollescal® FUN) to the drum and rotate for 10 minutes; check the Baumé degree to be 7.5; add 0.5% formic acid (diluted 1:20 with water) and rotate for 20 minutes; divide 1.2% sulfuric acid (diluted 1:20 with water) into three equal portions and add them in three separate additions, rotating for 10 minutes, 10 minutes, and 40 minutes respectively. Check the pH value to be 2.8 and ensure the incision is thoroughly inspected.

[0155] Step 18, Chrome Tanning: Add 3.5% chrome powder (Lanxess Tankrom AB) to the drum and rotate for 30 minutes; add 1% tanning aid (BASF Implenal® DC liq.) and rotate for 30 minutes; add 3.5% chrome powder (Lanxess Tankrom AB) and rotate for 60 minutes; check the penetration of the cut; pH value 2.5.

[0156] Step 19, Alkali Extraction: Add 30% water at 60℃ and 0.4% alkali extractant (BASF Neutrigan® MOS) to the drum and rotate for 240 min; pH value 3.5; temperature: 30℃. Add 80% hot water at 75℃ and rotate for 180 min; divide 0.4% baking soda (1:20 dilution) into three equal portions and add them in three batches, rotating for 20 min, 20 min, and 30 min respectively, and check the pH value at 3.8; temperature: 40℃. Drain the water.

[0157] Step 20, water washing and drum removal: Add 25℃, 150% water to the drum, rotate for 10 minutes, and remove the drum skin.

[0158] Step 21: Install the horse and let it stand still.

[0159] One week later, take the blue leather prepared in the comparative example, mark it, and perform the following operations: squeeze out water → evenly cut → weigh → retanning and dyeing (black) with fatliquoring → squeeze out water → vacuum drying → hang to air dry → high temperature drying → let stand.

[0160] The leather blanks made from the blue leather of this proportion, after being treated at high temperature, have a noticeable white bloom with a slightly yellowish tinge.

[0161] The above three specific embodiments demonstrate the beneficial effects of this invention: it solves the problem of white bloom forming on leather under high-temperature conditions. The solution involves adding "desulfurization" and "sulfur content detection" processes during the blue leather processing stage, effectively eliminating sulfur, the causative factor of sulfur bloom. A desulfurization process is added in the later stages of deliming, and sulfur content is detected. Since sulfur is still in an ionic state at this stage and is soluble in water, it can be thoroughly removed by extensive water washing. Otherwise, after entering the acid soaking process, sulfur ions will be oxidized to zero-valent elemental sulfur, existing between the leather fibers. Elemental sulfur is chemically stable at room temperature, insoluble in water, and has poor thermal stability (melting point 112.8℃). When heated, it migrates from the leather fibers to the leather surface, crystallizing to form sulfur bloom. Once sulfur bloom forms, it is very difficult to remove. Therefore, the only way to solve the sulfur bloom problem is to take preventative measures—desulfurization—during the blue leather stage. Once elemental sulfur forms within the leather fibers, there is no remedial measure.

[0162] The three embodiments described above represent the blue leather processes for cowhide shoe uppers, car seat cushions, and cowhide sofas, which include desulfurization and sulfur content testing. Since the blue leather process is a basic process, it may seem that there are not many changes and it is difficult for non-professionals to identify. However, different leathers have different requirements in subtle ways, so the process details of different leathers are different. For example, cowhide shoe uppers require firm, full leather with no loose grain; cowhide sofa leather requires fully opened leather fibers and a high yield, with less emphasis on grain firmness and fullness. Therefore, in the soaking process, the temperature and pH value of cowhide shoe uppers are relatively low to slow down the reaction, prevent over-watering, and prevent the loss of leather fibers due to hydrolysis, which can cause loose grain. Conversely, in the soaking process, the temperature and pH value are higher, and the rotation time is longer, resulting in a faster reaction, full watering, and full opening of leather fibers, which helps to increase the surface area. In the liming stage, cowhide shoe uppers require a lower temperature and less liming to ensure firm, full leather without loose grain, while cowhide sofa leather requires a slightly higher temperature, more liming, and a longer rotation time to open the leather fibers and increase the surface area. In the deliming stage, cowhide shoe uppers use mild ammonium sulfate to ensure firm, full leather without loose grain, while cowhide sofa leather uses ammonium chloride, which has a stronger deliming effect, to achieve the requirement of increasing the surface area. The subsequent pickling and chrome tanning processes remain largely unchanged. The requirements for automotive seat leather fall between those for shoe uppers and sofa leather. It is not as strict about preventing the surface from becoming loose as it is for shoe uppers, nor is it as demanding in terms of increasing the surface area as it is for sofa leather. Therefore, the temperature and pH value are higher than those for shoe uppers during the soaking stage, and the temperature and amount of ash are higher than those for shoe uppers but lower than those for sofa leather during the liming stage. Ammonium sulfate is used for deliming.

[0163] All three embodiments mentioned above include "desulfurization" and "sulfur content detection" processes, which can not only meet the requirements of different types of leather for leather properties, but also effectively solve the problem of sulfur bloom in finished leather or leather products under high temperature conditions.

[0164] In the comparative example, there is also a water washing process during the deashing process, but its purpose, task, operation method, testing items and means are different. The comparative example only checks whether the liquid is clear---whether the ash has been completely removed, and checks whether the pH value meets the standard. Examples 1-3 not only considered the degree of deashing and pH value checks, but also added a dedicated desulfurization process to check sulfur content; only when the sulfur content is qualified can the next process be carried out. Leather blanks made from blue leather produced by the two different processes will produce sulfur bloom after high-temperature processing, while those from Examples 1-3 will not. This clearly demonstrates the practicality of the present invention. The solution provided by this invention is not only applicable to large-scale high-end shoe upper leather manufacturers, because leather shoemaking involves a high-temperature setting process, with temperatures exceeding the melting point of sulfur (112.8℃). If the leather fibers contain elemental sulfur, sulfur bloom will form on the shoe surface. It is also applicable to large-scale high-end automotive seat leather manufacturers, because cars inevitably park in hot, sunny environments, generating high temperatures inside (exceeding the melting point of sulfur, 112.8℃). If the sulfur content in the leather fibers of genuine seat leather is too high, sulfur bloom will form. High-end sofa leather and high-end clothing leather also face the same problem. This invention can significantly improve the technical content of leather, increase product added value, and greatly improve product grade and customer satisfaction.

[0165] The above are embodiments utilizing the technology of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention, directly applying the key steps and concepts of the present invention to their own original processes, tracing the problem of leather sulfur bloom back to the blue leather stage for solution, and desulfurization technology in the ionic state all fall within the protection scope of the present invention.

Claims

1. A process for solving the problem of white bloom formation on leather under high-temperature conditions, characterized in that, The steps are as follows: I. Immersion Process Stage: Step 1, Weighing the fur: Determine the mass percentage of water and reagents to be used in subsequent processing steps based on the quality of the fur; Step 2, Putting the pelts in: Put the weighed pelts into the rotating drum; Step 3, water washing: Add water (130%-160% of the weight of the fur added in Step 2) and 0.12%-0.16% degreasing agent to the drum; rotate for 10 minutes, stop for 50 minutes, repeat the rotation and stop process twice, and then drain the water. Step 4, Pre-soaking: Add water (at 25℃-30℃, equal to 130%-160% of the weight of the fur added in Step 2), 0.12%-0.16% degreasing agent, 0.12%-0.16% rehumidifier, 0.12%-0.16% bactericide, and 0.2%-0.3% soda ash to the drum; rotate for 10 minutes, stop for 50 minutes, repeat the rotation and stop process twice, and then drain the water. Testing: pH 6.5-6.9; Baumé degree 4.2; temperature 27.7-27.9℃; out of drum; Step 5, Mechanical de-fleshing: Use a de-fleshing machine to remove the fat from the surface of the fur and then put it back into the drum; Step 6, Main Soaking: Add water (at 25℃-30℃, 130%-160% of the fur weight added in Step 2), 0.05%-0.10% degreasing agent, 0.3%-0.5% rehumidifier, 0.12%-0.16% bactericide, 0.5%-0.8% soda ash, and 0.5%-0.6% soaking aid to the drum and rotate for 30 minutes; check the pH value to be 10-10.2; add soaking enzyme (0.2% of the fur weight added in Step 2), rotate for 180 minutes, rotate for 5 minutes, stop for 55 minutes, repeat the rotation and stop process 14 times; check the pH value to be 9.0-9.4; Baume degree to be 3.2-3.

4. Temperature: 27.7-28.1℃, then drain; II. Lime Impregnation Process Stage Step 7, Lime Soaking and Hair Removal: Add water (60%-80% of the weight of the fur added in Step 2) at a temperature of 25℃-30℃, 1.0-1.8% liming agent, and 1.5-2.0% lime powder to the drum and rotate for 90 minutes; add 0. Add 4-0.6% sodium hydrosulfide and 0.6-0.9% sodium sulfide, rotate for 15 minutes, stop for 45 minutes, repeat twice; add 0.3-0.6% liming agent, 0.8-1.5% lime powder and 0.3-0.6% sodium sulfide, rotate for 10 minutes, stop for 50 minutes, repeat twice; add 0.2-0.3% sodium sulfide, 0.1-0.2% protease and 0.9-1.2% lime powder (based on the weight of fur added in step 2), rotate for 5 minutes, stop for 55 minutes, repeat four times; add water at 70-90% of the weight of fur added in step 2 and a temperature of 25-28℃, rotate for 3 minutes, stop for 57 minutes, repeat 14 times; test: pH value > 12; Temperature: 27℃; then drain; Step 8, water washing: Add water to the drum at a temperature of 25-28°C, which is 150-200% of the mass of water added in step 2. Rotate for 10 minutes, then drain the water and remove the drum. Step 9, Mechanical degreasing: Use a degreasing machine to remove excess fat from the inside of the gray skin to obtain gray skin; Step 10, Slicing: Cut the grey leather into first-layer grey leather and second-layer grey leather of specified thickness, and process the first-layer grey leather and second-layer grey leather separately; III. Ash Removal Process Stage Step 11, Weighing: Weigh the cut top layer of skin and use this weight as a basis to determine the percentage of water and reagents to be used in subsequent process steps; Step 12, Putting the Skin: Put the weighed first-layer ash skin into the rotating drum; Step 13, Water washing: Add water at a temperature of 28-30°C to the drum at a mass ratio of 150-200% of the first-layer ash described in Step 12, rotate for 10 minutes, and then drain the water; Step 14, Pre-de-ashing: Add water (100-150% of the weight of the first-layer ash as stated in Step 12) at a temperature of 20-35℃, 0.1%-0.2% degreasing agent, 0.1%-0.2% masking agent, and 0.5%-0.6% ammonium sulfate to the drum, rotate for 20 minutes, and check the pH value to 9.5-9.8; then drain the water. Step 15, Main De-ashing and Softening: Add water (50%-70% of the mass of the top-grain ash leather mentioned in Step 12) at a temperature of 28-30℃, 0.1-0.2% montmorillonite, and 1.0-1.5% ammonium sulfate to the drum and rotate for 30 minutes; check the pH value to be 7.8-8.0; then add water (90-110% of the mass of the top-grain leather mentioned in Step 12) at a temperature of 25-35℃, 0.2%-0.3% softening enzyme, and 0.2%-0.3% degreasing agent, rotate for 30 minutes, check the skin incision line with phenolphthalein, drain the water, wash with water, and then drain again; IV. Desulfurization process stages: Step 16, Desulfurization: Add water to the drum at a temperature of 30-35℃, which is 180-220% of the mass of the first-layer ash product mentioned in Step 12. Rotate for 15 minutes, then drain the water. Repeat twice. Step 17, Sulfur content test: Add water at 20-30℃, which is 50-70% of the mass of the first layer of ash weighed in Step 12, to the drum. Rotate for 15 minutes and take a sample for testing: Take an appropriate amount of liquid in a colorless mineral water bottle and add 5% dilute sulfuric acid. If the liquid becomes cloudy and a light milky white solution appears, repeat Step 16 for processing. If the liquid is clear and does not become cloudy, it is qualified. V. Pickling and Chrome Tanning Process Stages: Step 18, Acid Immersion: After measuring the sulfur content, add water (60-70% by weight of the first-layer grey leather product mentioned in Step 12, at a temperature of 18-25℃), 7%-8% by weight of salt, and 0.1-0.2% by weight of acid immersion aid to the drum, and rotate for 10 minutes; check the Baume degree: 7.5-7.6; add 0.5%-0.6% formic acid diluted at 1:20, and rotate for 20 minutes; add 1.2%-1.4% sulfuric acid diluted at 1:20 in three equal portions, rotating for 10 minutes, 10 minutes, and 40 minutes respectively; check the pH value (2.8-3.0), and check the penetration of the cut; check the penetration of the cut. Step 19, Chrome Tanning: Add 3.5%-4.5% chrome powder (based on the weight of the top-grain grey leather in Step 12) to the drum and rotate for 30 minutes; add 1%-1.5% tanning aid (based on the weight of the top-grain leather in Step 12) and rotate for 30 minutes; add 3.5%-4.0% chrome powder (based on the weight of the top-grain grey leather in Step 12) and rotate for 60 minutes; check the penetration of the cut and test; pH value 2.5-2.7; Step 20, Alkali Extraction: Add water (30%-40% of the mass of the first-layer ash skin weighed in Step 12) and 0.4%-0.5% alkali extraction agent to the drum and rotate for 240 minutes; the pH value should be 3.5-3.

6. Temperature: 28-30℃; Add hot water at 75-80℃, accounting for 70-80% of the mass ratio of the first-layer ash used in step 12, and rotate for 180 minutes; Add 0.4%-0.5% baking soda, accounting for the mass ratio of the first-layer ash used in step 12, diluted with water at a 1:20 mass ratio, and add it in three equal portions in three separate additions, rotating for 20 minutes, 20 minutes, and 30 minutes respectively, and check the pH value to be 3.8-4.0; Temperature: 40℃-42℃, then drain the water; Step 21, water washing and drum removal: Add water to the drum at a mass ratio of 150%-200% of the water drained in Step 20 and a temperature of 25-28℃, rotate for 10 minutes, and then pour the water out of the drum. Step 22: Install the horse and let it stand still.

2. The process for solving the problem of white bloom formation on leather under high temperature conditions according to claim 1, characterized in that: In step 6, the rotation is carried out overnight, rotating for 5 minutes and stopping for 55 minutes, and the rotation and stopping are repeated 14 times; in step 7, the rotation is carried out overnight, rotating for 3 minutes and stopping for 57 minutes, and the rotation and stopping are repeated 14 times.

3. The process for solving the problem of white bloom formation on leather under high temperature conditions according to claim 1, characterized in that: In step 18, the penetration of the incision is checked by using litmus reagent to detect whether the acid has penetrated and whether the inside and outside of the incision are consistent. If they are inconsistent, the rotation time is increased.

4. The process for solving the problem of white bloom formation on leather under high temperature conditions according to claim 1, characterized in that: The grey leather is sliced ​​into top-layer grey leather of the specified thickness using a splitting machine, with an allowable error of less than 0.2 mm.