Composite softening enzyme preparation for tanning, application thereof and tanning method

Abstract

The invention discloses a compound softening enzyme preparation for tanning, application of the compound softening enzyme preparation and a tanning method, and relates to the technical field of tanning industrial production. The compound softening enzyme preparation for tanning provided by the invention comprises protease (softening enzyme) and the regulating agent, and the purpose of self-regulating the temperature of the softening enzyme can be achieved by regulating the type and dosage of the regulating agent, so that the compound softening enzyme preparation has relatively high energy efficiency under the softening condition before tanning, and the tanning quality is improved. And when the temperature rises, the activity of the softening enzyme is inhibited, so that the safety of the softening enzyme in leather making production is ensured.

Description

Technical Field

[0001] This invention relates to the field of leather production technology, and more specifically, to a compound softening enzyme preparation for leather making, its application, and a leather making method. Background Technology

[0002] Softening enzymes are among the most widely used enzymes in the leather industry. During the softening process, enzyme preparations are used, and chemical agents often cannot replace them. Due to the requirements of leather production conditions, the temperature of the pre-tanning softening section can be controlled at 30-40℃, depending on the specific products such as sofa leather, shoe upper leather, and bag leather. However, during production, due to limitations in actual production conditions, temperature instability sometimes occurs within the drum, leading to overheating. This increased temperature causes a corresponding increase in the activity of conventional softening enzymes, intensifying the enzyme's action on collagen fibers in the raw hide. This can result in excessive hydrolysis of collagen, leading to problems such as loose or damaged surfaces, ultimately affecting the quality and performance of the finished leather.

[0003] Therefore, there is an urgent need to develop softening enzyme preparations with self-regulating temperature stability, which can inhibit softening enzyme activity when the temperature rises, thereby ensuring the safety of softening enzymes in leather production.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a compound softening enzyme preparation for leather making, its application, and a leather making method. When the temperature deviates from the softening conditions, the enzyme activity is self-regulated to inhibit, so as to ensure that the application process does not damage the collagen fibers of the leather, thereby ensuring the high efficiency and safety of the softening enzyme.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a compound softening enzyme preparation for leather making, comprising a protease and a regulator, wherein the regulator is selected from at least one of polyethyleneimine, polyethylene oxide, polyacrylamide, povidone K30 and polyvinyl alcohol; the mass ratio of the protease to the regulator is (1-5):10.

[0007] In an optional embodiment, the softening enzyme has an enzyme activity of 500 U / g-2000 U / g.

[0008] In an optional embodiment, the protease contained in the softening enzyme is selected from at least one of bacterial protease, fungal protease, animal protease and plant protease, with an activity of 5000 U / g-100000 U / g.

[0009] Secondly, the present invention provides the application of any of the aforementioned embodiments of the compound softening enzyme preparation for leather making in leather softening.

[0010] In an optional embodiment, the mass ratio of the compound softening enzyme preparation for leather making to the sample to be softened is (0.1-10):100.

[0011] In an optional implementation, the softening temperature is controlled at 25℃-40℃, and the softening time is controlled at 30min-12h; And / or, the softening pH is 7-9.

[0012] Thirdly, the present invention provides a leather-making method, comprising: sequentially performing a pre-softening treatment, a softening process, and a post-softening treatment on a sample to be treated; The softening process is carried out using any of the leather-making compound softening enzyme preparations described in the aforementioned embodiments.

[0013] In an optional implementation, the pre-softening treatment includes sequentially performing water soaking, hair removal, liming, pre-liming, main liming, and degreasing.

[0014] In an optional embodiment, during the pre-deashing step, water and ammonium sulfate are added, and the mixture is rotated for 10-30 minutes. The mass ratio of water to the material to be treated is (1.8-2.2):1, and the mass ratio of ammonium sulfate to the material to be treated is (0.3-0.8):100. And / or, in the main deashing step, water is added and the pH of the solution is adjusted to 8.5-9.0, and the mixture is rotated for 30-90 minutes. The mass ratio of water added to the material to be treated is (0.8-1.2):1.

[0015] In an optional embodiment, the softening post-treatment includes sequentially washing with water, pickling, and tanning; The washing process includes: first washing with warm water at a temperature of 30℃-35℃, and then washing with cold water at a temperature of 20℃-25℃.

[0016] The present invention has the following beneficial effects: The compound softening enzyme preparation for leather making provided by the present invention includes a protease (softening enzyme) and a regulator. By regulating the type and amount of the regulator, the temperature of the softening enzyme can be self-regulated, so that the compound softening enzyme preparation has high energy efficiency under pre-tanning softening conditions. When the temperature rises, the activity of the softening enzyme is inhibited, thereby ensuring the safety of the softening enzyme in leather making production. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 The changes in the activity of softening enzymes at different temperatures; Figure 2 To assess the softening effect of the self-regulating temperature-stability softening enzyme; Figure 3 The effect of temperature deviation on the softening effect of self-regulating temperature-stability softening enzyme. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] This invention provides a compound softening enzyme preparation for leather tanning, comprising a protease (softening enzyme) and a regulator. The regulator enables the softening enzyme to self-regulate its temperature, thereby improving the safety of the leather-tanning enzyme. The regulator is selected from at least one of polyethyleneimine, polyethylene oxide, polyacrylamide, povidone K30, and polyvinyl alcohol. The regulator can be any one or more of these, and all of these regulators are commercially available raw materials. The mass ratio of protease to regulator is (1-5):10, such as 1:10, 2:10, 3:10, 4:10, 5:10, etc.

[0021] It should be noted that by controlling the type and dosage of the regulator, the temperature of the softening enzyme can be self-regulated, enabling the compound softening enzyme preparation to have high efficiency under pre-tanning softening conditions. When the external temperature deviates significantly from the required softening temperature, the activity of the softening enzyme can be effectively inhibited, avoiding excessive degradation of collagen fibers and production accidents. This effectively solves the problem of excessive degradation of dermal collagen fibers caused by temperature runaway due to equipment, environment, or human operation during production, ensuring the safety of the softening enzyme preparation and simplifying the softening process. Specifically, when the softening temperature rises significantly, the regulator can change the conformation of the protease in the softening enzyme, distorting the structure of the active site and weakening its ability to hydrolyze peptide bonds, thus inhibiting enzyme activity. At the same time, since the regulator's action is allosteric inhibition, it is reversible. When the temperature returns to normal, softening can proceed effectively without loss of softening enzyme activity.

[0022] Commonly used softening enzymes are all within the protection scope of this invention, meeting the requirement of enzyme activity of 500 U / g-2000 U / g, i.e., the characteristics of the softening enzymes comply with QBT 5905-2023. The protease in the softening enzyme is selected from at least one of bacterial proteases, fungal proteases, animal proteases, and plant proteases, with an activity of 5000 U / g-100000 U / g. The protease can be any one or more of the above. All of the above proteases are commercially available raw materials and are suitable for use in the softening stage.

[0023] This invention also provides the application of a compound softening enzyme preparation for leather making in leather softening. The compound softening enzyme preparation for leather making has high energy efficiency under pre-tanning softening conditions. The pre-tanning softening conditions are pH=8-8.5 and temperature=30-40℃ according to the leather making process requirements. The amount of softening enzyme used in the softening process is controlled at 0.1-10%.

[0024] In some embodiments, the mass ratio of the compound softening enzyme preparation for leather tanning provided by the present invention to the sample to be softened is (0.1-10):100, such as 0.1:100, 0.5:100, 1.0:100, 2.0:100, 3.0:100, 4.0:100, 5.0:100, 6.0:100, 7.0:100, 8.0:100, 9.0:100, 10.0:100, etc. The softening temperature is controlled at 25℃-40℃, such as 25℃, 30℃, 35℃, 40℃, etc.; the softening time is 30min-12h, such as 30min, 1h, 3h, 5h, 8h, 10h, 12h, etc. The softening pH value is 8.0-8.5, such as 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, etc. By adjusting the softening parameters, the softening effect can be ensured while avoiding excessive degradation of dermal collagen fibers.

[0025] This invention also provides a leather-making method, comprising: sequentially performing a pre-softening treatment, a softening process, and a post-softening treatment on the sample to be treated. The softening process uses a compound softening enzyme preparation for leather making. The specific steps and parameters of the softening process are described above in the specification.

[0026] In some embodiments, the pre-softening treatment includes sequentially performing soaking in water, hair removal, liming, pre-deliming, main deliming, and degreasing. The steps are described below: Soaking: Soaking involves placing the raw hide in water to restore the moisture lost during preservation (salting or drying), making it closer to the state of fresh hide. It can also remove impurities such as blood, salt, and soluble proteins.

[0027] Hair removal: Hair removal refers to the removal of the epidermis and hair while preserving the dermis (collagen fibers). Traditional methods include enzymatic hair removal and sodium sulfide hair removal, while modern methods often use sodium sulfide + lime treatment.

[0028] Lime treatment: Lime is used in combination with sodium sulfide to further expand collagen fibers and remove residual hair roots, epidermis and mucoprotein.

[0029] Pre-deliming: Water and ammonium sulfate are added to initially neutralize the alkalinity and lower the pH of the hides (from 12 to 8-9), preparing them for softening. This also removes residual lime and prevents tanning agent precipitation. In some embodiments, during the pre-deliming step, water and ammonium sulfate are added and the mixture is rotated for 10-30 minutes (e.g., 10, 20, 30 minutes, etc.). The mass ratio of water to the material being treated is (1.8-2.2):1 (e.g., 1.8:1, 2.0:1, 2.2:1, etc.), and the mass ratio of ammonium sulfate to the material being treated is (0.3-0.8):100 (e.g., 0.3:100, 0.4:100, 0.5:100, 0.6:100, 0.7:100, 0.8:100, etc.). By optimizing the pre-deliming operating parameters, residual lime can be better removed, and the pH value can be adjusted to meet process requirements.

[0030] Main deashing: Ammonium salt treatment is added to thoroughly remove the lime bound to the inner layer, providing a suitable environment for softening (enzyme treatment). In some embodiments, during the main deashing step, water is added and the pH of the solution is adjusted to 8.5-9.0, such as 8.5, 8.8, 9.0, etc.; the mixture is rotated for 30-90 minutes, such as 30 minutes, 50 minutes, 70 minutes, 90 minutes, etc.; the mass ratio of water added to the material to be treated is (0.8-1.2):1, such as 0.8:1, 1.0:1, 1.2:1, etc.

[0031] Degreasing: Using solvents, surfactants, or lipases to remove intradermal fat and prevent uneven tanning.

[0032] Specifically, deashing and softening can be done in the same bath or the solution can be changed. If the solution is changed, the water temperature should be adjusted to 30℃-35℃ after the solution is changed, and the pH of the bath solution should be adjusted to 7-9 before adding the skin.

[0033] In some embodiments, the softening post-treatment includes sequential washing, pickling, and tanning. The washing can be performed first with warm water at a temperature of 30°C-35°C, followed by washing with cold water at a temperature of 20°C-25°C. The pickling and tanning processes can be carried out according to conventional leather tanning procedures.

[0034] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0035] The enzyme activity of the softening enzyme preparation with self-regulating temperature stability in this invention was determined by the following method: (1) Prepare buffer solution: Take 3.56 g sodium dihydrogen phosphate dihydrate (NaH2PO4·2H2O) solution in 740 mL of distilled water, adjust the pH to the required conditions with 1 mol / L NaOH solution, and make up to 1000 mL.

[0036] (2) Trichloroacetic acid solution: Dissolve 6.54 g of trichloroacetic acid (CCl3COOH) in distilled water and bring the volume up to 100 mL.

[0037] (3) Sodium carbonate solution: Dissolve 21.2 g of sodium carbonate (Na2CO3) in distilled water and bring the volume up to 500 mL.

[0038] (4) Folin reagent: Dilute 1 part Folin reagent with 2 parts distilled water.

[0039] (5) Substrate solution: Take 1 g of casein (biochemical reagent), moisten it with a small amount of 0.5 mol / L NaOH solution, add about 80 mL of buffer solution of the corresponding pH, place it in a boiling water bath and heat and stir until completely dissolved, cool it, transfer it to a 100 mL volumetric flask, and dilute it to the mark with a suitable pH buffer solution.

[0040] (6) 100 μg / mL tyrosine standard solution: Weigh 0.1000 g of L-tyrosine, accurate to 0.0002 g, add 60 mL of 1 mol / L hydrochloric acid solution and dilute to 100 mL to obtain 1 mg / mL tyrosine standard solution; Take 10.00 mL of 1 mg / mL tyrosine standard solution and dilute to 100 mL with 0.1 mol / L hydrochloric acid to obtain 100 μg / mL tyrosine standard solution.

[0041] (7) Definition of enzyme activity: Under certain temperature and pH conditions, proteases hydrolyze casein substrates to produce amino acids containing phenolic groups. Under alkaline conditions, they reduce Folin reagent to produce molybdenum blue and tungsten blue. The absorbance of the solution is measured at a wavelength of 680 nm using a spectrophotometer. Relative activity = (enzyme activity under experimental conditions / standard enzyme activity) × 100%. It should be noted that in the following examples and comparative examples, the type of raw hide includes sheepskin or cowhide.

[0042] Example 1 This embodiment provides a leather tanning method, the steps of which are as follows: (1) Pretreatment before softening The process involves soaking in water, hair removal, ash soaking, pre-ash removal, main ash removal, and degreasing in sequence.

[0043] Soaking: Soak the raw hides to be treated in water for 24 hours.

[0044] Hair removal: The soaked raw hide is treated with sulfide for hair removal, with sodium sulfide used at 5% of the hide weight.

[0045] Lime treatment: The dehaired raw hide is reacted with lime, with the amount of lime being 2.5% of the hide's weight.

[0046] Pre-deliming: Mix the limed raw hides with water and ammonium sulfate at a liquid ratio of 1, and use ammonium sulfate at a rate of 0.8% of the hide weight.

[0047] Main deashing: Continue to add ammonium sulfate to the pre-deashing bath at a rate of 1.2%, maintain the temperature at 30℃, rotate for 60 min, and check the solution pH to 8.5-9.

[0048] Degreasing: Raise the temperature to 38℃, add degreasing agent (D117) to the bath solution at 0.8% of the tare weight (i.e., the mass ratio of degreasing agent to material is 0.8:100), rotate for 60 min, and after degreasing, the pH is 8.0.

[0049] (2) Softening process Add a compound softening enzyme preparation for leather tanning to the defatting bath solution at a dosage of 0.5% of the leather weight, at a temperature of 38℃, for a softening time of 30 minutes. The compound softening enzyme preparation for leather tanning contains bacterial protease (50,000 U / g) and polyethyleneimine, with a protease to regulator mass ratio of 3:10. The activity of the softening enzyme preparation is 1200 U / g.

[0050] The activation changes of the compound softening enzyme preparation for leather tanning provided in this embodiment at different temperatures are as follows: Figure 1 As shown in the figure, it can be seen that the activity is significantly inhibited when the temperature exceeds 40℃.

[0051] (3) Post-softening treatment The softened material is then washed, pickled, and tanned in sequence.

[0052] Washing: First wash twice with warm water at 35℃, then wash twice with cold water at 25℃.

[0053] Acid soaking: After adjusting the liquid ratio and water temperature, add diluted and cooled formic acid and rotate for 20 minutes. Then, slowly add sulfuric acid from the rotating shaft and rotate for 90 minutes until the final acid soaking solution reaches a pH of about 3. The skin sensory evaluation meets the requirements.

[0054] Tanning: Add 7% chromium powder and simmer for 1 hour, then add 1% sodium acetate and simmer for 2 hours. Dilute baking soda at a ratio of 1:20 and add it in five portions at 20-minute intervals. After simmering for 1 hour, raise the water temperature to 40°C and stop the drum overnight.

[0055] The softening effect in this embodiment is as follows: Figure 2 As shown, the intradermal non-collagenous matrix was significantly removed.

[0056] Example 2 This embodiment provides a leather tanning method, the steps of which are as follows: (1) Pretreatment before softening The only difference from Example 1 is that degreasing is replaced by washing with water at 30°C.

[0057] (2) Softening process A compound softening enzyme preparation for leather tanning was added to the degreasing bath at a dosage of 0.3% and a temperature of 38°C. After pre-deliming, the pH value during softening was 8.5, and the softening time was 30 min. The compound softening enzyme preparation for leather tanning contained animal protease (6000 U / g) and polyethyleneimine, with a protease to regulator mass ratio of 3:10, and the activity of the softening enzyme preparation was 1000 U / g.

[0058] (3) Post-softening treatment Same as Example 1.

[0059] Example 3 This embodiment provides a leather tanning method, the steps of which are as follows: (1) Pretreatment before softening Same as Example 1.

[0060] (2) Softening process Add 1% of a compound softening enzyme preparation for leather tanning to the defatting bath solution at a temperature of 38℃, a softening pH of 8.0, and a softening time of 30 minutes. The compound softening enzyme preparation for leather tanning includes bacterial protease (30,000 U / g) and the regulator povidone K30, with a mass ratio of protease to regulator of 1:2. The activity of the softening enzyme preparation is 1500 U / g.

[0061] (3) Post-softening treatment Same as Example 1.

[0062] Example 4 The only difference from Example 1 is that the leather-making compound softening enzyme preparation in step (2) includes fungal protease (20000 U / g) and regulator povidone K30, the mass ratio of protease to regulator is 1:3, and the activity of softening enzyme preparation is 1000 U / g.

[0063] Example 5 The only difference from Example 1 is that in step (2), the leather-making compound softening enzyme preparation includes animal protease (5000 U / g) and regulator povidone K30, the mass ratio of protease to regulator is 2:7, and the activity of the softening enzyme preparation is 800 U / g.

[0064] Example 6 The only difference from Example 1 is that in step (2), the regulator is replaced with an equal amount of polyethylene oxide.

[0065] Example 7 The only difference from Example 1 is that the regulator is replaced with an equal amount of polyvinyl alcohol in step (2).

[0066] Example 8 The only difference from Example 1 is that in step (2), the leather-making compound softening enzyme preparation includes animal protease (5000 U / g) and polyethylene oxide, the mass ratio of protease to regulator is 1:3, and the activity of the softening enzyme preparation is 1000 U / g.

[0067] Example 9 The only difference from Example 1 is that in step (2), the compound softening enzyme preparation for leather making includes animal protease (5000 U / g) and polyvinyl alcohol, the mass ratio of protease to regulator is 1:3, and the activity of the softening enzyme preparation is 700 U / g. When using, the amount of compound softening enzyme is 0.8% of the leather weight.

[0068] Example 10 The only difference from Example 9 is that the regulator is replaced with an equal amount of polyacrylamide in step (2).

[0069] Example 11 The only difference from Example 10 is that the compound softening enzyme preparation for leather tanning includes fungal protease (20,000 U / g) and polyacrylamide, with a mass ratio of protease to regulator of 1:3, and the activity of the softening enzyme preparation is 700 U / g. The dosage of the compound softening enzyme is 0.8% of the leather weight.

[0070] Comparative Example 1 (1) Pretreatment before softening Same as Example 1.

[0071] (2) Softening process The only difference from Example 1 is that the softening temperature is shifted to 60°C.

[0072] A comparison was made using a commercial softening enzyme (1200 U / g) at the same addition level (0.5%).

[0073] (3) Post-softening treatment Same as Example 1.

[0074] Comparative Example 1: Softening effect diagram as shown Figure 3 As shown in the figure, after the application of the softening enzyme of the present invention, the structure of the blue skin collagen fibers remains intact, while the collagen fibers of the comparative commercial enzyme have been damaged.

[0075] Comparative Example 2 (1) Pretreatment before softening Same as Example 1.

[0076] (2) Softening process The only difference from Example 5 is that the softening temperature is adjusted to 60°C.

[0077] A comparison was made using a commercial softening enzyme (800 U / g) at the same addition level (0.5%).

[0078] (3) Post-softening treatment Experimental Example 1 The softening effect of the test examples and comparative examples in step (2) and the hydroxyproline content results are shown in Table 1.

[0079] Table 1. Hydroxyproline content in bath solution (μg / mL)

[0080] It can be seen that the hydroxyproline content of the commercial enzyme increases significantly at high temperatures after softening, which indicates an increase in collagen degradation. Excessive degradation of collagen fibers by the enzyme leads to accidents such as loose and rotten surfaces during the leather making process. Therefore, the softening enzyme preparation in this invention has better safety when facing temperature changes.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A compound softening enzyme preparation for leather tanning, characterized in that, It includes a protease and a regulator, wherein the regulator is selected from at least one of polyethyleneimine, polyethylene oxide, polyacrylamide, povidone K30 and polyvinyl alcohol; the mass ratio of the protease to the regulator is (1-5):

10.

2. The compound softening enzyme preparation for leather tanning according to claim 1, characterized in that, The softening enzyme has an enzyme activity of 500 U / g-2000 U / g.

3. The compound softening enzyme preparation for leather tanning according to claim 2, characterized in that, The protease contained therein is selected from at least one of bacterial proteases, fungal proteases, animal proteases, and plant proteases, with an activity of 5000 U / g-100000 U / g.

4. The use of the compound softening enzyme preparation for leather making according to any one of claims 1-3 in leather softening.

5. The application according to claim 4, characterized in that, The mass ratio of the compound softening enzyme preparation for leather making to the sample to be softened is (0.1-10):

100.

6. The application according to claim 5, characterized in that, The softening temperature is controlled at 25℃-40℃, and the softening time is 30min-12h; And / or, the softening pH is 7-9.

7. A method for tanning leather, characterized in that, include: The samples to be processed are subjected to a pre-softening treatment, a softening process, and a post-softening treatment in sequence. The softening process is carried out using the composite softening enzyme preparation for leather making as described in any one of claims 1-3.

8. The leather-making method according to claim 7, characterized in that, The softening pretreatment includes sequentially soaking in water, hair removal, liming, pre-liming, main liming, and degreasing.

9. The leather-making method according to claim 8, characterized in that, In the pre-deashing step, water and ammonium sulfate are added, and the mixture is rotated for 10-30 minutes. The mass ratio of water to the material to be treated is (1.8-2.2):1, and the mass ratio of ammonium sulfate to the material to be treated is (0.3-0.8):

100. And / or, in the main deashing step, water is added and the pH of the solution is adjusted to 8.5-9.0, and the mixture is rotated for 30-90 minutes. The mass ratio of water added to the material to be treated is (0.8-1.2):

1.

10. The leather-making method according to claim 7, characterized in that, The softening post-treatment includes sequential washing, pickling, and tanning. The washing process includes: first washing with warm water at a temperature of 30℃-35℃, and then washing with cold water at a temperature of 20℃-25℃.

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