CN117587173A - Softening method for preventing leather damage - Google Patents
Softening method for preventing leather damage Download PDFInfo
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- CN117587173A CN117587173A CN202311782906.9A CN202311782906A CN117587173A CN 117587173 A CN117587173 A CN 117587173A CN 202311782906 A CN202311782906 A CN 202311782906A CN 117587173 A CN117587173 A CN 117587173A
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- softening
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- pelt
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- 239000010985 leather Substances 0.000 title claims abstract description 71
- 238000000034 method Methods 0.000 title claims abstract description 57
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 87
- 239000011575 calcium Substances 0.000 claims abstract description 87
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 87
- 102000004190 Enzymes Human genes 0.000 claims abstract description 38
- 108090000790 Enzymes Proteins 0.000 claims abstract description 38
- 230000008569 process Effects 0.000 claims abstract description 32
- 239000003795 chemical substances by application Substances 0.000 claims description 26
- 239000004365 Protease Substances 0.000 claims description 16
- 108091005804 Peptidases Proteins 0.000 claims description 14
- 102100037486 Reverse transcriptase/ribonuclease H Human genes 0.000 claims description 14
- 241001465754 Metazoa Species 0.000 claims description 8
- AEQDJSLRWYMAQI-UHFFFAOYSA-N 2,3,9,10-tetramethoxy-6,8,13,13a-tetrahydro-5H-isoquinolino[2,1-b]isoquinoline Chemical compound C1CN2CC(C(=C(OC)C=C3)OC)=C3CC2C2=C1C=C(OC)C(OC)=C2 AEQDJSLRWYMAQI-UHFFFAOYSA-N 0.000 claims description 6
- 241001494479 Pecora Species 0.000 claims description 6
- 150000003863 ammonium salts Chemical class 0.000 claims description 6
- 150000003839 salts Chemical class 0.000 claims description 6
- 235000012207 sodium gluconate Nutrition 0.000 claims description 6
- 239000000176 sodium gluconate Substances 0.000 claims description 6
- 229940005574 sodium gluconate Drugs 0.000 claims description 6
- 238000011282 treatment Methods 0.000 claims description 6
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 claims description 5
- 235000019982 sodium hexametaphosphate Nutrition 0.000 claims description 5
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 claims description 5
- 241000282994 Cervidae Species 0.000 claims description 4
- OVBJJZOQPCKUOR-UHFFFAOYSA-L EDTA disodium salt dihydrate Chemical compound O.O.[Na+].[Na+].[O-]C(=O)C[NH+](CC([O-])=O)CC[NH+](CC([O-])=O)CC([O-])=O OVBJJZOQPCKUOR-UHFFFAOYSA-L 0.000 claims description 4
- 241000272534 Struthio camelus Species 0.000 claims description 4
- 230000000813 microbial effect Effects 0.000 claims description 3
- 150000007522 mineralic acids Chemical class 0.000 claims description 3
- 150000007524 organic acids Chemical class 0.000 claims description 3
- 239000003002 pH adjusting agent Substances 0.000 claims description 3
- 239000003715 calcium chelating agent Substances 0.000 claims description 2
- 238000005554 pickling Methods 0.000 abstract description 24
- 230000000694 effects Effects 0.000 abstract description 8
- 238000005516 engineering process Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 37
- 229940088598 enzyme Drugs 0.000 description 33
- 239000007788 liquid Substances 0.000 description 28
- 210000003491 skin Anatomy 0.000 description 20
- 230000000052 comparative effect Effects 0.000 description 14
- 239000000463 material Substances 0.000 description 13
- 102000008186 Collagen Human genes 0.000 description 12
- 108010035532 Collagen Proteins 0.000 description 12
- 229920001436 collagen Polymers 0.000 description 11
- 235000019419 proteases Nutrition 0.000 description 11
- 230000001105 regulatory effect Effects 0.000 description 10
- 230000001276 controlling effect Effects 0.000 description 8
- 239000000835 fiber Substances 0.000 description 8
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 6
- 102000004142 Trypsin Human genes 0.000 description 5
- 108090000631 Trypsin Proteins 0.000 description 5
- 239000012588 trypsin Substances 0.000 description 5
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 4
- 235000011941 Tilia x europaea Nutrition 0.000 description 4
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 4
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 4
- 235000011130 ammonium sulphate Nutrition 0.000 description 4
- 239000004571 lime Substances 0.000 description 4
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 4
- 241000194108 Bacillus licheniformis Species 0.000 description 3
- 238000004043 dyeing Methods 0.000 description 3
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical class [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 2
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 2
- PMMYEEVYMWASQN-DMTCNVIQSA-N Hydroxyproline Chemical compound O[C@H]1CN[C@H](C(O)=O)C1 PMMYEEVYMWASQN-DMTCNVIQSA-N 0.000 description 2
- 108090000526 Papain Proteins 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- 239000004280 Sodium formate Substances 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 description 2
- 238000004380 ashing Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- PMMYEEVYMWASQN-UHFFFAOYSA-N dl-hydroxyproline Natural products OC1C[NH2+]C(C([O-])=O)C1 PMMYEEVYMWASQN-UHFFFAOYSA-N 0.000 description 2
- 235000019253 formic acid Nutrition 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 229960002591 hydroxyproline Drugs 0.000 description 2
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 235000005985 organic acids Nutrition 0.000 description 2
- 229940055729 papain Drugs 0.000 description 2
- 235000019834 papain Nutrition 0.000 description 2
- HLBBKKJFGFRGMU-UHFFFAOYSA-M sodium formate Chemical compound [Na+].[O-]C=O HLBBKKJFGFRGMU-UHFFFAOYSA-M 0.000 description 2
- 235000019254 sodium formate Nutrition 0.000 description 2
- FGMPLJWBKKVCDB-UHFFFAOYSA-N trans-L-hydroxy-proline Natural products ON1CCCC1C(O)=O FGMPLJWBKKVCDB-UHFFFAOYSA-N 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 102000009027 Albumins Human genes 0.000 description 1
- 108010088751 Albumins Proteins 0.000 description 1
- 241000193830 Bacillus <bacterium> Species 0.000 description 1
- 239000003109 Disodium ethylene diamine tetraacetate Substances 0.000 description 1
- 102000016942 Elastin Human genes 0.000 description 1
- 108010014258 Elastin Proteins 0.000 description 1
- 102000006395 Globulins Human genes 0.000 description 1
- 108010044091 Globulins Proteins 0.000 description 1
- 239000004471 Glycine Substances 0.000 description 1
- 229940124158 Protease/peptidase inhibitor Drugs 0.000 description 1
- 108090000787 Subtilisin Proteins 0.000 description 1
- 239000001361 adipic acid Substances 0.000 description 1
- 235000011037 adipic acid Nutrition 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000001413 amino acids Chemical class 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 159000000007 calcium salts Chemical class 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 235000019301 disodium ethylene diamine tetraacetate Nutrition 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 229920002549 elastin Polymers 0.000 description 1
- 210000002615 epidermis Anatomy 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000004310 lactic acid Substances 0.000 description 1
- 235000014655 lactic acid Nutrition 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000000137 peptide hydrolase inhibitor Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000003223 protective agent Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 235000017557 sodium bicarbonate Nutrition 0.000 description 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C14—SKINS; HIDES; PELTS; LEATHER
- C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
- C14C1/00—Chemical treatment prior to tanning
- C14C1/08—Deliming; Bating; Pickling; Degreasing
Abstract
The invention belongs to the technical field of leather processing and manufacturing, and discloses a softening method for preventing leather damage, which comprises the steps of firstly adjusting the pH of limed pelts to the optimal pH range of softening enzyme after the liming process of leather making is finished, and keeping the calcium content in the pelts to be not lower than 65% of the calcium content of the limed pelts; then using softening enzyme to carry out softening operation; after softening, the calcium in the softened pelts is removed. The invention can solve the technical problem that the existing leather softening technology is easy to damage or loosen the leather, can ensure pickling and tanning effects and improve the quality of finished leather.
Description
Technical Field
The invention belongs to the technical field of leather processing and manufacturing, and particularly relates to a softening method for preventing leather from being damaged.
Background
Softening is a process of removing non-collagen proteins such as albumin, globulin, elastin and the like in skin by catalytic hydrolysis with protease, and properly dispersing collagen fibers. Softening is an indispensable biological treatment procedure in the leather making process, and can improve the softness and water vapor permeability of the finished leather and make grain surfaces finer. In addition, the smooth operation of the softening process can also create proper conditions for the penetration and combination of materials in the subsequent processes of pickling, tanning, retanning, dyeing, fatliquoring and the like.
However, the existing softening method has a plurality of technical problems which are difficult to solve. One of the main problems is that after the deashing process, the deashed pelt treated by the softening process is free from fur and epidermis protection and is subjected to strong alkali action, and softening operation is slightly careless, so that the pelt is easily damaged by softening enzyme, and leather quality defects such as damaged surface, loose surface, empty loose surface and the like are generated. In order to obtain high quality leather, the damage to the collagen fibers of the leather must be minimized during the softening process, ensuring that the structure of the collagen fibers of the leather is substantially intact. This is the technical problem that the leather softening process is urgently needed to solve at present.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a softening method capable of preventing leather from being damaged.
The embodiment of the invention provides a softening method for preventing leather from being damaged, after the tanning and liming process is finished, the pH of liming pelts is firstly adjusted to the optimal pH range of softening enzyme, and the calcium content in pelts is kept to be not lower than 65% of the calcium content of liming pelts; then using softening enzyme to carry out softening operation; after softening, the calcium in the softened pelts is removed.
Preferably, the raw skin of the liming pelt is any one of animal skins.
Preferably, the animal skin comprises cow leather, sheep skin, pig skin, horse skin, deer skin, ostrich skin, etc.
Preferably, the pH of the limed pelts is adjusted using a pH adjuster selected from any one or more of inorganic acids and salts thereof, organic acids and salts thereof.
Preferably, the softening enzyme comprises any one or more of microbial protease, animal protease and plant protease.
Preferably, the softened pelt is subjected to a deliming or decalcification treatment with a deliming or decalcification agent to remove calcium from the softened pelt.
Preferably, the ash remover is selected from any one or more of ammonium salt ash remover, less ammonium salt ash remover and ammonia-free ash remover.
Preferably, the decalcifying agent is selected from one or more of calcium chelating agents such as sodium hexametaphosphate, sodium gluconate, disodium edetate and the like.
The invention also discloses leather obtained by adopting any softening method for preventing leather damage.
Compared with the prior art, the invention has the following beneficial effects:
1. the softening method provided by the invention adopts a mode of softening before deashing, and the calcium content of the naked leather is controlled to be not lower than 65% of the calcium content of the liming naked leather in the softening process, so that the operation sequence of the steps of the leather making deashing and softening process in the prior art is changed, and the technical problem that leather is easy to damage in the existing leather making softening technology is solved.
2. The softening method provided by the invention can also properly prolong the softening time, so that the softening enzyme is distributed more uniformly on the inner and outer layers of the pelt, and the dispersion uniformity of the leather collagen fibers is improved.
3. The softening method provided by the invention does not need to additionally add special auxiliary agents such as protease inhibitor, grain surface protective agent and the like, and has low cost and convenient operation.
4. The softening method provided by the invention can effectively remove calcium in the pelts after softening, and the calcium content of the obtained pelts (namely the calcium content of the pelts before pickling) is even lower than that of the pelts subjected to conventional softening (namely the calcium content of the pelts before conventional pickling), so that the subsequent tanning, dyeing and finishing processing are facilitated, and the quality of finished leather can be improved.
Drawings
FIG. 1 is a scanning electron micrograph of the softened pelt obtained in example 1, comparative example 1 and comparative example 2;
fig. 2 is a stereomicrograph of the finished grain obtained in example 1, comparative example 1 and comparative example 2.
Detailed Description
The present invention will be further described in detail with reference to the following embodiments, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the description is only illustrative and is not intended to limit the scope of the invention. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the present invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
In the process of realizing the invention, the applicant finds that lime introduced in the liming process not only has the function of loosening the collagen fibers, but also can improve the structural stability of the collagen fibers and help the collagen fibers resist the hydrolysis of softening enzymes. In the existing leather making process, the liming process is always followed by the deliming process to remove calcium from the limed pelts, and then the softening operation is performed. Such "liming-deliming-softening" operations obviously do not fully exploit the natural protective effect of the lime/calcium salt introduced in the pelts during liming on the collagen fibres.
Based on the above, the embodiment of the invention provides a softening technical scheme of liming-pH adjusting-softening-deliming/decalcification, namely a softening method for preventing leather damage, which comprises the steps of firstly adjusting the pH of liming pelts to the optimal pH range of softening enzymes after the liming process of leather preparation is finished, and keeping the calcium content in the pelts to be not lower than 65% of the calcium content of liming pelts; then using softening enzyme to carry out softening operation; after softening, the calcium in the softened pelts is removed.
The key point of the embodiment of the invention is that the calcium content of the pelts is higher (not lower than 65% of the calcium content of the limed pelts) during softening, and the deliming or decalcification operation is carried out after the softening is completed, so that the low calcium content (not higher than 20% of the calcium content of the limed pelts) required for pickling or tanning the pelts is obtained. The pH of the limed pelts is generally 12-13 after liming, and the optimal pH of the softening enzyme is 8-10, so that the pH range of the limed pelts is not suitable for the action of the softening enzyme, the pH of the limed pelts needs to be adjusted, and part of calcium is inevitably dissolved in the process of adjusting the pH. In order to realize the effect of this patent, need guaranteeing wherein calcium content when adjusting liming naked skin pH, soften earlier on this basis and then deliming, just can both solve the easy technical problem who damages leather of current tanning softening technology, can guarantee pickling, tanning effect again, finally improve the finished leather quality.
The liming pelts are liming pelts prepared from animal leather commonly used in the leather making field, such as cow leather, sheep leather, pig leather, horse leather, deer leather, ostrich leather and the like, and are all within the protection scope of the invention.
The pH of the limed pelt is regulated to the optimal pH range of the softening enzyme by using a pH regulator, wherein the pH regulator is a pH regulator used in the common tanning process, the regulated pH is determined according to the softening enzyme used, and the softening enzyme used is the softening enzyme commonly used in the tanning field, so that a person skilled in the art can select a proper pH regulator to regulate the pH of the limed pelt to a proper range according to actual conditions.
In some preferred embodiments, the pH adjuster may be selected from any one or more of inorganic acids and salts thereof, organic acids and salts thereof.
In some preferred embodiments, the softening enzyme comprises any one or more of a microbial protease, an animal protease, and a plant protease.
The removal of calcium in the softened pelt means the use of a deliming agent or decalcification agent for deliming or decalcification treatment of the softened pelt, wherein the deliming or decalcification treatment is a common method in the leather making field, and a person skilled in the art can select the deliming agent or decalcification agent to be used according to actual needs.
In some preferred embodiments, the deliming agent is selected from any one or more of an ammonium salt deliming agent, a low ammonium salt deliming agent, an ammonia-free deliming agent.
In some preferred embodiments, the decalcifying agent is selected from any one or more of sodium hexametaphosphate, sodium gluconate, disodium edetate, and the like.
The softening and deashing/decalcification process adopted in the embodiment of the invention is not particularly limited, and is a commonly used softening and deashing/decalcification process in the leather making field, and the specific process does not affect the effect of the patent.
For example, the specific process of softening and deashing/decalcification may be: according to the mass percentage of the liming pelts, the liming pelts are put into a rotary drum, 50-300% of water is added, the temperature is regulated to 20-40 ℃, a pH regulator is added to regulate the pH of the system to the optimum pH range of the corresponding softening enzyme, the system is rotated for 5-20min, and the calcium content in the pelts is controlled to be not lower than 65% of the calcium content of the liming pelts; then changing liquid, adding 50-300% of water, adjusting the temperature to 20-40 ℃, adding 0.1-2.0% of softening enzyme, rotating for 30min, and adjusting to intermittent rotation or continuous rotation, wherein the total time is 30-600min; then changing the liquid, adding 50-300% of water, adjusting the temperature to 20-40 ℃, adding 0.5-6.0% of a deliming agent or decalcification agent, and rotating for 30-180min to obtain the pelt which can be used for pickling or tanning.
The softening and deashing/decalcification process may also be: according to the mass percentage of the liming pelts, the liming pelts are put into a rotary drum, 50-300% of water is added, the temperature is regulated to 20-40 ℃, a pH regulator is added to regulate the pH of the system to the optimum pH range of the corresponding softening enzyme, the system is rotated for 5-20min, and the calcium content in the pelts is controlled to be not lower than 65% of the calcium content of the liming pelts; then adding 0.1-2.0% of softening enzyme without changing liquid, rotating for 30min, and adjusting to intermittent rotation or continuous rotation for 30-600min; then changing the liquid, adding 50-300% of water, adjusting the temperature to 20-40 ℃, adding 0.5-6.0% of a deliming agent or decalcification agent, and rotating for 30-180min to obtain the pelt which can be used for pickling or tanning.
In order to make the present invention more clear, the softening method and effect of preventing leather damage will be described in detail by a plurality of specific examples.
Example 1
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Placing the limed cowhide into a rotary drum, adding 100% water, adjusting the temperature to 32 ℃, adding a pH regulator glycine to adjust the pH to about 8.5, and rotating for 10min, wherein the calcium content in the pelt is controlled to be 72.3% of the calcium content of the limed pelt; then changing the liquid, adding 100% water, adjusting the temperature to 32 ℃, adding 1.0% softening enzyme (containing trypsin 2000U/g), and rotating for 150min; then changing the liquid, adding 100% water, adjusting the temperature to 32 ℃, adding 1.0% ammonium sulfate, and rotating for 50min to obtain the pelt which can be used for pickling or tanning, wherein the calcium content of the pelt is 16.7% of the calcium content of the limed pelt.
Comparative example 1
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Placing the limed cowhide into a rotary drum, adding 100% water, adjusting the temperature to 32 ℃, adding 3.0% ammonium sulfate, adjusting the pH to about 8.5, rotating for 60min to delicately remove the lime, and controlling the calcium content in the pelt to be 33.1% of the calcium content of the limed pelt; then changing the liquid, adding 100% water, adjusting the temperature to 32 ℃, adding 1.0% softening enzyme (containing trypsin 2000U/g), and rotating for 150min; the obtained pelts can be used for pickling or tanning, and the calcium content of the pelts is 22.3 percent of the calcium content of the limed pelts.
Comparative example 2
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Placing the limed cowhide into a rotary drum, adding 100% water, adjusting the temperature to 32 ℃, adding 2.0% ammonium sulfate, adjusting the pH to about 8.5, rotating for 60min to delicately remove the lime, and controlling the calcium content in the pelt to be 49.7% of the calcium content of the limed pelt; then changing the liquid, adding 100% water, adjusting the temperature to 32 ℃, adding 1.0% softening enzyme (containing trypsin 2000U/g), and rotating for 150min; the obtained pelts can be used for pickling or tanning, and the calcium content of the pelts is 28.4% of the calcium content of the limed pelts.
Corresponding softening effect tests were performed on example 1, comparative example 1 and comparative example 2; meanwhile, the pelts obtained in example 1, comparative example 1 and comparative example 2 were subjected to the same conventional pickling, tanning, dyeing and finishing treatments to obtain finished leather, and the finished leather morphology and performance were examined, and the test results are shown in fig. 1 and table 1. From the results of fig. 1, it can be seen that the grain of the pelts and finished leather obtained in example 1 is more complete and clear than the pelts and finished leather obtained in comparative example 1, indicating that example 1 is able to protect the grain of the leather from being damaged by the softening enzymes. As can be seen from the data in table 1, in the process of softening the leather, the example 1 ensures that the pelts used for softening have a higher residual calcium rate (72.3%), and after softening is completed, the deliming agent is used to remove the calcium in the softened pelts, so that the low calcium content (16.7% of residual calcium rate, even lower than 22.3% of comparative example 1 and 28.4% of comparative example 2) required for pickling or tanning the pelts is obtained, which is more favorable for the smooth proceeding of the subsequent pickling and tanning processes); the concentration of hydroxyproline in the softening waste liquid in the example 1 is obviously lower than that in the comparison examples 1 and 2, which shows that the damage of the softening enzyme to the collagen fibers of the leather can be effectively reduced by the method provided by the invention; the mechanical strength of the finished leather of the example 1 is higher than that of the comparative examples 1 and 2, which shows that the method provided by the invention can ensure pickling and tanning effects and finally improve the quality of the finished leather. In summary, the softening method for preventing leather damage provided by the invention can effectively solve the technical problem that the existing softening technology is easy to damage or loosen the surface.
Table 1 softening effect comparison table
Note that: a. calcium residual rate = calcium content of pelts/calcium content of limed pelts x 100%.
b. The higher the concentration of hydroxyproline (collagen characteristic amino acid) in the softening waste liquid, the greater the degree of damage to the collagen fibrils of the skin.
Example 2
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Placing the limed cowhide into a rotary drum, adding 200% water, adjusting the temperature to 35 ℃, adding a pH regulator boric acid to adjust the pH to about 8, rotating for 20min, and controlling the calcium content in the pelt to be 66.3% of the calcium content of the limed pelt; then changing liquid, adding 50% water, adjusting the temperature to 35 ℃, adding 0.5% softening enzyme (containing 2000U/g of papain), rotating for 30min, and adjusting to intermittent rotation or continuous rotation, wherein the total time is 210min; then changing the liquid, adding 50% of water, regulating the temperature to 30 ℃, adding 2.0% of ammonia-free deliming agent, and rotating for 180min to obtain the pelt which can be used for pickling or tanning, wherein the calcium content of the pelt is 12.5% of the calcium content of the limed pelt.
Example 3
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Placing the limed cowhide into a rotary drum, adding 50% of water, adjusting the temperature to 20 ℃, adding a pH regulator formic acid to adjust the pH to about 8.5, and rotating for 10min, wherein the calcium content in the pelt is controlled to be 71.5% of the calcium content of the limed pelt; then changing liquid, adding 200% water, adjusting the temperature to 20 ℃, adding 0.1% softening enzyme (containing subtilisin 5000U/g), rotating for 30min, and adjusting to intermittent rotation or continuous rotation, wherein the total time is 600min; then changing the liquid, adding 200% of water, adjusting the temperature to 20 ℃, adding 4.0% of ammonium salt-less de-ashing agent, and rotating for 100min to obtain the pelt which can be used for pickling or tanning, wherein the calcium content of the pelt is 15.6% of the calcium content of the limed pelt.
Example 4
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Charging the limed sheep skin into a rotary drum, adding 300% water, adjusting the temperature to 35 ℃, adding a pH regulator formic acid and sodium formate to adjust the pH to about 8, rotating for 20min, and controlling the calcium content in the pelt to be 67.4% of the calcium content of the limed pelt; then changing liquid, adding 300% water, adjusting the temperature to 35 ℃, adding 1.0% softening enzyme (containing bacillus protease 2000U/g), rotating for 30min, and adjusting to intermittent rotation or continuous rotation, wherein the total time is 120min; then changing the liquid, adding 300% of water, adjusting the temperature to 35 ℃, adding 6.0% of sodium hexametaphosphate, and rotating for 60 minutes to obtain the pelt which can be used for pickling or tanning, wherein the calcium content of the pelt is 11.4% of the calcium content of the limed pelt.
Example 5
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Filling the limed sheep skin into a rotary drum, adding 100% water, adjusting the temperature to 30 ℃, adding a pH regulator sodium formate to adjust the pH to about 10, and rotating for 5min, wherein the calcium content in the naked skin is controlled to be 76.4% of the calcium content of the limed naked skin; then changing liquid, adding 100% water, adjusting the temperature to 28 ℃, adding 1.0% softening enzyme (containing bacillus licheniformis protease 3000U/g), rotating for 30min, and adjusting to intermittent rotation or continuous rotation, wherein the total time is 180min; then changing the liquid, adding 100% of water, regulating the temperature to 30 ℃, adding 2.0% of ammonium-free deliming agent and 1.0% of sodium hexametaphosphate, and rotating for 90min to obtain the pelt which can be used for pickling or tanning, wherein the calcium content of the pelt is 17.3% of the calcium content of the limed pelt.
Example 6
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Charging the limed sheep skin into a rotary drum, adding 50% water, adjusting the temperature to 25 ℃, adding pH regulator acetic acid to adjust the pH to about 8, rotating for 10min, and controlling the calcium content in the pelt to be 65.6% of the calcium content of the limed pelt; then adding 0.5% of softening enzyme (containing trypsin 5000U/g) without changing the liquid, and rotating for 30min; then changing the liquid, adding 50% of water, adjusting the temperature to 25 ℃, adding 0.5% of disodium ethylenediamine tetraacetate, and rotating for 60min to obtain the pelt which can be used for pickling or tanning, wherein the calcium content of the pelt is 10.4% of the calcium content of the limed pelt.
Example 7
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Charging the limed pigskin into a rotary drum, adding 300% water, adjusting the temperature to 40 ℃, adding a pH regulator sodium bicarbonate to adjust the pH to about 9.5, rotating for 20min, and controlling the calcium content in the pelt to be 70.6% of the calcium content of the limed pelt; then changing liquid, adding 300% water, adjusting the temperature to 40 ℃, adding 2.0% softening enzyme (containing bacillus licheniformis protease 3000U/g), rotating for 30min, and adjusting to intermittent rotation or continuous rotation, wherein the total time is 90min; then changing the liquid, adding 300% of water, regulating the temperature to 40 ℃, adding 1.0% of sodium gluconate and 1.0% of ammonium chloride, and rotating for 120min to obtain the pelt which can be used for pickling or tanning, wherein the calcium content of the pelt is 14.7% of the calcium content of the limed pelt.
Example 8
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Charging the limed corium equi into a rotary drum, adding 200% water, adjusting the temperature to 32 ℃, adding pH regulator acetic acid to adjust the pH to about 8.5, rotating for 10min, and controlling the calcium content in the pelt to be 70.9% of the calcium content of the limed pelt; then changing the liquid, adding 200% of water, adjusting the temperature to 32 ℃, adding 2.0% of softening enzyme (containing trypsin 5000U/g), rotating for 30min, and adjusting to intermittent rotation or continuous rotation, wherein the total time is 300min; then changing the liquid, adding 200% of water, regulating the temperature to 32 ℃, adding 3.0% of ammonium sulfate, and rotating for 90min to obtain the pelt which can be used for pickling or tanning, wherein the calcium content of the pelt is 16.2% of the calcium content of the limed pelt.
Example 9
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Filling the limed deer skin into a rotary drum, adding 100% water, adjusting the temperature to 32 ℃, adding a pH regulator lactic acid to adjust the pH to about 9.5, and rotating for 10min, wherein the calcium content in the naked skin is controlled to be 65.8% of the calcium content of the limed naked skin; then adding 0.3% of softening enzyme (containing bacillus licheniformis protease 3000U/g) without changing liquid, rotating for 30min, and adjusting to intermittent rotation or continuous rotation, wherein the total time is 120min; then changing the liquid, adding 50% of water, regulating the temperature to 32 ℃, adding 1.0% of ammonium salt-less de-ashing agent and 2.0% of sodium gluconate, and rotating for 90min to obtain the pelt which can be used for pickling or tanning, wherein the calcium content of the pelt is 8.6% of the calcium content of the limed pelt.
Example 10
The following materials were used in the following amounts in mass percent (wt%) of the limed pelts.
Charging the ash-impregnated ostrich skin into a rotary drum, adding 200% water, adjusting the temperature to 40 ℃, adding a pH regulator adipic acid to adjust the pH to about 8.0, rotating for 5min, and controlling the calcium content in the pelt to be 66.7% of the calcium content of the ash-impregnated pelt; then adding 0.1% of softening enzyme (containing 5000U/g of papain) without changing the liquid, rotating for 30min, and adjusting to intermittent rotation or continuous rotation for 90min; then changing the liquid, adding 200% of water, regulating the temperature to 40 ℃, adding 2.0% of sodium gluconate, and rotating for 30min to obtain the pelt which can be used for pickling or tanning, wherein the calcium content of the pelt is 9.6% of the calcium content of the limed pelt.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A softening method for preventing leather damage is characterized in that after the tanning and liming process is finished, the pH of liming pelts is adjusted to the optimal pH range of softening enzyme, and the calcium content in pelts is kept to be not lower than 65% of the calcium content of liming pelts; then using softening enzyme to carry out softening operation; after softening, the calcium in the softened pelts is removed.
2. The softening method for preventing leather damage according to claim 1, wherein the raw hide of the limed pelt is any one of animal skins.
3. The softening method for preventing leather damage of claim 1, wherein the animal skin comprises cow leather, sheep leather, pig leather, horse leather, deer leather, ostrich leather.
4. The softening method for preventing leather damage according to claim 1, wherein the pH of the limed pelt is adjusted using a pH adjuster selected from any one or more of an inorganic acid and its salt, an organic acid and its salt.
5. A softening process for preventing leather damage in accordance with claim 1, wherein the softening enzyme comprises any one or more of microbial protease, animal protease and plant protease.
6. A softening method for preventing leather damage according to claim 1, wherein the softened pelt is subjected to a deliming or decalcification treatment using a deliming or decalcification agent to remove calcium from the softened pelt.
7. The softening process for preventing leather damage of claim 6, wherein the deliming agent is selected from any one or more of ammonium salt deliming agents, less ammonium salt deliming agents, and ammonia-free deliming agents.
8. The softening process for preventing leather damage in accordance with claim 6, wherein the decalcifying agent is selected from any one or more of calcium chelating agents such as sodium hexametaphosphate, sodium gluconate, disodium edetate, etc.
9. Leather obtainable by a softening process according to any one of claims 1 to 8, which prevents damage to the leather.
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