CN111793726A - Method for preparing leather retanning agent by taking waste animal hair as raw material - Google Patents
Method for preparing leather retanning agent by taking waste animal hair as raw material Download PDFInfo
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- CN111793726A CN111793726A CN202010715290.3A CN202010715290A CN111793726A CN 111793726 A CN111793726 A CN 111793726A CN 202010715290 A CN202010715290 A CN 202010715290A CN 111793726 A CN111793726 A CN 111793726A
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- retanning agent
- hydrolysis reaction
- leather retanning
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- 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
- C14C3/00—Tanning; Compositions for tanning
- C14C3/02—Chemical tanning
- C14C3/08—Chemical tanning by organic agents
Abstract
The invention relates to the technical field of animal hair treatment, and provides a method for preparing a leather retanning agent by using waste animal hair as a raw material, which comprises the following steps: mixing the waste animal hair, sodium sulfide, sodium hydroxide and water, and carrying out hydrolysis reaction to obtain a leather retanning agent solution; the temperature of the hydrolysis reaction is 35-40 ℃, and the time of the hydrolysis reaction is 16-24 hours; the pH value of the leather retanning agent solution is 5-7; and then drying the leather retanning agent solution to obtain the leather retanning agent. According to the method, the sodium sulfide is used for hydrolyzing the waste animal hair, the hydrolysis reaction temperature is only 35-40 ℃, and compared with the prior art, the hydrolysis reaction temperature is reduced to 35-40 ℃ from 130-190 ℃. Experimental results show that the leather retanning agent provided by the invention has a good selective filling effect and can better promote the uniformity of the final leather thickness.
Description
Technical Field
The invention relates to the technical field of animal hair treatment, in particular to a method for preparing a leather retanning agent by taking waste animal hair as a raw material.
Background
The hair-protecting unhairing method is a common process in the leather industry, but the hair-protecting unhairing process can generate a large amount of waste animal hair. Taking cow leather as an example, statistics show that the weight of waste wool generated by one raw cow leather is about 1.5-2.5 kg, and if the annual processing amount of one enterprise is 60 ten thousand cow leathers, the total amount of the waste wool generated by the enterprise can reach about 1000 tons, so that more waste animal wool is generated for numerous tanning enterprises in China. Therefore, the effective treatment and utilization of the waste animal hair of the tanning enterprises become the problem which needs to be solved urgently by the tanning enterprises.
The method is one of means for effectively utilizing the waste animal hair, wherein the protein filler is prepared by hydrolyzing the waste animal hair to obtain protein hydrolysate, and the protein filler is used as a leather retanning agent in the leather making process. The alkaline hydrolysis method is the first choice for the animal hair hydrolysis method due to the characteristics of high reaction rate, simple operation and low equipment requirement. At present, in the prior art, sodium hydroxide is generally used as an alkali source, and the leather retanning agent is prepared by hydrolyzing waste animal hair at 130-190 ℃, but the energy consumption of an enterprise is increased under the high-temperature condition of 130-190 ℃. Therefore, it is desirable to provide a method for preparing a leather retanning agent without the need for high temperature conditions of 100 ℃ or higher during hydrolysis.
Disclosure of Invention
In view of the above, the invention aims to provide a method for preparing a leather retanning agent by using waste animal hair as a raw material, and the hydrolysis temperature of the preparation method provided by the invention is 35-40 ℃, so that the energy consumption in the hydrolysis process is greatly reduced.
In order to achieve the above object, the present invention provides the following technical solutions:
a method for preparing a leather retanning agent by taking waste animal hair as a raw material comprises the following steps:
mixing the waste animal hair, sodium sulfide, sodium hydroxide and water, and carrying out hydrolysis reaction to obtain a leather retanning agent solution;
the temperature of the hydrolysis reaction is 35-40 ℃, and the time of the hydrolysis reaction is 16-24 hours; the pH value of the leather retanning agent solution is 5-7;
and then drying the leather retanning agent solution to obtain the leather retanning agent.
Preferably, the reaction vessel of the hydrolysis reaction is a rotating drum or a rotary spherical digester.
Preferably, the pH adjusting agent used to adjust the pH of the leather retanning agent solution comprises formic acid and/or oxalic acid.
Preferably, the hydrolysis reaction further comprises the following steps:
mixing the product of the hydrolysis reaction with an oxidant, carrying out an oxidation reaction, and removing the residual sodium sulfide after the hydrolysis reaction; then mixing with a reducing agent to remove the residual oxidizing agent after the oxidation reaction; mixing with stabilizer, and filtering.
Preferably, the stabilizer comprises sodium cumene sulfonate and/or trehalose.
Preferably, the oxidant is hypochlorite and/or hydrogen peroxide.
Preferably, the reducing agent is at least one of ascorbic acid, hydroxylamine hydrochloride, hydrazine hydrate, sodium bisulfite, sodium sulfite and sodium hydrosulfite.
Preferably, the reducing agent is ascorbic acid.
Preferably, the temperature of the oxidation reaction is 35-40 ℃.
Preferably, the temperature of the reduction reaction is 35-40 ℃.
The invention provides a method for preparing a leather retanning agent by taking waste animal hair as a raw material, which comprises the following steps: mixing waste animal hair, sodium sulfide, sodium hydroxide and water, carrying out hydrolysis reaction at the reaction temperature of 35-40 ℃ for 16-24 h to obtain a leather retanning agent solution, and drying the obtained leather retanning agent solution to obtain a leather retanning agent; the pH value of the leather retanning agent solution is 5-7. According to the invention, sodium sulfide is utilized to hydrolyze waste animal hair, the hydrolysis reaction temperature is only 35-40 ℃, and the reaction can be fully carried out, so that the leather retanning agent is prepared. Compared with the prior art, the method reduces the energy consumption, and the temperature of the hydrolysis reaction is reduced to 35-40 ℃ from 130-190 ℃. Experimental results show that the leather retanning agent prepared by the preparation method provided by the invention has a good retanning filling effect (easy to be absorbed by wet blue leather), particularly has an obvious effect on filling the part between the ribs and the hips with loose fiber weaves (such as RT-1826), has an effect superior to that of a protein product used in the current market, and can promote the uniformity of the final leather thickness.
Detailed Description
The invention provides a method for preparing a leather retanning agent by taking waste animal hair as a raw material, which comprises the following steps:
mixing the waste animal hair, sodium sulfide, sodium hydroxide and water, and carrying out hydrolysis reaction to obtain a leather retanning agent solution;
the temperature of the hydrolysis reaction is 35-40 ℃, and the time of the hydrolysis reaction is 16-24 hours; the pH value of the leather retanning agent solution is 5-7; and then drying the leather retanning agent solution to obtain the leather retanning agent.
The method comprises the steps of mixing the waste animal hair, sodium sulfide, sodium hydroxide and water, and carrying out hydrolysis reaction to obtain the leather retanning agent solution.
In the present invention, the waste animal hair is preferably pretreated before use; the pretreatment preferably includes water washing and drying which are performed in this order. The operation of the water washing is not specially specified, and the impurities in the waste animal hair are washed away by water. In the present invention, the drying mode is preferably natural airing. The invention adopts a natural drying mode, on one hand, extra energy consumption is not needed, on the other hand, the material components of the animal hair can be ensured not to be damaged by drying conditions, and the performance of the retanning agent is improved. The invention utilizes the characteristic that the waste animal hair contains a large amount of high molecular compounds and can obtain keratin after hydrolysis, and takes the waste animal hair as the source of the main components of the retanning agent, thereby realizing the effective utilization of the waste animal hair.
In the invention, the weight part of the sodium sulfide is preferably 1 to 5 parts, and more preferably 4.5 parts, based on 100 parts of the waste animal hair. The method selects sodium sulfide as a reducing agent to hydrolyze the waste animal hair, so that the temperature of hydrolysis reaction can be greatly reduced.
In the present invention, the purity of the sodium sulfide is preferably industrial grade or higher.
In the invention, the weight part of the sodium hydroxide is preferably 1 to 10 parts, more preferably 1 to 6 parts, and most preferably 3 parts based on 100 parts of the waste animal hair. In the present invention, sodium hydroxide provides the alkaline conditions required for the hydrolysis reaction.
In the present invention, the purity of the sodium hydroxide is preferably industrial grade or more.
In the present invention, the weight part of the water is preferably 100 to 300 parts, more preferably 150 to 250 parts, and most preferably 200 parts, based on 100 parts of the waste animal hair. In the present invention, water is used as a raw material for the hydrolysis reaction and a solvent for the reaction.
In the invention, the temperature of the hydrolysis reaction is 35-40 ℃, preferably 36-38 ℃; the time of the hydrolysis reaction is 16-24 hours, and preferably 18-20 hours. The invention selects the temperature and the time for hydrolysis reaction, and can ensure the full progress of the hydrolysis reaction.
In the present invention, the reaction vessel for the hydrolysis reaction is preferably a rotary drum or a rotary spherical digester, and more preferably a rotary spherical digester. The invention takes the rotary spherical digester as a reaction container, which can form a closed environment, prevent the peculiar smell generated in the production process from diffusing into the air, and simultaneously has simple reaction control process and no three wastes.
In the embodiment of the present invention, the temperature of the hydrolysis reaction is preferably provided by introducing steam into the system of the hydrolysis reaction. The invention heats the hydrolysis reaction system by introducing steam, on one hand, the temperature required by the hydrolysis reaction can be provided, on the other hand, the water is conveniently added in the subsequent operation process, and simultaneously heat is provided for the reaction system. The invention has no special regulation on the dosage of the water vapor, and can meet the requirement of hydrolysis reaction on temperature.
In the present invention, the hydrolysis reaction is preferably carried out under stirring. The stirring mode is not specially specified, and the raw materials can be fully reacted. In the embodiment of the present invention, the stirring manner of the hydrolysis reaction is preferably a rotary spherical digester. In the present invention, the rotary manner of the rotary spherical digester is preferably intermittent rotary. The invention adopts the mode of intermittently rotating the rotary spherical digester, can reduce the energy consumed by realizing the rotation of the rotary spherical digester and reduce the production cost.
After the hydrolysis reaction is finished, the invention preferably mixes the product of the hydrolysis reaction with an oxidant to carry out an oxidation reaction, and removes the residual sodium sulfide after the hydrolysis reaction; then mixing with a reducing agent to remove the residual oxidizing agent after the oxidation reaction; mixing with stabilizer, and filtering.
The invention preferably mixes the products of the hydrolysis reaction with water and then with an oxidizing agent. In the present invention, the weight part of the water mixed with the product of the hydrolysis reaction is preferably 100 to 300 parts, more preferably 150 to 250 parts, and most preferably 200 parts, based on 100 parts by weight of the waste animal hair. According to the invention, before the oxidant is added, the water in parts by weight is added into the reaction system, so that the over-violent oxidation reaction is avoided, and the production safety is improved. In the present invention, the water is preferably added by introducing steam into the reaction system. The invention adopts a mode of introducing water vapor to add water, on one hand, the water adding mode is convenient, and on the other hand, the temperature required by the oxidation reaction can be provided.
In the present invention, the oxidizing agent preferably includes hypochlorite and/or hydrogen peroxide, and more preferably hydrogen peroxide. The invention selects hydrogen peroxide as an oxidant to remove the residual sodium sulfide after hydrolysis reaction, and the products are sulfur and sodium hydroxide, thereby avoiding generating toxic gas of hydrogen sulfide.
In the present invention, the oxidizing agent is preferably added in the form of an oxidizing agent solution; the mass concentration of the oxidant solution is preferably 1-5%, and more preferably 2-3%. The preparation method of the oxidant solution is not specially specified, and the preparation method of the solution with certain mass concentration, which is well known by the technical personnel in the field, can be adopted. The invention adopts the addition mode and the solution concentration, can avoid over violent reaction and improve the production safety.
The invention preferably controls the dosage of the oxidant by detecting the solution after the oxidation reaction by starch potassium iodide test paper. The invention preferably uses starch potassium iodide test paper to detect the solution after the oxidation reaction, and stops adding the oxidant when the test paper turns blue. The method controls the dosage of the oxidant, and can fully react the residual sodium sulfide in the reaction system.
In the invention, the temperature of the oxidation reaction is preferably 35-40 ℃, and more preferably 36-38 ℃. The invention adopts the temperature to carry out the oxidation reaction, and can ensure that the oxidation reaction is carried out smoothly.
In the present invention, the reaction vessel for the oxidation reaction is preferably a rotary drum or a rotary spherical digester, and more preferably a rotary spherical digester. In the present invention, the oxidation reaction is preferably carried out under stirring. In the present invention, the stirring manner of the oxidation reaction is not particularly specified, and the sufficient reaction of the raw materials can be achieved. In an embodiment of the present invention, the oxidation reaction is preferably stirred by a rotary spherical digester.
In the present invention, the reducing agent preferably includes at least one of ascorbic acid, hydroxylamine hydrochloride, hydrazine hydrate, sodium bisulfite, sodium sulfite, and sodium hydrosulfite, and more preferably ascorbic acid. The method selects the ascorbic acid as the reducing agent to remove the residual oxide after the oxidation reaction, has the minimum influence on the performance of the leather retanning agent, and is favorable for obtaining the leather retanning agent with better quality.
In the present invention, the reducing agent is preferably added in the form of a reducing agent solution; the mass concentration of the reducing agent solution is preferably 0.1-2.0%, and more preferably 0.5-1.5%. The preparation method of the reducing agent solution is not specially specified, and the preparation method of the solution with certain mass concentration, which is well known by the technical personnel in the field, can be adopted. The invention adopts the addition mode and the solution concentration, can avoid over violent reaction and improve the production safety.
The invention preferably controls the dosage of the reducing agent by detecting the solution after the reduction reaction by starch potassium iodide test paper. The invention preferably uses starch potassium iodide test paper to detect the solution, and when the test paper does not change blue, the addition of the reducing agent is stopped. The method controls the dosage of the reducing agent, and can fully react the rest of the oxidizing agent in the reaction system.
In the invention, the temperature of the reduction reaction is preferably 35-40 ℃, and more preferably 36-38 ℃. The invention adopts the temperature to carry out the reduction reaction, and can ensure that the reduction reaction is carried out smoothly.
In the present invention, the reaction vessel for the reduction reaction is preferably a rotary drum or a rotary spherical digester, and more preferably a rotary spherical digester. In the present invention, the reduction reaction is preferably carried out under stirring. The invention has no special regulation on the stirring mode of the reduction reaction, and can realize the full reaction of the raw materials. In an embodiment of the present invention, the reduction reaction is preferably stirred by a rotary spherical digester.
In the invention, the pH value of the leather retanning agent solution is 5-7, and preferably 6-7. In the present invention, the pH of the leather retanning agent solution is in the above range, facilitating the use of the retanning agent. In the present invention, the pH adjusting agent used to adjust the pH of the leather retanning agent solution preferably includes formic acid and/or oxalic acid. The invention selects formic acid and/or oxalic acid to adjust the pH value of the leather retanning agent solution, the damage to the molecules of the leather retanning agent is minimum, and the obtained leather retanning agent has the best property. In the present invention, the pH adjuster is preferably added in the form of a solution. In the present invention, the concentration of the pH adjuster solution is preferably 0.1 to 2.0%, and more preferably 0.5 to 1.5%. The invention adopts the addition mode and the solution concentration, can avoid over violent reaction and improve the production safety.
The time for adjusting the pH value of the leather retanning agent solution is not specially specified, and the final pH value required by the leather retanning agent solution is ensured. In the present invention, the pH adjustment of the leather retanning agent solution is preferably performed after the reduction reaction is completed or after being mixed with a stabilizer. In a particular embodiment of the invention, the pH adjustment of the leather retanning agent solution is preferably carried out after the reduction reaction is completed.
After the reduction reaction is finished, the product of the reduction reaction is preferably mixed with water and then mixed with a stabilizer, and then the mixture is filtered after the pH value is adjusted to obtain a leather retanning agent solution; or adjusting the pH value of the product of the reduction reaction, then mixing the product after the pH value adjustment with water, mixing with a stabilizer, and filtering to obtain the leather retanning agent solution.
In the present invention, the mixing of the product of the reduction reaction or the pH-adjusted product with water and the stabilizer is preferably performed in a stirred tank. In the present invention, it is preferable that the product of the reduction reaction or the product after pH adjustment is sequentially stirred and transferred, and then mixed with water and a stabilizer. The stirring and transferring operations are not particularly specified in the present invention, and the solution stirring and transferring technical scheme known to those skilled in the art can be adopted. The present invention preferably washes the reactor in which the transfer reduction reaction is completed with water to obtain a washing solution, and then mixes the product of the reduction reaction or the product after pH adjustment with water and a stabilizer during mixing. In the present invention, the operation of the water washing is not particularly limited, and the residual substances in the reactor may be washed. The reactor is washed by water in order to transfer the products of the reduction reaction or the products after the pH value is adjusted to another reactor, thereby avoiding the waste of materials. The invention mixes in the stirring tank, which is beneficial to the smooth proceeding of the subsequent spray drying.
In the present invention, the weight part of the water mixed with the stabilizer is preferably 100 to 300 parts, more preferably 150 to 250 parts, and most preferably 200 parts, based on 100 parts by weight of the waste animal hair. The water with the weight percentage is added in the invention, so that the raw materials are mixed more uniformly.
In the present invention, the stabilizer preferably includes sodium cumene sulfonate and/or trehalose, more preferably sodium cumene sulfonate. According to the invention, sodium cumenesulfonate is selected as a stabilizer, so that on one hand, the sodium cumenesulfonate can be combined with keratin serving as a hydrolysate of a main component of the leather retanning agent in the filtrate obtained after filtration, the stability of the keratin is improved, and meanwhile, the keratin is prevented from being hydrolyzed in the subsequent drying operation process, so that the performance of the sodium cumenesulfonate serving as the leather retanning agent is ensured; on the other hand, the viscosity of the keratin solution can be reduced, which is beneficial to the separation of solid impurities and keratin in a solution system and the subsequent drying of the solution.
In the invention, the weight part of the stabilizer is preferably 1 to 2 parts, and more preferably 1.5 parts, based on 100 parts of the waste animal hair. The stabilizing agent with the above dosage is selected, and the leather retanning agent has the best property.
The filtering mode is not specially specified in the invention, and the solid impurities in the reaction system and the leather retanning agent solution are separated by adopting a filtering mode which is well known to a person skilled in the art.
After the leather retanning agent solution is obtained, the leather retanning agent solution is dried to obtain the leather retanning agent.
The drying mode is not specially specified, and the moisture in the leather retanning agent solution is removed. In the embodiment of the present invention, the drying manner is preferably spray drying. The spray drying method is high in drying rate, granular products with certain particle sizes can be directly obtained, block products are prevented from being formed by other heating methods, and meanwhile, the granular products can improve the using effect of the leather retanning agent in the leather making process.
Compared with the prior art, the preparation method provided by the invention reduces the energy consumption, and the temperature of the hydrolysis reaction is reduced to 35-40 ℃ from 130-190 ℃.
The following examples are provided to illustrate the method of preparing a leather retanning agent using waste animal hair as a raw material according to the present invention in detail, but they should not be construed as limiting the scope of the present invention.
Example 1:
(1) and washing the collected tanning waste cattle hairs with tap water, draining water, and naturally drying.
(2) Adding 100 parts by weight of the cow hair obtained in the step (1) into a rotary spherical digester, then sequentially adding 200 parts by weight of tap water, 4.5 parts by weight of industrial sodium sulfide and 3 parts by weight of industrial sodium hydroxide, sealing a feed inlet, starting the rotary spherical digester to rotate, introducing steam in the rotating process to heat the materials until the system temperature is 36 ℃, stopping introducing the steam, and keeping the rotary for 2 hours; the rotary spherical digester was then turned intermittently until the total treatment time was 20 hours.
(3) Gradually adding 200 parts by weight of tap water into the material obtained in the step (2) through a steam inlet in the rotary process of the rotary spherical digester; rotating for 30 minutes; then gradually adding a hydrogen peroxide solution with the mass concentration of 3% into the material, removing the residual sodium sulfide in the material, sampling at intervals until a potassium iodide starch test paper is used for detecting the solution, the test paper turns blue, and stopping adding the hydrogen peroxide; the rotation was continued for 60 minutes.
(4) In the rotary process of the rotary spherical digester, gradually adding an ascorbic acid solution with the mass concentration of 1% into the material obtained in the step (3) through a steam inlet, sampling at intervals until a potassium iodide starch test paper is used for detecting the solution, the test paper does not turn blue, and stopping adding the ascorbic acid; and then, gradually adding an oxalic acid solution with the mass concentration of 1%, sampling at intervals until the pH value of the solution is 6-7, stopping adding the oxalic acid, and continuing rotating for 60 minutes.
(5) Opening a discharge hole of the rotary spherical digester, pouring out the material obtained in the step (4), and transferring the material to a stirring tank which is started to stir and is added with 200 weight parts of tap water and 1.5 weight parts of sodium cumenesulfonate in advance; meanwhile, 100 parts by weight of tap water is added into the unloaded spherical digester for washing, and the washing liquid is transferred into a stirring tank and fully stirred for 60 minutes to obtain feed liquid with the concentration of about 10%; filtering and spray drying the feed liquid to obtain light yellow brown powder, namely the leather retanning agent.
Example 2:
(I) and washing the collected tanning waste cattle hairs with tap water, draining water, and naturally drying.
(II) adding 100 parts by weight of the cow hair obtained in the step (I) into a rotary spherical digester, then sequentially adding 200 parts by weight of tap water, 4.5 parts by weight of industrial sodium sulfide and 3 parts by weight of industrial sodium hydroxide, sealing a charging hole, starting the rotary spherical digester to rotate, introducing steam in the rotating process to heat the materials until the system temperature is 36 ℃, stopping introducing the steam, and keeping the rotary for 2 hours; the rotary spherical digester was then turned intermittently until the total treatment time was 20 hours.
(III) in the rotary process of the rotary spherical digester, gradually adding 200 parts by weight of tap water into the material obtained in the step (II) through a steam inlet; rotating for 30 minutes; and then gradually adding a hydrogen peroxide solution with the mass concentration of 3% into the material to remove the residual sodium sulfide in the material, (the initial mass concentration of the hydrogen peroxide solution is 30%, and the hydrogen peroxide solution with the mass concentration of 30% is diluted by ten times of water before use) and sampling at intervals until a potassium iodide starch test paper is used for detecting the solution, the test paper turns blue, the addition of the hydrogen peroxide solution is stopped, and the rotation is continued for 60 minutes.
(IV) in the rotary process of the rotary spherical digester, gradually adding an ascorbic acid solution with the mass concentration of 1% into the material obtained in the step (III) through a steam inlet, sampling at intervals until the solution is detected by a starch potassium iodide test paper, wherein the test paper does not turn blue, and stopping adding the ascorbic acid; and gradually adding a 1% formic acid solution at certain intervals, stopping adding oxalic acid until the pH value of the solution is 6-7, and continuing to rotate for 60 minutes.
(V) opening a discharge hole of the rotary spherical digester, pouring out the material obtained in the step (IV), and transferring the material to a stirring tank which is started to stir and is added with 200 weight parts of tap water and 1.5 weight parts of sodium cumenesulfonate in advance; meanwhile, 100 parts by weight of tap water is added into the unloaded spherical digester for washing, and the washing liquid is transferred into a stirring tank and fully stirred for 60 minutes to obtain feed liquid with the concentration of about 10%; filtering and spray drying the feed liquid to obtain light yellow brown powder, namely the leather retanning agent.
Effect of product application
The chrome tanned wet cowhide blue leather was used as a raw material, and the operation was performed according to the wet dyeing and finishing process for tanning, and the product obtained in example 1 and a conventional retanning agent (protein filler product) (RT-1826, a product of yozhou hongfeng polymer materials ltd.) were applied to the retanning and dyeing process after neutralization, and finally, a retanned and dyed leather blank was obtained. The process parameters are shown in table 1.
TABLE 1 parameters of the retanning dyeing process (Kraft clothing leather Process)
Comparative analysis of the thickness change of the hip, back and rib part and the uniformity of the color of the leather blanks was conducted for the leather blanks 1-1# and 2-1# and the results are shown in Table 2.
Table 2 comparison of the results of the application of the retanning agent prepared according to the invention and the retanning agent commercially available in the preparation of leather blanks
As can be seen from the results in table 2, the product of this example 1 has a good retanning filling effect (easy to be absorbed by wet blue leather) on a leather blank, and especially has a remarkable filling effect on the part between the ribs and the hips with loose fiber weaves (RT-1826), and the effect is superior to that of the protein product (RT-1826) currently used in the market, so that the uniformity of the final leather thickness can be promoted, and the utilization rate can be improved.
Meanwhile, the thickness of the leather blanks obtained without adding the retanning agent (only dye and fatliquoring agent are used) and the uniformity of the color of the leather blanks are examined by adopting the process shown in the table 1 in the experiment, and the result is shown in the table 3.
TABLE 3 parameters of leather blanks obtained without any retanning agent addition
As can be seen from the results in tables 2 and 3, the product of this example 1 not only has good selective filling property for wet blue leather blanks, but also has good level dyeing effect (no colored flower), and can effectively promote the uniformity of dyeing.
The product prepared in example 2 was subjected to the above performance tests, and the experimental results show that the final effect of the retanning agent prepared in example 2 is equivalent to that of the retanning agent prepared in example 1. This indicates that the acid used to adjust the pH of the retanning agent solution has little effect on the retanning agent performance when oxalic acid or formic acid is selected.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A method for preparing a leather retanning agent by taking waste animal hair as a raw material comprises the following steps:
mixing the waste animal hair, sodium sulfide, sodium hydroxide and water, and carrying out hydrolysis reaction to obtain a leather retanning agent solution;
the temperature of the hydrolysis reaction is 35-40 ℃, and the time of the hydrolysis reaction is 16-24 hours; the pH value of the leather retanning agent solution is 5-7;
and then drying the leather retanning agent solution to obtain the leather retanning agent.
2. The process of claim 1, wherein the reaction vessel for the hydrolysis reaction is a rotating drum or a rotary spherical digester.
3. A method according to claim 1, characterized in that the pH adjusting agent used to adjust the pH of the leather retanning agent solution comprises formic acid and/or oxalic acid.
4. The method of claim 1, further comprising the step of, after the hydrolysis reaction:
mixing the product of the hydrolysis reaction with an oxidant, carrying out an oxidation reaction, and removing the residual sodium sulfide after the hydrolysis reaction; then mixing with a reducing agent to remove the residual oxidizing agent after the oxidation reaction; mixing with stabilizer, and filtering.
5. The method of claim 4, wherein the stabilizer comprises sodium cumene sulfonate and/or trehalose.
6. The method of claim 4, wherein the oxidizing agent is hypochlorite and/or hydrogen peroxide.
7. The method of claim 4, wherein the reducing agent is at least one of ascorbic acid, hydroxylamine hydrochloride, hydrazine hydrate, sodium bisulfite, sodium sulfite, and sodium hydrosulfite.
8. The method of claim 7, wherein the reducing agent is ascorbic acid.
9. The method according to claim 4, wherein the temperature of the oxidation reaction is 35 to 40 ℃.
10. The method according to claim 4, wherein the temperature of the reduction reaction is 35 to 40 ℃.
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