Amphoteric retanning agent based on cane sugar and preparation method
Amphoteric retanning agents are synthesized through the nucleophilic substitution reaction of sucrose, lysine and epoxy compounds, and the isoelectric point regulation is solved by the problem of insufficient hydroxyl reactive activity of sucrose, achieving efficient leather retanning effect and environmentally friendly production.
Patent Information
- Application Number
- CN202510476587.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-16
- Publication Date
- 2025-07-04
AI Technical Summary
In the prior art, sucrose has insufficient hydroxyl reactive activity and is difficult to cross-link to form polymers. The structure and charge properties of existing polysucrose are difficult to meet the requirements of the leather making process, resulting in poor retanning performance.
The amphoteric retanning agent is synthesized by nucleophilic substitution reaction, and the isoelectric point of the retanning agent is regulated to 4.0~5.0 by introducing active carboxylic compounds, thereby improving its absorption rate and binding ability in leather.
The prepared amphoteric retanner shows good absorption and bonding ability in leather, improves the fullness of the leather, and is environmentally friendly in process and low-cost, suitable for large-scale industrial production.
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Figure CN120249573A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of leather-making chemicals, and particularly relates to an amphoteric retanning agent based on sucrose and a preparation method thereof. Background Art
[0002] Sucrose is a natural and renewable biomass resource, which has the advantages of wide sources, low price, environmental friendliness, etc., and thus has received extensive attention. As a common non-reducing sugar, sucrose has two rigid sugar rings with stable structures. The polymer synthesized with it as a monomer may play a good filling role when filled in leather. However, the hydroxyl reaction activity of sucrose is insufficient and it is not easy to crosslink to form a polymer. At present, only polysucrose synthesized with epichlorohydrin as a crosslinking agent is industrially produced, but the structure and charge properties of this polysucrose are difficult to meet the technological requirements of leather-making. Therefore, it is of great practical significance and urgent need to develop an amphoteric retanning agent with sugar compounds as raw materials, a green and environmentally friendly preparation process and low cost.
[0003] In view of this, the present invention is specifically proposed. Summary of the Invention
[0004] The purpose of the present invention is to provide an amphoteric retanning agent based on sucrose and a preparation method thereof in view of the deficiencies of the prior art. The amphoteric retanning agent provided by the present invention has a high absorption rate and can improve the absorption rate of fatliquor, providing a new idea for the preparation of amphoteric retanning agents.
[0005] To achieve the above object, the first technical solution adopted by the present invention is: An amphoteric retanning agent based on sucrose, calculated by weight, its raw materials include: 10 - 40 parts of sucrose, 2 - 15 parts of lysine, 5 - 50 parts of epoxide compound, and 1 - 6 parts of active carboxyl compound; wherein, the epoxide compound is any one of epichlorohydrin, ethylene glycol diglycidyl ether, and glycerol triglycidyl ether.
[0006] Preferably, the active carboxyl compound is selected from at least one of monochloroacetic acid, 2-chloropropionic acid, and glyoxylic acid.
[0007] The second technical solution adopted by the present invention is: A preparation method of an amphoteric retanning agent based on sucrose, comprising the following steps: Dissolve sucrose in water, mix it with an epoxide compound, and react at 30 - 60 °C in the presence of a strong base for 1 - 4 h to obtain a polysucrose prepolymer; Mix the polysucrose prepolymer with lysine and react at 50 - 80 °C in the presence of a strong base for 1 - 3 h to obtain a polysucrose-lysine polymer; Mix the polysucrose-lysine polymer with an active carboxyl compound at 50 - 80 °C and react for 1 - 4 h; Among them, the epoxide is any one of epichlorohydrin, ethylene glycol diglycidyl ether, and glycerol triglycidyl ether.
[0008] Preferably, the active carboxyl compound is selected from at least one of monochloroacetic acid, 2-chloropropionic acid, and glyoxylic acid.
[0009] Preferably, the dosages of each raw material are calculated by weight as follows: 10 - 40 parts of sucrose, 2 - 15 parts of lysine, 5 - 50 parts of epoxide, and 1 - 6 parts of active carboxyl compound.
[0010] Preferably, the molar ratio of sucrose, epoxide, and lysine is 1:(1.1 - 1.8):(0.2 - 0.5), and the molar ratio of lysine to active carboxyl compound is 1:0.6 - 1:1.2.
[0011] Preferably, the strong base is sodium hydroxide and / or potassium hydroxide.
[0012] Preferably, the mass concentration of the sodium hydroxide and potassium hydroxide solutions is both 30 - 50%.
[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) For the amphoteric retanning agent prepared by the present invention, sucrose is used as the main raw material for the first time, and lysine and epoxide are used as crosslinking agents, and it is synthesized through nucleophilic substitution reaction. This retanning agent not only has green and environmentally friendly raw materials, but also has a simple preparation process, a non-toxic and harmless preparation process, and low cost, and has the potential for large-scale industrial production and application.
[0014] (2) In view of the charge matching problem existing in the application of this retanning agent in leather retanning, the present invention proposes an innovative solution. Since polysucrose itself is electrically neutral and the isoelectric point of lysine is relatively high (pI = 9.74), the isoelectric point of the polymer formed by crosslinking the two is also relatively high (pI > 7). In the retanning bath solution with a pH of 5.0 - 5.5, this polymer is difficult to effectively penetrate and combine with the positively charged chrome-tanned leather due to charge repulsion, resulting in poor retanning performance. Therefore, the present invention introduces an active carboxyl compound, and by precisely controlling the ratio of lysine to the active carboxyl compound in the reaction, the isoelectric point of the polysucrose-lysine polymer is controlled between 4.0 and 5.0. This method makes the retanning agent negatively charged during the retanning process, generating electrostatic attraction with the positively charged chrome-tanned leather, significantly improving the absorption rate. In the subsequent acid fixation stage, the amphoteric nature of the retanning agent makes it turn into a positive charge, creating favorable conditions for the absorption and combination of anionic fatliquor, and realizing the synergistic optimization of the retanning-fatliquoring process.
[0015] (3) The amphoteric retanning agent based on sucrose prepared by the present invention has active groups such as amino groups, carboxyl groups and hydroxyl groups, and binds firmly to leather collagen fibers through electrostatic interaction and hydrogen bond interaction. The crosslinking of polysucrose prepolymer and lysine not only increases the molecular weight of the retanning agent, but also the rigid sugar ring structure can play a good filling role in the leather after retanning, effectively improving the fullness of the leather. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 FIG. is the infrared spectrum of sucrose (SUC), polysucrose prepolymer (FP), polysucrose-lysine polymer (LF) and amphoteric retanning agent based on sucrose (GLF) in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0017] It should be understood that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments. The experimental materials used in the examples and comparative examples of the present invention are all conventional experimental materials in the art and can be obtained through commercial channels.
[0018] The first embodiment of the present invention provides an amphoteric retanning agent based on sucrose. By weight, its raw materials include: 10-40 parts of sucrose, 2-15 parts of lysine, 5-50 parts of epoxide, and 1-6 parts of active carboxyl compound; wherein, the epoxide is any one of epichlorohydrin, ethylene glycol diglycidyl ether, and glycerol triglycidyl ether.
[0019] The epoxide used in the embodiment of the present invention has 1-3 epoxy groups but does not contain methoxy or ethoxy. During the reaction process, sucrose is used as the main raw material, lysine and epoxide are used as crosslinking agents, and the active carboxyl compound is carboxylated to regulate the isoelectric point of the retanning agent to 4.0-5.0, so that it is negatively charged and positively charged during the retanning and fatliquoring processes respectively.
[0020] The amphoteric retanning agent based on sucrose provided by the embodiments of the present invention undergoes the following reactions among its raw materials: First, the epoxy group of the epoxy compound undergoes a ring-opening reaction with the primary hydroxyl group of sucrose to crosslink and form a polysucrose prepolymer with a relatively small molecular weight, retaining active terminals (epoxy groups or active chlorine). Among them, epichlorohydrin has one more active chlorine group than glycidyl ether. Epichlorohydrin will undergo a ring-opening and ring-closing reaction, that is, after the ring-opening reaction with the primary hydroxyl group of sucrose, it will then dechlorinate and re-close the ring to become an epoxy group, serving as the active terminal group of the polysucrose prepolymer. However, a small amount of active chlorine will be retained and can also serve as the active terminal group. While glycidyl ether only undergoes the ring-opening reaction of the epoxy group, only retaining the active terminal groups of some epoxy groups and having no active chlorine terminal groups. After obtaining the above polysucrose prepolymer with active terminal groups, it then undergoes a ring-opening reaction of the epoxy group or a nucleophilic substitution reaction of the active chlorine with the primary amino group of lysine to crosslink and obtain a polysucrose-lysine polymer with a relatively large molecular weight. At this time, the isoelectric point of the polysucrose-lysine polymer is relatively high (pI > 7), which does not match the charge of the chrome-tanned leather, making it difficult to be absorbed by the chrome-tanned leather. Subsequently, the active groups (active chlorine or aldehyde group) on the active carboxyl compound are used to carry out a nucleophilic substitution reaction or a Schiff base reaction with the unreacted primary amino groups on the polysucrose-lysine polymer, reducing both the positively charged primary amino groups and increasing the negatively charged carboxyl groups, thereby regulating the isoelectric point of the polysucrose-lysine polymer to a suitable range (4.0 - 5.0), and finally obtaining the amphoteric retanning agent based on sucrose.
[0021] In some preferred embodiments, the active carboxyl compound is selected from at least one of monochloroacetic acid, 2-chloropropionic acid, and glyoxylic acid.
[0022] The second embodiment of the present invention provides a preparation method of an amphoteric retanning agent based on sucrose, including the following steps: Dissolve sucrose in water, mix it with an epoxy compound, and react at 30 - 60 °C in the presence of a strong base for 1 - 4 h to obtain a polysucrose prepolymer product; mix the polysucrose prepolymer product with lysine and react at 50 - 80 °C in the presence of a strong base for 1 - 3 h to obtain a polysucrose-lysine polymer; mix the polysucrose-lysine polymer with an active carboxyl compound and react at 50 - 80 °C for 1 - 4 h; wherein, the epoxy compound is any one of epichlorohydrin, ethylene glycol diglycidyl ether, and glycerol triglycidyl ether.
[0023] In this embodiment, first, the hydroxyl groups of sucrose and the amino groups of lysine are respectively reacted step by step with the epoxy groups or active chlorine of the epoxide to improve the water solubility of the retanning agent and increase its molecular weight. Finally, an active carboxyl compound is used to adjust the amphoteric properties of the product, so that it carries a negative charge during the retanning process and a positive charge during the fatliquoring process, thereby preparing an amphoteric retanning agent based on sucrose. During the actual application process, active groups such as amino groups, carboxyl groups, and hydroxyl groups in the retanning agent are combined with leather collagen fibers through electrostatic interaction and hydrogen bond interaction, endowing it with good filling effect. In addition, the raw materials used in this method are green and environmentally friendly, the prepared retanning agent has a high absorption rate, and can improve the absorption rate of the fatliquoring agent, providing a new idea for the preparation of amphoteric retanning agents.
[0024] It should be noted that in the above preparation method, the epoxide needs to be reacted with sucrose first and then cross-linked with lysine. This is because the reaction activity of the primary hydroxyl group of sucrose is much lower than that of the primary amino group of lysine. Just because the primary hydroxyl group of sucrose has insufficient activity, some active epoxy ends will be retained in the later stage of the reaction between sucrose and the epoxide (as the reaction progresses, the steric hindrance becomes larger and the reaction activity will gradually decrease, resulting in some active ends not being reacted and being retained due to insufficient activity). Also because the reaction activity of the primary hydroxyl group of sucrose is low, lysine is used to replace sucrose to continue the reaction in the follow-up (the primary amino group with high activity replaces the primary hydroxyl group that has reacted mostly, re-improving the reaction efficiency), which can not only increase the reaction rate but also endow the retanning agent with amphoteric properties.
[0025] As some preferred embodiments, to make the prepared amphoteric retanning agent based on sucrose have the best effect, the dosage of each raw material is calculated by weight as follows: 10 - 40 parts of sucrose, 2 - 15 parts of lysine, 5 - 50 parts of epoxide, and 1 - 6 parts of active carboxyl compound.
[0026] If the dosage is determined by the molar ratio between the raw materials, the dosage relationship of each raw material can also be expressed as: the molar ratio of sucrose, epoxide, and lysine is 1: (1.1 - 1.8): (0.2 - 0.5), and the molar ratio of lysine to active carboxyl compound is 1: 0.6 - 1: 1.2.
[0027] It should be noted that the presence of strong base in the above reaction process is to drive the nucleophilic substitution reaction by the base, which is well known in the art, and the dosage of the strong base can be adjusted adaptively according to the dosage of the raw materials. The strong base used is generally sodium hydroxide and / or potassium hydroxide. As an example, the mass concentration of sodium hydroxide and potassium hydroxide is both 30 - 50%.
[0028] To make the technical solution of the present invention clearer, the amphoteric retanning agent based on sucrose and its effects are described in detail below through multiple specific examples.
[0029] It should be noted that the softness, thickening rate, retanning agent absorption rate, and fatliquor absorption rate of the wet blue leather after retanning are measured by a softness meter, a thickness meter, and a total organic carbon analyzer, respectively. The Zeta potential of the retanning agent is measured by a nanoparticle size and zeta potential analyzer.
[0030] Example 1 Dissolve 20 g of sucrose in 10 g of pure water, mix evenly with 9.7 g of epichlorohydrin at room temperature, heat to 40 °C under strong alkaline conditions and stir for 2 h to obtain a polysucrose prepolymer; add 2.6 g of lysine and mix evenly at room temperature, heat to 60 °C under strong alkaline conditions and stir and react for 1 h to obtain a polysucrose-lysine polymer; add 1.5 g of glyoxylic acid and stir and mix at 60 °C for 2 h to obtain a sucrose-based amphoteric retanning agent with an isoelectric point of 4.63.
[0031] The infrared spectra of sucrose (SUC), polysucrose prepolymer (FP), polysucrose-lysine polymer (LF), and sucrose-based amphoteric retanning agent (GLF) in this example are as Figure 1 shown. As can be seen from Figure 1 the infrared spectrum of SUC, the sharp absorption peak at 3663 cm -1 comes from the free hydroxyl groups on the sucrose molecule, the strong and broad absorption peak at 3386 cm -1 is the characteristic absorption peak of the hydroxyl groups forming associated hydrogen bonds, the doublet peaks at 2931 cm -1 and 2871 cm -1 belong to the stretching vibration peaks of methylene and methyl groups, and the group of peaks near 1069 cm -1 are the absorption peaks of C2-OH, C3-OH, and C6-OH in the sugar ring structure. In the infrared spectrum of FP, compared with sucrose, the absorption peaks of associated hydrogen bonds, methylene, methyl, and sugar ring structure are all enhanced, indicating that epichlorohydrin cross-links with sucrose to form a low-molecular-weight polysucrose prepolymer. Moreover, the absorption peak at 1648 cm -1 is the characteristic absorption peak after the internal ring adsorbed water of sucrose, which is a typical infrared characteristic peak mark of polysucrose. The absorption peaks at 1267 cm -1 and 855 cm -1 are the characteristic absorption peaks of epoxy groups, and the absorption peak at 681 cm -1 is the stretching vibration peak of the carbon-chlorine bond, indicating that a polysucrose prepolymer with active groups has been successfully prepared. In the infrared spectrum of LF, due to the introduction of lysine, a new carbonyl absorption peak appears at 1731 cm -1 , and the absorption peak at 1577 cm -1The bending vibration absorption peak of the amino group at [location], and the absorption peaks of the epoxy group and the carbon-chlorine bond in FP decreased significantly, indicating that the epoxy group was almost completely consumed by the reaction with the primary amino group of lysine, confirming that lysine continued to crosslink with FP to form the polysucrose-lysine polymer LF. In the infrared spectrum of GLF, the absorption peak at 1648 cm -1 increased and showed a slight red shift at [location], which was due to the reaction of glyoxylic acid with the excess amino groups in LF to form a Schiff base structure, that is, the superposition of the stretching vibration peak of the imine bond and the absorption peak of the adsorbed water of the sugar ring, proving that glyoxylic acid was grafted onto LF, adjusting the isoelectric point of the product, and successfully preparing a sucrose-based amphoteric retanning agent.
[0032] Example 2 Dissolve 30 g of sucrose in 20 g of pure water, mix evenly with 14.6 g of epichlorohydrin at room temperature, heat to 50 °C under strong alkaline conditions and stir for 2 h to obtain a polysucrose prepolymer; add 5.6 g of lysine and mix evenly at room temperature, heat to 70 °C under strong alkaline conditions and stir for 1 h to obtain a polysucrose-lysine polymer; add 2.5 g of chloroacetic acid and stir at 50 °C for 3 h to obtain a sucrose-based amphoteric retanning agent with an isoelectric point of 4.79.
[0033] Example 3 Dissolve 25 g of sucrose in 12.5 g of pure water, mix evenly with 21.2 g of ethylene glycol diglycidyl ether at room temperature, heat to 30 °C under strong alkaline conditions and stir for 4 h to obtain a polysucrose prepolymer; add 5.3 g of lysine and mix evenly at room temperature, heat to 50 °C under strong alkaline conditions and stir for 3 h to obtain a polysucrose-lysine polymer; add 4.0 g of chloroacetic acid and stir at 60 °C for 4 h to obtain a sucrose-based amphoteric retanning agent with an isoelectric point of 4.28.
[0034] Example 4 Dissolve 15 g of sucrose in 8 g of pure water, mix evenly with 18.3 g of glycerol triglycidyl ether at room temperature, heat to 40 °C under strong alkaline conditions and stir for 3 h to obtain a polysucrose prepolymer; add 3.1 g of lysine and mix evenly at room temperature, heat to 80 °C under strong alkaline conditions and stir for 1 h to obtain a polysucrose-lysine polymer; add 2.7 g of 2-chloropropionic acid and stir at 70 °C for 2 h to obtain a sucrose-based amphoteric retanning agent with an isoelectric point of 4.57.
[0035] Example 5 Dissolve 40 g of sucrose in 20 g of pure water, mix it evenly with 36.5 g of glycerol triglycidyl ether at room temperature, heat it to 60 °C and stir for 1 h under strong alkaline conditions to obtain a polysucrose prepolymer; add 8.4 g of lysine and mix evenly at room temperature, heat it to 70 °C and stir and react for 2 h under strong alkaline conditions to obtain a polysucrose-lysine polymer; add 3.8 g of glyoxylic acid and stir and mix at 80 °C for 1 h to obtain a sucrose-based amphoteric retanning agent with an isoelectric point of 4.16.
[0036] Comparative Example 1 It is the polysucrose prepolymer prepared in Example 1, and this polysucrose prepolymer has active terminals.
[0037] Comparative Example 2 It is the polysucrose-lysine polymer prepared in Example 1, and glyoxylic acid is not added to adjust the isoelectric point. The isoelectric point of this polysucrose-lysine polymer is 7.42.
[0038] Application Example 1 In this application example, a nano particle size and zeta potential analyzer was used to measure the isoelectric points of the amphoteric retanning agents prepared in Examples 1-5 and Comparative Example 2 and the commercial amino resin retanning agent (CML). The isoelectric points of the retanning agents in Examples 1-5 were 4.63, 4.79, 4.28, 4.57, and 4.16 respectively. The isoelectric point of the retanning agent in the comparative example was 7.42, and the isoelectric point of the commercial amino resin retanning agent was 2.87.
[0039] The results show that the present invention successfully reduces the isoelectric point of the polysucrose-lysine polymer from 7.42 to between 4.0 and 5.0 through carboxylation modification to obtain a sucrose-based amphoteric retanning agent, while the isoelectric point of CML is only 2.87. Therefore, the retanning agent prepared by the present invention has a suitable isoelectric point, making it show negative and positive charges respectively in the retanning and fatliquoring stages, not only improving its absorption rate in leather, but also showing stronger positive charge compared to CML after adjusting the bath solution pH to 3.0-3.5 in the acid fixing stage. Therefore, it has a stronger absorption and binding ability for the subsequent fatliquoring agent and a higher absorption rate.
[0040] Application Example 2 In this application example, the amphoteric retanning agent prepared in Example 1 was used to retan cowhide upper leather: Put the raw blue wet cowhide upper leather into a rotating drum, and carry out softening, neutralization, and water washing in sequence according to the conventional process, then add 8% of the amphoteric retanning agent based on the weight of the blue wet leather and 100% of water, and rotate it at a temperature of 35 °C and a pH of 5.0-5.5 for 1 h, and then complete the retanning and fatliquoring process according to the conventional fixing process.
[0041] The thickening rate of the wet blue cowhide processed by this process is 18.45% after retanning, the softness is 7.55 mm, the absorption rate of the retanning agent is 91.32%, the absorption rate of the fatliquoring agent is 88.26%, and the leather is plump and the grain surface is delicate.
[0042] Application Example 3 In this application example, the retanning of cowhide garment leather was carried out using the amphoteric retanning agent prepared in Example 3: Put the shaved wet blue cowhide garment leather into a rotating drum, and carry out softening, neutralization, and water washing in sequence according to the conventional process. Then add 8% of the amphoteric retanning agent based on the weight of the wet blue leather and 100% water, and rotate it at a temperature of 35°C and a pH of 5.0 - 5.5 for 1 h. Then complete the retanning and fatliquoring process according to the conventional fixation process.
[0043] The thickening rate of the wet blue cowhide processed by this process is 18.38% after retanning, the softness is 7.63 mm, the absorption rate of the retanning agent is 90.06%, the absorption rate of the fatliquoring agent is 86.77%, and the leather is plump and the grain surface is flat.
[0044] Application Example 4 In this application example, the retanning of sheepskin garment leather was carried out using the amphoteric retanning agent prepared in Example 5: Put the raw wet blue sheepskin garment leather into a rotating drum, and carry out softening, neutralization, and water washing in sequence according to the conventional process. Then add 8% of the amphoteric retanning agent based on the weight of the wet blue leather and 100% water, and rotate it at a temperature of 35°C and a pH of 5.0 - 5.5 for 1 h. Then complete the retanning and fatliquoring process according to the conventional fixation process.
[0045] The thickening rate of the wet blue sheepskin processed by this process is 17.23% after retanning, the softness is 7.31 mm, the absorption rate of the retanning agent is 90.68%, the absorption rate of the fatliquoring agent is 86.47%, the leather body is soft and the grain surface is smooth.
[0046] Application Comparative Example 1 In this application comparative example, the retanning of cowhide upper leather was carried out using the polysucrose prepolymer in Comparative Example 1: Put the shaved wet blue cowhide upper leather into a rotating drum, and carry out softening, neutralization, and water washing in sequence according to the conventional process. Then add 8% of the polysucrose prepolymer based on the weight of the wet blue leather and 100% water, and rotate it at a temperature of 35°C and a pH of 5.0 - 5.5 for 1 h. Then complete the retanning and fatliquoring process according to the conventional fixation process.
[0047] The thickening rate of the wet blue cowhide processed by the process is 7.18% after retanning, the softness is 6.41 mm, the absorption rate of the retanning agent is 53.72%, the absorption rate of the fatliquoring agent is 65.98%, the leather body is flat and thin, and the grain surface is rough.
[0048] Application Comparative Example 2 The comparative example of this application is the retanning of cowhide upper leather with the polysucrose-lysine polymer whose isoelectric point was not adjusted in Comparative Example 2: Put the buffed blue wet cowhide upper leather into a rotating drum, and successively carry out softening, neutralization, and water washing according to the conventional process. Then add 8% of the polysucrose-lysine polymer based on the weight of the blue wet leather and 100% water, and rotate it at a temperature of 35 °C and a pH of 5.0 - 5.5 for 1 h. Then complete the retanning and fatliquoring process according to the conventional fixing process.
[0049] After retanning, the thickening rate of the cowhide blue wet leather treated by the process is 5.32%, the softness is 6.03 mm, the absorption rate of the retanning agent is 40.12%, the absorption rate of the fatliquoring agent is 35.74%, the leather body is flat and thin, and the grain surface is rigid.
[0050] Comparative Example 3 of the application The comparative example of this application is the retanning of cowhide upper leather with a commercial amino resin retanning agent (CML): Put the buffed blue wet cowhide upper leather into a rotating drum, and successively carry out softening, neutralization, and water washing according to the conventional process. Then add 8% of the commercial amino resin retanning agent based on the weight of the blue wet leather and 100% water, and rotate it at a temperature of 35 °C and a pH of 5.0 - 5.5 for 1 h. Then complete the retanning and fatliquoring process according to the conventional fixing process.
[0051] After retanning, the thickening rate of the cowhide blue wet leather treated by the process is 10.96%, the softness is 6.93 mm, the absorption rate of the retanning agent is 86.17%, the absorption rate of the fatliquoring agent is 81.72%, the finished leather is firm, and the grain surface is flat.
[0052] Compare the thickening rate, softness, absorption rate of the retanning agent, and absorption rate of the fatliquoring agent of the finished leathers obtained after retanning and fatliquoring in Application Example 2 and Comparative Examples 1, 2, and 3 of the application. The results are shown in Table 1.
[0053] Table 1 Comparison of the properties of finished leathers under different conditions 。
[0054] The results show that in Comparative Application Example 1, due to the problems of insufficient molecular weight and fewer active groups of the polysucrose prepolymer, the polysucrose prepolymer cannot bind well with the collagen fibers in the leather, resulting in the leather after retanning being flat, thin and rough, and the application effect is poor. In Comparative Application Example 2, due to the charge matching problem of the polysucrose-lysine polymer in the retanned leather, the absorption rates of the retanning agent and the fatliquor are low, and the retanning effect is poor. In Application Example 2, by crosslinking lysine on the basis of the polysucrose prepolymer, the molecular weight of the retanning agent is increased, and an active carboxyl compound is introduced to successfully and precisely regulate the isoelectric point of the sucrose-based amphoteric retanning agent, solving the charge matching problem in the cowhide upper leather and significantly improving its application effect in the retanning of cowhide upper leather. Moreover, the cowhide upper leather treated with the sucrose-based amphoteric retanning agent is superior to the traditional commercial amino resin retanning agent (CML) in terms of the key performance indicators such as the thickening rate, softness, absorption rate of the retanning agent and absorption rate of the fatliquor. In addition, formaldehyde is not used as a condensing agent at all in the preparation process of this retanning agent, and epoxy compounds, sucrose and lysine are used as raw materials, ensuring the safety and environmental protection of the product. This not only meets the needs of the leather industry for high-performance retanning agents, but also conforms to the current trend of green and low-carbon development, providing a new solution for the sustainable development of the leather industry.
[0055] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A sucrose-based amphoteric retanning agent, characterized in that, By weight, its raw materials include: 10-40 parts of sucrose, 2-15 parts of lysine, 5-50 parts of epoxide compound, and 1-6 parts of active carboxyl compound; wherein, the epoxide compound is any one of epichlorohydrin, ethylene glycol diglycidyl ether, and glycerol triglycidyl ether.
2. The sucrose-based amphoteric retanning agent according to claim 1, characterized in that, The active carboxyl compound is selected from at least one of monochloroacetic acid, 2-chloropropionic acid, and glyoxylic acid.
3. Preparation method of sucrose-based amphoteric retanning agent, characterized in that, It includes the following steps: Dissolve sucrose in water, mix it with the epoxide compound, and react at 30-60 °C in the presence of a strong base for 1-4 h to obtain a polysucrose prepolymer; Mix the polysucrose prepolymer with lysine and react at 50-80 °C in the presence of a strong base for 1-3 h to obtain a polysucrose-lysine polymer; Mix the polysucrose-lysine polymer with the active carboxyl compound at 50-80 °C and react for 1-4 h; Wherein, the epoxide compound is any one of epichlorohydrin, ethylene glycol diglycidyl ether, and glycerol triglycidyl ether.
4. The preparation method of the sucrose-based amphoteric retanning agent according to claim 3, characterized in that, The active carboxyl compound is selected from at least one of monochloroacetic acid, 2-chloropropionic acid, and glyoxylic acid.
5. The preparation method of the sucrose-based amphoteric retanning agent according to claim 3, characterized in that, The dosage of each raw material is by weight: 10-40 parts of sucrose, 2-15 parts of lysine, 5-50 parts of epoxide compound, and 1-6 parts of active carboxyl compound.
6. The preparation method of the sucrose-based amphoteric retanning agent according to claim 3, wherein, The molar ratio of sucrose, epoxide compound, and lysine is 1:(1.1-1.8):(0.2-0.5), and the molar ratio of lysine to active carboxyl compound is 1:0.6-1:1.
2.
7. The preparation method of the sucrose-based amphoteric retanning agent according to claim 3, characterized in that, The strong base is sodium hydroxide and / or potassium hydroxide.
8. The preparation method of the sucrose-based amphoteric retanning agent according to claim 7, characterized in that, The mass concentration of the sodium hydroxide and potassium hydroxide solutions is both 30-50%.