Acrylic retanning agent and method for its preparation

Abstract

The application discloses an acrylic re-tanning agent and a preparation method thereof, and belongs to the technical field of re-tanning agents. The preparation raw materials of the acrylic re-tanning agent include water, an acrylic monomer, an acrylic ester monomer, an unsaturated dicarboxylic acid monoester, a functional monomer, maleic anhydride, caprolactone grafted hydroxyethyl acrylate, an oxidizing agent, a reducing agent, a chain transfer agent, a pH regulator and a bactericide. The acrylic re-tanning agent takes the acrylic monomer as a basic component, is compounded with the acrylic ester monomer, the unsaturated dicarboxylic acid monoester, the functional monomer and the chain transfer agent, and simultaneously adds the caprolactone grafted hydroxyethyl acrylate, so that the acrylic re-tanning agent can form high-density hydrogen bonds with carboxyl and hydroxyl on dermal fibers in the dermal drying process, thereby achieving a three-dimensional network structure of mutual crosslinking of the acrylic re-tanning agent, chromium ions and dermal fibers, the dermis has high tightness and resilience, and the tensile strength and tear resistance of the dermis can also be significantly improved.

Description

Technical Field

[0001] This invention relates to the field of retanning agents, and more particularly to an acrylic retanning agent and its preparation method. Background Technology

[0002] Genuine leather car seat cushions need to withstand long-term repeated sitting pressure to avoid sagging, deformation, cracking, and wear, while ensuring driving and riding support, comfort, and service life. Therefore, genuine leather car seat cushions require leather with strong firmness and high resilience.

[0003] While acrylic retanning agents used for water treatment of genuine leather can improve the firmness of genuine leather to some extent, they are insufficient for improving the firmness of genuine leather used in car seat cushions. This is because ordinary acrylic retanning agents are made by polymerizing conventional acrylic acid and acrylic monomers. They can usually only form a stable cross-link with chromium ions in chrome-tanned leather, but cannot form strong hydrogen bonds with the carboxyl and hydroxyl groups in genuine leather fibers. Ultimately, this results in a loose genuine leather fiber network after treatment, with low tear resistance and tensile strength, which cannot meet the high firmness requirements of genuine leather for car seat cushions.

[0004] It is evident that existing technologies need improvement and enhancement. Summary of the Invention

[0005] The purpose of this invention is to provide an acrylic retanning agent and its preparation method, aiming to solve the problems that existing acrylic retanning agents are insufficient in improving the firmness of genuine leather used in car seat cushions, and that the tear resistance and tensile strength of genuine leather after treatment still need to be improved.

[0006] To address the aforementioned technical problems, the first aspect of this invention provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0007] 55-65 parts water, 16-17.4 parts acrylic acid monomer, 2-2.6 parts maleic anhydride, 3-5 parts acrylate monomer, 1-2 parts unsaturated dicarboxylic acid monoester, 5-7 parts functional monomer, 5-7 parts caprolactone-grafted hydroxyethyl acrylate, 2-3 parts oxidant, 2-3 parts reducing agent, 0.5-1 part chain transfer agent, 2-3 parts pH adjuster, and 0.1 part bactericide.

[0008] In the aforementioned acrylic retanning agent, the acrylic monomer is at least one of acrylic acid and methacrylic acid.

[0009] In the acrylic retanning agent, the acrylate monomer is at least one of methyl methacrylate and ethyl acrylate.

[0010] In the acrylic retanning agent, the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester.

[0011] In the aforementioned acrylic retanning agent, the functional monomer is at least one of acrylonitrile, hydroxy functional monomer, and N-hydroxymethylacrylamide.

[0012] In the acrylic retanning agent, the hydroxyl functional monomer is a mixture of hydroxyethyl methacrylate and hydroxypropyl acrylate.

[0013] In the acrylic retanning agent, the chain transfer agent is at least one of n-dodecyl mercaptoethanol and mercaptoethanol.

[0014] In the acrylic retanning agent, the oxidant is at least one of ammonium persulfate, sodium persulfate, potassium persulfate, and tert-butyl hydroperoxide.

[0015] In the acrylic retanning agent, the reducing agent is at least one of sodium bisulfite, ascorbic acid, sodium metabisulfite, Brügmann FF6, and Brügmann 1328.

[0016] A second aspect of the present invention provides a method for preparing the aforementioned acrylic retanning agent, comprising the following steps:

[0017] S001. Add 26 to 36 parts of water to the reactor, and then raise the temperature of the reactor to 32 to 37°C.

[0018] S002. Add 15 parts of water to the stirrer, then add acrylic monomer, maleic anhydride, acrylate monomer, unsaturated dicarboxylic acid monoester, functional monomer, caprolactone-grafted hydroxyethyl acrylate and chain transfer agent to the stirrer. After stirring and dispersing evenly, divide the obtained monomer mixture into 3 parts, namely monomer mixture a, monomer mixture b and monomer mixture c.

[0019] S003. Mix 1.8 to 2.8 parts of oxidant with 6 parts of water until homogeneous, and divide the resulting oxidant solution into 3 equal parts, namely oxidant solution a, oxidant solution b and oxidant solution c; mix 0.2 parts of oxidant with 1 part of water until homogeneous to obtain oxidant solution d;

[0020] S004. Mix 1.8 to 2.8 parts of reducing agent with 6 parts of deionized water evenly, and divide the resulting reducing agent solution into 3 equal parts, namely reducing agent solution a, reducing agent solution b and reducing agent solution c; mix 0.2 parts of reducing agent with 1 part of water evenly to obtain reducing agent solution d;

[0021] S005. Add monomer mixture a to the reactor in step S001, then add oxidant solution a, stir and disperse evenly, add reducing agent solution a to the reactor, and raise the temperature inside the reactor to 85-90°C. After the temperature rise is complete, lower the temperature inside the reactor to 50-55°C.

[0022] S006. Continue to add monomer mixture b into the reactor, then add oxidant solution b, stir and disperse evenly, then add reducing agent solution b into the reactor and raise the temperature inside the reactor to 85-90℃. After the temperature rise is complete, lower the temperature inside the reactor to 55-60℃.

[0023] S007. Continue to add monomer mixture c to the reactor, then add oxidant solution c, stir and disperse evenly, then add reducing agent solution c to the reactor and raise the temperature inside the reactor to 85-90℃. After the temperature rise is complete, keep it at that temperature for 180 minutes.

[0024] S008. After the heat preservation is completed, the temperature inside the reactor is reduced to 60-63°C, and then oxidant solution d and reducing agent solution d are added to the reactor to remove residual monomers.

[0025] S009. Add pH adjuster and bactericide to the reaction vessel, stir and mix evenly to obtain the acrylic retanning agent.

[0026] The beneficial effects of this invention are:

[0027] The first aspect of this invention provides an acrylic retanning agent, which is based on acrylic monomers and compounded with maleic anhydride, acrylate monomers, unsaturated dicarboxylic acid monoesters, functional monomers, and chain transfer agents. Simultaneously, by adding caprolactone-grafted hydroxyethyl acrylate, the acrylic retanning agent can form high-density hydrogen bonds with the carboxyl and hydroxyl groups on the leather fibers during the leather drying process. This enables the acrylic retanning agent to achieve a three-dimensional network structure where the acrylic retanning agent, chromium ions, and leather fibers are mutually cross-linked, resulting in high firmness and resilience of the leather, and significantly improving its tensile and tear strength.

[0028] The second aspect of this invention provides a method for preparing an acrylic retanning agent. This method employs a seed-semi-continuous dripping process, in which a monomer mixture, an oxidant, and a reducing agent are added in three steps. This avoids reaction imbalance during monomer polymerization, ensuring that the molecular weight of the polymer is in a low to medium range, and that the polymer can dissolve or be uniformly dispersed in water. This ensures the basic tanning properties of the retanning agent and provides a basic firmness for the leather. Attached Figure Description

[0029] Figure 1 This is a flowchart of the preparation method of the acrylic retanning agent provided by the present invention.

[0030] Figure 2 The image shows genuine leather obtained by retanning with the acrylic retanning agent provided in Example 1. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] The first aspect of this invention provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0033] 55-65 parts water, 16-17.4 parts acrylic acid monomer, 2-2.6 parts maleic anhydride, 3-5 parts acrylate monomer, 1-2 parts unsaturated dicarboxylic acid monoester, 5-7 parts functional monomer, 5-7 parts caprolactone-grafted hydroxyethyl acrylate, 2-3 parts oxidant, 2-3 parts reducing agent, 0.5-1 part chain transfer agent, 2-3 parts pH adjuster, and 0.1 part bactericide.

[0034] In the raw materials for preparing the aforementioned acrylic retanning agent, acrylic monomers provide carboxyl groups, which can form stable crosslinks with chromium ions in chrome-tanned leather. This is crucial for ensuring the bonding strength between the acrylic retanning agent and the leather base. Simultaneously, the presence of carboxyl groups gives the acrylic retanning agent good water solubility and dispersibility, facilitating its penetration during leather water treatment. Maleic anhydride can introduce additional crosslinking sites, strengthening the three-dimensional network structure of the polymer and thus improving the tear resistance of the leather. The ester groups in the acrylate monomers are hydrophobic, balancing the strong hydrophilicity of the polymer backbone in the retanning agent and preventing the leather from excessively absorbing water and softening after treatment. Furthermore, the polymer segments formed after copolymerization of acrylate monomers have a certain film-forming property, forming a thin and elastic film on the surface of leather fibers, enhancing the leather's abrasion resistance and tear resistance. The molecular structure of unsaturated dicarboxylic acid monoesters contains unsaturated double bonds and carboxyl groups, which can introduce additional cross-linking sites, enhance the physical entanglement and chemical bonding between retanning agents and dermal fibers, and further densify the bonding network between acrylic retanning agents and dermal fibers, thereby enhancing the firmness of the dermal leather.

[0035] The functional monomers enhance the cross-linking of acrylic retanning agents with leather fibers and chromium ions, further strengthening the dense three-dimensional network, thereby improving the firmness of the leather and giving it high tensile strength and high tear strength. The chain transfer agent reduces the molecular weight of the acrylic polymer in the retanning agent, giving the acrylic retanning agent good penetration properties. The acrylic retanning agent can fully penetrate into the leather fibers and fully cross-link with chromium ions and groups on the leather fibers, resulting in high firmness and fullness of the leather.

[0036] In the above-mentioned raw materials, the caprolactone-grafted hydroxyethyl acrylate is a graft copolymer formed by ring-opening polymerization of hydroxyethyl acrylate and caprolactone. Its molecular structure contains polyhydroxyl and ester groups with strong polarity, which can form high-density hydrogen bonds with the carboxyl and hydroxyl groups on the leather fibers during the leather drying process. This enables the acrylic retanning agent to achieve a three-dimensional network structure with chromium ions and leather fibers, resulting in high firmness and resilience of the leather. Furthermore, the tensile strength and tear resistance of the leather can also be significantly improved.

[0037] Furthermore, in an optional embodiment, the acrylic monomer is at least one of acrylic acid and methacrylic acid.

[0038] Specifically, acrylic acid has high reactivity and readily copolymerizes with acrylate monomers, functional monomers, and hydroxyethyl acrylate grafted with caprolactone, rapidly constructing the polymer backbone. Furthermore, the strong hydrophilicity of acrylic acid gives retanning agents excellent water solubility and dilution stability, facilitating rapid penetration into the leather fibers during leather water treatment and preventing clumping on the leather surface. The presence of methyl groups in the molecular structure of methacrylic acid provides steric hindrance, making the polymer backbone more rigid and reducing sagging and deformation of leather after long-term use, thus meeting the requirements of repeated sitting pressure in car seat cushions.

[0039] It should be noted that in the acrylic retanning agent provided by the present invention, the proportion of acrylic monomer is relatively high, which enables the molecular weight of the polymer in the acrylic retanning agent to be in the low to medium range, and the polymer can be dissolved or uniformly dispersed in water, thereby ensuring the basic tanning performance of the retanning agent and providing basic firmness for genuine leather.

[0040] Furthermore, in an optional embodiment, the acrylate monomer is at least one of methyl methacrylate and ethyl acrylate. The side chain structure of methyl methacrylate and ethyl acrylate can increase the flexible segments of the polymer, reduce the stiffness of the dermis, and thus improve the resilience of the dermis.

[0041] Furthermore, in an optional embodiment, the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester. The molecular structure of itaconic acid monobutyl ester contains unsaturated double bonds, allowing it to participate in free radical copolymerization. Moreover, the carboxyl groups in itaconic acid monobutyl ester can crosslink with chromium ions and form hydrogen bonds with hydroxyl and amino groups on leather fibers, thereby further densifying the polymer-leather fiber bonding network, enhancing the firmness of the leather, and improving its tensile and tear strength.

[0042] Furthermore, the long side chains of itaconic acid monobutyl ester are flexible, allowing it to physically entangle with leather fibers, increasing the strength of physical cross-linking and reducing fiber slippage. Even with repeated sitting pressure on leather-containing seat cushions over long periods, the fiber network maintains a stable structure, ensuring that car seat cushions do not collapse or deform over extended use. Moreover, the physical entanglement of itaconic acid monobutyl ester with leather fibers enables the dispersed leather fibers to form a tighter network. When the leather is subjected to localized external forces, the stress can be transferred to surrounding fibers through the entangled fibers, thus preventing fiber breakage caused by localized stress concentration and reducing the risk of leather cracking and damage.

[0043] Furthermore, in an optional embodiment, the functional monomer is at least one of acrylonitrile, hydroxy functional monomer, and N-hydroxymethylacrylamide.

[0044] Specifically, the acrylonitrile molecule contains a highly polar cyano group, which enhances the interaction between the retanning agent and the amino and hydroxyl groups in the leather fibers, thereby strengthening cross-linking. Furthermore, the electron-withdrawing effect of the cyano group makes the polymer backbone more rigid, thus improving the tensile and compressive strength of the leather and reducing tensile deformation after long-term pressure. The hydroxyl functional monomer provides the acrylic retanning agent with hydroxyl groups that react with the carboxyl groups on the leather fibers, further densifying the three-dimensional network and improving the bonding durability between the acrylic retanning agent and the leather. N-hydroxymethylacrylamide contains a hydroxymethyl group, which can undergo dehydration condensation with the amino groups on the leather fibers to form stable CN covalent bonds, further enhancing the bonding durability between the acrylic retanning agent and the leather.

[0045] Furthermore, in an optional embodiment, the hydroxyl functional monomer is a mixture of hydroxyethyl methacrylate and hydroxypropyl acrylate.

[0046] Specifically, hydroxyethyl methacrylate has high hydroxyl activity, which can form a dense cross-link with the active groups on the surface of dermal fibers, enhancing the abrasion resistance and tear resistance of the dermal surface. Hydroxypropyl acrylate, on the other hand, has a slightly longer molecular chain than hydroxyethyl methacrylate, making it more flexible. It can penetrate into the interior of dermal fibers to form deep cross-links and fill the cross-link gaps on the dermal surface, resulting in uniform strength throughout the dermal surface. This prevents the dermal surface from experiencing a decrease in tensile strength and tear resistance due to strength vacuum zones when subjected to external forces.

[0047] Furthermore, in an optional embodiment, the chain transfer agent is at least one of n-dodecyl mercaptoethanol and mercaptoethanol.

[0048] Specifically, the long alkyl chain of n-dodecyl mercaptan exhibits steric hindrance, which can disrupt the linear growth trend of the polymer backbone during chain transfer, promoting the branching of the molecular chain and forming a hyperbranched structure. The increased branching points provide more crosslinking sites, thereby densifying the bonding network between the acrylic retanning agent and the leather fibers, enhancing the firmness of the leather. Mercaptoethanol has higher reactivity than n-dodecyl mercaptan, rapidly capturing free radicals and effectively suppressing the risk of explosive polymerization. In redox-initiated systems, it can avoid excessive chain growth caused by rapid monomer polymerization. Furthermore, the hydroxyl groups (-OH) in the mercaptoethanol molecule can participate in copolymerization reactions and can be embedded into polymer segments during chain transfer, providing additional crosslinking sites.

[0049] Furthermore, in optional embodiments, the oxidant is at least one selected from ammonium persulfate, sodium persulfate, potassium persulfate, and tert-butyl hydroperoxide. The reducing agent is at least one selected from sodium bisulfite, ascorbic acid, sodium metabisulfite, Brügmann FF6, and Brügmann 1328. The oxidants and reducing agents described above can constitute a redox initiation system, lowering the initiation temperature and regulating the polymerization rate. Moreover, the oxidants and reducing agents can treat residual monomers, reducing the generation of irritating odors in acrylic retanning agents.

[0050] Furthermore, in an optional embodiment, the pH adjuster is at least one selected from sodium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonia, and sodium hydroxide. The pH adjuster is used to adjust the pH value of the finished acrylic retanning agent, enabling the acrylic retanning agent to meet the requirements of the genuine leather retanning process.

[0051] Furthermore, in an optional embodiment, the bactericide can be an isothiazolinone bactericide. Isothiazolinone bactericides are broad-spectrum and highly effective, require low dosage, and have good compatibility with acrylic polymer systems, thus not affecting the performance of acrylic retanning agents.

[0052] like Figure 1 As shown, a second aspect of the present invention provides a method for preparing the aforementioned acrylic retanning agent, comprising the following steps:

[0053] S001. Add 26-36 parts of water to the reactor, and then raise the temperature of the reactor to 32-37°C.

[0054] S002. Add 15 parts of water to the stirrer, then add acrylic monomer, maleic anhydride, acrylate monomer, unsaturated dicarboxylic acid monoester, functional monomer, caprolactone-grafted hydroxyethyl acrylate and chain transfer agent to the stirrer. After stirring and dispersing evenly, divide the obtained monomer mixture into 3 parts, namely monomer mixture a, monomer mixture b and monomer mixture c.

[0055] S003. Mix 1.8 to 2.8 parts of oxidant with 6 parts of water until homogeneous, and divide the resulting oxidant solution into 3 equal parts, namely oxidant solution a, oxidant solution b and oxidant solution c; mix 0.2 parts of oxidant with 1 part of water until homogeneous to obtain oxidant solution d;

[0056] S004. Mix 1.8 to 2.8 parts of reducing agent with 6 parts of deionized water evenly, and divide the resulting reducing agent solution into 3 equal parts, namely reducing agent solution a, reducing agent solution b and reducing agent solution c; mix 0.2 parts of reducing agent with 1 part of water evenly to obtain reducing agent solution d;

[0057] S005. Add monomer mixture a to the reactor in step S001, then add oxidant solution a, stir and disperse evenly, add reducing agent solution a to the reactor, and raise the temperature inside the reactor to 85-90°C. After the temperature rise is complete, lower the temperature inside the reactor to 50-55°C.

[0058] S006. Continue to add monomer mixture b into the reactor, then add oxidant solution b, stir and disperse evenly, then add reducing agent solution b into the reactor and raise the temperature inside the reactor to 85-90℃. After the temperature rise is complete, lower the temperature inside the reactor to 55-60℃.

[0059] S007. Continue to add monomer mixture c to the reactor, then add oxidant solution c, stir and disperse evenly, then add reducing agent solution c to the reactor and raise the temperature inside the reactor to 85-90℃. After the temperature rise is complete, keep it at that temperature for 180 minutes.

[0060] S008. After the heat preservation is completed, the temperature inside the reactor is reduced to 60-63℃. Then, oxidant solution d and reducing agent solution d are added to the reactor to remove residual monomers. After the oxidant solution d and reducing agent solution d are added, the reactor is kept warm for another 30 minutes.

[0061] S009. Add pH adjuster and bactericide to the reaction vessel, stir and mix evenly to obtain an acrylic retanning agent with a pH value of 5-6.

[0062] The preparation method provided by this invention adopts a seed semi-continuous dripping process. By dripping monomer mixture, oxidant and reducing agent in three steps, the reaction imbalance during monomer polymerization can be avoided, so that the molecular weight of polymer can be in a low to medium range, and the polymer can be dissolved or uniformly dispersed in water. This ensures the basic tanning performance of retanning agent and provides basic firmness for leather.

[0063] To further illustrate the acrylic retanning agent provided by the present invention, the following examples and comparative examples are provided. The caprolactone-grafted hydroxyethyl acrylate used in the following examples and comparative examples was manufactured by Daissai Road Co., Ltd., Japan.

[0064] Example 1

[0065] This embodiment provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0066] 60 parts water, 17.4 parts acrylic acid monomer, 3 parts acrylate monomer, 2 parts maleic anhydride, 1.5 parts unsaturated dicarboxylic acid monoester, 5 parts functional monomer, 6 parts caprolactone-grafted hydroxyethyl acrylate, 2 parts oxidant (ammonium persulfate), 2 parts reducing agent (sodium bisulfite), 0.5 parts chain transfer agent (n-dodecyl mercaptan), 2 parts pH adjuster (sodium carbonate), and 0.1 parts bactericide (isothiazolinone bactericide).

[0067] The acrylic monomer is a mixture of acrylic acid and methacrylic acid, with 7.4 parts acrylic acid and 10 parts methacrylic acid.

[0068] The acrylate monomers are a mixture of methyl methacrylate and ethyl acrylate, with 2 parts methyl methacrylate and 1 part ethyl acrylate.

[0069] Among them, the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester.

[0070] The functional monomers are a mixture of acrylonitrile, hydroxyethyl methacrylate, hydroxypropyl acrylate, and N-hydroxymethylacrylamide, with acrylonitrile comprising 2 parts, hydroxyethyl methacrylate comprising 1 part, hydroxypropyl acrylate comprising 1 part, and N-hydroxymethylacrylamide comprising 1 part.

[0071] This embodiment also provides a method for preparing the aforementioned acrylic retanning agent, comprising the following steps:

[0072] S001. Add 31 parts of water to the reactor, and then raise the temperature of the reactor to 35°C.

[0073] S002. Add 15 parts of water to the stirrer, then add acrylic monomer, maleic anhydride, acrylate monomer, unsaturated dicarboxylic acid monoester, functional monomer, caprolactone-grafted hydroxyethyl acrylate and chain transfer agent to the stirrer. After stirring and dispersing evenly, divide the obtained monomer mixture into 3 parts, namely monomer mixture a, monomer mixture b and monomer mixture c.

[0074] S003. Mix 1.8 parts of oxidant and 6 parts of water evenly, and divide the resulting oxidant solution into 3 equal parts, namely oxidant solution a, oxidant solution b and oxidant solution c; mix 0.2 parts of oxidant and 1 part of water evenly to obtain oxidant solution d;

[0075] S004. Mix 1.8 parts of reducing agent and 6 parts of deionized water evenly, and divide the resulting reducing agent solution into 3 equal parts, namely reducing agent solution a, reducing agent solution b and reducing agent solution c; mix 0.2 parts of reducing agent and 1 part of water evenly to obtain reducing agent solution d;

[0076] S005. Add monomer mixture a to the reactor in step S001, then add oxidant solution a, stir and disperse evenly, add reducing agent solution a to the reactor, and raise the temperature inside the reactor to 85°C. After the temperature rise is complete, lower the temperature inside the reactor to 50°C.

[0077] S006. Continue to add monomer mixture b into the reactor, then add oxidant solution b, stir and disperse evenly, then add reducing agent solution b into the reactor and raise the temperature inside the reactor to 85°C. After the temperature rise is complete, lower the temperature inside the reactor to 55°C.

[0078] S007. Continue to add monomer mixture c to the reactor, then add oxidant solution c, stir and disperse evenly, then add reducing agent solution c to the reactor and raise the temperature inside the reactor to 85℃. After the temperature rise is complete, keep it at that temperature for 180 minutes.

[0079] S008. After the heat preservation is completed, the temperature inside the reactor is reduced to 60°C. Then, oxidant solution d and reducing agent solution d are added to the reactor to remove residual monomers. After the oxidant solution d and reducing agent solution d are added, the reactor is kept warm for another 30 minutes.

[0080] S009. Add pH adjuster and bactericide to the reaction vessel, stir and mix evenly to obtain acrylic retanning agent with pH value of 5.2.

[0081] Example 2

[0082] This embodiment provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0083] 55 parts water, 16 parts acrylic acid monomer, 4 parts acrylate monomer, 2 parts maleic anhydride, 1 part unsaturated dicarboxylic acid monoester, 6 parts functional monomer, 5 parts caprolactone-grafted hydroxyethyl acrylate, 2.5 parts oxidant (ammonium persulfate), 2.5 parts reducing agent (sodium bisulfite), 0.8 parts chain transfer agent (mercaptoethanol), 2.5 parts pH adjuster (sodium carbonate), and 0.1 parts bactericide (isothiazolinone bactericide).

[0084] The acrylic monomer is a mixture of acrylic acid and methacrylic acid, with 7.4 parts of acrylic acid and 8.6 parts of methacrylic acid.

[0085] The acrylate monomers are a mixture of methyl methacrylate and ethyl acrylate, with 2 parts methyl methacrylate and 2 parts ethyl acrylate.

[0086] Among them, the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester.

[0087] The functional monomers are a mixture of acrylonitrile, hydroxyethyl methacrylate, hydroxypropyl acrylate, and N-hydroxymethylacrylamide, with acrylonitrile comprising 2 parts, hydroxyethyl methacrylate comprising 1 part, hydroxypropyl acrylate comprising 1 part, and N-hydroxymethylacrylamide comprising 2 parts.

[0088] This embodiment also provides a method for preparing the aforementioned acrylic retanning agent, comprising the following steps:

[0089] S001. Add 26 parts of water to the reactor, and then raise the temperature of the reactor to 35°C.

[0090] S002. Add 15 parts of water to the stirrer, then add acrylic monomer, maleic anhydride, acrylate monomer, unsaturated dicarboxylic acid monoester, functional monomer, caprolactone-grafted hydroxyethyl acrylate and chain transfer agent to the stirrer. After stirring and dispersing evenly, divide the obtained monomer mixture into 3 parts, namely monomer mixture a, monomer mixture b and monomer mixture c.

[0091] S003. Mix 2.3 parts of oxidant and 6 parts of water evenly, and divide the resulting oxidant solution into 3 equal parts, namely oxidant solution a, oxidant solution b and oxidant solution c; mix 0.2 parts of oxidant and 1 part of water evenly to obtain oxidant solution d;

[0092] S004. Mix 2.3 parts of reducing agent and 6 parts of deionized water evenly, and divide the resulting reducing agent solution into 3 equal parts, namely reducing agent solution a, reducing agent solution b and reducing agent solution c; mix 0.2 parts of reducing agent and 1 part of water evenly to obtain reducing agent solution d;

[0093] S005. Add monomer mixture a to the reactor in step S001, then add oxidant solution a, stir and disperse evenly, add reducing agent solution a to the reactor, and raise the temperature inside the reactor to 85°C. After the temperature rise is complete, lower the temperature inside the reactor to 50°C.

[0094] S006. Continue to add monomer mixture b into the reactor, then add oxidant solution b, stir and disperse evenly, then add reducing agent solution b into the reactor and raise the temperature inside the reactor to 85°C. After the temperature rise is complete, lower the temperature inside the reactor to 55°C.

[0095] S007. Continue to add monomer mixture c to the reactor, then add oxidant solution c, stir and disperse evenly, then add reducing agent solution c to the reactor and raise the temperature inside the reactor to 85℃. After the temperature rise is complete, keep it at that temperature for 180 minutes.

[0096] S008. After the heat preservation is completed, the temperature inside the reactor is reduced to 60°C. Then, oxidant solution d and reducing agent solution d are added to the reactor to remove residual monomers. After the oxidant solution d and reducing agent solution d are added, the reactor is kept warm for another 30 minutes.

[0097] S009. Add pH adjuster and bactericide to the reaction vessel, stir and mix evenly to obtain acrylic retanning agent with pH value of 5.4.

[0098] Example 3

[0099] This embodiment provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0100] 65 parts water, 17.4 parts acrylic acid monomer, 5 parts acrylate monomer, 2.6 parts maleic anhydride, 2 parts unsaturated dicarboxylic acid monoester, 7 parts functional monomer, 7 parts caprolactone-grafted hydroxyethyl acrylate, 3 parts oxidant (ammonium persulfate), 3 parts reducing agent (sodium bisulfite), 1 part chain transfer agent (n-dodecyl mercaptan), 2 parts pH adjuster (sodium carbonate), and 0.1 parts bactericide (isothiazolinone bactericide).

[0101] The acrylic monomer is a mixture of acrylic acid and methacrylic acid, with 7.4 parts acrylic acid and 10 parts methacrylic acid.

[0102] The acrylate monomers are a mixture of methyl methacrylate and ethyl acrylate, with methyl methacrylate comprising 3 parts and ethyl acrylate comprising 2 parts.

[0103] Among them, the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester.

[0104] The functional monomers are a mixture of acrylonitrile, hydroxyethyl methacrylate, hydroxypropyl acrylate, and N-hydroxymethylacrylamide, with acrylonitrile comprising 3 parts, hydroxyethyl methacrylate comprising 1 part, hydroxypropyl acrylate comprising 1 part, and N-hydroxymethylacrylamide comprising 2 parts.

[0105] This embodiment also provides a method for preparing the aforementioned acrylic retanning agent, comprising the following steps:

[0106] S001. Add 36 parts of water to the reactor, and then raise the temperature of the reactor to 35°C.

[0107] S002. Add 15 parts of water to the stirrer, then add acrylic monomer, maleic anhydride, acrylate monomer, unsaturated dicarboxylic acid monoester, functional monomer, caprolactone-grafted hydroxyethyl acrylate and chain transfer agent to the stirrer. After stirring and dispersing evenly, divide the obtained monomer mixture into 3 parts, namely monomer mixture a, monomer mixture b and monomer mixture c.

[0108] S003. Mix 2.8 parts of oxidant and 6 parts of water evenly, and divide the resulting oxidant solution evenly into 3 parts, namely oxidant solution a, oxidant solution b and oxidant solution c; mix 0.2 parts of oxidant and 1 part of water evenly to obtain oxidant solution d;

[0109] S004. Mix 2.8 parts of reducing agent and 6 parts of deionized water evenly, and divide the resulting reducing agent solution into 3 equal parts, namely reducing agent solution a, reducing agent solution b and reducing agent solution c; mix 0.2 parts of reducing agent and 1 part of water evenly to obtain reducing agent solution d;

[0110] S005. Add monomer mixture a to the reactor in step S001, then add oxidant solution a, stir and disperse evenly, add reducing agent solution a to the reactor, and raise the temperature inside the reactor to 85°C. After the temperature rise is complete, lower the temperature inside the reactor to 50°C.

[0111] S006. Continue to add monomer mixture b into the reactor, then add oxidant solution b, stir and disperse evenly, then add reducing agent solution b into the reactor and raise the temperature inside the reactor to 85°C. After the temperature rise is complete, lower the temperature inside the reactor to 55°C.

[0112] S007. Continue to add monomer mixture c to the reactor, then add oxidant solution c, stir and disperse evenly, then add reducing agent solution c to the reactor and raise the temperature inside the reactor to 85℃. After the temperature rise is complete, keep it at that temperature for 180 minutes.

[0113] S008. After the heat preservation is completed, the temperature inside the reactor is reduced to 60°C. Then, oxidant solution d and reducing agent solution d are added to the reactor to remove residual monomers. After the oxidant solution d and reducing agent solution d are added, the reactor is kept warm for another 30 minutes.

[0114] S009. Add pH adjuster and bactericide to the reaction vessel, stir and mix evenly to obtain acrylic retanning agent with pH value of 5.2.

[0115] Comparative Example 1

[0116] This comparative example provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0117] 60 parts water, 17.4 parts acrylic acid monomer, 3 parts acrylate monomer, 2 parts maleic anhydride, 1.5 parts unsaturated dicarboxylic acid monoester, 5 parts functional monomer, 3 parts caprolactone-grafted hydroxyethyl acrylate, 2 parts oxidant (ammonium persulfate), 2 parts reducing agent (sodium bisulfite), 0.5 parts chain transfer agent (n-dodecyl mercaptan), 2 parts pH adjuster (sodium carbonate), and 0.1 parts bactericide (isothiazolinone bactericide).

[0118] The acrylic monomer is a mixture of acrylic acid and methacrylic acid, with 7.4 parts acrylic acid and 10 parts methacrylic acid.

[0119] The acrylate monomers are a mixture of methyl methacrylate and ethyl acrylate, with 2 parts methyl methacrylate and 1 part ethyl acrylate.

[0120] Among them, the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester.

[0121] The functional monomers are a mixture of acrylonitrile, hydroxyethyl methacrylate, hydroxypropyl acrylate, and N-hydroxymethylacrylamide, with acrylonitrile comprising 2 parts, hydroxyethyl methacrylate comprising 1 part, hydroxypropyl acrylate comprising 1 part, and N-hydroxymethylacrylamide comprising 1 part.

[0122] This comparative example also provides a method for preparing an acrylic retanning agent, which is the same as the method provided in Example 1.

[0123] Comparative Example 2

[0124] This comparative example provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0125] 60 parts water, 17.4 parts acrylic acid monomer, 3 parts acrylate monomer, 2 parts maleic anhydride, 1.5 parts unsaturated dicarboxylic acid monoester, 5 parts functional monomer, 9 parts caprolactone-grafted hydroxyethyl acrylate, 2 parts oxidant (ammonium persulfate), 2 parts reducing agent (sodium bisulfite), 0.5 parts chain transfer agent (n-dodecyl mercaptan), 2 parts pH adjuster (sodium carbonate), and 0.1 parts bactericide (isothiazolinone bactericide).

[0126] The acrylic monomer is a mixture of acrylic acid and methacrylic acid, with 7.4 parts acrylic acid and 10 parts methacrylic acid.

[0127] The acrylate monomers are a mixture of methyl methacrylate and ethyl acrylate, with 2 parts methyl methacrylate and 1 part ethyl acrylate.

[0128] Among them, the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester.

[0129] The functional monomers are a mixture of acrylonitrile, hydroxyethyl methacrylate, hydroxypropyl acrylate, and N-hydroxymethylacrylamide, with acrylonitrile comprising 2 parts, hydroxyethyl methacrylate comprising 1 part, hydroxypropyl acrylate comprising 1 part, and N-hydroxymethylacrylamide comprising 1 part.

[0130] This comparative example also provides a method for preparing an acrylic retanning agent, which is the same as the method provided in Example 1.

[0131] Comparative Example 3

[0132] This comparative example provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0133] 60 parts water, 17.4 parts acrylic acid monomer, 2 parts maleic anhydride, 3 parts acrylate monomer, 5 parts functional monomer, 6 parts caprolactone-grafted hydroxyethyl acrylate, 2 parts oxidant (ammonium persulfate), 2 parts reducing agent (sodium bisulfite), 0.5 parts chain transfer agent (n-dodecyl mercaptan), 2 parts pH adjuster (sodium carbonate), 0.1 parts bactericide (isothiazolinone bactericide).

[0134] The acrylic monomer is a mixture of acrylic acid and methacrylic acid, with 7.4 parts acrylic acid and 10 parts methacrylic acid.

[0135] The acrylate monomers are a mixture of methyl methacrylate and ethyl acrylate, with 2 parts methyl methacrylate and 1 part ethyl acrylate.

[0136] The functional monomers are a mixture of acrylonitrile, hydroxyethyl methacrylate, hydroxypropyl acrylate, and N-hydroxymethylacrylamide, with acrylonitrile comprising 2 parts, hydroxyethyl methacrylate comprising 1 part, hydroxypropyl acrylate comprising 1 part, and N-hydroxymethylacrylamide comprising 1 part.

[0137] This comparative example also provides a method for preparing an acrylic retanning agent, which is the same as the method provided in Example 1.

[0138] Comparative Example 4

[0139] This comparative example provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0140] 60 parts water, 17.4 parts acrylic acid monomer, 2 parts maleic anhydride, 3 parts acrylate monomer, 3 parts unsaturated dicarboxylic acid monoester, 5 parts functional monomer, 6 parts caprolactone-grafted hydroxyethyl acrylate, 2 parts oxidant (ammonium persulfate), 2 parts reducing agent (sodium bisulfite), 0.5 parts chain transfer agent (n-dodecyl mercaptan), 2 parts pH adjuster (sodium carbonate), and 0.1 parts bactericide (isothiazolinone bactericide).

[0141] The acrylic monomer is a mixture of acrylic acid and methacrylic acid, with 7.4 parts acrylic acid and 10 parts methacrylic acid.

[0142] The acrylate monomers are a mixture of methyl methacrylate and ethyl acrylate, with 2 parts methyl methacrylate and 1 part ethyl acrylate.

[0143] Among them, the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester.

[0144] The functional monomers are a mixture of acrylonitrile, hydroxyethyl methacrylate, hydroxypropyl acrylate, and N-hydroxymethylacrylamide, with acrylonitrile comprising 2 parts, hydroxyethyl methacrylate comprising 1 part, hydroxypropyl acrylate comprising 1 part, and N-hydroxymethylacrylamide comprising 1 part.

[0145] This comparative example also provides a method for preparing an acrylic retanning agent, which is the same as the method provided in Example 1.

[0146] Comparative Example 5

[0147] This comparative example provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0148] 60 parts water, 17.4 parts acrylic acid monomer, 2 parts maleic anhydride, 3 parts acrylate monomer, 1.5 parts unsaturated dicarboxylic acid monoester, 5 parts functional monomer, 6 parts caprolactone-grafted hydroxyethyl acrylate, 2 parts oxidant (ammonium persulfate), 2 parts reducing agent (sodium bisulfite), 0.5 parts chain transfer agent (n-dodecyl mercaptan), 2 parts pH adjuster (sodium carbonate), and 0.1 parts bactericide (isothiazolinone bactericide).

[0149] The acrylic monomer is a mixture of acrylic acid and methacrylic acid, with 7.4 parts acrylic acid and 10 parts methacrylic acid.

[0150] The acrylate monomers are a mixture of methyl methacrylate and ethyl acrylate, with 2 parts methyl methacrylate and 1 part ethyl acrylate.

[0151] Among them, the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester.

[0152] The functional monomers are a mixture of acrylonitrile, hydroxyethyl methacrylate, and N-hydroxymethylacrylamide, with acrylonitrile comprising 2 parts, hydroxyethyl methacrylate comprising 2 parts, and N-hydroxymethylacrylamide comprising 1 part.

[0153] This comparative example also provides a method for preparing an acrylic retanning agent, which is the same as the method provided in Example 1.

[0154] Comparative Example 6

[0155] This comparative example provides an acrylic retanning agent, the raw materials for which, by weight, are:

[0156] 60 parts water, 17.4 parts acrylic acid monomer, 2 parts maleic anhydride, 3 parts acrylate monomer, 1.5 parts unsaturated dicarboxylic acid monoester, 5 parts functional monomer, 6 parts caprolactone-grafted hydroxyethyl acrylate, 2 parts oxidant (ammonium persulfate), 2 parts reducing agent (sodium bisulfite), 0.5 parts chain transfer agent (n-dodecyl mercaptan), 2 parts pH adjuster (sodium carbonate), and 0.1 parts bactericide (isothiazolinone bactericide).

[0157] The acrylic monomer is a mixture of acrylic acid and methacrylic acid, with 7.4 parts acrylic acid and 10 parts methacrylic acid.

[0158] The acrylate monomers are a mixture of methyl methacrylate and ethyl acrylate, with 2 parts methyl methacrylate and 1 part ethyl acrylate.

[0159] Among them, the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester.

[0160] The functional monomers are a mixture of acrylonitrile, hydroxypropyl acrylate, and N-hydroxymethylacrylamide, with acrylonitrile comprising 2 parts, hydroxypropyl acrylate comprising 2 parts, and N-hydroxymethylacrylamide comprising 1 part.

[0161] This comparative example also provides a method for preparing an acrylic retanning agent, which is the same as the method provided in Example 1.

[0162] Comparative Example 7

[0163] This comparative example provides an acrylic retanning agent, which, by weight, uses the same raw materials as in Example 1.

[0164] This comparative example also provides a method for preparing the aforementioned acrylic retanning agent, comprising the following steps:

[0165] S001. Add 31 parts of water to the reactor, and then raise the temperature of the reactor to 35°C.

[0166] S002. Add 15 parts of water to the stirrer, then add acrylic monomer, maleic anhydride, acrylate monomer, unsaturated dicarboxylic acid monoester, functional monomer, caprolactone-grafted hydroxyethyl acrylate and chain transfer agent to the stirrer, stir and disperse evenly to obtain the monomer mixture.

[0167] S003. Mix 1.8 parts of oxidant and 6 parts of water evenly to obtain oxidant solution e; mix 0.2 parts of oxidant and 1 part of water evenly to obtain oxidant solution f;

[0168] S004. Mix 1.8 parts of reducing agent and 6 parts of deionized water evenly to obtain reducing agent solution e; mix 0.2 parts of reducing agent and 1 part of water evenly to obtain reducing agent solution f;

[0169] S005. Add the monomer mixture to the reactor in step S001, then add the oxidant solution e, stir and disperse evenly, add the reducing agent solution e to the reactor, and raise the temperature inside the reactor to 85°C. After the temperature rise is complete, keep it at that temperature for 180 minutes.

[0170] S006. After the heat preservation is completed, the temperature inside the reactor is reduced to 60°C. Then, oxidant solution f and reducing agent solution f are added to the reactor to remove residual monomers. After the oxidant solution f and reducing agent solution f are added, the reactor is kept warm for another 30 minutes.

[0171] S007. After the heat preservation is completed, add pH adjuster and bactericide to the reaction vessel, stir and mix evenly to obtain acrylic retanning agent with a pH value of 5.4.

[0172] Comparative Example 8

[0173] This comparative example uses commercially available acrylic retanning agents.

[0174] The acrylic retanning agents provided in the above embodiments and comparative examples were subjected to performance tests. Before the tests, the acrylic retanning agents provided in the above embodiments and comparative examples were used for retanning genuine leather. The retanning process is shown in Table 1 below. After the retanning process, the genuine leather was dried for one week before testing. The test methods for each test are shown in Table 2 below, and the test results are shown in Tables 3 and 4 below.

[0175] Table 1:

[0176]

[0177] Table 2

[0178]

[0179] Table 3

[0180]

[0181] Table 4

[0182]

[0183] Note: Comparative Example 9 in Table 4 is a retanning and filling treatment without the use of acrylic retanning agent.

[0184] As can be seen from Tables 3 and 4 above, compared with the respective comparative examples, the genuine leather retanned with the acrylic retanning agents provided in Examples 1 to 3 has higher tear strength and tensile strength (e.g., ...). Figure 2 As shown in the figure, the good fullness indicates that the acrylic retanning agent provided by the present invention can achieve a three-dimensional network structure in which the acrylic retanning agent, chromium ions, and leather fibers are cross-linked, so that the leather has high firmness and resilience, and the tensile strength and tear strength of the leather can also be significantly improved.

[0185] Furthermore, comparing Comparative Example 1 with Example 1, it was found that the tear strength and tensile strength of the leather treated with the acrylic retanning agent provided in Comparative Example 1 decreased, and the fullness changed from good to average. This is because the amount of caprolactone-grafted hydroxyethyl acrylate in the acrylic retanning agent provided in Comparative Example 1 was too small, resulting in a decrease in crosslinking density.

[0186] Furthermore, comparing Comparative Example 2 with Example 1, it was found that the tear strength and tensile strength of the leather treated with the acrylic retanning agent provided in Comparative Example 2 decreased, and the fullness changed from good to average. This is because the amount of caprolactone-grafted hydroxyethyl acrylate in the acrylic retanning agent provided in Comparative Example 2 was too high, which made it easy for self-polymerization to occur between molecules, resulting in a reduction in the effective binding sites of caprolactone-grafted hydroxyethyl acrylate with the leather fibers and a decrease in crosslinking density.

[0187] Furthermore, comparing Comparative Example 3 with Example 1, it was found that the tear strength and tensile strength of the leather retanned with the acrylic retanning agent provided in Comparative Example 3 decreased, and the fullness changed from good to poor. This is because the acrylic retanning agent provided in Comparative Example 3 did not use itaconic acid monobutyl ester. The long, flexible side chains of itaconic acid monobutyl ester can form physical entanglement with leather fibers, improve the physical cross-linking strength, and reduce fiber slippage. Without itaconic acid monobutyl ester, the binding force between leather fibers is insufficient, and relative displacement easily occurs under stress, resulting in a decrease in mechanical strength; at the same time, the filling effect of physical entanglement disappears, making the fullness of the leather worse.

[0188] Furthermore, comparing Comparative Example 4 with Example 1, it was found that the tear strength and tensile strength of the leather treated with the acrylic retanning agent provided in Comparative Example 4 decreased, and the fullness changed from good to average. This is because the amount of itaconic acid monobutyl ester in the acrylic retanning agent provided in Comparative Example 4 was too high. Excessive physical winding will lead to an overly dense fiber network, which will reduce the flexibility of the leather. In addition, when the amount of itaconic acid monobutyl ester is excessive, the monomer is easy to remain, affecting the uniformity of crosslinking, so that the mechanical strength and fullness of the leather cannot be improved.

[0189] Furthermore, comparing Comparative Example 5 with Example 1, it was found that the tear strength and tensile strength of the leather retanned with the acrylic retanning agent provided in Comparative Example 5 decreased, and the fullness changed from good to average. This is because the acrylic retanning agent provided in Comparative Example 5 lacks hydroxypropyl acrylate, a hydroxy functional monomer. Without hydroxypropyl acrylate, the hydroxy functional monomer can only form surface crosslinks, resulting in insufficient crosslinking within the leather. When the leather is subjected to external force, a strength vacuum zone exists, leading to a decrease in tensile and tear strength.

[0190] Furthermore, comparing Comparative Example 6 with Example 1, it was found that the tear strength and tensile strength of the leather retanned with the acrylic retanning agent provided in Comparative Example 6 decreased, and the fullness deteriorated from good to average. This is because the acrylic retanning agent provided in Comparative Example 6 lacks hydroxyethyl methacrylate, a hydroxy functional monomer, which prevents the formation of dense cross-links on the leather surface, thus weakening the abrasion resistance and tear resistance of the leather surface. Simultaneously, the lack of dense filling on the leather surface also affects the fullness.

[0191] Furthermore, comparing Comparative Example 7 with Example 1, it was found that the tear strength and tensile strength of the leather treated with the acrylic retanning agent provided in Comparative Example 7 decreased significantly, and the fullness and permeability deteriorated. This is because in the preparation method of Comparative Example 7, the monomer mixture was added all at once, which caused the monomers to polymerize rapidly, resulting in excessively large molecular weights and uneven distribution. As a result, the large molecular weight retanning agent could not penetrate into the interior of the leather, and thus could not play the role of filling the leather fibers and improving mechanical strength.

[0192] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An acrylic re-tanning agent, characterized in that, The raw materials for its preparation, by weight, include: The composition includes 55-65 parts water, 16-17.4 parts acrylic acid monomer, 2-2.6 parts maleic anhydride, 3-5 parts acrylate monomer, 1-2 parts unsaturated dicarboxylic acid monoester, 5-7 parts functional monomer, 5-7 parts caprolactone-grafted hydroxyethyl acrylate, 2-3 parts oxidant, 2-3 parts reducing agent, 0.5-1 part chain transfer agent, 2-3 parts pH adjuster, and 0.1 part bactericide; wherein the unsaturated dicarboxylic acid monoester is itaconic acid monobutyl ester. The functional monomer is a mixture of acrylonitrile, hydroxyethyl methacrylate, hydroxypropyl acrylate, and N-hydroxymethylacrylamide; The preparation method of the acrylic retanning agent includes the following steps: S001. Add 26 to 36 parts of water to the reactor, and then raise the temperature inside the reactor to 32 to 37°C. S002. Add 15 parts of water to the stirrer, then add acrylic monomer, maleic anhydride, acrylate monomer, unsaturated dicarboxylic acid monoester, functional monomer, caprolactone-grafted hydroxyethyl acrylate and chain transfer agent to the stirrer. After stirring and dispersing evenly, divide the obtained monomer mixture into 3 parts, namely monomer mixture a, monomer mixture b and monomer mixture c. S003. Mix 1.8 to 2.8 parts of oxidant with 6 parts of water until homogeneous, and divide the resulting oxidant solution into 3 equal parts, namely oxidant solution a, oxidant solution b and oxidant solution c; mix 0.2 parts of oxidant with 1 part of water until homogeneous to obtain oxidant solution d; S004. Mix 1.8 to 2.8 parts of reducing agent with 6 parts of deionized water evenly, and divide the resulting reducing agent solution into 3 equal parts, namely reducing agent solution a, reducing agent solution b and reducing agent solution c; mix 0.2 parts of reducing agent with 1 part of water evenly to obtain reducing agent solution d; S005. Add monomer mixture a to the reactor in step S001, then add oxidant solution a, stir and disperse evenly, add reducing agent solution a to the reactor, and raise the temperature inside the reactor to 85-90°C. After the temperature rise is complete, lower the temperature inside the reactor to 50-55°C. S006. Continue to add monomer mixture b into the reactor, then add oxidant solution b, stir and disperse evenly, then add reducing agent solution b into the reactor and raise the temperature inside the reactor to 85-90℃. After the temperature rise is complete, lower the temperature inside the reactor to 55-60℃. S007. Continue to add monomer mixture c to the reactor, then add oxidant solution c, stir and disperse evenly, then add reducing agent solution c to the reactor and raise the temperature inside the reactor to 85-90℃. After the temperature rise is complete, keep it at that temperature for 180 minutes. S008. After the heat preservation is completed, the temperature inside the reactor is reduced to 60-63°C, and then oxidant solution d and reducing agent solution d are added to the reactor to remove residual monomers. S009. Add pH adjuster and bactericide to the reaction vessel, stir and mix evenly to obtain the acrylic retanning agent.

2. The acrylic retanning agent according to claim 1, characterized in that, The acrylic monomer is at least one of acrylic acid and methacrylic acid.

3. The acrylic re-tanning agent according to claim 1, characterized in that, The acrylate monomer is at least one of methyl methacrylate and ethyl acrylate.

4. The acrylic re-tanning agent according to claim 1, characterized in that, The chain transfer agent is at least one of n-dodecyl mercaptoethanol and mercaptoethanol.

5. The acrylic re-tanning agent according to claim 1, characterized in that, The oxidant is at least one of ammonium persulfate, sodium persulfate, potassium persulfate, and tert-butyl hydroperoxide.

6. The acrylic re-tanning agent according to claim 1, characterized in that, The reducing agent is at least one of sodium bisulfite, ascorbic acid, sodium metabisulfite, and Brügmann FF6.

Images