A self-crosslinking multi-component graft copolymer paper strengthening agent and preparation method

Abstract

This invention discloses a self-crosslinking multi-component graft copolymer paper reinforcing agent and its preparation method, belonging to the field of papermaking technology. Using carboxymethyl cellulose as a dispersant, isopropanol as a chain transfer agent, and deionized water as a solvent, methacryloyloxyethyltrimethylammonium chloride, acrylamide, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid are polymerized at 50-80°C under the action of an initiator. The mass ratio of carboxymethyl cellulose, methacryloyloxyethyltrimethylammonium chloride, acrylamide, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid is (1-10):(1-5):(10-30):(1-10):(1-5). The pH of the resulting reaction solution is then adjusted to 4.5-5.5 to obtain the self-crosslinking multi-component graft copolymer paper reinforcing agent. This invention increases the stability of the crosslinking structure of the reinforcing agent, enhances the adhesive force, and significantly improves the strength and water resistance of paper.

Description

Technical Field

[0001] This invention belongs to the field of papermaking technology, specifically relating to a self-crosslinking multi-component graft copolymer paper reinforcing agent and its preparation method. Background Technology

[0002] With the rapid development of the paper industry, the requirements for paper quality and performance are constantly increasing, thus necessitating paper reinforcement technology. Paper reinforcement technology uses a series of processes and methods to improve the physical, chemical, and printability properties of paper to meet the high quality requirements of various fields. Paper strengthening agents are chemical additives specifically designed to improve the physical properties of paper. They are usually in the form of liquid coatings, composed of various chemicals, and possess characteristics such as enhancing paper toughness, water resistance, and anti-aging properties. During the papermaking process, adding paper strengthening agents to the pulp or coating the paper surface can significantly improve the tensile strength, tear strength, folding endurance, and bursting strength of the paper. Therefore, as a key auxiliary agent for improving the physical properties of paper, the research and application of paper strengthening agents have received widespread attention.

[0003] In existing paper strengthening technologies, commonly used strengthening agents have various limitations. For example, single-component strengthening agents have limited effects and are difficult to comprehensively improve all performance indicators of paper. Some strengthening agents only improve a specific property of paper, while having a weak effect on improving other important properties. Furthermore, the preparation process of some strengthening agents is complex and cumbersome, resulting in high costs and hindering large-scale production and widespread application. In addition, some traditional strengthening agents can also have adverse environmental impacts, which is inconsistent with current green and environmentally friendly concepts.

[0004] In recent years, polymer-based paper reinforcing agents have attracted much attention due to their unique properties. However, existing polymer reinforcing agents often suffer from complex processes, high costs, and unstable performance during preparation. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a self-crosslinking multi-component graft copolymer paper reinforcing agent and its preparation method. The preparation process is simple, low-cost, and environmentally friendly. By copolymerizing each component monomer and grafting it with carboxymethyl cellulose, a crosslinking network structure is formed, which increases the stability of the crosslinking structure, increases the adhesion, and can significantly improve the strength and water resistance of paper.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing a self-crosslinking multi-component graft copolymer paper reinforcing agent involves using carboxymethyl cellulose as a dispersant, isopropanol as a chain transfer agent, and deionized water as a solvent. Methacryloxyethyltrimethylammonium chloride, acrylamide, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid are polymerized at 50-80°C under the action of an initiator. The mass ratio of carboxymethyl cellulose, methacryloxyethyltrimethylammonium chloride, acrylamide, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid is (1-10):(1-5):(10-30):(1-10):(1-5). The pH of the resulting reaction solution is then adjusted to 4.5-5.5 to obtain the self-crosslinking multi-component graft copolymer paper reinforcing agent.

[0008] A further improvement of the present invention is that:

[0009] Specifically, the following steps are included:

[0010] S1, carboxymethyl cellulose is dissolved in deionized water, then isopropanol is added and stirred to obtain the first mixed solution;

[0011] S2, dissolve methacryloyloxyethyltrimethylammonium chloride, acrylamide, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid in deionized water to obtain a second mixed solution;

[0012] The initiator was dissolved in deionized water to obtain an aqueous solution;

[0013] S3, simultaneously and uniformly add the second mixed solution and aqueous solution to the first mixed solution at 50-80℃, then keep it at 50-80℃, and then adjust the pH of the resulting reaction solution to 4.5-5.5 to obtain a self-crosslinking multi-component graft copolymer paper reinforcing agent.

[0014] The carboxymethyl cellulose described in S1 is 1%-5% of the total mass of methacryloyloxyethyltrimethylammonium chloride, acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid.

[0015] The initiator described in S2 is ammonium persulfate or potassium persulfate.

[0016] The ammonium persulfate or potassium persulfate is 0.1%-3% of the total mass of methacryloyloxyethyltrimethylammonium chloride, acrylamide, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid.

[0017] In the first mixed solution S1, the mass ratio of carboxymethyl cellulose to deionized water is (1-5):100.

[0018] In the second mixed solution S2, the mass ratio of acrylamide to deionized water is (1-3):(1-5), and in the aqueous solution, the mass ratio of initiator to deionized water is (0.1-1):(1-20).

[0019] The second mixed solution and aqueous solution in S3 are added at a time of 1-3 hours.

[0020] The heat preservation time described in S3 is 1-3 hours.

[0021] A self-crosslinking multi-component graft copolymer paper reinforcing agent obtained by the preparation method of any one of the above-described self-crosslinking multi-component graft copolymer paper reinforcing agents.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] This invention discloses a method for preparing a self-crosslinking multi-component graft copolymer paper reinforcing agent. CMC exhibits good dispersibility and water solubility, making the reaction system more stable and helping to ensure the consistency and reliability of the reinforcing agent's quality. It reduces performance fluctuations caused by reaction instability and improves the controllability of the preparation process. Isopropanol is used as a chain transfer agent, and an initiator initiates the polymerization reaction. The monomers methacryloyloxyethyltrimethylammonium chloride, acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid are copolymerized while simultaneously grafted with carboxymethyl cellulose. The initiator decomposes at 50-80°C to generate free radicals. These free radicals attack monomers containing carbon-carbon double bonds. Taking AM as an example, the free radical attacks the double bond of AM, causing it to open and forming a reactive monomeric free radical (·CH-CH(CONH2)). This monomeric free radical has high reactivity and will rapidly react with the double bonds of other monomer molecules. In systems with multiple monomers, they compete to participate in chain growth. The growing polymer chain reacts with the carboxymethyl cellulose (CMC) backbone. The CMC backbone has many active groups, such as hydroxyl groups (-OH). When the polymeric free radical approaches the CMC backbone, it will capture hydrogen atoms from the CMC hydroxyl groups to form water molecules. At the same time, the polymeric free radical and the CMC backbone are connected by forming new chemical bonds. When the growing polymeric free radical comes from AMPS... Upon encountering the hydroxyl groups on the CMC backbone, the reaction formula is: CH2-CH(CONHCH2C(CH3)2SO3H) + CMC-OH. This reaction forms CMC-O-CH2-CH(CONHCH2C(CH3)2SO3H), achieving grafting of AMPS segments onto the CMC backbone. This creates a cross-linked network structure, increasing the stability of the cross-linked structure and enhancing adhesion. The resulting paper strengthening agent exhibits excellent performance, moderate cost, environmental friendliness, and ease of operation. It provides good strengthening effect, stable performance, convenient use, and low cost, significantly improving paper strength and water resistance. It can be used to produce high-quality packaging paper, printing paper, and specialty paper, meeting the high quality requirements of various applications and better satisfying the evolving needs of the paper industry. Compared to single-component strengthening agents, the strengthening agent prepared in this invention provides a more comprehensive and significant improvement in paper performance. The raw materials used in the preparation process are relatively environmentally friendly, and the reaction generates fewer pollutants. Compared to some traditional strengthening agents, it has a smaller environmental impact, aligning with current green and environmentally friendly development concepts. By improving the strength and durability of paper, the amount of paper used can be reduced, thereby saving natural resources such as wood and meeting the requirements of sustainable development.

[0024] Furthermore, isopropanol was used as a chain transfer agent and ammonium persulfate as an initiator. Ammonium persulfate generates sulfate radicals (SO4). -The reaction conditions are mild and easy to control, avoiding the equipment requirements and safety risks posed by harsh reaction conditions such as high temperature and high pressure, reducing production costs and difficulty, and facilitating large-scale production and application. Attached Figure Description

[0025] Figure 1 The infrared spectrum of the self-crosslinking multi-component graft copolymer paper reinforcing agent described in this invention is shown.

[0026] Figure 2 This is a stability test diagram of the self-crosslinking multi-component graft copolymer paper reinforcing agent described in this invention.

[0027] Figure 3 This invention relates to the effect of AMPS content on the dry and wet tensile indices of paper.

[0028] Figure 4 This invention describes the effect of AMPS content on the folding strength and tear strength of paper. Detailed Implementation

[0029] The present invention will now be described in detail with reference to embodiments. The description in this section is merely illustrative and explanatory, and should not be construed as limiting the scope of protection of the present invention.

[0030] This invention discloses a self-crosslinking multi-component graft copolymer paper reinforcing agent. The raw materials include dispersant CMC (carboxymethyl cellulose), chain transfer agent isopropanol, initiator persulfate (ammonium persulfate or potassium persulfate), comonomer DMC (methacryloyloxyethyltrimethylammonium chloride), AM (acrylamide), AA (acrylic acid), and AMPS (2-acrylamido-2-methylpropanesulfonic acid). The mass ratio of CMC, DMC, AM, AA, and AMPS is (1-10):(1-5):(10-30):(1-10):(1-5). The isopropanol content is 1%-5% of the total mass of CMC, DMC, AM, AA, and AMPS, and the amount of initiator added is 0.1%-3% of the total mass of CMC, DMC, AM, AA, and AMPS.

[0031] This invention discloses a method for preparing a self-crosslinking multi-component graft copolymer paper reinforcing agent, comprising the following steps:

[0032] Step 1: Dissolving CMC

[0033] Dissolve CMC in deionized water at 60-80℃ to prepare a solution with a mass percentage of 1-5%, then add isopropanol and stir for 2-10 minutes to obtain a transparent and viscous mixed solution.

[0034] Step 2: Preparation of the reinforcing agent

[0035] (1) Dissolve AM, AA, AMPS and DMC in deionized water and stir until homogeneous to prepare a mixed solution, wherein the mass ratio of AM to deionized water is (1-3):(1-5).

[0036] (2) Dissolve the initiator in deionized water to prepare an initiator aqueous solution, wherein the mass ratio of initiator to deionized water is (0.1-1):(1-20).

[0037] (3) At 50-80℃, the solution prepared in steps (1) and (2) is slowly added dropwise to the mixed solution of CMC and isopropanol. The addition time is controlled at 60-180 min. After the addition is completed, the solution is kept at this temperature for 1-3 h, and then cooled to room temperature. The pH is adjusted to 4.5-5.5 with ammonia water at a mass percentage of 25-28%. The cross-linked multi-component graft copolymer paper strengthening agent sol is obtained to improve the strength properties of paper, including tensile index, folding strength, tear strength and bursting strength.

[0038] Example 1

[0039] Dissolve 2g of CMC in deionized water at 60℃ to prepare a 5% (w / w) solution. Then add 0.5g of isopropanol and stir for 10 minutes to obtain a transparent, viscous mixed solution.

[0040] The mixed solution of CMC and isopropanol is heated to 80℃. 10g AM, 3g AA, 0.5g AMPS, and 2g DMC are dissolved in 50g deionized water and stirred until homogeneous to prepare an aqueous solution.

[0041] Dissolve 0.2g of ammonium persulfate in 10g of deionized water to prepare an aqueous solution;

[0042] The two aqueous solutions were simultaneously added dropwise through a constant pressure funnel to a mixed solution of CMC and isopropanol, ensuring that the addition was completed at the same time. The addition time was controlled at 60 min. After the addition was completed, the solution was kept at a constant temperature for 2 h, and then cooled to room temperature. The pH was adjusted to 5 with 26% ammonia water by mass to obtain a cross-linked multi-component graft copolymer paper strengthening agent sol.

[0043] Example 2

[0044] Dissolve 2g of CMC in deionized water at 60℃ to prepare a 5% (w / w) solution. Then add 0.5g of isopropanol and stir for 10 minutes to obtain a transparent, viscous mixed solution.

[0045] The mixed solution of CMC and isopropanol is heated to 80°C. 10g AM, 3g AA, 1g AMPS and 2g DMC are dissolved in 50g deionized water and stirred evenly to prepare an aqueous solution.

[0046] Dissolve 0.2g of ammonium persulfate in 10g of deionized water to prepare an aqueous solution;

[0047] The two aqueous solutions were simultaneously added dropwise to a mixed solution of CMC and isopropanol through a constant pressure funnel, ensuring that the addition was completed at the same time. The addition time was controlled at 60 min. After the addition was completed, the solution was kept at a constant temperature for 2 h, and then cooled to room temperature. The pH was adjusted to 5 with 26% ammonia water by mass to obtain a cross-linked multi-component graft copolymer paper strengthening agent sol.

[0048] Example 3

[0049] Dissolve 2g of CMC in deionized water at 60℃ to prepare a 5% (w / w) solution. Then add 0.5g of isopropanol and stir for 10 minutes to obtain a transparent, viscous mixed solution.

[0050] The mixed solution of CMC and isopropanol is heated to 80℃. 10g AM, 3g AA, 1.5g AMPS, and 2g DMC are dissolved in 50g deionized water and stirred until homogeneous to prepare an aqueous solution.

[0051] Dissolve 0.2g of ammonium persulfate in 10g of deionized water to prepare an aqueous solution;

[0052] The two aqueous solutions were simultaneously added dropwise to a mixed solution of CMC and isopropanol through a constant pressure funnel, ensuring that the addition was completed at the same time. The addition time was controlled at 60 min. After the addition was completed, the solution was kept at a constant temperature for 2 h, and then cooled to room temperature. The pH was adjusted to 5 with 26% ammonia water by mass to obtain a cross-linked multi-component graft copolymer paper strengthening agent sol.

[0053] Example 4

[0054] Dissolve 2g of CMC in deionized water at 60℃ to prepare a 5% (w / w) solution. Then add 0.5g of isopropanol and stir for 10 minutes to obtain a transparent, viscous mixed solution.

[0055] Heat the mixed solution of CMC and isopropanol to 80℃, take 10g AM, 3g AA, 2.5g AMPS and 2g DMC and dissolve them in 50g deionized water and stir well to prepare an aqueous solution;

[0056] Dissolve 0.2g of ammonium persulfate in 10g of deionized water to prepare an aqueous solution;

[0057] The two aqueous solutions were simultaneously added dropwise through a constant pressure funnel to a mixed solution of CMC and isopropanol, ensuring that the addition was completed at the same time. The addition time was controlled at 60 min. After the addition was completed, the solution was kept at a constant temperature for 2 h, and then cooled to room temperature. The pH was adjusted to 5 with 28% ammonia water, and the cross-linked multi-component graft copolymer paper strengthening agent sol was obtained.

[0058] Comparative Example 1

[0059] Dissolve 2g of CMC in deionized water at 60℃ to prepare a 5% (w / w) solution. Then add 0.5g of isopropanol and stir for 10 minutes to obtain a transparent, viscous mixed solution.

[0060] The mixed solution of CMC and isopropanol is heated to 80℃. 10g AM, 3g AA and 2g DMC are dissolved in 50g deionized water and stirred evenly to prepare an aqueous solution.

[0061] Dissolve 0.2g of ammonium persulfate in 10g of deionized water to prepare an aqueous solution;

[0062] The two aqueous solutions were simultaneously added dropwise through a constant pressure funnel to a mixed solution of CMC and isopropanol, ensuring that the addition was completed at the same time. The addition time was controlled at 60 min. After the addition was completed, the solution was kept at a constant temperature for 2 h, and then cooled to room temperature. The pH was adjusted to 5 with 26% ammonia water to obtain the paper strengthening agent sol.

[0063] Structural and performance analysis of synthetic paper reinforcing agents

[0064] FT-IR analysis of self-crosslinking multi-component graft copolymer paper strengthening agent

[0065] Figure 1 In the spectrum, the broad, strong absorption peak at 3308 cm⁻¹ is the stretching vibration absorption peak of the hydroxyl group (—OH); the weak absorption peak at 2113 cm⁻¹ is the stretching vibration absorption peak of the sulfur-oxygen double bond (S=O); the strong absorption peak at 1641 cm⁻¹ is the stretching vibration peak of the amide carbonyl group (C=O); and the 1563 cm⁻¹ is the symmetric stretching vibration peak of COO-, indicating that the grafting of CMC and monomer was successful. The absorption peak at 1456 cm⁻¹ is the bending vibration absorption peak of N+(CH₃)₃, and the 1041 cm⁻¹ is the CO vibration absorption peak. No characteristic absorption peaks of carbon-carbon double bonds (C=C) were found in the polymer in the spectrum, indicating that the monomer reaction was complete, which is consistent with the structural characteristics of a self-crosslinking multi-component graft copolymer paper reinforcing agent.

[0066] Stability analysis of self-crosslinking multi-component graft copolymer paper strengthening agent

[0067] Depend on Figure 2It can be seen that the TSI values ​​of all sol samples showed an increasing trend during the 60-minute test. TSI is an indicator for evaluating the stability of liquid dispersion systems; within a fixed aging time, the lower the TSI index, the more stable the sol. When the AMPS addition reached 8.1%, the sol had the lowest TSI value and the best stability. This is because AMPS contains strongly anionic sulfonate groups, which can prevent polymer chains from entangled and agglomerated through charge repulsion. When the AMPS addition was 2.85%, due to the small number of sulfonate groups, the charge repulsion was weak, and there was some entanglement between polymer chains. Over time, the sol exhibited slight flocculation, leading to a decrease in sol stability. When the AMPS addition reached 8.1%, there were sufficient sulfonate groups to effectively expand the polymer chains, allowing them to be uniformly dispersed in the aqueous solution, resulting in good sol stability. When an excessive amount of AMPS is added, the excessive AMPS will lead to an excessively high charge density on the polymer chain, causing excessive electrostatic repulsion and making the polymer chain too loosely extended. Moreover, AMPS itself has a certain spatial structure, and the increase in the amount added will produce steric hindrance. This effect hinders the movement and reaction of other molecules in the system, resulting in a decrease in the stability of the system.

[0068] Performance testing experiment

[0069] The self-crosslinking multi-component graft copolymer paper strengthening agent prepared above was used to make sheets as follows, with a basis weight of 95 g / m³. 2 A certain mass of bleached refined cotton pulp was weighed, and 0.6% (by mass ratio to oven-dry pulp) of self-crosslinking multi-component graft copolymer paper strengthening agent and 1.6% (by mass ratio to oven-dry pulp) of PAE were added sequentially. The pulp was then decomposed in a standard fiber decomposer at 6000 rotations per minute, allowing the self-crosslinking multi-component graft copolymer paper strengthening agent to be adsorbed onto the fibers through hydrogen bonding and electrostatic interactions. The final sample was then formed using a paper sample take-up device with a basis weight of 95 g / m³. 2 The paper was then vacuum-dried at 105°C for 10 minutes, and the physical properties of the finished paper were tested.

[0070] The physical properties of the paper are tested and calculated in accordance with national standards. The tensile index is determined according to GB / T 12914-2008, "Determination of Tensile Strength of Paper and Paperboard"; the tear strength is determined according to GB / T 455-2002, "Determination of Tear Strength of Paper and Paperboard"; and the folding endurance is determined according to GB / T 457-2008, "Determination of Folding Endurance of Paper and Paperboard".

[0071] The effect of AMPS content on paper strength properties

[0072] To determine the optimal AMPS content, the strength properties of paper were tested when the self-crosslinking multi-component graft copolymer paper strengthening agent was added at a concentration of 0.6%. The results are as follows: Figure 3 and Figure 4 As shown. When the AMPS content is 0%, the prepared sized paper has a dry tensile index of 65.5 N·m / g, a wet tensile index of 15.1 N·m / g, a folding endurance of 130 cycles, and a tear strength of 13.4 N·m² / g. Figure 3 and Figure 4 It can be seen that the dry and wet tensile indices of sized paper initially increase with increasing AMPS content. This is because the positive charge carried by the self-crosslinking multi-component graft copolymer paper reinforcing agent attracts the negative charge on the cotton pulp fibers, adsorbing the self-crosslinking multi-component graft copolymer paper reinforcing agent onto the fiber surface. Furthermore, the amino, carbonyl, and carboxyl functional groups on the polymer chain segments also react with the hydroxyl groups on the cotton pulp fibers to form a crosslinked structure, thereby increasing the toughness and strength between fibers. When the AMPS content is 8.1%, the paper's dry tensile index reaches 68.4 N·m / g, wet tensile index reaches 18.8 N·m / g, folding endurance reaches 121 cycles, and tear strength reaches 14.2 N·m. 2 Compared to paper without internal sizing, the AMPS content increased by 32%, 487.5%, 348%, and 5.2% respectively. However, as the AMPS content increased, both the dry and wet strength indices of the paper decreased. This is because excessive self-polymerization of the polymer chains led to flocculation. In conclusion, an AMPS content of 8.1% is the optimal dosage.

Claims

1. A method for preparing a self-crosslinking multi-component graft copolymer paper reinforcing agent, characterized in that, Using carboxymethyl cellulose as a dispersant, isopropanol as a chain transfer agent, and deionized water as a solvent, methacryloyloxyethyltrimethylammonium chloride, acrylamide, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid were reacted at 50-80℃ under the action of an initiator. The mass ratio of carboxymethyl cellulose, methacryloyloxyethyltrimethylammonium chloride, acrylamide, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid was (1-10):(1-5):(10-30):(1-10):

1. The pH of the resulting reaction solution was then adjusted to 4.5-5.5 to obtain a self-crosslinking multi-component graft copolymer paper reinforcing agent.

2. The method for preparing the self-crosslinking multi-component graft copolymer paper reinforcing agent according to claim 1, characterized in that, Specifically, the following steps are included: S1, carboxymethyl cellulose is dissolved in deionized water, then isopropanol is added and stirred to obtain the first mixed solution; S2, dissolve methacryloyloxyethyltrimethylammonium chloride, acrylamide, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid in deionized water to obtain a second mixed solution; The initiator was dissolved in deionized water to obtain an aqueous solution; S3, simultaneously and uniformly add the second mixed solution and aqueous solution to the first mixed solution at 50-80℃, then keep it at 50-80℃, and then adjust the pH of the resulting reaction solution to 4.5-5.5 to obtain a self-crosslinking multi-component graft copolymer paper reinforcing agent.

3. The method for preparing the self-crosslinking multi-component graft copolymer paper reinforcing agent according to claim 2, characterized in that, The initiator described in S2 is ammonium persulfate or potassium persulfate.

4. The method for preparing the self-crosslinking multi-component graft copolymer paper reinforcing agent according to claim 3, characterized in that, The ammonium persulfate or potassium persulfate is 0.1%-3% of the total mass of methacryloyloxyethyltrimethylammonium chloride, acrylamide, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid.

5. The method for preparing the self-crosslinking multi-component graft copolymer paper reinforcing agent according to claim 2, characterized in that, In the first mixed solution S1, the mass ratio of carboxymethyl cellulose to deionized water is (1-5):

100.

6. The method for preparing the self-crosslinking multi-component graft copolymer paper reinforcing agent according to claim 2, characterized in that, In the second mixed solution S2, the mass ratio of acrylamide to deionized water is (1-3):(1-5), and in the aqueous solution, the mass ratio of initiator to deionized water is (0.1-1):(1-20).

7. The method for preparing the self-crosslinking multi-component graft copolymer paper reinforcing agent according to claim 2, characterized in that, The second mixed solution and aqueous solution in S3 are added at a time of 1-3 hours.

8. The method for preparing the self-crosslinking multi-component graft copolymer paper reinforcing agent according to claim 2, characterized in that, The heat preservation time described in S3 is 1-3 hours.

9. A self-crosslinking multi-component graft copolymer paper reinforcing agent obtained by the preparation method of the self-crosslinking multi-component graft copolymer paper reinforcing agent according to any one of claims 1-8.

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