Novel nanocellulose-modified dry strength enhancing agent

Abstract

The invention relates to the field of dry strength agents, and discloses a nano-cellulose modified novel reinforced dry strength agent, which is prepared from the following raw materials in parts by weight: 10 to 20 parts of nano-cellulose, 30 to 50 parts of acrylamide, 10 to 20 parts of methacryloyloxyethyl trimethyl ammonium chloride, 5 to 15 parts of dimethylaminoethyl methacrylate, 3 to 8 parts of itaconic acid, 3 to 8 parts of sodium methallyl sulfonate, 3 to 8 parts of N, N-dimethylformamide, 3 to 8 parts of sodium dodecyl benzene sulfonate, 3 to 8 parts of sodium dodecyl benzene sulfonate, 3 to 8 parts of sodium dodecyl benzene sulfonate, 3 to 8 parts of sodium dodecyl benzene sulfonate, 3 to 8 parts of sodium dodecyl benzene sulfonate and 5 to 10 parts of sodium dodecyl benzene sulfonate. 5 to 15 parts of N, N-dimethylacrylamide, and 5 to 15 parts of 2-acrylamido-2-methylpropanesulfonic acid. Nano cellulose is used as a core reinforcing component, by means of the nanoscale size and high reaction activity, a surface group and fibers form a hydrogen bond and are chemically bonded with a polymeric monomer, a three-dimensional network structure is constructed among the fibers, and electrostatic adsorption of a cationic monomer and the crosslinking effect of a polar group are cooperated, so that the binding force among the fibers of the paper is improved; and the tensile property is obviously enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of dry strength agents, in particular to a novel enhanced dry strength agent modified with nanocellulose. Background Art

[0002] Dry strength agents play a crucial stabilizing role in paper production lines. They reduce the likelihood of paper breaks due to insufficient strength during drying and winding, improving production continuity and stability, thereby increasing efficiency and reducing costs. Furthermore, they reduce equipment downtime and maintenance due to paper breaks, extending equipment life and further enhancing the company's economic benefits.

[0003] The dry strength agents in existing technologies rely on petroleum-based raw materials, have poor biodegradability and limited strengthening efficiency, have a single mechanism of action, and lack the synergistic effect of reinforcing components, making it difficult to build a high-strength bonding network between fibers, resulting in insufficient improvement in the dry strength of paper. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a new dry strength enhancing agent modified with nanocellulose, which solves the problem that the dry strength agents in the existing technology rely on petroleum-based raw materials, have poor biodegradability and limited enhancement efficiency, have a single mechanism of action, lack the synergistic effect of the reinforcing components, and are difficult to construct a high-strength bonding network between fibers, resulting in insufficient improvement in the dry strength of paper.

[0005] To achieve the above objectives, the present invention is implemented through the following technical scheme: a novel dry strength enhancing agent modified with nanocellulose, comprising the following raw materials in parts by weight: 10-20 parts of nanocellulose, 30-50 parts of acrylamide, 10-20 parts of methacryloyloxyethyltrimethylammonium chloride, 5-15 parts of dimethylaminoethyl methacrylate, 3-8 parts of itaconic acid, 3-8 parts of sodium methacryloylsulfonate, 5-15 parts of N,N-dimethylacrylamide, 5-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 3-10 parts of methacryloyloxyethyldimethylbenzylammonium chloride, 0.1-1 part of a chelating agent, 0.1-0.5 part of ammonium persulfate, 0.1-1 part of sodium sulfite, 0.05-0.2 part of a bactericide, 0.05-0.2 part of a defoaming agent, and some water.

[0006] Preferably, the purity of the acrylamide is not less than 98%, and the active matter content of the methacryloyloxyethyltrimethylammonium chloride is not less than 60%.

[0007] Preferably, the nanocellulose has a particle size of 5 to 50 nm, has a surface carboxylation treatment, and has a carboxyl content of 0.5 to 1.5 mmol / g.

[0008] Preferably, the preparation method of the novel dry strength enhancing agent modified with nanocellulose comprises the following steps:

[0009] Prepare and mix the materials. In a reaction kettle, mix nanocellulose, water, acrylamide, methacryloyloxyethyltrimethylammonium chloride, dimethylaminoethyl methacrylate, itaconic acid, sodium methacrylic acid, N,N-dimethylacrylamide, and a chelating agent according to a certain proportion.

[0010] Adjust pH and add sulfuric acid to adjust the pH value of the material;

[0011] In the initial polymerization, the material is heated and a chelating agent and ammonium persulfate are added, and nitrogen is passed through to replace the air to initiate the polymerization reaction;

[0012] The secondary polymerization mixed liquid is prepared by mixing acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl dimethylbenzylammonium chloride, N,N-dimethylacrylamide and itaconic acid into a mixed liquid;

[0013] Secondary polymerization: adding the mixed solution dropwise to the material after the primary polymerization and continuing the polymerization under controlled conditions;

[0014] Heat preservation and cross-linking, after polymerization, add ammonium persulfate for cross-linking, add sodium sulfite to stop the reaction, and then add bactericide and defoamer;

[0015] Filter and package, filter the material after cooling, remove impurities and fill and package.

[0016] Preferably, in the material preparation and mixing step, water and acrylamide are added through pipelines, methacryloyloxyethyltrimethylammonium chloride, dimethylaminoethyl methacrylate, and N,N-dimethylacrylamide are added through material pumps, and itaconic acid, sodium methacrylic acid, and a chelating agent are added through a solid feeder. The mixing time is 10 to 20 minutes.

[0017] Preferably, in the pH adjustment step, sulfuric acid is used to adjust the pH value of the material to 4.5-5.5.

[0018] Preferably, in the initial polymerization step, after heating to 90°C, a chelating agent and ammonium persulfate are added, nitrogen is passed to replace the air for 10 to 15 minutes, and the heating rate is controlled to be 0.8 to 1.2°C / min by cooling water, so that the material temperature is evenly raised to the reaction temperature and maintained for 30 to 40 minutes.

[0019] Preferably, in the secondary polymerization step, the mixed solution is added dropwise at a rate of 8 to 12 mL / min by a peristaltic pump, the temperature of the reactor is controlled to be 65 to 75° C. by a heating jacket during the addition process, the addition time is 60 to 90 minutes, and the reaction is kept warm for 20 to 30 minutes after the addition is completed.

[0020] Preferably, during the heat preservation and crosslinking step, a viscometer is used to monitor the viscosity of the material in real time. When the viscosity reaches 250-450 mPa·s and the total monomer content is ≤800 ppm, sodium sulfite is added in an amount of 1.2-1.4 times the total mass of ammonium persulfate.

[0021] Preferably, in the filtering and packaging step, a closed filter with a filtration accuracy of 20 to 40 μm is used for filtration.

[0022] The present invention provides a novel dry strength enhancing agent modified with nanocellulose. It has the following beneficial effects:

[0023] 1. The present invention uses nanocellulose as the core reinforcing component. With its nanoscale size and high reactivity, it forms hydrogen bonds with fibers through surface groups and chemically bonds with polymerized monomers, constructing a three-dimensional network structure between fibers. It synergizes the electrostatic adsorption of cationic monomers and the cross-linking effect of polar groups to enhance the binding force between paper fibers and significantly enhance the tensile properties.

[0024] 2. The present invention replaces part of the petroleum-based raw materials with biomass-based nanocellulose, and uses its excellent biodegradability to reduce environmental impact. Through high-purity raw materials and precise process control, it reduces the generation of polymerization reaction by-products and energy consumption, and reduces pollutant emissions. It meets the green transformation needs of the papermaking industry and is more environmentally friendly and sustainable than traditional dry strength agents.

[0025] 3. The present invention achieves uniform molecular weight distribution and controllable structure of the polymer through a segmented polymerization process, precise temperature control and real-time viscosity monitoring, avoiding explosion or agglomeration during the production process. Combined with precise material transportation and impurity filtration technology, it ensures the uniform dispersion of the dry strength agent on the fiber surface, improves product stability and coating adaptability, and meets the stringent requirements of industrial production for performance consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a flow chart of the preparation method of the novel nanocellulose-modified dry strength enhancing agent. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] Please see the attached Figure 1The embodiment of the present invention provides a novel dry strength enhancing agent modified with nanocellulose, comprising the following raw materials in parts by weight: 10-20 parts of nanocellulose, 30-50 parts of acrylamide, 10-20 parts of methacryloyloxyethyltrimethylammonium chloride, 5-15 parts of dimethylaminoethyl methacrylate, 3-8 parts of itaconic acid, 3-8 parts of sodium methacryloylsulfonate, 5-15 parts of N,N-dimethylacrylamide, 5-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 3-10 parts of methacryloyloxyethyldimethylbenzylammonium chloride, 0.1-1 part of a chelating agent, 0.1-0.5 part of ammonium persulfate, 0.1-1 part of sodium sulfite, 0.05-0.2 part of a bactericide, 0.05-0.2 part of a defoaming agent, and some water.

[0029] Specifically, nanocellulose: a nano-scale reinforcing material with a carboxylation surface treatment, which improves the bonding strength and mechanical properties of the dry strength agent and the fiber through high specific surface area and active groups.

[0030] Acrylamide: The main monomer, which forms the main chain skeleton of the polymer through polymerization. It is the core component of the dry strength agent to achieve fiber bonding and film formation.

[0031] Methacryloyloxyethyltrimethylammonium chloride: a cationic monomer containing a quaternary ammonium salt group, which provides a positive charge and enhances the adsorption and retention rate of negatively charged fibers through electrostatic interaction.

[0032] Dimethylaminoethyl methacrylate: Contains weakly basic dimethylamino groups, which regulate the charge density of the polymer and the flexibility of the molecular chain, and promote hydrogen bonding with the fiber surface.

[0033] Itaconic acid: a dibasic acid monomer containing dicarboxyl groups, which introduces polar groups to enhance hydrophilicity, improves adsorption capacity through the interaction between carboxyl groups and fibers and participates in cross-linking reactions.

[0034] Sodium methyl propylene sulfonate: an anionic monomer containing sulfonic acid groups, which balances the charge density of the system, improves water solubility and dispersibility, and enhances electrostatic and polar interactions with fibers.

[0035] N,N-dimethylacrylamide: a polar monomer that increases the flexibility and water resistance of the molecular chain and optimizes the film-forming and coating effects of the dry strength agent on the fiber surface.

[0036] 2-Acrylamido-2-methylpropanesulfonic acid: an amphoteric monomer containing strongly hydrophilic sulfonic acid and amide groups, which improves the water solubility, ionic strength and adsorption and dispersion ability of the polymer on fibers.

[0037] Methacryloyloxyethyl dimethylbenzyl ammonium chloride: a high charge density cationic monomer that enhances electrostatic adsorption and hydrophobicity through quaternary ammonium salt and benzyl structure, thereby improving fiber retention efficiency.

[0038] Chelating agent: complexes metal ions in the reaction system to prevent them from catalyzing oxidation or interfering with polymerization, and stabilizes the reaction environment.

[0039] Ammonium persulfate: a water-soluble initiator that decomposes when heated to produce free radicals, which initiate the polymerization reaction of monomers and form polymer chains.

[0040] Sodium sulfite: reducing agent, forming an initiation system with ammonium persulfate or acting as a terminator to control the degree of polymerization and molecular weight and avoid excessive cross-linking.

[0041] Bactericide: Inhibits the growth of microorganisms, prevents the spoilage of dry strength agents caused by the growth of bacteria and fungi during storage, and extends the shelf life.

[0042] Defoaming agent: Reduces surface tension and eliminates foam generated during the polymerization process to avoid affecting reaction efficiency or product appearance and performance.

[0043] Water: acts as a solvent to dissolve the components, provide a polymerization reaction medium, adjust the viscosity and fluidity of the system, and ensure uniform mixing of materials.

[0044] The purity of acrylamide is not less than 98%, and the active matter content of methacryloyloxyethyltrimethylammonium chloride is not less than 60%.

[0045] Specifically, an acrylamide purity of at least 98% reduces interference with the polymerization reaction from impurities, preventing problems such as chain termination and molecular weight reduction caused by polymerization inhibitors or other impurities. This ensures its efficient participation as the main monomer in the polymerization reaction, forming a high-molecular-weight, structurally stable main chain backbone, and providing a good bonding and film-forming foundation for the dry strength agent. A methacryloyloxyethyltrimethylammonium chloride active ingredient content of at least 60% ensures sufficient cationic groups participate in the copolymerization, avoiding insufficient active ingredients due to excessive solvent. This, through strong electrostatic interaction, enhances the dry strength agent's adsorption and retention on negatively charged fibers, improving interfiber bonding strength. Together, these two factors guarantee the polymerization efficiency and effectiveness of the dry strength agent, ensuring stable paper reinforcement properties.

[0046] The particle size of the nanocellulose is 5-50 nm, the surface of the nanocellulose is carboxylated, and the carboxyl content is 0.5-1.5 mmol / g.

[0047] Specifically, the nanocellulose particle size is controlled at 5-50nm, giving it an extremely high specific surface area. This allows it to be fully dispersed and evenly adsorbed on the fiber surface, significantly increasing the contact area with the fiber and other monomers, and improving the dispersibility and compatibility of the dry strength agent. The surface carboxylation treatment and the carboxyl content of 0.5-1.5mmol / g impart strong hydrophilicity and reactivity. The carboxyl groups can form hydrogen bonds with the hydroxyl groups on the fiber surface and chemically bind with monomers such as acrylamide, forming "nanoscale bridges" and a three-dimensional network structure between fibers. This significantly enhances the bonding between fibers and significantly improves the paper's dry strength properties, such as tensile strength and folding resistance.

[0048] The preparation method of the novel dry strength enhancing agent modified with nanocellulose comprises the following steps:

[0049] Prepare and mix the materials. In a reaction kettle, mix nanocellulose, water, acrylamide, methacryloyloxyethyltrimethylammonium chloride, dimethylaminoethyl methacrylate, itaconic acid, sodium methacrylic acid, N,N-dimethylacrylamide, and a chelating agent according to a certain proportion.

[0050] Adjust pH and add sulfuric acid to adjust the pH value of the material;

[0051] In the initial polymerization, the material is heated and a chelating agent and ammonium persulfate are added, and nitrogen is passed through to replace the air to initiate the polymerization reaction;

[0052] The secondary polymerization mixed liquid is prepared by mixing acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl dimethylbenzylammonium chloride, N,N-dimethylacrylamide and itaconic acid into a mixed liquid;

[0053] Secondary polymerization: adding the mixed solution dropwise to the material after the primary polymerization and continuing the polymerization under controlled conditions;

[0054] Heat preservation and cross-linking, after polymerization, add ammonium persulfate for cross-linking, add sodium sulfite to stop the reaction, and then add bactericide and defoamer;

[0055] Filter and package, filter the material after cooling, remove impurities and fill and package.

[0056] In the material preparation and mixing step, water and acrylamide are added through pipelines, methacryloyloxyethyltrimethylammonium chloride, dimethylaminoethyl methacrylate, and N,N-dimethylacrylamide are added through material pumps, and itaconic acid, sodium methacrylic acid, and a chelating agent are added through a solid feeder. The mixing time is 10 to 20 minutes.

[0057] Specifically, the use of different methods to add raw materials during the preparation and mixing steps allows for precise delivery and quantitative control based on the material state, preventing the flying of solid powder or uneven liquid addition, and ensuring that the various components, including nanocellulose, monomers, and chelating agents, are quickly dispersed and evenly mixed in the water. A mixing time of 10 to 20 minutes ensures that the solid raw materials are fully dissolved and the liquid raw materials are completely miscible, while also avoiding energy waste or material sedimentation caused by excessive mixing. This provides a uniform and stable initial system for the subsequent polymerization reaction, ensuring sufficient contact between the components, improving reaction efficiency and product performance consistency, and avoiding problems such as local agglomeration and incomplete reaction caused by uneven mixing.

[0058] In the pH adjustment step, sulfuric acid is used to adjust the pH value of the material to 4.5-5.5.

[0059] Specifically, sulfuric acid is used in the pH adjustment step to adjust the pH value of the material to 4.5-5.5, which can create a weakly acidic reaction environment, partially dissociate carboxyl monomers such as itaconic acid into ions, enhance their reactivity and promote copolymerization with other monomers. At the same time, acidic conditions are conducive to the efficient decomposition of ammonium persulfate to produce free radicals, initiate and accelerate the polymerization reaction, and avoid initiator failure or side reactions caused by alkaline environment. In addition, this pH range can stabilize the dispersion state of nanocellulose, prevent particle agglomeration caused by excessively high or low pH, ensure material uniformity, and provide a suitable chemical environment for subsequent polymerization reactions, thereby improving reaction efficiency, controlling polymer structure, and ensuring the molecular weight distribution of the dry strength agent and the stability of the enhanced performance.

[0060] In the initial polymerization step, after heating to 90°C, a chelating agent and ammonium persulfate are added, and nitrogen is passed to replace the air for 10 to 15 minutes. The heating rate is controlled at 0.8 to 1.2°C / min by cooling water, so that the material temperature is evenly raised to the reaction temperature and maintained for 30 to 40 minutes.

[0061] Specifically, in the initial polymerization step, after heating to 90°C, the chelating agent and ammonium persulfate are added, which can enable the chelating agent to fully complex the metal ions in the system, preventing it from inhibiting the generation of free radicals or initiating side reactions. At the same time, the ammonium persulfate efficiently decomposes at high temperature to produce free radicals, thereby starting the polymerization reaction. The air is replaced by nitrogen for 10 to 15 minutes to eliminate oxygen, creating an oxygen-free environment to ensure the smooth progress of the polymerization reaction. The heating rate is controlled at 0.8 to 1.2°C / min by cooling water and the temperature is evenly raised to the reaction temperature. This can avoid explosions or uneven molecular weight distribution caused by local overheating, ensure the synchronous reaction of various parts of the material, and maintain 30 to 40 minutes to allow the initial monomer to fully polymerize to form a stable prepolymer, providing a reaction substrate with a uniform structure for the subsequent secondary polymerization, thereby improving the controllability of the overall polymerization reaction and the consistency of product performance.

[0062] In the secondary polymerization step, the mixed liquid is added dropwise at a rate of 8 to 12 mL / min through a peristaltic pump. During the addition, the temperature of the reactor is controlled at 65 to 75° C. by a heating jacket. The addition time is 60 to 90 minutes. After the addition is completed, the mixture is kept warm for 20 to 30 minutes.

[0063] Specifically, in the secondary polymerization step, the mixed solution is added dropwise at a rate of 8 to 12 mL / min via a peristaltic pump, allowing functional monomers such as 2-acrylamido-2-methylpropanesulfonic acid and methacryloyloxyethyl dimethylbenzyl ammonium chloride to participate in the reaction uniformly and slowly, avoiding explosion polymerization or uneven molecular weight distribution caused by local excessive concentration, and forming a structurally controllable gradient copolymer. During the addition process, the temperature is controlled at 65 to 75°C by a heating jacket, which can not only ensure the effective decomposition of the initiator and maintain a stable free radical concentration, but also avoid monomer decomposition or side reactions caused by high temperature, ensuring that the newly added monomers are fully grafted or copolymerized with the primary polymerization product; the addition time of 60 to 90 minutes, combined with the 20 to 30 minutes of heat preservation reaction after the addition, can evenly introduce functional groups into the molecular chain, optimize the charge distribution and spatial structure of the polymer, enhance the adsorption capacity and cross-linking effect on the fiber, and ultimately improve the reinforcing performance and application stability of the dry strength agent.

[0064] During the heat preservation and crosslinking step, a viscometer is used to monitor the viscosity of the material in real time. When the viscosity reaches 250 to 450 mPa·s and the total monomer content is ≤800 ppm, sodium sulfite is added in an amount of 1.2 to 1.4 times the total mass of ammonium persulfate.

[0065] Specifically, during the heat-insulating crosslinking step, real-time material viscosity monitoring using a viscometer, combined with total monomer content control, accurately determines the degree of polymerization reaction. When the viscosity reaches 250-450 mPa·s, the polymer molecular weight has reached the appropriate range. A total monomer content of ≤800 ppm ensures a sufficient reaction and minimal residual monomer, thus preventing any degradation of paper performance. At this point, sodium sulfite, added at a rate of 1.2-1.4 times the total mass of ammonium persulfate, acts as a free radical scavenger to promptly terminate the polymerization reaction, preventing excessive molecular weight growth or uncontrolled crosslinking. This ensures that the dry strength agent viscosity remains within the applicable application range and reduces residual unreacted monomer, improving product safety and enhancing adsorption and film-forming properties on paper fibers, ultimately ensuring uniformity and stability in the final enhanced performance.

[0066] In the filtering and packaging step, a closed filter with a filtration accuracy of 20 to 40 μm is used for filtration.

[0067] Specifically, a closed filter with an accuracy of 20 to 40 μm is used in the filtering and packaging step, which can effectively remove residual solid particles in the material, prevent impurities from clogging the nozzle or coating equipment during the papermaking process, and ensure the uniform dispersion of the dry strength agent on the paper surface.

[0068] The following is an introduction with reference to specific embodiments:

[0069] Example 1

[0070] Raw material ratio:

[0071] 10 parts of nanocellulose, 30 parts of acrylamide, 10 parts of methacryloyloxyethyltrimethylammonium chloride, 5 parts of dimethylaminoethyl methacrylate, 3 parts of itaconic acid, 3 parts of sodium methacryloylsulfonate, 5 parts of N,N-dimethylacrylamide, 5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 3 parts of methacryloyloxyethyldimethylbenzylammonium chloride, 0.1 part of chelating agent, 0.1 part of ammonium persulfate, 0.1 part of sodium sulfite, 0.05 part of bactericide, 0.05 part of defoaming agent, and some water.

[0072] Preparation steps:

[0073] Preparation and mixing: In a reactor, mix 10 parts of nanocellulose, water, 30 parts of acrylamide, 10 parts of methacryloyloxyethyltrimethylammonium chloride, 5 parts of dimethylaminoethyl methacrylate, 3 parts of itaconic acid, 3 parts of sodium methacrylic acid, 5 parts of N,N-dimethylacrylamide, and 0.1 part of a chelating agent. Water and 30 parts of acrylamide are added via a pipeline, 10 parts of methacryloyloxyethyltrimethylammonium chloride, 5 parts of dimethylaminoethyl methacrylate, and 5 parts of N,N-dimethylacrylamide are added via a material pump, and 3 parts of itaconic acid, 3 parts of sodium methacrylic acid, and 0.1 part of a chelating agent are added via a solid feeder. The mixing time is 10-20 minutes.

[0074] Adjust pH: Add sulfuric acid to adjust the pH value of the material to 4.5-5.5.

[0075] Initial polymerization: After heating the material to 90°C, add 0.1 parts of chelating agent and 0.1 parts of ammonium persulfate, replace the air with nitrogen for 10-15 minutes, and control the heating rate to 0.8-1.2°C / min by cooling water to uniformly raise the material temperature to the reaction temperature and maintain it for 30-40 minutes to initiate the polymerization reaction.

[0076] Preparation of secondary polymerization mixed liquid: The remaining parts of acrylamide (i.e., the total 30 parts minus the part added in the preparation and mixing step; here, assuming that all the materials are mixed and added, no acrylamide is added in this step), 5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 3 parts of methacryloyloxyethyl dimethylbenzyl ammonium chloride, 5 parts of N,N-dimethylacrylamide, and 3 parts of itaconic acid are prepared into a mixed liquid.

[0077] Secondary polymerization: The above mixed solution is added dropwise to the material after the primary polymerization at a rate of 8-12 mL / min through a peristaltic pump. During the addition process, the temperature of the reactor is controlled at 65-75°C by a heating jacket. The addition time is 60-90 minutes. After the addition is completed, the reaction is kept warm for 20-30 minutes.

[0078] Heat preservation crosslinking: Use a viscometer to monitor the viscosity of the material in real time. When the viscosity reaches 250-450 mPa·s and the total monomer content is ≤800 ppm, add 0.12-0.14 parts of sodium sulfite (the amount is 1.2-1.4 times the total mass of 0.1 parts of ammonium persulfate) to terminate the reaction, and then add 0.05 parts of fungicide and 0.05 parts of defoamer.

[0079] Filtration and packaging: After cooling, the material is filtered through a closed filter with a filtration accuracy of 20-40μm to remove impurities and then filled and packaged.

[0080] Example 2

[0081] Differences from Example 1:

[0082] Raw material ratio:

[0083] 15 parts of nanocellulose, 35 parts of acrylamide, 15 parts of methacryloyloxyethyltrimethylammonium chloride, 10 parts of dimethylaminoethyl methacrylate, 5 parts of itaconic acid, 5 parts of sodium methacryloylsulfonate, 10 parts of N,N-dimethylacrylamide, 10 parts of 2-acrylamido-2-methylpropanesulfonic acid, 6 parts of methacryloyloxyethyldimethylbenzylammonium chloride, 0.5 parts of chelating agent, 0.3 parts of ammonium persulfate, 0.5 parts of sodium sulfite, 0.1 parts of bactericide, 0.1 parts of defoaming agent, and some water.

[0084] Preparation steps:

[0085] Preparation and mixing: In a reactor, mix 15 parts of nanocellulose, water, 35 parts of acrylamide, 15 parts of methacryloyloxyethyl trimethylammonium chloride, 10 parts of dimethylaminoethyl methacrylate, 5 parts of

[0086] Mix itaconic acid, 5 parts sodium methacrylic acid sulfonate, 10 parts N,N-dimethylacrylamide, and 0.5 parts chelating agent. Add water and 35 parts acrylamide via a pipeline. Add 15 parts methacryloyloxyethyltrimethylammonium chloride, 10 parts dimethylaminoethyl methacrylate, and 10 parts N,N-dimethylacrylamide via a material pump. Add 5 parts itaconic acid, 5 parts sodium methacrylic acid sulfonate, and 0.5 parts chelating agent via a solid feeder. Adjust the mixing time to 15-25 minutes.

[0087] Adjust pH: The pH value of the material is adjusted in the range of 5.0-6.0.

[0088] Initial polymerization: raise the heating temperature to 95°C, add 0.5 parts of chelating agent and 0.3 parts of ammonium persulfate, replace the air with nitrogen for 15-20 minutes, adjust the heating rate to 1.0-1.5°C / min, and maintain the reaction for 40-50 minutes.

[0089] Preparation of secondary polymerization mixed liquid: The remaining parts of acrylamide (assuming that part of the equipment materials have been mixed and added, add the remaining part in this step, if all the equipment materials have been mixed and added, do not add it), 10 parts of 2-acrylamido-2-methylpropanesulfonic acid, 6 parts of methacryloyloxyethyl dimethylbenzyl ammonium chloride, 10 parts of N,N-dimethylacrylamide, and 5 parts of itaconic acid are prepared into a mixed liquid.

[0090] Secondary polymerization: The mixed solution is added dropwise at a rate of 10-15 mL / min through a peristaltic pump. The temperature of the reactor is controlled at 70-80°C. The addition time is 70-100 minutes. After the addition is completed, the mixture is kept warm for 30-40 minutes.

[0091] Heat preservation crosslinking: When the viscosity reaches 300-500 mPa·s and the total monomer content is ≤700 ppm, add 0.39-0.45 parts of sodium sulfite (the amount is 1.3-1.5 times the total mass of 0.3 parts of ammonium persulfate), and then add 0.1 parts of fungicide and 0.1 parts of defoamer.

[0092] Filter packaging: The filtration accuracy is adjusted to 30-50μm.

[0093] Example 3

[0094] Differences from Example 1:

[0095] Raw material ratio:

[0096] 20 parts of nanocellulose, 40 parts of acrylamide, 20 parts of methacryloyloxyethyltrimethylammonium chloride, 15 parts of dimethylaminoethyl methacrylate, 8 parts of itaconic acid, 8 parts of sodium methacryloylsulfonate, 15 parts of N,N-dimethylacrylamide, 15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10 parts of methacryloyloxyethyldimethylbenzylammonium chloride, 1 part of chelating agent, 0.5 parts of ammonium persulfate, 1 part of sodium sulfite, 0.2 parts of bactericide, 0.2 parts of defoaming agent, and some water.

[0097] Preparation steps:

[0098] Prepare and Mix: In a reactor, combine 20 parts of nanocellulose, water, 40 parts of acrylamide, 20 parts of methacryloyloxyethyltrimethylammonium chloride, 15 parts of dimethylaminoethyl methacrylate, 8 parts of itaconic acid, 8 parts of sodium methacrylic acid sulfonate, 15 parts of N,N-dimethylacrylamide, and 1 part of a chelating agent. Add water and 40 parts of acrylamide via a pipe, 20 parts of methacryloyloxyethyltrimethylammonium chloride, 15 parts of dimethylaminoethyl methacrylate, and 15 parts of N,N-dimethylacrylamide via a material pump, and add 8 parts of itaconic acid, 8 parts of sodium methacrylic acid sulfonate, and 1 part of a chelating agent via a solid feeder. Extend the mixing time to 20-30 minutes.

[0099] Adjust pH: The pH value adjustment range becomes 5.5-6.5.

[0100] Initial polymerization: Heat to 100°C, add 1 part of chelating agent and 0.5 parts of ammonium persulfate, replace the air with nitrogen for 20-25 minutes, change the heating rate to 1.2-1.8°C / min, and maintain the reaction for 50-60 minutes.

[0101] Preparation of secondary polymerization mixed liquid: The remaining parts of acrylamide (assuming that part of the equipment materials have been mixed and added, add the remaining part in this step, if all the equipment materials have been mixed and added, do not add it), 15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10 parts of methacryloyloxyethyl dimethylbenzyl ammonium chloride, 15 parts of N,N-dimethylacrylamide, and 8 parts of itaconic acid are prepared into a mixed liquid.

[0102] Secondary polymerization: The mixed solution is added dropwise at a rate of 12-18 mL / min through a peristaltic pump. The temperature of the reactor is controlled at 75-85°C. The addition time is 80-110 minutes. After the addition is completed, the mixture is kept warm for 40-50 minutes.

[0103] Heat preservation crosslinking: When the viscosity reaches 350-550 mPa·s and the total monomer content is ≤600 ppm, add 0.7-0.8 parts of sodium sulfite (the amount is 1.4-1.6 times the total mass of 0.5 parts of ammonium persulfate), and then add 0.2 parts of fungicide and 0.2 parts of defoamer.

[0104] Filter packaging: The filtration accuracy is adjusted to 40-60μm.

[0105] Table 1: Comparison between the embodiment and the prior art

[0106] Comparison Item Existing technology Example 1 Example 2 Example 3 Tensile strength improvement rate 15％ 25％ 30％ 35％ Viscosity retention 85％ 92％ 95％ 98％

[0107] Example 1 uses a relatively low raw material ratio: 10 parts nanocellulose, 30 parts acrylamide, and basic amounts of other functional monomers. This solution is suitable for strengthening conventional paper, with key advantages in cost control and process simplicity. While achieving a 25% increase in tensile strength and a 92% viscosity retention, it reduces production complexity and costs, meeting the basic dry strength requirements of ordinary paper production.

[0108] In Example 2, the dosage of each raw material was optimized and adjusted, increasing the amount of nanocellulose to 15 parts, and the amount of acrylamide and other functional monomers was also increased accordingly. In terms of preparation parameters, small adjustments were made to the mixing time, pH adjustment range, polymerization temperature, etc., resulting in a balanced performance of the dry strength agent in key performance indicators such as tensile strength increase rate and viscosity retention rate, with a tensile strength increase rate of 30% and a viscosity retention rate of 95%. This balanced performance makes it suitable for large-scale industrial production, meeting the needs of efficient production while ensuring product quality stability, and is a solution that combines performance and practicality.

[0109] Example 3 utilizes a higher raw material ratio, increasing the nanocellulose content to 20 parts, and further increasing the amounts of acrylamide and other functional monomers. Suitable for the production of high-strength specialty paper or water-resistant materials, the high proportion of nanocellulose and other functional monomers enables the formation of a stronger interfiber bonding network, imparting higher tensile strength and excellent water resistance to the paper. The tensile strength is increased by 35%, and the viscosity retention rate is 98%, meeting the stringent requirements of specialty paper in specific application scenarios.

[0110] By flexibly adjusting the raw material ratio, this invention creates a dry strength agent system that meets different application requirements, providing diverse options for the papermaking industry. Furthermore, compared to existing technologies, the use of biomass-based nanocellulose replaces some petroleum-based raw materials, making it more environmentally friendly and biodegradable. The synergistic effect of nanocellulose and various monomers creates a three-dimensional network structure between fibers, resulting in more stable performance and a balance of high efficiency, environmental friendliness, and application flexibility.

[0111] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A novel dry strength enhancing agent modified with nanocellulose, characterized in that: The invention comprises the following raw materials in parts by weight: 10-20 parts of nanocellulose, 30-50 parts of acrylamide, 10-20 parts of methacryloyloxyethyltrimethylammonium chloride, 5-15 parts of dimethylaminoethyl methacrylate, 3-8 parts of itaconic acid, 3-8 parts of sodium methacryloylsulfonate, 5-15 parts of N,N-dimethylacrylamide, 5-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 3-10 parts of methacryloyloxyethyldimethylbenzylammonium chloride, 0.1-1 part of a chelating agent, 0.1-0.5 part of ammonium persulfate, 0.1-1 part of sodium sulfite, 0.05-0.2 part of a bactericide, 0.05-0.2 part of a defoaming agent and some water.

2. The novel dry strength enhancing agent modified with nanocellulose according to claim 1, characterized in that: The purity of the acrylamide is not less than 98%, and the active matter content of the methacryloyloxyethyltrimethylammonium chloride is not less than 60%.

3. The novel dry strength enhancing agent modified with nanocellulose according to claim 1, characterized in that: The particle size of the nanocellulose is 5 to 50 nm, the surface of the nanocellulose is carboxylated, and the carboxyl content is 0.5 to 1.5 mmol / g.

4. A method for preparing a novel nanocellulose-modified dry strength enhancing agent, which is used for the novel nanocellulose-modified dry strength enhancing agent according to any one of claims 1 to 3, characterized in that: The following steps are involved: Prepare and mix the materials. In a reaction kettle, mix nanocellulose, water, acrylamide, methacryloyloxyethyltrimethylammonium chloride, dimethylaminoethyl methacrylate, itaconic acid, sodium methacrylic acid, N,N-dimethylacrylamide, and a chelating agent according to a certain proportion. Adjust pH and add sulfuric acid to adjust the pH value of the material; In the initial polymerization, the material is heated and a chelating agent and ammonium persulfate are added, and nitrogen is passed through to replace the air to initiate the polymerization reaction; The secondary polymerization mixed liquid is prepared by mixing acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl dimethylbenzylammonium chloride, N,N-dimethylacrylamide and itaconic acid into a mixed liquid; Secondary polymerization: adding the mixed solution dropwise to the material after the primary polymerization and continuing the polymerization under controlled conditions; Heat preservation and cross-linking, after polymerization, add ammonium persulfate for cross-linking, add sodium sulfite to stop the reaction, and then add bactericide and defoamer; Filter and package, filter the material after cooling, remove impurities and fill and package.

5. The method for preparing the novel dry strength enhancing agent modified with nanocellulose according to claim 4, characterized in that: In the material preparation and mixing step, water and acrylamide are added through pipelines, methacryloyloxyethyltrimethylammonium chloride, dimethylaminoethyl methacrylate, and N,N-dimethylacrylamide are added through material pumps, and itaconic acid, sodium methacrylic acid, and a chelating agent are added through a solid feeder. The mixing time is 10 to 20 minutes.

6. The method for preparing the novel dry strength enhancing agent modified with nanocellulose according to claim 4, characterized in that: In the pH adjustment step, sulfuric acid is used to adjust the pH value of the material to 4.5-5.

5.

7. The novel dry strength enhancing agent modified with nanocellulose according to claim 4, characterized in that: In the initial polymerization step, after heating to 90°C, a chelating agent and ammonium persulfate are added, nitrogen is passed to replace the air for 10 to 15 minutes, and the heating rate is controlled at 0.8 to 1.2°C / min by cooling water to uniformly raise the material temperature to the reaction temperature and maintain it for 30 to 40 minutes.

8. The method for preparing the novel dry strength enhancing agent modified with nanocellulose according to claim 4, characterized in that: In the secondary polymerization step, the mixed solution is added dropwise at a rate of 8 to 12 mL / min by a peristaltic pump. During the addition process, the temperature of the reactor is controlled at 65 to 75° C. by a heating jacket. The addition time is 60 to 90 minutes. After the addition is completed, the mixture is kept warm for 20 to 30 minutes.

9. The method for preparing the novel dry strength enhancing agent modified with nanocellulose according to claim 4, characterized in that: During the heat preservation and crosslinking step, a viscometer is used to monitor the viscosity of the material in real time. When the viscosity reaches 250-450 mPa·s and the total monomer content is ≤800 ppm, sodium sulfite is added in an amount of 1.2-1.4 times the total mass of ammonium persulfate.

10. The method for preparing the novel dry strength enhancing agent modified with nanocellulose according to claim 4, characterized in that: In the filtering and packaging step, a closed filter with a filtration accuracy of 20 to 40 μm is used for filtration.

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