High-performance environment-friendly papermaking neutral glue

Abstract

The invention relates to the technical field of neutral glue for papermaking, and discloses high-performance environment-friendly neutral glue for papermaking, which is prepared from 8 to 15 parts of alkyl ketene dimer, 0.3 to 1.0 part of cationized carboxylated nano cellulose, 5 to 15 parts of starch emulsifier and 1 to 5 parts of auxiliary component, wherein the cationized carboxylated nanocellulose is modified by grafting a cationic polymer, and the cationized carboxylated nanocellulose is adsorbed on an alkyl ketene dimer liquid droplet interface as a solid particle emulsifier in a Pickering emulsifier to form a composite emulsion. A cationic polymer is grafted on the surface of carboxylated nano-cellulose, so that the carboxylated nano-cellulose has cationic electrostatic adsorption and carboxyl interface activity, cationic groups are electrostatically combined with negative electricity fibers, the binding force between the fibers is enhanced, the tensile strength of paper is improved, meanwhile, nano-scale carboxyl adsorbs alkyl ketene dimer liquid drops to form a stable interface film, and the tensile strength of the paper is improved. The sizing efficiency of the neutral glue and the mechanical property of paper are improved.

Description

Technical Field

[0001] The invention relates to the technical field of neutral adhesives for papermaking, in particular to high-performance and environmentally friendly neutral adhesives for papermaking. Background Art

[0002] In the papermaking industry, alkyl ketene dimer (AKD) is the mainstream neutral sizing agent. Its emulsion stability and sizing efficiency directly affect the water resistance and production efficiency of paper. Neutral sizing agents can significantly reduce equipment corrosion and improve paper quality because they adapt to the neutral or alkaline environment of modern papermaking processes. In recent years, nanocellulose, due to its high specific surface area and interfacial activity, has provided new ideas for improving the dispersion stability and environmental performance of sizing agents in the construction of composite emulsions. Traditional neutral glues mostly use alkyl ketene dimer as the mainstream neutral sizing agent, which can replace the aluminum sulfate system.

[0003] However, in the current technology, alkyl ketene dimer is mostly a single emulsifier, which lacks the dual regulation ability of fiber interface and emulsion stability, making it difficult to effectively enhance the bonding force between fibers and limit the tensile strength of paper. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a high-performance environmentally friendly papermaking neutral glue to solve the problems of lack of dual regulation ability of fiber interface and emulsion stability, difficulty in effectively enhancing the bonding force between fibers, and limiting the tensile strength of paper.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: high-performance environmentally friendly papermaking neutral glue, including:

[0006] 8-15 parts of alkyl ketene dimer, 0.3-1.0 parts of cationized carboxylated nanocellulose, 5-15 parts of starch emulsifier and 1-5 parts of auxiliary ingredients;

[0007] The cationic carboxylated nanocellulose is modified by grafting a cationic polymer, and the cationic carboxylated nanocellulose is used as a solid particle emulsifier in a Pickering emulsifier and is adsorbed on the interface of alkyl ketene dimer droplets to form a composite emulsion.

[0008] Preferably, the carboxylated nanocellulose includes bacterial cellulose, wood cellulose or bamboo pulp cellulose.

[0009] Preferably, the cationic polymer includes polydimethyldiallylammonium chloride or chitosan or polyethyleneimine, with a grafting rate of 5% to 20%, and the carboxylation degree of the cationic carboxylated nanocellulose is maintained at 0.1-0.5 mmol / g.

[0010] Preferably, the starch emulsifier includes starch, sodium hydroxide solution and an etherifying agent, and the auxiliary components include a ripening accelerator, aluminum sulfate, zirconium oxychloride and a synergist.

[0011] The preparation method of high-performance environmentally friendly neutral glue for papermaking comprises the following steps:

[0012] S1. Cationization of carboxylated nanocellulose: dispersing the carboxylated nanocellulose in deionized water, adding a cationic polymer, stirring and reacting at 30-50° C. and pH 6-8 for 2-4 hours, and centrifuging and washing to a neutral pH to obtain surface cationized carboxylated nanocellulose;

[0013] S2, starch emulsifier preparation, bottom water, solid sodium hydroxide solution, starch are added to the reactor, the temperature is raised to 80 ℃ -85 ℃, the etherifying agent is added, the reaction is kept warm for 5-6 hours, and water is added to dilute to a solid content of 20% to 22%;

[0014] S3. Melt the AKD wax powder and melt the alkyl ketene dimer wax powder into liquid at 40-60°C;

[0015] S4, premixing and emulsification, adding a ripening accelerator, ionized carboxylated nanocellulose and water to an emulsifying kettle, heating to 95-105° C., adding a starch emulsifier in stages and continuously stirring, then slowly adding the melted alkyl ketene dimer wax powder, heating to 50±5° C., gradient stirring for 15-25 minutes to prepare a composite emulsion, and forming submicron alkyl ketene dimer particles by ultrasonic-assisted dispersion technology on the composite emulsion;

[0016] S5, preparation and homogenization treatment, transferring the composite emulsion to a homogenizer, adding aluminum sulfate and zirconium oxychloride and performing multi-stage homogenizer treatment to reduce the emulsion particle size to 0.8-1.2 μm;

[0017] S6, synergizing and filtering, cooling the homogenized composite emulsion to 20-30°C, adding a synergist, mixing evenly by magnetic stirring, and filtering to obtain a finished product.

[0018] Preferably, the amount of the cationic polymer added in S1 is 5% to 15% of the mass of the nanocellulose.

[0019] Preferably, the etherifying agent in S2 includes propylene oxide or sodium chloroacetate, and its usage accounts for 3% to 8% of the mass of starch.

[0020] Preferably, the starch emulsifier is added in stages in S4 three times, each time with an interval of 10 to 20 minutes, and the total amount of starch emulsifier added is 10% to 25% of the mass of the system in the emulsification kettle. The particle size of the submicron alkyl ketene dimer particles is 0.3-0.8 μm.

[0021] Preferably, the multi-stage homogenization treatment in S5 includes:

[0022] The initial homogenization pressure is 8-12MPa;

[0023] The secondary homogenization pressure is 10-15MPa;

[0024] Among them, the number of homogenization cycles is 2-3 times.

[0025] Preferably, the emulsion in S6 is cooled by circulating water cooling, and the cooling rate is controlled at 1-2°C / min. During the cooling process, the emulsion is continuously stirred, and the magnetic stirring speed is set to 150-200 r / min.

[0026] The present invention provides a high-performance environmentally friendly neutral adhesive for papermaking. It has the following beneficial effects:

[0027] 1. The present invention grafts cationic polymers onto the surface of carboxylated nanocellulose, making it have both cationic electrostatic adsorption and carboxyl interfacial activity. The cationic groups electrostatically bond with the negatively charged fibers, strengthening the binding force between fibers and improving the tensile strength of paper. At the same time, nano-scale carboxyl groups adsorb alkyl ketene dimer droplets to form a stable interfacial film, thereby improving the sizing efficiency of neutral glue and the mechanical properties of paper.

[0028] 2. The present invention avoids uneven dispersion caused by excessive local concentration by adding starch emulsifier three times, so that the emulsifier is gradually adsorbed on the droplet interface, reducing interfacial tension, and cooperates with ultrasonic assisted dispersion technology to break up large particles to form submicron particles with uniform particle size, thereby enhancing particle adsorption efficiency and reducing emulsion instability, thereby ensuring uniform adhesion of alkyl ketene dimer and improving sizing uniformity and water resistance.

[0029] 3. The present invention uses multi-stage homogenization treatment and gradient pressure to gradually break up particles, overcome agglomeration, avoid energy loss and overheating, combine aluminum sulfate and zirconium oxychloride to adjust the ion environment, strengthen the synergistic effect of cationic carboxylated nanocellulose and starch emulsifier, form a dual stabilization mechanism of electrostatic adsorption and steric hindrance, ensure the stability and uniform particle size of neutral glue, and achieve efficient penetration and spreading during glue application, significantly improving the water resistance and surface quality of paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a flow chart of the method for preparing the high-performance environmentally friendly neutral glue for papermaking. DETAILED DESCRIPTION

[0031] 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.

[0032] Please see the attached Figure 1 The embodiment of the present invention provides a high-performance environmentally friendly neutral adhesive for papermaking, including:

[0033] 8-15 parts of alkyl ketene dimer, 0.3-1.0 parts of cationized carboxylated nanocellulose, 5-15 parts of starch emulsifier and 1-5 parts of auxiliary ingredients;

[0034] Among them, the cationic carboxylated nanocellulose is modified by grafting cationic polymers, and the cationic carboxylated nanocellulose serves as a solid particle emulsifier in the Pickering emulsifier and is adsorbed on the interface of the alkyl ketene dimer droplets to form a composite emulsion.

[0035] Specifically, alkyl ketene dimer is a key hydrophobic component in neutral glue for papermaking. During the papermaking sizing process, it can be oriented and chemically reacted on the surface of paper fibers to form a continuous and tight hydrophobic film, effectively preventing moisture from penetrating into the interior of the paper. At the same time, it undergoes an esterification reaction with the hydroxyl groups on the cellulose molecules, thereby firmly bonding to the fiber surface and improving the water resistance of the paper.

[0036] After the cationic carboxylated nanocellulose is grafted with a cationic polymer, the abundant cationic groups on its surface can be tightly bound to the negatively charged fiber surface through electrostatic adsorption, thereby enhancing the interaction between the fibers and improving the strength of the paper. At the same time, as a solid particle emulsifier in the Pickering emulsifier, the nanocellulose carboxyl group forms hydrogen bonds with the ketone group of the alkyl ketene dimer, and can be adsorbed on the interface of the alkyl ketene dimer droplets, thereby promoting the uniform spreading of the hydrophobic film and solving the problem of uneven sizing caused by the coarse particle size of the alkyl ketene dimer emulsion. The interfacial modification of nanocellulose is used to improve the sizing efficiency of the alkyl ketene dimer and the mechanical properties of the paper, effectively improving the mechanical strength (tensile strength and tear strength) of the paper and making the paper tougher and more durable. The cationic carboxylated nanocellulose promotes the retention of the alkyl ketene dimer, thereby reducing the emission of hydrolysis products and achieving an environmentally friendly effect.

[0037] Starch emulsifiers are based on starch and have an amphiphilic structure that is both hydrophilic and lipophilic. Their hydrophilic groups interact with the aqueous phase, while their hydrophobic groups tend to combine with oily substances such as alkyl ketene dimers. They can disperse alkyl ketene dimers into tiny droplets and form a protective film on the surface of the droplets to prevent the droplets from colliding and merging with each other, thereby maintaining the stability of the emulsion.

[0038] Auxiliary ingredients can effectively shorten the aging cycle of paper, enable paper to reach its optimal performance state more quickly, meet the high-efficiency requirements of industrial production, enhance the stability of the composite emulsion, and ensure that each component maintains good activity and synergistic effects during preparation and use.

[0039] Carboxylated nanocellulose includes bacterial cellulose, wood cellulose or bamboo pulp cellulose.

[0040] Specifically, carboxylated bacterial cellulose, wood cellulose or bamboo pulp cellulose, by virtue of their nanoscale size and surface carboxyl groups, is adsorbed on the interface of alkyl ketene dimer droplets, forming a stable interfacial film through electrostatic and hydrogen bonding, thereby improving the rheological properties of the composite emulsion and enhancing fiber bonding.

[0041] The cationic polymer includes polydimethyldiallylammonium chloride or chitosan or polyethyleneimine, with a grafting rate of 5% to 20%, and maintains the carboxylation degree of the cationic carboxylated nanocellulose at 0.1 to 0.5 mmol / g.

[0042] Specifically, cationic polymers such as polydimethyldiallylammonium chloride, chitosan or polyethyleneimine are grafted onto carboxylated nanocellulose, giving it surface cationic properties. In combination with the existing carboxyl groups, the cations can be tightly electrostatically adsorbed to the negatively charged fibers, strengthening the connection between the fibers and improving the internal structure of the paper. The carboxyl groups play a role in stabilizing the composite emulsion and cooperate with other ingredients to optimize the emulsion state, thereby improving the mechanical properties of the paper, making the paper tougher, and ensuring the stability of the composite emulsion in each link, ensuring a good sizing effect.

[0043] The starch emulsifier comprises starch, sodium hydroxide solution and an etherifying agent, and the auxiliary components comprise a ripening accelerator, aluminum sulfate, zirconium oxychloride and a synergist.

[0044] Specifically, the starch in the starch emulsifier reacts with the etherifying agent in the alkaline environment created by the sodium hydroxide solution to form a substance with emulsifying properties, which can evenly disperse the alkyl ketene dimer in the aqueous phase, stabilize the composite emulsion, and enable the neutral glue to better adhere to the surface of the paper fiber. Among the auxiliary ingredients, the ripening accelerator accelerates the reaction between the alkyl ketene dimer and the fiber, improving production efficiency. Aluminum sulfate and zirconium oxychloride adjust the pH and ionic strength of the system and enhance the stability of the emulsion. The subsequent synergists (wet strength agents, dry strength agents and waterproofing agents, etc.) can comprehensively improve the sizing effect, strength and other properties of the paper.

[0045] The preparation method of high-performance environmentally friendly neutral glue for papermaking comprises the following steps:

[0046] S1. Cationization of carboxylated nanocellulose: dispersing the carboxylated nanocellulose in deionized water, adding a cationic polymer, stirring and reacting at 30-50° C. and pH 6-8 for 2-4 hours, and centrifuging and washing to a neutral pH to obtain surface cationized carboxylated nanocellulose;

[0047] S2, starch emulsifier preparation, bottom water, solid sodium hydroxide solution, starch are added to the reactor, the temperature is raised to 80 ℃ -85 ℃, the etherifying agent is added, the reaction is kept warm for 5-6 hours, and water is added to dilute to a solid content of 20% to 22%;

[0048] S3. Melt the AKD wax powder and melt the alkyl ketene dimer wax powder into liquid at 40-60°C;

[0049] S4, premixing and emulsification, adding a ripening accelerator, ionized carboxylated nanocellulose and water to an emulsifying kettle, heating to 95-105° C., adding a starch emulsifier in stages and continuously stirring, then slowly adding the melted alkyl ketene dimer wax powder, heating to 50±5° C., gradient stirring for 15-25 minutes to prepare a composite emulsion, and forming submicron alkyl ketene dimer particles by ultrasonic-assisted dispersion technology on the composite emulsion;

[0050] S5, preparation and homogenization treatment, transferring the composite emulsion to a homogenizer, adding aluminum sulfate and zirconium oxychloride and performing multi-stage homogenizer treatment to reduce the emulsion particle size to 0.8-1.2 μm;

[0051] S6, synergizing and filtering, cooling the homogenized composite emulsion to 20-30°C, adding a synergist, mixing evenly by magnetic stirring, and filtering to obtain a finished product.

[0052] Specifically, by dispersing the carboxylated nanocellulose in deionized water through S1 and then adding a cationic polymer, the cationic polymer and the carboxylated nanocellulose can be fully grafted and reacted, so that the nanocellulose originally with carboxyl groups on the surface can be successfully introduced with cationic groups to achieve surface cationization. The cationic carboxylated nanocellulose then produces strong electrostatic adsorption with the negatively charged paper fibers through the surface cations, thereby enhancing the bonding force between the fibers and significantly improving the strength of the paper. At the same time, when used as a Pickering emulsifier component, it can better adsorb on the interface of the alkyl ketene dimer droplets, optimize the stability of the composite emulsion, and lay the foundation for the subsequent preparation of high-performance papermaking neutral glue and improvement of the comprehensive performance of the paper.

[0053] In S2, bottom water, solid sodium hydroxide solution, and starch are added to the reactor together. The starch molecular structure is modified, and its hydrophilicity and lipophilicity are optimized, thereby achieving excellent emulsification ability. After the reaction is completed, water is added to dilute and adjust the system concentration to ensure that the starch emulsifier effectively disperses the alkyl ketene dimer, stabilizes the composite emulsion system, and ensures that the sizing agent acts evenly on the paper fibers, comprehensively improving the paper sizing effect and enhancing key properties such as water resistance and strength.

[0054] S3 heats and melts the alkyl ketene dimer wax powder into a liquid state. The melted liquid alkyl ketene dimer has good fluidity, which facilitates uniform mixing with other ingredients such as cationic carboxylated nanocellulose and starch emulsifier in subsequent steps, thereby ensuring the stability and uniformity of the composite emulsion system. This also lays the foundation for the alkyl ketene dimer to be evenly distributed on the surface of paper fibers during papermaking and sizing, thereby enhancing the paper's water resistance.

[0055] In step S4, a ripening accelerator, ionized carboxylated nanocellulose, and water are sequentially added, and the temperature is raised to activate the ripening accelerator and disperse the nanocellulose. Subsequently, a starch emulsifier is added in sections and stirred to allow it to be evenly dispersed and emulsify. Then, melted alkyl ketene dimer wax powder is slowly added, and the temperature is raised to perform gradient stirring to ensure that all ingredients are fully mixed and emulsified. Finally, ultrasound-assisted dispersion is performed to disperse the alkyl ketene dimer into submicron particles, effectively reducing sedimentation caused by gravity and the probability of collision and agglomeration between particles. At the same time, a continuous and dense hydrophobic layer is formed, thereby improving the water resistance of the paper.

[0056] S5 aluminum sulfate and zirconium oxychloride can adjust the pH and ionic strength of the emulsion system, optimize the system environment, and help enhance the interaction between the various components in the emulsion. The shearing and extrusion mechanical forces generated by the multi-stage homogenizer can further break up large particles in the emulsion, accurately reducing the emulsion particle size to 0.8-1.2μm, thereby improving the uniformity and stability of the emulsion, making it less prone to problems such as stratification and flocculation during storage and transportation. During subsequent paper sizing, it can spread and penetrate more evenly on the paper fiber surface, ensuring the consistency of the sizing effect, thereby improving the overall water resistance and surface quality of the paper.

[0057] The homogenized composite emulsion is cooled by S6 to avoid fluctuations in component properties or emulsion instability caused by high temperature. After the synergist is added, magnetic stirring is used to achieve uniform dispersion, so that the synergist and emulsion components are fully in contact and play a synergistic role. The subsequent filtration operation can effectively remove undispersed particles, impurities and possible flocs, ensuring the purity and uniformity of the finished emulsion, and ensuring that the finished emulsion made from the final neutral glue is highly stable and has few impurities, which can ensure a smooth sizing process when used in papermaking.

[0058] The amount of cationic polymer added in S1 is 5% to 15% of the mass of nanocellulose.

[0059] Specifically, cationic polymers are added at a ratio of 5% to 15% of the mass of carboxylated nanocellulose to ensure that sufficient cationic groups are grafted onto the surface of the nanocellulose, giving it strong cationic properties, while avoiding entanglement or agglomeration of molecular chains due to excessive addition. Its cationic groups can produce electrostatic adsorption with negatively charged paper fibers, strengthen the bonding force between fibers, and significantly improve the dry and wet strength of the paper.

[0060] The etherifying agent in S2 includes propylene oxide or sodium chloroacetate, and its usage accounts for 3% to 8% of the mass of starch.

[0061] Specifically, the etherifying agent (propylene oxide or sodium chloroacetate) participates in the reaction in an amount of 3% to 8% of the mass of starch, undergoes an etherification reaction with the starch molecules under alkaline conditions, introduces hydrophilic groups such as hydroxypropyl and carboxymethyl, breaks the original tight structure of the starch molecules, and makes it have both hydrophilic and lipophilic properties, thereby obtaining an emulsifying function, ensuring that the starch is fully modified to meet the emulsification requirements, and avoiding side reactions or cost increases due to excessive addition.

[0062] The starch emulsifier is added in stages in S4 three times, with an interval of 10 to 20 minutes between each addition, and the total amount of starch emulsifier added is 10% to 25% of the mass of the system in the emulsification kettle. The particle size of the submicron alkyl ketene dimer particles is 0.3-0.8 μm.

[0063] Specifically, the starch emulsifier is added at intervals of three times. By replenishing the emulsifier in stages, the problem of excessive local concentration or uneven dispersion caused by one-time addition can be avoided, so that the emulsifier molecules are gradually adsorbed on the interface of the alkyl ketene dimer droplets, continuously reducing the interfacial tension, promoting the uniform dispersion of the droplets and forming a stable emulsified structure, and finally forming submicron alkyl ketene dimer particles with a particle size of 0.3-0.8μm in combination with ultrasonic assisted dispersion technology, ensuring that the particles have a large specific surface area to enhance the fiber adsorption efficiency, while avoiding the problem of insufficient interfacial film stability due to excessively fine particles or sedimentation caused by excessively coarse particles.

[0064] The multi-stage homogenization process in S5 includes:

[0065] The initial homogenization pressure is 8-12MPa;

[0066] The secondary homogenization pressure is 10-15MPa;

[0067] Among them, the number of homogenization cycles is 2-3 times.

[0068] Specifically, the composite emulsion is initially crushed at a pressure of 8-12 MPa to initially refine the larger particles, and then further sheared and squeezed at a higher pressure of 10-15 MPa. Combined with 2-3 cycles of homogenization, the emulsion particle size is gradually and precisely controlled to 0.8-1.2 μm, which can effectively overcome the agglomeration force between the particles, avoid energy loss or local overheating caused by a single high pressure, and ensure uniform refinement of the emulsion particles. At the same time, in conjunction with the regulation of the system's ionic environment by aluminum sulfate and zirconium oxychloride, the homogenization treatment strengthens the interfacial stabilization effect of cationic carboxylated nanocellulose and starch emulsifier on the alkyl ketene dimer droplets, significantly improving the uniformity and storage stability of the emulsion, so that the refined emulsion can more efficiently penetrate the fiber pores and spread evenly when sizing paper, forming a dense and stable hydrophobic layer, and improving the consistency and surface quality of the paper's water resistance.

[0069] In S6, the emulsion is cooled by circulating water cooling, and the cooling rate is controlled at 1-2°C / min. During the cooling process, the emulsion is continuously stirred, and the magnetic stirring speed is set to 150-200r / min.

[0070] Specifically, the use of circulating water cooling can prevent the emulsion from coagulating components or precipitating alkyl ketene dimers due to sudden temperature changes through a controllable cooling process, ensuring that the system temperature drops evenly. Continuous stirring can effectively inhibit particle sedimentation, allowing the synergist to remain evenly mixed with the emulsion components during the cooling process, avoiding stratification or local uneven concentration problems.

[0071] Example 1

[0072] The ratio of high-performance environmentally friendly neutral glue for papermaking is: 12 parts of alkyl ketene dimer, 0.5 parts of cationic carboxylated nanocellulose (bacterial cellulose grafted with polydimethyldiallylammonium chloride, grafting rate 10%, carboxylation degree 0.3mmol / g), 10 parts of starch emulsifier and 3 parts of auxiliary ingredients;

[0073] The auxiliary components include 0.5 parts of a ripening accelerator, 1.5 parts of aluminum sulfate, 0.8 parts of zirconium oxychloride and 0.2 parts of a chitosan synergist.

[0074] Preparation steps:

[0075] S101, dispersing bacterial cellulose in deionized water, adding polydimethyldiallyl ammonium chloride (10% of the mass of nanocellulose), reacting at 40° C. and pH 7 for 3 hours, and centrifuging and washing until neutral;

[0076] S102, adding bottom water, sodium hydroxide solution and starch to a reactor, heating to 82°C, adding propylene oxide (5% of the mass of starch), keeping the temperature for reaction for 5.5 hours, and diluting to a solid content of 21%;

[0077] S103, melt the alkyl ketene dimer wax powder into liquid at 50°C

[0078] S104. Add a ripening accelerator, cationized cellulose, and water to an emulsifier and heat to 100°C. Add a starch emulsifier three times (15-minute intervals) to a total amount of 18% of the system mass. Slowly add liquid alkyl ketene dimer, heat to 50°C, and stir gradually for 20 minutes. Ultrasonic-assisted dispersion is then performed to obtain alkyl ketene dimer particles with a particle size of 0.5 μm.

[0079] S105, adding aluminum sulfate and zirconium oxychloride to the composite emulsion, and homogenizing twice (first at 10 MPa, second at 12 MPa, for 2 cycles) until the particle size is reduced to 0.9 μm;

[0080] S106, cooling to 25°C (cooling rate 1.5°C / min, magnetic stirring 180r / min), adding chitosan synergist, and filtering to obtain the finished product;

[0081] Example 2

[0082] The ratio of high-performance environmentally friendly neutral glue for papermaking is as follows: 9 parts of alkyl ketene dimer (AKD), 0.8 parts of cationic carboxylated nanocellulose (cellulose grafted with chitosan, grafting rate 15%, carboxylation degree 0.2 mmol / g), 8 parts of starch emulsifier (starch etherified with sodium chloroacetate, etherification degree 7%) and 4 parts of auxiliary ingredients;

[0083] The auxiliary components include 0.8 parts of a ripening accelerator, 2.0 parts of aluminum sulfate, 1.0 parts of zirconium oxychloride, and 0.2 parts of a sodium alginate synergist.

[0084] Preparation steps:

[0085] S201, dispersing lignocellulose in deionized water, adding chitosan (12% of the mass of nanocellulose), reacting at 35°C and pH 6.5 for 4 hours, and centrifuging and washing until neutral;

[0086] S202, add bottom water, sodium hydroxide solution and starch to the reactor, heat to 83 ° C, add sodium chloroacetate (7% of the mass of starch), keep warm for 6 hours, and dilute to a solid content of 20%;

[0087] S203, melting the alkyl ketene dimer wax powder into a liquid at 45° C.;

[0088] S204. Add a ripening accelerator, cationized cellulose, and water to an emulsifying kettle and heat to 98°C. Add a starch emulsifier three times (20-minute intervals) to a total amount of 22% of the system mass. Slowly add liquid alkyl ketene dimer, heat to 48°C, stir gradually for 25 minutes, and obtain alkyl ketene dimer particles by ultrasonic-assisted dispersion. The particle size is controlled to be 0.4 μm.

[0089] S205, adding aluminum sulfate and zirconium oxychloride to the composite emulsion, and homogenizing three times (8 MPa for the first time, 15 MPa for the second time, and 3 cycles) until the particle size is reduced to 0.7 μm;

[0090] S206, cooling to 22°C (cooling rate 1°C / min, magnetic stirring 200 r / min), adding sodium alginate synergist, and filtering to obtain the finished product.

[0091] Table 1 is a comparison table of the performance of neutral glue between various examples

[0092] Example 1 Example 2 Hydrolysis rate (72 hours) 8.5％ 10.2％ Paper tensile strength higher high Preparation cost middle Low

[0093] Among them, the degree of carboxylation of the nanocellulose in Example 1 is higher than that in Example 2. It is more tightly bound to the ketone group of the alkyl ketene dimer through hydrogen bonds, reducing the chance of the alkyl ketene dimer being exposed to water, thereby significantly inhibiting hydrolysis. At the same time, Example 1 uses two homogenizations to avoid excessive shearing to damage the AKD particle structure. Example 2 uses three homogenizations. The higher shear force may partially damage the interfacial protective layer, resulting in a slightly higher hydrolysis rate.

[0094] The bacterial cellulose grafted in Example 1 is more likely to form a uniform three-dimensional network than the wood cellulose grafted chitosan in Example 2, where the natural rigidity of the latter limits the flexibility of the network;

[0095] The cost of the bio-based chitosan raw material used in Example 1 is higher than that of the chitosan bio-based raw material used in Example 2.

[0096] 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. High performance environmentally friendly papermaking neutral glue, characterized by: include: 8-15 parts of alkyl ketene dimer, 0.3-1.0 parts of cationized carboxylated nanocellulose, 5-15 parts of starch emulsifier and 1-5 parts of auxiliary ingredients; The cationic carboxylated nanocellulose is modified by grafting a cationic polymer, and the cationic carboxylated nanocellulose is used as a solid particle emulsifier in a Pickering emulsifier and is adsorbed on the interface of alkyl ketene dimer droplets to form a composite emulsion.

2. The high-performance environmentally friendly neutral adhesive for papermaking according to claim 1, characterized in that: The carboxylated nanocellulose includes bacterial cellulose, wood cellulose or bamboo pulp cellulose.

3. The high-performance environmentally friendly neutral adhesive for papermaking according to claim 1, characterized in that: The cationic polymer includes polydimethyldiallylammonium chloride or chitosan or polyethyleneimine, with a grafting rate of 5% to 20%, and maintains the carboxylation degree of the cationic carboxylated nanocellulose at 0.1 to 0.5 mmol / g.

4. The high-performance environmentally friendly neutral adhesive for papermaking according to claim 1, characterized in that: The starch emulsifier comprises starch, sodium hydroxide solution and an etherifying agent, and the auxiliary components comprise a ripening accelerator, aluminum sulfate, zirconium oxychloride and a synergist.

5. A method for preparing high-performance environmentally friendly neutral glue for papermaking, characterized in that: The high-performance environmentally friendly neutral glue for papermaking according to any one of claims 1 to 4 comprises the following steps: S1. Cationization of carboxylated nanocellulose: dispersing the carboxylated nanocellulose in deionized water, adding a cationic polymer, stirring and reacting at 30-50° C. and pH 6-8 for 2-4 hours, and centrifuging and washing to a neutral pH to obtain surface cationized carboxylated nanocellulose; S2, starch emulsifier preparation, bottom water, solid sodium hydroxide solution, starch are added to the reactor, the temperature is raised to 80 ℃ -85 ℃, the etherifying agent is added, the reaction is kept warm for 5-6 hours, and water is added to dilute to a solid content of 20% to 22%; S3. Melt the AKD wax powder and melt the alkyl ketene dimer wax powder into liquid at 40-60°C; S4, premixing and emulsification, adding a ripening accelerator, ionized carboxylated nanocellulose and water to an emulsifying kettle, heating to 95-105° C., adding a starch emulsifier in stages and continuously stirring, then slowly adding the melted alkyl ketene dimer wax powder, heating to 50±5° C., gradient stirring for 15-25 minutes to prepare a composite emulsion, and forming submicron alkyl ketene dimer particles by ultrasonic-assisted dispersion technology on the composite emulsion; S5, preparation and homogenization treatment, transferring the composite emulsion to a homogenizer, adding aluminum sulfate and zirconium oxychloride and performing multi-stage homogenizer treatment to reduce the emulsion particle size to 0.8-1.2 μm; S6, synergizing and filtering, cooling the homogenized composite emulsion to 20-30°C, adding a synergist, mixing evenly by magnetic stirring, and filtering to obtain a finished product.

6. The method for preparing high-performance environmentally friendly neutral glue for papermaking according to claim 5, characterized in that: The amount of the cationic polymer added in S1 is 5% to 15% of the mass of the nanocellulose.

7. The method for preparing high-performance environmentally friendly neutral glue for papermaking according to claim 5, characterized in that: The etherifying agent in S2 includes propylene oxide or sodium chloroacetate, and its usage accounts for 3% to 8% of the mass of starch.

8. The method for preparing high-performance environmentally friendly neutral glue for papermaking according to claim 5, characterized in that: The starch emulsifier is added in stages in S4 three times, each time with an interval of 10 to 20 minutes, and the total amount of starch emulsifier added is 10% to 25% of the mass of the system in the emulsification kettle. The particle size of the submicron alkyl ketene dimer particles is 0.3-0.8 μm.

9. The method for preparing high-performance environmentally friendly neutral glue for papermaking according to claim 5, characterized in that: The multi-stage homogenization process in S5 includes: The initial homogenization pressure is 8-12MPa; The secondary homogenization pressure is 10-15MPa; Among them, the number of homogenization cycles is 2-3 times.

10. The method for preparing high-performance environmentally friendly neutral glue for papermaking according to claim 5, characterized in that: The emulsion in S6 is cooled by circulating water, and the cooling rate is controlled at 1-2°C / min. During the cooling process, the emulsion is continuously stirred, and the magnetic stirring speed is set to 150-200r / min.

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