AKD (alkyl ketene dimer) emulsion and preparation method thereof

Abstract

The invention relates to the technical field of papermaking chemicals, in particular to an AKD emulsion and a preparation method thereof. The AKD emulsion is prepared from, by mass, 18-22 parts of modified alkyl ketene dimer, 1.5-2 parts of dopamine modified silicon dioxide, 2.5-3 parts of emulsifier, 1.8-2.2 parts of dispersing agent, 1.3-1.5 parts of synergist, 1-1.2 parts of stabilizer and 80-85 parts of water, and the emulsifier is prepared by mixing modified cationic starch emulsifier and polymer emulsifier according to the mass part ratio of 1: 1. Through reasonable raw material selection and proportioning, the AKD emulsion with excellent stability, sizing performance and water resistance is prepared, and a better solution is provided for production of paper products.

Description

Technical Field

[0001] The present application relates to the technical field of papermaking chemicals, and in particular to an AKD emulsion and a preparation method thereof. Background Art

[0002] In recent years, due to the continuous increase in rosin prices, the cost of traditional rosin sizing has also increased, and AKD neutral sizing has attracted more and more attention. During the use of AKD sizing, since AKD itself has no charge, it is difficult to stay on the fiber. Generally, cationic emulsifiers are needed to emulsify AKD so that AKD carries a positive charge and adsorbs to the negatively charged fiber.

[0003] At present, the papermaking industry widely uses alkyl ketene dimer (AKD) emulsion to improve the waterproof performance of paper. This emulsion is usually white and easily hydrolyzed, playing a key role in the papermaking process. However, traditional AKD emulsion has problems such as poor stability and poor sizing effect in practical applications, especially when facing specific paper types, such as copperplate paper, copy paper, archival paper, dictionary paper and high-quality writing paper, etc., it is often difficult to achieve the desired effect. In addition, the traditional process has high energy consumption and a greater impact on the environment. Contents of the invention The purpose of this application is to provide an AKD emulsion and a preparation method thereof in view of the deficiencies of the current technology. The AKD emulsion prepared in this application has excellent stability, sizing performance and low cost, and can significantly improve the water resistance of paper.

[0004] In the first aspect, the present application provides an AKD emulsion, which adopts the following technical solution: An AKD emulsion comprises the following raw materials, measured by weight: 18-22 parts of modified alkyl ketene dimer, 1.5-2 parts of dopamine-modified silicon dioxide, 2.5-3 parts of emulsifier, 1.8-2.2 parts of dispersant, 1.3-1.5 parts of synergist, 1-1.2 parts of stabilizer and 80-85 parts of water, wherein the emulsifier is prepared by mixing a modified cationic starch emulsifier and a polymer emulsifier in a weight ratio of 1:1.

[0005] By adopting the above technical scheme, modified alkyl ketene dimer (AKD): as the main raw material, it is modified by polyethylene imine to improve the adhesion rate of emulsion particles on the fiber, which helps to improve the stability and retention rate of AKD emulsion. Dopamine modified silica: silica is modified by dopamine to make silica have higher adhesion, can form an interfacial film at the oil-water interface, reduce interfacial tension and interfacial energy, prevent droplet aggregation, and improve the stability of AKD emulsion after emulsification. Emulsifier: It is prepared by mixing modified cationic starch emulsifier and polymer emulsifier in a mass ratio of 1:1. The modified cationic starch emulsifier forms a supramolecular composite system through the electrostatic and hydrogen bonding forces of different components, thereby improving the emulsification properties of potato starch; the polymer emulsifier is added with polydiallyl dimethyl ammonium chloride, and cross-linked with dimethyl diallyl ammonium chloride to make the resulting emulsion have strong positive charge, which can be well adsorbed on the negatively charged fiber surface, thereby improving the retention rate on the fiber surface. The two work synergistically to significantly improve the emulsification properties of AKD emulsion, thereby improving the stability, sizing performance and retention rate of AKD emulsion. Dispersant: used to improve the dispersibility of the emulsion, so that each component is evenly distributed in the emulsion, and improve the comprehensive performance of the AKD emulsion. Synergist: modified guar gum can promote the ripening of AKD. Stabilizer: used to maintain the stability of the emulsion and prevent stratification or precipitation. Water: as a solvent, dissolves and mixes the components together. In summary, the components in the present application improve the stability, sizing performance and low cost of AKD emulsion through synergistic effect, and can significantly improve the water resistance of paper.

[0006] Preferably, the preparation method of the modified alkyl ketene dimer is as follows: 10 parts of alkyl ketene dimer wax powder are heated and melted in a water bath according to the mass fraction, and after the alkyl ketene dimer wax powder is completely melted, 4.5 parts of 73° C. polyethyleneimine solution with a mass concentration of 35% is slowly added to the melted alkyl ketene dimer, and after high-speed shear stirring for 10 minutes, 3 parts of deionized water are added, and high-speed shear stirring is continued for 20 minutes. After standing for 3 hours, the mixture is cooled to room temperature to obtain the modified alkyl ketene dimer.

[0007] By adopting the above technical scheme, the alkyl ketene dimer wax powder is first heated and melted in a water bath, and then the polyethyleneimine solution is slowly added and high-speed shear stirring is performed. This process mainly reacts with the alkyl ketene dimer through the hydrophilic and lipophilic groups in the polyethyleneimine, thereby changing its properties. Next, deionized water is added and high-speed shear stirring is continued, which is to further promote the reaction and make the reaction product more uniform. Finally, it is left to cool to room temperature to obtain a modified alkyl ketene dimer. The role of the modified alkyl ketene dimer is mainly to increase the adhesion rate of the emulsion particles on the fiber, thereby helping to enhance the stability and retention rate of the AKD emulsion. At the same time, since polyethyleneimine has hydrophilic and lipophilic characteristics, the emulsification performance of the emulsion can also be improved.

[0008] Preferably, the preparation method of the dopamine-modified silica is as follows: 40 parts of potassium hydroxide and 1000 parts of deionized water are mixed according to mass fractions, stirred evenly, and then heated to 42°C to obtain a potassium hydroxide solution, and then 50 parts of dopamine are added to the potassium hydroxide solution and stirred for 30 minutes, and then 80 parts of silica with an average particle size of 50 nanometers are added, and the reaction is carried out for 3 hours while keeping the temperature constant. Finally, the product is filtered and washed with deionized water for 3 times, and then placed in an oven at 80°C for drying after washing, and then ground after drying to obtain dopamine-modified silica.

[0009] By adopting the above technical scheme, the prepared dopamine-modified silica is modified by dopamine to make silica have higher adhesion. This enables the AKD emulsion to better adhere to the fiber during the sizing process, thereby improving the water resistance of the paper. Dopamine-modified silica can form an interfacial film at the oil-water interface, thereby reducing interfacial tension and interfacial energy. This helps to prevent droplet aggregation, thereby improving the stability of the emulsion after AKD emulsification to a certain extent. Synergistically with modified cationic starch emulsifiers and polymer emulsifiers, the emulsification properties of the AKD emulsion are significantly improved. This synergistic effect helps to improve the stability, sizing performance and retention rate of the AKD emulsion, thereby reducing production costs and improving paper quality. In summary, dopamine-modified silica in this application significantly improves the performance of the AKD emulsion by improving adhesion, forming an interfacial film and synergizing with other components, providing strong support for the preparation of high-performance, low-cost paper.

[0010] Preferably, the preparation method of the modified cationic starch emulsifier comprises the following steps: S41, adding 50 parts of potato starch, 2 parts of ammonium persulfate, 2 parts of triallylamine and 6 parts of polydiallyldimethylammonium chloride into a flask according to their weight parts, and gelatinizing at 93° C. for 50 min to obtain a mixture; S42. After diluting the mixture by weight, 98 parts of deionized water were added, and the mixture was stirred at a stirring speed of 1500 r / min for 60 minutes. Finally, the pH value was adjusted to 2.5 with acetic acid to obtain a modified cationic starch emulsifier.

[0011] By adopting the above technical solution, the prepared modified cationic starch emulsifier forms a supramolecular composite system through the electrostatic and hydrogen bonding forces of different components, thereby improving the emulsification performance of potato starch. The modified cationic starch emulsifier and the polymer emulsifier work synergistically to significantly improve the emulsification performance of AKD emulsion, thereby improving the stability, sizing performance and retention rate of AKD emulsion.

[0012] Preferably, the method for preparing the polymer emulsifier comprises the following steps: S51. According to the mass ratio, 30 parts of deionized water, 0.1 parts of sodium sulfite and 0.15 parts of ammonium persulfate are prepared into an initiator solution for standby use; S52, according to the mass fraction, 17 parts of a 67% dimethyldiallyl ammonium chloride solution are added dropwise to the reaction kettle, and the temperature is raised to 73°C under stirring; within 2 hours, 48 ​​parts of a 63% dimethyldiallyl ammonium chloride solution are slowly added dropwise to the reaction kettle; then within 1 hour, 5 parts of polydiallyldimethylammonium chloride and 4 parts of diallylamine are slowly added dropwise to the reaction kettle to obtain a reaction solution; S53. According to the mass fraction, the reaction liquid is stirred and heated to 85° C., the initiator solution is slowly added dropwise to the reaction liquid within 3 hours, the reaction is stirred for 3 hours, and the reaction is cooled to room temperature to obtain a polymer emulsifier.

[0013] By adopting the above technical scheme, the prepared polymer emulsifier can be cross-linked and polymerized with dimethyldiallyl ammonium chloride by adding polydiallyl dimethyl ammonium chloride, due to its high charge density, so that the resulting emulsion has a strong positive charge, can be well adsorbed on the negatively charged fiber surface, and improve the retention rate on the fiber surface. The polymer emulsifier and the modified cationic starch emulsifier work synergistically to significantly improve the emulsification performance of the AKD emulsion, thereby improving the stability of the AKD emulsion. The polymer emulsifier has a strong positive charge and can be well adsorbed on the negatively charged fiber surface, improve the retention rate on the fiber surface, and thus help to improve the sizing performance of the AKD emulsion. The polymer emulsifier can promote the maturation of AKD, shorten the maturation time, and reduce the false sizing phenomenon that occurs during the sizing process.

[0014] Preferably, the dispersant is prepared by mixing hexenyl bisstearamide, polyoxyethylene sorbitan monostearate and sorbitan monopalmitate in a mass ratio of 3:2:3.

[0015] By adopting the above technical scheme, the three substances of hexenyl bis stearamide, polyoxyethylene sorbitan monostearate and sorbitan monopalmitate can form a composite system in the emulsion, and through the interaction force between them, the components in the emulsion can be evenly distributed in the emulsion, thereby improving the dispersibility of the emulsion. The composite system formed by these three substances in the emulsion can effectively reduce the surface tension and interfacial energy of the emulsion, thereby preventing the aggregation of droplets and improving the stability of the emulsion. The composite system formed by the three substances of hexenyl bis stearamide, polyoxyethylene sorbitan monostearate and sorbitan monopalmitate in the emulsion can effectively improve the adhesion rate of emulsion particles on the fiber, thereby helping to enhance the stability and retention rate of the AKD emulsion. The composite system formed by these three substances in the emulsion can produce a synergistic effect, further improve the emulsification performance of the AKD emulsion, thereby improving the stability, sizing performance and retention rate of the AKD emulsion. In summary, when hexenyl bisstearamide, polyoxyethylene sorbitan monostearate and sorbitan monopalmitate are used as dispersants in AKD emulsion, they can significantly improve the dispersibility, stability, sizing performance and retention rate of the emulsion, and at the same time produce a synergistic effect to further improve the performance of AKD emulsion.

[0016] Preferably, the stabilizer is aluminum sulfate.

[0017] Preferably, the synergist is modified guar gum.

[0018] Preferably, the preparation method of the modified guar gum is as follows: according to the mass fraction, 500 parts of a sodium hydroxide solution with a mass concentration of 20% are added to a reaction kettle, then 200 parts of guar gum are added under the stirring condition of 200rpm, and then 10 parts of galactose oxidase and 15 parts of mannosidase are added when the stirring speed is adjusted to 800rpm, and after being evenly dispersed, the mixture is reacted at 125°C for 8h, the obtained product is poured into an ethanol aqueous solution and the pH value is adjusted to 7, the supernatant is filtered out, the precipitate is washed with an ethanol aqueous solution, and the modified guar gum is obtained after drying and crushing.

[0019] In a second aspect, the present application provides a method for preparing an AKD emulsion, using the following technical solution: As a general technical concept, the present application also provides a method for preparing the above-mentioned AKD emulsion, comprising the following steps: 101. Adding modified alkyl ketene dimer, dopamine-modified silica, emulsifier, dispersant, synergist and water to a reactor in order according to their mass fractions, stirring and reacting for 60 minutes, then heating to 70-75° C., keeping the temperature for reaction for 60 minutes, and obtaining a mixture A; S102, emulsifying the mixture A at a high shear emulsifier at a speed of 10000 r / min for 30 min to obtain an emulsified mixture A, adding a stabilizer to the emulsified mixture A and stirring evenly to obtain a mixture B, and then homogenizing the mixture B with a homogenizer for 30 minutes, cooling to room temperature, and obtaining an AKD emulsion.

[0020] In summary, the beneficial technical effects of this application are: 1. Improved stability: The use of modified alkyl ketene dimer and dopamine-modified silica, as well as the optimized ratio of emulsifiers, significantly improves the stability of AKD emulsion. This makes it less likely for the emulsion to stratify or precipitate during storage and use, thus ensuring the stability of product quality.

[0021] 2. Enhanced sizing performance: The synergistic effect of modified cationic starch emulsifier and polymer emulsifier improves the emulsification performance of AKD emulsion, thereby improving the sizing performance. This means that during the paper production process, AKD emulsion can be more evenly distributed on the fiber surface, improving the water resistance of the paper.

[0022] 3. Cost reduction: The preparation method of the present application is simple and easy to implement, and the raw materials are easily available, which reduces the production cost. At the same time, since the stability and sizing performance of the AKD emulsion are improved, the waste during use can be reduced, further reducing the cost.

[0023] 4. Environmental performance: The raw materials used in this application are all environmentally friendly materials, do not contain toxic and harmful substances, and meet the requirements of green environmental protection. In addition, AKD emulsion will not produce harmful substances during use and is harmless to the environment and human body.

[0024] 5. Wide application: The AKD emulsion prepared in this application is suitable for the production of various papers, such as packaging paper, printing paper, toilet paper, etc., and has broad application prospects. DETAILED DESCRIPTION

[0025] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0026] In the following examples and preparation examples, 1 part means 100 g.

[0027] Preparation Example 1 Preparation of modified alkyl ketene dimer The preparation method of the modified alkyl ketene dimer is as follows: according to the mass fraction, 10 parts of alkyl ketene dimer wax powder are heated and melted in a water bath, after the alkyl ketene dimer wax powder is completely melted, 4.5 parts of 73°C polyethyleneimine solution with a mass concentration of 35% are slowly added to the melted alkyl ketene dimer, after high-speed shear stirring for 10 minutes, 3 parts of deionized water are added, and high-speed shear stirring is continued for 20 minutes. After standing for 3 hours, it is cooled to room temperature to obtain the modified alkyl ketene dimer.

[0028] Preparation Example 2 Preparation of dopamine-modified silica The preparation method of dopamine-modified silica is as follows: 40 parts of potassium hydroxide and 1000 parts of deionized water are mixed according to mass fractions, stirred evenly, and then heated to 42°C to obtain a potassium hydroxide solution, and then 50 parts of dopamine are added to the potassium hydroxide solution and stirred for 30 minutes, and then 80 parts of silica with an average particle size of 50 nanometers are added, and the reaction is carried out for 3 hours while keeping the temperature constant. Finally, the product is filtered and washed with deionized water for 3 times, and then placed in an oven at 80°C for drying. After drying, it is ground to obtain dopamine-modified silica.

[0029] Preparation Example 3 Preparation of modified cationic starch emulsifier The preparation method of the modified cationic starch emulsifier comprises the following steps: S41, adding 50 parts of potato starch, 2 parts of ammonium persulfate, 2 parts of triallylamine and 6 parts of polydiallyldimethylammonium chloride into a flask according to their weight parts, and gelatinizing at 93° C. for 50 min to obtain a mixture; S42. After diluting the mixture by weight, 98 parts of deionized water were added, and the mixture was stirred at a stirring speed of 1500 r / min for 60 minutes. Finally, the pH value was adjusted to 2.5 with acetic acid to obtain a modified cationic starch emulsifier.

[0030] Preparation Example 4 Preparation of polymer emulsifier The preparation method of the polymer emulsifier comprises the following steps: S51. According to the mass ratio, 30 parts of deionized water, 0.1 parts of sodium sulfite and 0.15 parts of ammonium persulfate are prepared into an initiator solution for standby use; S52, according to the mass fraction, 17 parts of a 67% dimethyldiallyl ammonium chloride solution are added dropwise to the reaction kettle, and the temperature is raised to 73°C under stirring; within 2 hours, 48 ​​parts of a 63% dimethyldiallyl ammonium chloride solution are slowly added dropwise to the reaction kettle; then within 1 hour, 5 parts of polydiallyldimethylammonium chloride and 4 parts of diallylamine are slowly added dropwise to the reaction kettle to obtain a reaction solution; S53. According to the mass fraction, the reaction liquid is stirred and heated to 85° C., the initiator solution is slowly added dropwise to the reaction liquid within 3 hours, the reaction is stirred for 3 hours, and the reaction is cooled to room temperature to obtain a polymer emulsifier.

[0031] Preparation Example 5 Preparation of modified guar gum The preparation method of the modified guar gum comprises the following steps: adding 500 parts of a sodium hydroxide solution with a mass concentration of 20% into a reaction kettle according to the mass fraction, then adding 200 parts of guar gum under the stirring condition of 200 rpm, and then adding 10 parts of galactose oxidase and 15 parts of mannosidase when the stirring speed is adjusted to 800 rpm, and reacting for 8 hours at 125° C. after being evenly dispersed, and the obtained product is poured into an ethanol aqueous solution to adjust the pH value to 7, and after filtering out the supernatant, the precipitate is washed with an ethanol aqueous solution, and after drying and crushing, the modified guar gum is obtained.

[0032] Example 1 An AKD emulsion comprises the following raw materials, measured by weight: 18 parts of modified alkyl ketene dimer, 1.5 parts of dopamine-modified silicon dioxide, 2.5 parts of emulsifier, 1.8 parts of dispersant, 1.3 parts of modified guar gum, 1 part of aluminum sulfate, and 80 parts of water, wherein the emulsifier is prepared by mixing a modified cationic starch emulsifier and a polymer emulsifier in a weight ratio of 1:1, and the dispersant is prepared by mixing hexenyl bis stearamide, polyoxyethylene sorbitan monostearate, and sorbitan monopalmitate in a weight ratio of 3:2:3.

[0033] The preparation method of the above-mentioned AKD emulsion comprises the following steps: 101. Add modified alkyl ketene dimer, dopamine-modified silica, emulsifier, dispersant, modified guar gum and water into a reactor in order according to their weight fractions, stir and react for 60 minutes, then heat to 70° C. and keep the temperature for 60 minutes to obtain a mixture A; S102, emulsifying the mixture A by high-shear emulsifier at a speed of 10000 r / min for 30 minutes to obtain an emulsified mixture A, and then adding aluminum sulfate to the emulsified mixture A and stirring evenly to obtain a mixture B, and then homogenizing the mixture B by a homogenizer for 30 minutes, and cooling to room temperature to obtain an AKD emulsion.

[0034] Example 2 An AKD emulsion comprises the following raw materials, measured by weight: 22 parts of modified alkyl ketene dimer, 2 parts of dopamine-modified silicon dioxide, 3 parts of emulsifier, 2.2 parts of dispersant, 1.5 parts of modified guar gum, 1.2 parts of aluminum sulfate, and 85 parts of water, wherein the emulsifier is prepared by mixing a modified cationic starch emulsifier and a polymer emulsifier in a weight ratio of 1:1, and the dispersant is prepared by mixing hexenyl bis stearamide, polyoxyethylene sorbitan monostearate, and sorbitan monopalmitate in a weight ratio of 3:2:3.

[0035] The preparation method of the above-mentioned AKD emulsion comprises the following steps: 101. Add modified alkyl ketene dimer, dopamine-modified silica, emulsifier, dispersant, modified guar gum and water into a reactor in order according to their weight fractions, stir and react for 60 minutes, then heat to 75° C. and keep the temperature for 60 minutes to obtain a mixture A; S102, emulsifying the mixture A by high-shear emulsifier at a speed of 10000 r / min for 30 minutes to obtain an emulsified mixture A, and then adding aluminum sulfate to the emulsified mixture A and stirring evenly to obtain a mixture B, and then homogenizing the mixture B by a homogenizer for 30 minutes, and cooling to room temperature to obtain an AKD emulsion.

[0036] Example 3 An AKD emulsion comprises the following raw materials, measured by weight: 20 parts of modified alkyl ketene dimer, 1.8 parts of dopamine-modified silica, 2.7 parts of emulsifier, 2 parts of dispersant, 1.4 parts of modified guar gum, 1.1 parts of aluminum sulfate, and 83 parts of water, wherein the emulsifier is prepared by mixing a modified cationic starch emulsifier and a polymer emulsifier in a weight ratio of 1:1, and the dispersant is prepared by mixing hexenyl bis stearamide, polyoxyethylene sorbitan monostearate, and sorbitan monopalmitate in a weight ratio of 3:2:3.

[0037] The preparation method of the above-mentioned AKD emulsion comprises the following steps: 101. Add modified alkyl ketene dimer, dopamine-modified silica, emulsifier, dispersant, modified guar gum and water into a reactor in order according to their weight fractions, stir and react for 60 minutes, then heat to 73° C. and keep the temperature for 60 minutes to obtain a mixture A; S102, emulsifying the mixture A by high-shear emulsifier at a speed of 10000 r / min for 30 minutes to obtain an emulsified mixture A, and then adding aluminum sulfate to the emulsified mixture A and stirring evenly to obtain a mixture B, and then homogenizing the mixture B by a homogenizer for 30 minutes, and cooling to room temperature to obtain an AKD emulsion.

[0038] Comparative Example 1 The same as Example 3, except that an equal amount of alkyl ketene dimer is used instead of the modified alkyl ketene dimer.

[0039] Comparative Example 2 The same as Example 3, except that an equal amount of silicon dioxide with an average particle size of 50 nanometers is used instead of dopamine-modified silicon dioxide.

[0040] Comparative Example 3 The same as Example 3, except that the emulsifier is a modified cationic starch emulsifier.

[0041] Comparative Example 4 The same as Example 3, except that the emulsifier is a polymer emulsifier.

[0042] Comparative Example 5 The same as Example 3, except that the dispersant is hexenyl bisstearamide.

[0043] Comparative Example 6 The same as Example 3, except that the dispersant is polyoxyethylene sorbitan monostearate.

[0044] Comparative Example 7 The same as Example 3, except that the dispersant is sorbitan monopalmitate.

[0045] Performance Testing The AKD emulsions prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were coated on base paper using a 2# coating rod, controlling the coating amount of sizing agent to be 6 g per square meter. After drying for 10 minutes, samples were obtained and tested in the following experiments. The test results are shown in Table 1.

[0046] Glue application amount: Test the paper Cobb value of the sample according to GB / T1540-2002. The smaller the Cobb value Cobb60 is, the more glue is applied and the better the water resistance is. Storage stability: After storing the AKD emulsion at room temperature of 25°C for 1 day, 6 months and 12 months, use a 2# coating rod to coat the base paper, control the coating of sizing agent to be 6g per square meter, and test the Cobb value Cobb60 after drying for 10 minutes. Calculate the increase percentage of the Cobb value p1 of the sizing agent after storage for 6 and 12 months compared with the Cobb value of the sizing agent after storage for 1 day, the increase percentage = (p1-p0) / p0×100%, and grade it, where level 1 is the increase percentage less than 3%, level 2 is the increase percentage less than 5%, greater than or equal to 3%, level 3 is the increase percentage less than 10%, greater than or equal to 5%, level 4 is the increase percentage less than 20%, greater than or equal to 10%, and level 5 is the increase percentage greater than or equal to 20%; Stability test method: Place the AKD emulsion in a TDL-5C centrifuge (at 4000 r / min 1 Centrifuge for 15 min and observe whether stratification occurs); Viscosity test method: measured using a Brookfield rotational viscometer (rotor No. 2, speed 50 r / min -1 , measured at 25°C); the tensile strength was measured in accordance with the method specified in GB / T12914-2018 Determination of tensile strength of paper and paperboard.

[0047] Table 1 Performance test Analyzing the data in Table 1, we can see that: 1) The AKD emulsions prepared in Examples 1 to 3 have excellent stability, sizing performance and low cost, and can significantly improve the water resistance of paper.

[0048] 2) The performance comparison analysis of the AKD emulsions prepared in Example 3 and Comparative Example 1 shows that the prepared modified alkyl ketene dimer increases the adhesion rate of the emulsion particles on the fiber, thereby helping to improve the stability and retention rate of the AKD emulsion. At the same time, since polyethyleneimine has hydrophilic and lipophilic properties, it can also improve the emulsification performance and overall performance of the emulsion.

[0049] 3) The performance comparison analysis of the AKD emulsion prepared in combination with Example 3 and Comparative Example 2 shows that the dopamine-modified silica prepared in the present application modifies silica by dopamine, which can make silica have higher adhesion. This allows the AKD emulsion to better adhere to the fiber during the sizing process, thereby improving the water resistance of the paper. The dopamine-modified silica can form an interfacial film at the oil-water interface, thereby reducing the interfacial tension and interfacial energy. This helps to prevent droplet aggregation, thereby improving the stability of the emulsion after AKD emulsification to a certain extent. And then help to improve the stability, sizing performance and retention rate of the AKD emulsion, thereby reducing production costs and improving paper quality.

[0050] 4) The performance comparison analysis of the AKD emulsions prepared in combination with Example 3 and Comparative Examples 3-4 shows that the emulsifier is prepared by mixing a modified cationic starch emulsifier and a polymer emulsifier in a mass ratio of 1:1, and the modified cationic starch emulsifier and the polymer emulsifier act synergistically to significantly improve the emulsifying properties of the AKD emulsion, thereby improving the stability, sizing performance and retention rate of the AKD emulsion.

[0051] 5) The performance comparison analysis of the AKD emulsion prepared in combination with Example 3 and Comparative Examples 5-7 shows that the dispersant is prepared by mixing hexenyl bis stearamide, polyoxyethylene sorbitan monostearate and sorbitan monopalmitate in a mass fraction ratio of 3:2:3. These three substances can form a composite system in the emulsion, and through the interaction force between them, each component in the emulsion can be evenly distributed in the emulsion, thereby improving the dispersibility of the emulsion. The composite system formed by these three substances in the emulsion can effectively reduce the surface tension and interfacial energy of the emulsion, thereby preventing the aggregation of droplets and improving the stability of the emulsion. The composite system formed by these three substances in the emulsion can effectively improve the adhesion rate of the emulsion particles on the fiber, thereby helping to enhance the stability and retention rate of the AKD emulsion. The composite system formed by these three substances in the emulsion can produce a synergistic effect, further improve the emulsification performance of the AKD emulsion, thereby improving the stability, sizing performance and retention rate of the AKD emulsion. In summary, when hexenyl bisstearamide, polyoxyethylene sorbitan monostearate and sorbitan monopalmitate are used as dispersants in AKD emulsion, the synergistic effect between them can significantly improve the dispersibility, stability, sizing performance and retention rate of the emulsion, and at the same time produce a synergistic effect to further improve the performance of AKD emulsion.

[0052] The above embodiments are only used to explain the technical solutions of the present application rather than to limit them. Although the above embodiments provide a specific description of the present application, relevant technical personnel should understand that the specific implementation methods of the present application can still be modified or replaced by equivalents, and any modifications and equivalent replacements that do not depart from the spirit and scope of the present application should be included in the protection scope of the present application.

Claims

1. An AKD emulsion, characterized in that: The preparation raw materials include the following by weight: 18-22 parts of modified alkyl ketene dimer, 1.5-2 parts of dopamine modified silicon dioxide, 2.5-3 parts of emulsifier, 1.8-2.2 parts of dispersant, 1.3-1.5 parts of synergist, 1-1.2 parts of stabilizer and 80-85 parts of water, wherein the emulsifier is prepared by mixing a modified cationic starch emulsifier and a polymer emulsifier in a weight ratio of 1:

1.

2. An AKD emulsion according to claim 1, characterized in that, The preparation method of the modified alkyl ketene dimer is as follows: 10 parts of alkyl ketene dimer wax powder are heated and melted in a water bath according to the mass fraction, and after the alkyl ketene dimer wax powder is completely melted, 4.5 parts of 73° C. polyethyleneimine solution with a mass concentration of 35% are slowly added to the melted alkyl ketene dimer, and after high-speed shear stirring for 10 minutes, 3 parts of deionized water are added, and high-speed shear stirring is continued for 20 minutes, and the mixture is allowed to stand for 3 hours and then cooled to room temperature to obtain the modified alkyl ketene dimer.

3. An AKD emulsion according to claim 1, characterized in that, The preparation method of the dopamine-modified silica is as follows: 40 parts of potassium hydroxide and 1000 parts of deionized water are mixed according to mass fractions, stirred evenly, and then heated to 42° C. to obtain a potassium hydroxide solution, and then 50 parts of dopamine are added to the potassium hydroxide solution and stirred for 30 minutes, and then 80 parts of silica with an average particle size of 50 nanometers are added, and the reaction is carried out for 3 hours while keeping the temperature constant, and finally the product is filtered and washed with deionized water for 3 times, and then placed in an oven at 80° C. for drying, and then ground after drying to obtain dopamine-modified silica.

4. An AKD emulsion according to claim 1, characterized in that, The preparation method of the modified cationic starch emulsifier comprises the following steps: S41, adding 50 parts of potato starch, 2 parts of ammonium persulfate, 2 parts of triallylamine and 6 parts of polydiallyldimethylammonium chloride into a flask according to their weight parts, and gelatinizing at 93° C. for 50 min to obtain a mixture; S42. After diluting the mixture by weight, 98 parts of deionized water were added, and the mixture was stirred at a stirring speed of 1500 r / min for 60 minutes. Finally, the pH value was adjusted to 2.5 with acetic acid to obtain a modified cationic starch emulsifier.

5. An AKD emulsion according to claim 1, characterized in that, The preparation method of the polymer emulsifier comprises the following steps: S51. According to the mass ratio, 30 parts of deionized water, 0.1 parts of sodium sulfite and 0.15 parts of ammonium persulfate are prepared into an initiator solution for standby use; S52, according to the mass fraction, 17 parts of a 67% dimethyldiallyl ammonium chloride solution are added dropwise to the reaction kettle, and the temperature is raised to 73°C under stirring; within 2 hours, 48 ​​parts of a 63% dimethyldiallyl ammonium chloride solution are slowly added dropwise to the reaction kettle; then within 1 hour, 5 parts of polydiallyldimethylammonium chloride and 4 parts of diallylamine are slowly added dropwise to the reaction kettle to obtain a reaction solution; S53. According to the mass fraction, the reaction liquid is stirred and heated to 85° C., the initiator solution is slowly added dropwise to the reaction liquid within 3 hours, the reaction is stirred for 3 hours, and the reaction is cooled to room temperature to obtain a polymer emulsifier.

6. An AKD emulsion according to claim 1, characterized in that: The dispersant is prepared by mixing hexenyl bis stearamide, polyoxyethylene sorbitan monostearate and sorbitan monopalmitate in a mass ratio of 3:2:

3.

7. An AKD emulsion according to claim 1, characterized in that: The stabilizer is aluminum sulfate.

8. An AKD emulsion according to claim 1, characterized in that: The synergist is modified guar gum.

9. An AKD emulsion according to claim 8, characterized in that: The preparation method of the modified guar gum comprises the following steps: adding 500 parts of a sodium hydroxide solution with a mass concentration of 20% into a reaction kettle according to the mass fraction, then adding 200 parts of guar gum under the stirring condition of 200 rpm, and then adding 10 parts of galactose oxidase and 15 parts of mannosidase when the stirring speed is adjusted to 800 rpm, and reacting for 8 hours at 125° C. after being evenly dispersed, and then pouring the obtained product into an ethanol aqueous solution to adjust the pH value to 7, filtering out the supernatant, washing the precipitate with the ethanol aqueous solution, and drying and crushing to obtain the modified guar gum.

10. A method for preparing an AKD emulsion according to any one of claims 1 to 9, comprising the following steps: S101, adding modified alkyl ketene dimer, dopamine modified silica, emulsifier, dispersant, synergist and water to a reactor in order according to their mass fractions, stirring and reacting for 60 minutes, then heating to 70-75° C., keeping the temperature for reaction for 60 minutes, and obtaining a mixture A; S102, emulsifying the mixture A at a high shear emulsifier at a speed of 10000 r / min for 30 min to obtain an emulsified mixture A, adding a stabilizer to the emulsified mixture A and stirring evenly to obtain a mixture B, and then homogenizing the mixture B with a homogenizer for 30 minutes, cooling to room temperature, and obtaining an AKD emulsion.

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