Preparation process of high water resistance surface sizing agent

Abstract

The application relates to the technical field of papermaking auxiliaries, in particular to a preparation process of a high-water-resistance surface sizing agent, which comprises the following steps: S1, each component substance is weighed according to the mass fraction and is prepared for use; S2, a polyvinyl alcohol solution is prepared; S3, an anionic polyacrylate dispersant and a cationic high-molecular polymer emulsifier are prepared into a solution; S4, a primary emulsion is prepared; S5, a homogeneous emulsion is prepared; and S6, an iron-free aluminum sulfate and zirconyl chloride aqueous solution is prepared, then the high-water-resistance surface sizing agent is obtained after mixing, stirring, pH adjusting and solid content adjusting in S7. Through strict control of components and process sequence, the stable surface sizing agent is constructed, long-acting stability of the surface sizing agent is realized, water resistance is rapidly exhibited, and the final film strength is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of papermaking additives, specifically to a preparation process for a highly water-resistant surface sizing agent. Background Technology

[0002] With the rapid development of the paper industry, surface sizing agents are playing an increasingly important role in improving the water resistance, printability, and mechanical strength of paper. However, existing surface sizing agents still have shortcomings in terms of water resistance, emulsion stability, and curing speed, which limits their application in the production of high-performance paper.

[0003] CN109371752B discloses a surface sizing agent for paper, published on December 31, 2021. This patent describes a modified starch-based surface sizing agent prepared by graft copolymerization of starch with monomers such as butyl acrylate after mixing and treating starch with sodium periodate solution, combined with a Bacillus subtilis fermentation process. This sizing agent exhibits strong water resistance and high viscosity. However, the fermentation process requires high-temperature sterilization and prolonged sealed fermentation, increasing process complexity and production cycle. Furthermore, impurities may be introduced during fermentation, affecting the emulsion stability of the sizing agent and thus reducing its sizing effect.

[0004] CN112236557B discloses a surface sizing agent for papermaking, published on October 15, 2021. This patent describes a surface sizing agent with good low foaming properties and mechanical stability prepared by copolymerizing styrene and (meth)acrylate monomers in the presence of starch. This sizing agent exhibits excellent sizing performance under a wide range of application conditions. However, the high proportion of styrene monomers (10%-30%) in this technical solution may lead to a slower emulsion maturation rate, affecting the production efficiency of the sizing agent. Furthermore, the high proportion of hydrophobic monomers may reduce the water resistance of the sizing agent, limiting its application in high-humidity environments.

[0005] The above problems indicate that existing surface sizing agents still have certain shortcomings in terms of water resistance, emulsion stability, and curing speed. Summary of the Invention

[0006] The purpose of this invention is to provide a preparation process for a highly water-resistant surface sizing agent, so as to overcome the shortcomings of the surface sizing agents mentioned in the background art in terms of water resistance, emulsion stability and curing speed.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A preparation process for a highly water-resistant surface sizing agent includes the following steps:

[0009] S1. Weigh out the following by mass:

[0010] 100 portions of AKD wax powder;

[0011] 20-35 parts of cationic polymer emulsifier;

[0012] 3-6 parts of anionic polyacrylate dispersant;

[0013] 80-150 parts of iron-free aluminum sulfate;

[0014] 2-5 parts of zirconium oxychloride;

[0015] 0.5-2 parts of isothiazolinone preservative;

[0016] 5-15 parts of polyvinyl alcohol;

[0017] spare;

[0018] S2. Dissolve polyvinyl alcohol in 90-100 parts of hot water with stirring to prepare a polyvinyl alcohol solution with a mass fraction of 5%-15%.

[0019] S3. Add deionized water to the emulsification reactor, turn on the stirrer and heat to 80-85℃. Then add the anionic polyacrylate dispersant and polyvinyl alcohol solution to the reactor and stir at 300-500 r / min for 5-15 min to completely dissolve them. Then slowly add the cationic polymer emulsifier and stir at 500-800 r / min at 80-85℃ for 10-30 min until a homogeneous solution is formed.

[0020] S4. Maintain the temperature at 80-85℃, slowly add the AKD wax powder, control the feeding time to 20-40 min, and after the feeding is completed, continuously shear emulsify at 80-85℃ at a speed of 1500-3000 r / min for 25-40 min to obtain the primary emulsion.

[0021] S5. The primary emulsion is transferred into a high-pressure homogenizer and homogenized 2-3 times under a pressure of 20-30 MPa to obtain a homogenized emulsion.

[0022] S6. Prepare aqueous solutions of the iron-free aluminum sulfate and zirconium oxychloride with a mass concentration of 10%-15% for later use;

[0023] S7. Transfer the homogenized emulsion to a mixing tank and cool it to ≤40℃. First, add the prepared iron-free aluminum sulfate solution and stir at 200-400 r / min for 10-15 min. Then, add the prepared zirconium oxychloride solution and stir at 200-400 r / min for 15-20 min. Next, add the isothiazolinone preservative and stir for 10-20 min. Adjust the pH value to 4.0-5.5 and add deionized water to adjust the solid content of the system to 15%-30%. Filter the mixture through a 100-200 mesh filter to obtain the highly water-resistant surface sizing agent.

[0024] In S7, the preparation time for adding zirconium oxychloride solution is ≤30 min, and the solution temperature is 0-40℃.

[0025] The high water resistance of this preparation method stems from the synergistic effect of each functional component under a precise process sequence. Its essence is a process of gradually building a stable system and ultimately triggering an efficient interfacial reaction.

[0026] First, the dispersant and cationic emulsifier are pre-formed into a homogeneous aqueous phase at 80-85℃ and under shear stress. Upon addition of AKD wax powder, it melts into a liquid phase and is immediately encapsulated by the emulsifier molecules. The stability of the primary emulsion formed in this step directly depends on the feeding process; therefore, the feeding must not be rapid, ensuring at least 20 minutes to match the shear strength. Feeding too quickly will lead to incomplete encapsulation and the formation of defective particles. A high-pressure homogenization process further breaks down the emulsion to the submicron level. This step is crucial, as it significantly increases the reaction surface area and provides a physical stability basis for subsequent resistance to strong electrolytes, forming a highly stable AKD capsule carrier.

[0027] Iron-free aluminum sulfate and zirconium oxychloride solutions need to be added in steps. The aluminum sulfate solution added first does not directly promote the reaction; its primary function is to regulate the charge. Through its electrolyte properties, it pre-neutralizes some of the negative charge in the system, moderately compressing the electric double layer. This creates a buffer environment for the subsequent addition of the more active but sensitive zirconium compound, preventing drastic changes in the system's charge environment that could lead to demulsification. The zirconium oxychloride solution added subsequently must be freshly prepared and used immediately (≤30 min), and the preparation and addition temperature must be maintained between 0-40℃, as its active ingredient is a nano-sized zirconium oxide ion cluster ([Zr4(OH)8(H2O)). 16 ] 8+ These zirconium clusters exhibit strong time and temperature sensitivity; delayed use or improper temperature can deactivate their polymerization, transforming them from highly efficient catalysts into inactive precipitates. Under the favorable conditions of aluminum sulfate pretreatment, these highly active zirconium clusters can efficiently adsorb onto the surfaces of AKD emulsion particles and fibers, acting as molecular bridges. Simultaneously, they coordinate with the hydroxyl groups of paper cellulose and the carbonyl groups of AKD, significantly reducing the energy barrier of the esterification reaction. This allows them to strongly catalyze the formation of covalent bonds while inhibiting AKD hydrolysis.

[0028] The entire process, through a sequential design of initial emulsification construction, high-pressure homogenization enhancement, stepwise electrolyte adaptation, and precise delivery of highly active catalysts, ensures that each component functions at the optimal time, ultimately forming a robust water-resistant film on the fiber surface. Any reversal of the order or deviation of key parameters (such as time and temperature) will disrupt this synergy, leading to system instability or reaction failure.

[0029] In this system, PVA acts as a protective colloid, and its long molecular chains can form a strong steric stabilizing effect in the aqueous phase. By forming a tough hydrated protective film around the AKD emulsion particles, it physically prevents particle collisions and aggregation, thereby greatly improving the long-term storage stability of the emulsion (anti-sedimentation, anti-stratification), which complements the electrostatic stabilizing effect provided by the cationic emulsifier. When the dosage is insufficient, a complete and effective protective layer cannot be formed, and the steric hindrance effect is weak. The emulsion still has a high risk of demulsification and stratification when strong electrolytes (aluminum sulfate, zirconium oxychloride) are subsequently added or during long-term storage. When the dosage is too high, the system viscosity will be too high, which will not only make emulsification, transportation and filtration difficult and increase energy consumption, but may also destroy the uniform distribution of emulsion particles due to excessive flocculation, thus reducing stability.

[0030] Preferably, the stirring rate for high-speed shear emulsification in S4 is 1500-3000 r / min.

[0031] Preferably, the cationic polymer emulsifier is one of polyquaternium-7, polyquaternium-10, or polyquaternium-47.

[0032] Preferably, the anionic polyacrylate dispersant is one of sodium polyacrylate or ammonium polyacrylate.

[0033] Preferably, the isothiazolinone preservative is a mixture of 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one.

[0034] Preferably, the filter used in step S7 is a 100-200 mesh stainless steel filter.

[0035] Preferably, the iron-free aluminum sulfate is of industrial or paper grade, wherein the iron content by mass percentage is not higher than 0.01%.

[0036] Preferably, in S7, the pH is adjusted to 4.0-5.5 by using a 5%-10% hydrochloric acid solution or a 5%-10% sodium hydroxide solution.

[0037] This process utilizes the electrolyte and ripening properties of aluminum sulfate while absolutely suppressing the hydrolysis side reaction of AKD during storage. Strictly controlling the iron content to an extremely low level (≤0.01%) is crucial to fundamentally eliminate the catalyst for hydrolysis, ensuring the stability of the AKD active ingredient upon contact with aluminum sulfate until it undergoes the targeted esterification reaction with the zirconium catalyst added during application on the paper. Excessive iron content will efficiently catalyze the hydrolysis of AKD with water, consuming the active ingredient. The resulting sizing agent emulsion will rapidly thin, decrease in viscosity, and change in solid content (due to AKD hydrolysis) within a very short storage period, ultimately becoming completely ineffective and losing all water resistance.

[0038] This solution also proposes a high water-resistant surface sizing agent prepared using the above-mentioned high water-resistant surface sizing agent preparation process.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] 1. In terms of components, an initial emulsification system is constructed using cationic polymer emulsifiers and anionic polyacrylate dispersants. Polyvinyl alcohol is preferred as a protective colloid to enhance steric stability. A highly efficient catalytic system is formed by the combination of iron-free aluminum sulfate and zirconium oxychloride. The former pretreats the charge environment and creates buffer conditions for zirconium oxychloride, while the latter strongly bridges cellulose and AKD molecules with freshly prepared nano-sized zirconium oxide ion clusters, achieving mutual coordination of components.

[0041] 2. In terms of process, strict control of AKD feeding rate and high-temperature shear emulsification ensures complete particle encapsulation. High-pressure homogenization achieves submicron particle size distribution to enhance system stability. Strict control of the addition sequence, first introducing aluminum sulfate solution to achieve charge balance transition, then adding zirconium oxychloride solution, controlling the stirring rate, and improving the physical stabilization of the entire system, thereby simultaneously solving problems such as poor storage stability, slow curing speed and insufficient water resistance of surface sizing agents. Detailed Implementation

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0043] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0044] A preparation process for a highly water-resistant surface sizing agent includes the following steps:

[0045] S1. Weigh out the following by mass:

[0046] 100 portions of AKD wax powder;

[0047] 20-35 parts of cationic polymer emulsifier;

[0048] 3-6 parts of anionic polyacrylate dispersant;

[0049] 80-150 parts of iron-free aluminum sulfate;

[0050] 2-5 parts of zirconium oxychloride;

[0051] 0.5-2 parts of isothiazolinone preservative;

[0052] 5-15 parts of polyvinyl alcohol

[0053] S2. Dissolve polyvinyl alcohol in 90-100 parts of hot water with stirring to prepare a polyvinyl alcohol solution with a mass fraction of 5%-15%.

[0054] S3. Add deionized water to the emulsification reactor, start stirring and heat to 80-85℃. Then add anionic polyacrylate dispersant to the reactor and stir at 300-500 r / min for 5-15 min until completely dissolved. Then slowly add cationic polymer emulsifier and stir at 500-800 r / min at 80-85℃ for 10-30 min until a homogeneous solution is formed. Add the polyvinyl alcohol solution prepared in S1 together with the anionic polyacrylate dispersant to the reactor.

[0055] The cationic polymer emulsifier is one of polyquaternium-7, polyquaternium-10, or polyquaternium-47;

[0056] The anionic polyacrylate dispersant is either sodium polyacrylate or ammonium polyacrylate;

[0057] S4. Maintain the temperature at 80-85℃, slowly add AKD wax powder, control the feeding time to 20-40 min, and after the feeding is completed, continuously shear emulsify at 80-85℃ at a speed of 1500-3000 r / min for 25-40 min to obtain the primary emulsion.

[0058] S5. Transfer the primary emulsion into a high-pressure homogenizer and homogenize it 2-3 times under a pressure of 20-30 MPa to obtain a homogenized emulsion.

[0059] S6. Prepare ferrous aluminum sulfate and zirconium oxychloride into aqueous solutions with a mass concentration of 10%-15% for later use;

[0060] Iron-free aluminum sulfate is of industrial or paper grade, with an iron content of no more than 0.01% by mass.

[0061] S7. Transfer the homogenized emulsion to a mixing tank and cool it to ≤40℃. First, add the prepared iron-free aluminum sulfate solution and stir at 200-400 r / min for 10-15 min. Then, add the 0-40℃ zirconium oxychloride solution prepared within 30 min and stir at 200-400 r / min for 15-20 min. Next, add the isothiazolinone preservative and stir for 10-20 min. Adjust the pH value to 4.0-5.5 and add deionized water to adjust the solid content of the system to 15%-30%. Filter the mixture through a 100-200 mesh stainless steel filter to obtain a highly water-resistant surface sizing agent.

[0062] In the examples and comparative examples, the isothiazolinone preservatives were a mixture of 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one in a mass ratio of 1:3.

[0063] According to the actual process, the pH is adjusted to 4.0-5.5 by using an 8% dilute hydrochloric acid solution or an 8% sodium hydroxide solution.

[0064] Example 1

[0065] A preparation process for a highly water-resistant surface sizing agent includes the following steps:

[0066] S1. Weigh out the following by mass:

[0067] 100 portions of AKD wax powder;

[0068] 27.5 parts of cationic polymer emulsifier;

[0069] 4.5 parts of anionic polyacrylate dispersant;

[0070] 115 parts of iron-free aluminum sulfate;

[0071] 3.5 parts of zirconium oxychloride;

[0072] 1.25 parts of isothiazolinone preservative;

[0073] 10 parts polyvinyl alcohol;

[0074] S2. Dissolve polyvinyl alcohol in 95 parts of hot water with stirring to prepare a 10% polyvinyl alcohol solution.

[0075] S3. Add deionized water to the emulsification reactor, start stirring and heat to 82.5℃. Then add anionic polyacrylate dispersant to the reactor and stir at 400 r / min for 10 min to completely dissolve it. After that, slowly add cationic polymer emulsifier and stir at 650 r / min at 82.5℃ for 20 min until a homogeneous solution is formed. Add the polyvinyl alcohol solution prepared in S1 together with the anionic polyacrylate dispersant to the reactor.

[0076] The cationic polymer emulsifier is polyquaternium-7;

[0077] The anionic polyacrylate dispersant is sodium polyacrylate;

[0078] S4. Maintain the temperature at 82.5℃, slowly add AKD wax powder, control the feeding time to 30 min, and after the feeding is completed, continuously shear emulsify at 2250 r / min at 82.5℃ for 32.5 min to obtain the primary emulsion.

[0079] S5. Transfer the primary emulsion into a high-pressure homogenizer and homogenize it twice at a pressure of 25 MPa to obtain a homogenized emulsion.

[0080] S6. Prepare aqueous solutions of ferrous aluminum sulfate and zirconium oxychloride with a mass concentration of 12.5% ​​for later use;

[0081] Iron-free aluminum sulfate is of industrial or paper grade, with an iron content of no more than 0.01% by mass.

[0082] S7. Transfer the homogenized emulsion to a mixing tank and cool it to 36°C. First, add the prepared iron-free aluminum sulfate solution and stir at 300 r / min for 12.5 min. Then, add the 20°C zirconium oxychloride solution prepared within 30 min and stir at 300 r / min for 17.5 min. Next, add the isothiazolinone preservative and stir for 15 min. Adjust the pH to 4.5 and add deionized water to adjust the solid content of the system to 22.5%. Filter the mixture through a 150-mesh stainless steel filter to obtain a highly water-resistant surface sizing agent.

[0083] Example 2

[0084] A preparation process for a highly water-resistant surface sizing agent includes the following steps:

[0085] S1. Weigh out the following by mass:

[0086] 100 portions of AKD wax powder;

[0087] 20 parts of cationic polymer emulsifier;

[0088] 3 parts of anionic polyacrylate dispersant;

[0089] 80 parts of iron-free aluminum sulfate;

[0090] Two parts of zirconium oxychloride;

[0091] 0.5 parts of isothiazolinone preservative;

[0092] 5 parts polyvinyl alcohol;

[0093] S2. Dissolve polyvinyl alcohol in 90 parts of hot water with stirring to prepare a 5% polyvinyl alcohol solution.

[0094] S3. Add deionized water to the emulsification reactor, turn on the stirrer and heat to 80°C. Then add anionic polyacrylate dispersant to the reactor and stir at 300 r / min for 5 min to completely dissolve it. Then slowly add cationic polymer emulsifier and stir at 500 r / min for 10 min at 80°C until a homogeneous solution is formed. Add the polyvinyl alcohol solution prepared in S1 and the anionic polyacrylate dispersant together to the reactor.

[0095] The cationic polymer emulsifier is polyquaternium-10;

[0096] The anionic polyacrylate dispersant is ammonium polyacrylate;

[0097] S4. Keep the temperature at 80℃, slowly add AKD wax powder, control the feeding time to 20 min, and after the feeding is completed, continuously shear emulsify at 80℃ and a speed of 1500 r / min for 25 min to obtain the primary emulsion.

[0098] S5. Transfer the primary emulsion into a high-pressure homogenizer and homogenize it twice under a pressure of 20 MPa to obtain a homogenized emulsion.

[0099] S6. Prepare 10% aqueous solutions of iron-free aluminum sulfate and zirconium oxychloride separately for later use;

[0100] Iron-free aluminum sulfate is of industrial or paper grade, with an iron content of no more than 0.01% by mass.

[0101] S7. Transfer the homogenized emulsion to a mixing tank and cool it to 39°C. First, add the prepared iron-free aluminum sulfate solution and stir at 200 r / min for 10 min. Then, add the 0°C zirconium oxychloride solution prepared within 30 min and stir at 200 r / min for 15 min. Next, add the isothiazolinone preservative and stir for 10 min. Adjust the pH to 4.0 and add deionized water to adjust the solid content of the system to 15%. Filter the mixture through a 100-mesh stainless steel filter to obtain a highly water-resistant surface sizing agent.

[0102] Example 3

[0103] A preparation process for a highly water-resistant surface sizing agent includes the following steps:

[0104] S1. Weigh out the following by mass:

[0105] 100 portions of AKD wax powder;

[0106] 35 parts of cationic polymer emulsifier;

[0107] 6 parts of anionic polyacrylate dispersant;

[0108] 150 parts of iron-free aluminum sulfate;

[0109] 5 parts of zirconium oxychloride;

[0110] Two parts of isothiazolinone preservative;

[0111] 15 parts polyvinyl alcohol;

[0112] S2. Dissolve polyvinyl alcohol in 100 parts of hot water with stirring to prepare a polyvinyl alcohol solution with a mass fraction of 15%.

[0113] S3. Add deionized water to the emulsification reactor, start stirring and heat to 85°C. Then add anionic polyacrylate dispersant to the reactor and stir at 500 r / min for 15 min to dissolve it completely. Then slowly add cationic polymer emulsifier and stir at 800 r / min at 85°C for 30 min until a homogeneous solution is formed. Add the polyvinyl alcohol solution prepared in S1 together with the anionic polyacrylate dispersant to the reactor.

[0114] The cationic polymer emulsifier is polyquaternium-47;

[0115] The anionic polyacrylate dispersant is sodium polyacrylate;

[0116] S4. Maintain the temperature at 85℃, slowly add AKD wax powder, control the feeding time to 40 min, and after the feeding is completed, continuously shear emulsify at 3000 r / min at 85℃ for 40 min to obtain the primary emulsion.

[0117] S5. Transfer the primary emulsion into a high-pressure homogenizer and homogenize it three times at a pressure of 30 MPa to obtain a homogenized emulsion.

[0118] S6. Prepare ferrous aluminum sulfate and zirconium oxychloride into 15% aqueous solutions for later use.

[0119] Iron-free aluminum sulfate is of industrial or paper grade, with an iron content of no more than 0.01% by mass.

[0120] S7. Transfer the homogenized emulsion to a mixing tank and cool it to 40°C. First, add the prepared iron-free aluminum sulfate solution and stir at 400 r / min for 15 min. Then, add the 40°C zirconium oxychloride solution prepared within 30 min and stir at 400 r / min for 20 min. Next, add the isothiazolinone preservative and stir for 20 min. Adjust the pH to 5.5 and add deionized water to adjust the solid content of the system to 30%. Filter the mixture through a 200-mesh stainless steel filter to obtain a highly water-resistant surface sizing agent.

[0121] Example 4

[0122] A preparation process for a highly water-resistant surface sizing agent includes the following steps:

[0123] S1. Weigh out the following by mass:

[0124] 100 portions of AKD wax powder;

[0125] 25 parts of cationic polymer emulsifier;

[0126] 4 parts of anionic polyacrylate dispersant;

[0127] 100 parts of iron-free aluminum sulfate;

[0128] 3 parts of zirconium oxychloride;

[0129] One part of isothiazolinone preservative;

[0130] 8 parts polyvinyl alcohol;

[0131] S2. Dissolve polyvinyl alcohol in 92 parts of hot water with stirring to prepare a polyvinyl alcohol solution with a mass fraction of 8%.

[0132] S3. Add deionized water to the emulsification reactor, start stirring and heat to 81°C. Then add anionic polyacrylate dispersant to the reactor and stir at 350 r / min for 8 min to completely dissolve it. After that, slowly add cationic polymer emulsifier and stir at 600 r / min at 81°C for 15 min until a homogeneous solution is formed. Add the polyvinyl alcohol solution prepared in S1 together with the anionic polyacrylate dispersant to the reactor.

[0133] The cationic polymer emulsifier is polyquaternium-7;

[0134] The anionic polyacrylate dispersant is ammonium polyacrylate;

[0135] S4. Maintain the temperature at 81℃, slowly add AKD wax powder, control the feeding time to 25 min, and after the feeding is completed, continuously shear emulsify at 81℃ and a speed of 1800 r / min for 28 min to obtain the primary emulsion.

[0136] S5. Transfer the primary emulsion into a high-pressure homogenizer and homogenize it twice at a pressure of 22 MPa to obtain a homogenized emulsion.

[0137] S6. Prepare ferrous aluminum sulfate and zirconium oxychloride into aqueous solutions with a mass concentration of 11% for later use.

[0138] Iron-free aluminum sulfate is of industrial or paper grade, with an iron content of no more than 0.01% by mass.

[0139] S7. Transfer the homogenized emulsion to a mixing tank and cool it to 39°C. First, add the prepared iron-free aluminum sulfate solution and stir at 250 r / min for 11 min. Then, add the zirconium oxychloride solution prepared within 30 min at 10°C and stir at 250 r / min for 16 min. Next, add the isothiazolinone preservative and stir for 12 min. Adjust the pH value to 4.2 and add deionized water to adjust the solid content of the system to 18%. Filter the mixture through a 120-mesh stainless steel filter to obtain a highly water-resistant surface sizing agent.

[0140] Example 5

[0141] A preparation process for a highly water-resistant surface sizing agent includes the following steps:

[0142] S1. Weigh out the following by mass:

[0143] 100 portions of AKD wax powder;

[0144] 32 parts of cationic polymer emulsifier;

[0145] 5 parts of anionic polyacrylate dispersant;

[0146] 130 parts of iron-free aluminum sulfate;

[0147] 4 parts of zirconium oxychloride;

[0148] 1.5 parts of isothiazolinone preservative;

[0149] 12 parts polyvinyl alcohol;

[0150] S2. Dissolve polyvinyl alcohol in 98 parts of hot water with stirring to prepare a polyvinyl alcohol solution with a mass fraction of 12%.

[0151] S3. Add deionized water to the emulsification reactor, start stirring and heat to 84°C. Then add anionic polyacrylate dispersant to the reactor and stir at 450 r / min for 12 min to completely dissolve it. After that, slowly add cationic polymer emulsifier and stir at 700 r / min at 84°C for 25 min until a homogeneous solution is formed. Add the polyvinyl alcohol solution prepared in S1 together with the anionic polyacrylate dispersant to the reactor.

[0152] The cationic polymer emulsifier is polyquaternium-10;

[0153] The anionic polyacrylate dispersant is sodium polyacrylate;

[0154] S4. Maintain the temperature at 84℃, slowly add AKD wax powder, control the feeding time to 35 min, and after the feeding is completed, continuously shear emulsify at 2700 r / min at 84℃ for 35 min to obtain the primary emulsion.

[0155] S5. Transfer the primary emulsion into a high-pressure homogenizer and homogenize it three times at a pressure of 28 MPa to obtain a homogenized emulsion.

[0156] S6. Prepare ferrous aluminum sulfate and zirconium oxychloride into aqueous solutions with a mass concentration of 14% for later use.

[0157] Iron-free aluminum sulfate is of industrial or paper grade, with an iron content of no more than 0.01% by mass.

[0158] S7. Transfer the homogenized emulsion to a mixing tank and cool it to 38°C. First, add the prepared iron-free aluminum sulfate solution and stir at 350 r / min for 14 min. Then, add the zirconium oxychloride solution prepared within 30 min at 30°C and stir at 350 r / min for 18 min. Next, add the isothiazolinone preservative and stir for 18 min. Adjust the pH to 5.2 and add deionized water to adjust the solid content of the system to 28%. Filter the mixture through a 180-mesh stainless steel filter to obtain a highly water-resistant surface sizing agent.

[0159] Comparative Example 1

[0160] The difference from Example 1 is that the same weights of each component as in Example 1 were weighed, and 12.5% ​​(w / w) of iron-free aluminum sulfate and zirconium oxychloride aqueous solution and 10% (w / w) of polyvinyl alcohol solution were prepared. These were then directly added to a high-pressure homogenizer and homogenized three times at a pressure of 28 MPa.

[0161] Comparative Example 2

[0162] The difference from Example 1 is that no polyvinyl alcohol solution was added.

[0163] Comparative Example 3

[0164] The difference from Example 1 is that the total amount of polyvinyl alcohol added is 20 parts.

[0165] Comparative Example 4

[0166] The difference from Example 1 is that the AKD wax powder was added too quickly, with an addition time of 15 minutes.

[0167] Comparative Example 5

[0168] The difference from Example 1 is that in S4, homogenization is performed three times under a pressure of 18 MPa.

[0169] Comparative Example 6

[0170] The difference from Example 1 is that aluminum sulfate solution was added, and the iron ion content was 0.1%.

[0171] Comparative Example 7

[0172] The difference from Example 1 is that only iron-free aluminum sulfate solution was added, and zirconium oxychloride solution was not added.

[0173] Comparative Example 8

[0174] The difference from Example 1 is that only zirconium oxychloride solution was added, and iron-free aluminum sulfate solution was not added.

[0175] Comparative Example 9

[0176] The difference from Example 1 is that zirconium oxychloride solution is added first, followed by iron-free aluminum sulfate solution.

[0177] Comparative Example 10

[0178] The difference from Example 1 is that the zirconium oxychloride solution was allowed to stand for 6 hours after preparation before use.

[0179] Comparative Example 11

[0180] The difference from Example 1 is that the prepared iron-free aluminum sulfate solution was added first and stirred at a speed of 450 r / min; then the prepared zirconium oxychloride solution was added and stirred at a speed of 450 r / min.

[0181] Comparative Example Twelve

[0182] The difference from Example 1 is that the prepared iron-free aluminum sulfate solution was added first and stirred at a speed of 150 r / min; then the prepared zirconium oxychloride solution was added and stirred at a speed of 150 r / min.

[0183] Comparative Example Thirteen

[0184] The difference from Example 1 is that in S7, the homogenized emulsion is maintained at 43°C after being transferred to the mixing tank.

[0185] Comparative Example 14

[0186] The difference from Example 1 lies in the addition of different components. S2, weigh out the following by mass:

[0187] 100 portions of AKD wax powder;

[0188] 18 parts of cationic polymer emulsifier;

[0189] 8 parts of anionic polyacrylate dispersant;

[0190] 60 parts of iron-free aluminum sulfate;

[0191] 8 parts of zirconium oxychloride;

[0192] 2.3 parts of isothiazolinone preservative.

[0193] Comparative Example 15

[0194] The difference from Example 1 lies in the addition of different components. S2, weigh out the following by mass:

[0195] 100 portions of AKD wax powder;

[0196] 36 parts of cationic polymer emulsifier;

[0197] Two parts of anionic polyacrylate dispersant;

[0198] 155 parts of iron-free aluminum sulfate;

[0199] 1 part of zirconium oxychloride;

[0200] 0.4 parts of isothiazolinone preservative.

[0201] Performance testing:

[0202] I. The surface adhesive itself:

[0203] Its solid content was determined according to GB / T 2793-2015 standard, its pH value was determined according to GB / T 9724-2007 standard, and its viscosity was determined according to GB / T 22235-2008 standard;

[0204] Stability test: Seal equal masses of samples in transparent sealed containers of the same shape and let them stand at room temperature for 30 days. Observe and record whether phenomena such as layering, water separation, paste formation, or floating oil occur. Seal equal masses of samples in transparent sealed containers of the same shape and place them in an oven at 50-60℃. Observe whether phenomena such as layering, water separation, paste formation, or floating oil occur after 24 hours. The test results are shown in Table 1.

[0205] Table 1. Performance test results of the surface sizing agents in the examples and comparative examples.

[0206] Sample number Solid content (%) pH value Viscosity (mPa·s) Stability at room temperature (30 days) Thermal stability (50-60℃, 24h) Example 1 22.5 4.5 280 No layering, no floating oil No layering, no floating oil Example 2 15 4 150 No layering, no floating oil No layering, no floating oil Example 3 30 5.5 450 No layering, no floating oil No layering, no floating oil Example 4 18 4.2 200 No layering, no floating oil No layering, no floating oil Example 5 28 5.2 400 No layering, no floating oil No layering, no floating oil Comparative Example 1 22 4.6 120 Severe stratification, large amount of floating oil Severe stratification, large amount of floating oil Comparative Example 2 22.3 4.5 260 Slight separation, small amount of floating oil Slight separation, small amount of floating oil Comparative Example 3 23 4.4 650 No layering, with slight curdling No layering, with slight curdling Comparative Example 4 22.4 4.5 270 Slight separation, small amount of floating oil Slight separation, small amount of floating oil Comparative Example 5 22.2 4.5 250 Slight separation, small amount of floating oil Slight separation, small amount of floating oil Comparative Example 6 22.1 4.4 200 Severe stratification, large amount of floating oil Severe stratification, large amount of floating oil Comparative Example 7 22.5 4.6 290 No layering, no floating oil No layering, no floating oil Comparative Example 8 22.5 4.3 270 Slight separation, small amount of floating oil Slight separation, small amount of floating oil Comparative Example 9 22.4 4.5 260 Severe stratification, large amount of floating oil Severe stratification, large amount of floating oil Comparative Example 10 22.5 4.5 280 No layering, no floating oil No layering, no floating oil Comparative Example 11 22.5 4.5 280 No layering, no floating oil No layering, no floating oil Comparative Example Twelve 22.5 4.5 280 Slight separation, small amount of floating oil Slight separation, small amount of floating oil Comparative Example Thirteen 22.5 4.5 270 Severe stratification, large amount of floating oil Severe stratification, large amount of floating oil Comparative Example 14 19 4.8 220 Severe stratification, large amount of floating oil Severe stratification, large amount of floating oil Comparative Example 15 24 4.2 320 Severe stratification, large amount of floating oil Severe stratification, large amount of floating oil

[0207] In this embodiment, a uniform aqueous phase is first formed by premixing the dispersant and cationic emulsifier at a specific temperature. Then, the AKD wax powder is slowly fed and emulsified at high speed to ensure that the wax phase is fully encapsulated to form a primary emulsion. Subsequent high-pressure homogenization further refines the particles. The steric stabilization of the PVA protective colloid and the electrostatic stabilization of the cationic emulsifier complement each other. At the same time, the stepwise addition of iron-free aluminum sulfate avoids abrupt changes in the system charge. Finally, an emulsion with uniform particles and strong anti-interference ability is formed. Each comparative example exhibited emulsion stability defects due to deviations from the optimization logic caused by a single variable: Comparative Example 1 skipped the aqueous phase preconstruction and stepwise emulsification, directly mixing and homogenizing. The AKD wax powder was fully coated before entering high-pressure processing, resulting in easily agglomerated particles, leading to severe stratification and oil floating; Comparative Example 2 lacked PVA protective colloids and relied solely on the electrostatic stability of the cationic emulsifier, which could not withstand the double-layer compression after the addition of electrolytes, resulting in slight stratification and oil floating; Comparative Example 3 had excessive PVA, causing the system viscosity to be too high, and the excessive long molecular chains easily caused emulsion particle flocculation, resulting in slight paste formation although no stratification occurred; Comparative Example 4 had AKD wax powder added. Excessive shearing emulsification prevents timely encapsulation of the molten wax phase, resulting in structural defects in the formed particles, leading to slight stratification and oil floating after settling. In Comparative Example 5, insufficient homogenization pressure resulted in emulsion particles not being refined to the target level, having a small specific surface area and weak electrolyte tolerance, causing slight stratification and oil floating. In Comparative Example 6, excessive aluminum sulfate and iron content led to highly efficient catalysis of AKD hydrolysis by iron ions, disrupting the emulsion's colloidal structure and causing severe stratification and oil floating. Comparative Example 7 lacked only zirconium oxychloride, which catalyzes subsequent paper esterification reactions and does not affect the emulsion's own colloidal stability; therefore, the emulsion showed no stratification or oil floating. Comparative Example 8 lacked only... In Comparative Example 9, the direct addition of zirconium oxychloride to iron-free aluminum sulfate caused a drastic change in the system's charge, disrupting the charge balance on the surface of the emulsion particles and resulting in slight stratification and oil floating. Comparative Example 9 reversed the electrolyte addition order, adding the sensitive zirconium oxychloride first. Without aluminum sulfate to pre-regulate the charge, the zirconium ion clusters rapidly polymerized, became inactive, and agglomerated, damaging the emulsion structure and causing severe stratification and oil floating. In Comparative Example 10, prolonged standing of the zirconium oxychloride solution led to the inactivation of zirconium ion clusters, but the inactivated zirconium compounds did not interfere with the emulsion's colloidal stability; therefore, the emulsion performance remained normal. In Comparative Example 11, a slightly higher stirring speed only slightly improved mixing efficiency without damaging the emulsion structure; therefore, no stratification or oil floating occurred. Oil floatation was observed in Comparative Example XII due to excessively low stirring speed, resulting in uneven mixing of components and uneven distribution of emulsion particles, leading to slight stratification and oil floatation after standing. In Comparative Example XIII, the homogeneous emulsion temperature exceeded the standard, and the high temperature damaged the stability of zirconium oxychloride and the hydration film on the surface of emulsion particles, causing severe stratification and oil floatation. In Comparative Example XIV, the component dosage deviated from the optimized range, the emulsifier could not fully encapsulate AKD, and the excessive dispersant exacerbated particle agglomeration, resulting in severe stratification and oil floatation. In Comparative Example XV, the component dosage deviated from the optimized range, the excessive adsorption of emulsifier caused charge imbalance in the emulsion particles, and the insufficient dispersant could not inhibit particle aggregation, resulting in severe stratification and oil floatation.

[0208] II. Performance Testing of Sizing Paper:

[0209] Water resistance test: Cobb value is determined according to ISO535:2014 standard, and the curing rate is determined according to the process of Cobb value decreasing over time (time required for Cobb value to decrease by 50%).

[0210] According to GB / T12914-2018, the tensile strength of paper was tested; GB / T454-2020, the bursting strength was tested; and GB / T26705-2022, the surface strength was tested. The test results are shown in Table 2.

[0211] Table 2. Performance test results of surface sizing agents on paper in the examples and comparative examples.

[0212] Sample number Cobb value ripening speed Tensile strength Bursting strength Surface strength Example 1 18.5 12 5.8 385 2.2 Example 2 25 18 5.2 350 1.9 Example 3 15 8 6.5 420 2.5 Example 4 22 15 5.5 370 2 Example 5 16.5 10 6.2 405 2.4 Comparative Example 1 45 >48 4 280 1.2 Comparative Example 2 22 16 5.6 375 2.1 Comparative Example 3 20 14 5.7 380 2.1 Comparative Example 4 23.5 17 5.4 365 2 Comparative Example 5 24 18 5.3 360 1.9 Comparative Example 6 42 >48 4.2 290 1.3 Comparative Example 7 35 30 5.1 340 1.8 Comparative Example 8 28 24 5 330 1.7 Comparative Example 9 40 >48 4.3 300 1.4 Comparative Example 10 38 >48 4.5 310 1.5 Comparative Example 11 18.8 12.5 5.7 380 2.2 Comparative Example Twelve 21 15.5 5.5 370 2 Comparative Example Thirteen 39 >48 4.4 305 1.4 Comparative Example 14 43 >48 4.1 285 1.3 Comparative Example 15 44 >48 4 280 1.2

[0213] The excellent water resistance, fast curing speed, and high physical strength of the sized paper in this example are fundamentally due to the process design that achieves a highly efficient esterification reaction between AKD and cellulose: submicron-sized AKD emulsion particles provide sufficient reaction surface area, iron-free aluminum sulfate pre-adjusts the charge to create a suitable environment for zirconium ion clusters, and the readily available highly active zirconium ion clusters efficiently catalyze the formation of covalent bonds between AKD carbonyl groups and cellulose hydroxyl groups, while PVA ensures that the emulsion is evenly distributed on the fiber surface, maximizing reaction efficiency. Each comparative example experienced a decline in paper performance due to key variables disrupting the reaction process: Comparative Example 1, direct mixing and homogenization resulted in incomplete AKD coating, significant hydrolysis loss, and a low amount of AKD effectively participating in esterification, leading to poor water resistance, extremely slow curing speed, and low physical strength; Comparative Example 2, lacking PVA, exhibited uneven distribution of the emulsion on the fiber surface, causing localized aggregation or hydrolysis of AKD and incomplete reaction, resulting in slightly poorer water resistance and a slightly slower curing speed, but its physical strength was close to that of the example; Comparative Example 3, with excessive PVA, formed a film that slightly hindered the contact between AKD and fibers, reducing reaction efficiency and resulting in slightly poorer water resistance and a slightly slower curing speed; (Comparison) Example 4: Defective particles formed by excessively rapid addition of AKD wax powder agglomerate on the fiber surface, resulting in insufficient esterification reaction and slightly poorer water resistance and slower curing speed. Comparative Example 5: Insufficient homogenization pressure causes AKD particles to be too large, resulting in low contact efficiency with the fiber and a slow reaction speed, leading to poor water resistance and slow curing speed. Comparative Example 6: Excessive aluminum sulfate and iron content catalyzes a large amount of AKD hydrolysis, almost depleting the effective AKD and preventing it from reacting with the fiber, thus resulting in poor water resistance, extremely slow curing speed, and low physical strength. Comparative Example 7: Lack of zirconium oxychloride means there is no catalyst to lower the esterification reaction energy barrier, making it difficult for AKD to form covalent bonds with cellulose, resulting in poor water resistance. The curing speed was slow; Comparative Example 8 lacked iron-free aluminum sulfate, the system charge was not adjusted, and the directly added zirconium ion clusters were deactivated, unable to catalyze the reaction, resulting in poor water resistance and slow curing speed; Comparative Example 9 reversed the electrolyte addition order, causing the zirconium ion clusters to deactivate and lose their catalytic ability, making it difficult for AKD to bind with the fiber, resulting in poor water resistance, extremely slow curing speed, and low physical strength; Comparative Example 10 was deactivated by prolonged standing of the zirconium oxychloride solution, lacking an effective catalyst, making it difficult to advance the reaction, resulting in poor water resistance, extremely slow curing speed, and low physical strength; Comparative Example 11 had a slightly higher stirring speed, which only slightly improved the mixing efficiency and did not affect the core reaction process, so the paper... The performance of Comparative Example XII is close to that of the Example; the stirring speed of Comparative Example XII is too low, which causes uneven distribution of the emulsion on the fiber surface and insufficient local reaction, resulting in slightly poor water resistance and slightly slower curing speed; the temperature of the homogenized emulsion in Comparative Example XIII exceeds the standard, which deactivates the zirconium ion cluster and causes catalytic failure, resulting in poor water resistance, extremely slow curing speed and low physical strength; the component dosage deviation in Comparative Example XIV causes insufficient emulsification of AKD and a small amount of effective reaction, resulting in poor water resistance, extremely slow curing speed and low physical strength; the component dosage deviation in Comparative Example XV causes poor dispersion of AKD on the fiber surface and low reaction efficiency, resulting in poor water resistance, extremely slow curing speed and low physical strength.

[0214] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary; within the framework of this invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0215] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A preparation process for a highly water-resistant surface sizing agent, characterized in that, Includes the following steps: S1. Weigh out the following by mass: 100 portions of AKD wax powder; 20-35 parts of cationic polymer emulsifier; 3-6 parts of anionic polyacrylate dispersant; 80-150 parts of iron-free aluminum sulfate; 2-5 parts of zirconium oxychloride; 0.5-2 parts of isothiazolinone preservative; 5-15 parts of polyvinyl alcohol; spare; S2. Dissolve polyvinyl alcohol in 90-100 parts of hot water with stirring to prepare a polyvinyl alcohol solution with a mass fraction of 5%-15%. S3. Add deionized water to the emulsification reactor, turn on the stirring and heat to 80-85℃. Then add the anionic polyacrylate dispersant and polyvinyl alcohol solution to the reactor, stir to dissolve, and slowly add the cationic polymer emulsifier. Stir at 80-85℃ until a uniform solution is formed. S4. Maintain the temperature at 80-85℃, slowly add the AKD wax powder, control the feeding time to 20-40 min, and after the feeding is completed, emulsify it at 80-85℃ using high-speed shearing to obtain the primary emulsion. S5. The primary emulsion is transferred into a high-pressure homogenizer and homogenized 2-3 times under a pressure of 20-30 MPa to obtain a homogenized emulsion. S6. Prepare aqueous solutions of the iron-free aluminum sulfate and zirconium oxychloride with a mass concentration of 10%-15% for later use; S7. Transfer the homogenized emulsion to a mixing tank and cool it to ≤40℃. First, add the prepared iron-free aluminum sulfate solution and stir evenly at a speed of 200-400 r / min. Then, add the prepared zirconium oxychloride solution and stir evenly at a speed of 200-400 r / min. Next, add the isothiazolinone preservative and stir evenly. Adjust the pH value to 4.0-5.5 and add deionized water to adjust the solid content of the system to 15%-30%. Filter the material to obtain the high water-resistant surface sizing agent. In S7, the preparation time for adding zirconium oxychloride solution is ≤30 min, and the solution temperature is 0-40℃.

2. The preparation process of the high water-resistant surface sizing agent as described in claim 1, characterized in that, The stirring rate for high-speed shear emulsification described in S4 is 1500-3000 r / min.

3. The preparation process of the high water-resistant surface sizing agent as described in claim 1, characterized in that, The cationic polymer emulsifier is one of polyquaternium-7, polyquaternium-10, or polyquaternium-47.

4. The preparation process of the high water-resistant surface sizing agent as described in claim 1, characterized in that, The anionic polyacrylate dispersant is either sodium polyacrylate or ammonium polyacrylate.

5. The preparation process of the high water-resistant surface sizing agent as described in claim 1, characterized in that, The isothiazolinone preservative is a mixture of 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one.

6. The preparation process of the high water-resistant surface sizing agent as described in claim 1, characterized in that, The filter used in step S7 is a 100-200 mesh stainless steel filter.

7. The preparation process of the high water-resistant surface sizing agent as described in claim 1, characterized in that, The iron-free aluminum sulfate is of industrial or paper grade, wherein the iron content by mass percentage is not higher than 0.01%.

8. The preparation process of the high water-resistant surface sizing agent as described in claim 1, characterized in that, In S7, the pH is adjusted to 4.0-5.5 by using a 5%-10% dilute hydrochloric acid solution or a 5%-10% sodium hydroxide solution.

9. A highly water-resistant surface sizing agent prepared by a preparation process according to any one of claims 1-8.