An asa paper sizing emulsion, its preparation method and application

Abstract

This invention discloses an ASA paper sizing emulsion, its preparation method, and its application, belonging to the field of papermaking additives. By weight, it comprises the following components: 1.75 parts of 3.5 wt% cationic starch solution; 5.25 parts of 1.5 wt% amphoteric polyacrylamide solution; 0.01 parts surfactant; and 1 part ASA stock solution. The D90 particle size of the sizing emulsion is 0.5-5.0 μm and / or the average particle size is 0.5-3.0 μm. This invention mixes cationic starch and amphoteric PAM in a certain proportion and reacts them under specific conditions to prepare an ASA emulsion mixture. The stability of the prepared emulsion is significantly improved, especially its stability at low temperatures, which is significantly better than that of emulsions emulsified with pure cationic starch emulsifier. Furthermore, the prepared ASA emulsion can be used for different pulp layers, meeting the needs of on-site applications.

Description

Technical Field

[0001] This invention belongs to the field of papermaking additives, and in particular to an ASA papermaking sizing emulsion, its preparation method and application. Background Technology

[0002] ASA (alkenyl succinic anhydride) is a commonly used reactive neutral sizing agent in papermaking, increasingly favored due to its rapid curing characteristics and wet heat stability. ASA sizing achieves a curing rate of over 80% off the machine, while AKD sizing is less than 50%. The curing rate of rosin sizing depends heavily on the amount of aluminum sulfate added to the system. Large amounts of aluminum sulfate create an acidic environment in the paper machine, hindering calcium carbonate addition and easily causing inorganic deposits that are difficult to clean. Therefore, ASA sizing offers unique advantages. ASA concentrate is an amber-colored oily liquid, insoluble in water, and cannot be uniformly added in an aqueous environment. It needs to be emulsified into an oil-in-water emulsion under emulsifier conditions before it can be dispersed in an aqueous environment for use in the papermaking system. Because of its high chemical reactivity, ASA is easily hydrolyzed into dibasic acid hydrolysates that hinder sizing; therefore, ASA must be prepared through on-site emulsification.

[0003] The on-site preparation method and process of ASA emulsion directly affect its performance. The stability and affinity of the emulsion directly affect the sizing effect of ASA. Therefore, in addition to a mature and stable emulsification process, the selection of emulsifier is crucial. Currently, commonly used ASA emulsifiers include natural polymeric emulsifiers (cationic starch) and synthetic polymeric emulsifiers (CPAM). The three commonly accepted emulsifiers (cationic starch, polyethylene glycol grafted polyacrylamide (GPAM), and amphoteric polyacrylamide (AM-DMC-DADMAC-AAS copolymer, amphoteric PAM)) each have their advantages and disadvantages: cationic starch emulsifiers have a strong fiber selective affinity due to their similarity to fiber structure, and have a certain resistance to ash and other system waste. They are generally used for highly filled cultural paper. GPAM and amphoteric PAM, on the other hand, have the ability to emulsify ASA, and are widely used as ASA emulsifiers in packaging paper systems because of their portability (no cooking required), high stability of the emulsion, and high anionic waste shielding performance. However, its molecular chain characteristics make it very easy for filler particles such as calcium carbonate to be adsorbed, so it is rarely used in high-ash environments due to its poor performance.

[0004] For papermaking systems using multiple pulp types, such as coated whiteboard paper and grey-backed whiteboard paper, the surface layer is a high-filler cultural paper making system, the liner layer is a newsprint making system using deinked pulp, and the core and bottom layers are packaging paper making systems using OCC pulp. Traditional single-emulsifier emulsification ASA systems are not suitable for all these pulp types. Generally, AKD sizing is used for the surface and liner layers, while ASA sizing is used for the core and bottom layers. Because ASA sizing has a significant cost advantage, customers prefer it. Therefore, we need an ASA sizing system that can be used for multiple pulp types to meet their urgent needs. Summary of the Invention

[0005] To overcome the above-mentioned technical defects, the present invention provides an ASA paper sizing emulsion, its preparation method and application, so as to solve the problems involved in the background art.

[0006] This invention provides an ASA paper sizing emulsion, comprising the following components by weight:

[0007]

[0008] Furthermore, the D90 particle size of the sizing emulsion is 0.5-5.0 μm and / or the average particle size is 0.5-3.0 μm.

[0009] Preferably or optionally, the alkenyl succinic anhydride stock solution is a mixture of 30-50 wt% C196 alkenyl succinic anhydride and 50-70 wt% C18 alkenyl succinic anhydride.

[0010] Preferably or optionally, the cationic starch is a cationic starch obtained by cationic etherification treatment of one or more starches selected from corn starch, cassava starch, and potato starch.

[0011] Preferably or optionally, the degree of substitution of the cationic starch is greater than 0.025%.

[0012] Preferably or optionally, the amphoteric polyacrylamide is a copolymer of any two or more monomers selected from acrylamide, methacryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, acrylic acid and its salts, and methacrylic acid and its salts.

[0013] Preferably or optionally, the molecular weight of the amphoteric polyacrylamide is 200,000-1,000,000.

[0014] Preferably or optionally, the surfactant includes one or more of alkyl alcohol polyether phosphate, fatty alcohol polyoxyethylene ether phosphate, fatty alcohol polyoxyethylene ether phosphate salt, fatty alcohol amide phosphate, fatty acid sulfonate, saturated alcohol ether sulfonate, sulfosuccinate, etc.

[0015] This invention also provides a method for preparing an ASA paper sizing emulsion, comprising the following steps:

[0016] A cationic starch solution and an amphoteric polyacrylamide solution were prepared into a mixture at a mass ratio of 1:1 to 1:5. A surfactant was added and the pH was adjusted to weakly acidic.

[0017] Instead, the ASA stock solution and the mixture are mixed at a mass ratio of 1:5 to 1:9, and then sheared and emulsified in a shearing machine to adjust the D90 particle size of the sizing emulsion to 0.5-5.0 μm and / or an average particle size of 0.5-3.0 μm.

[0018] Preferably or optionally, the rotation speed of the shearing machine is 10,000 rpm; the emulsification time is 90 s.

[0019] The present invention also provides an application of the aforementioned ASA paper sizing emulsion in the preparation of paper.

[0020] This invention relates to an ASA paper sizing emulsion, its preparation method and application. Compared with the prior art, it has the following beneficial effects: When the cationic starch and amphoteric PAM are mixed in a certain proportion and reacted under specific conditions to prepare an ASA emulsion mixture, the stability of the prepared emulsion is significantly improved, especially the stability at low temperature is significantly better than that of emulsion emulsified with pure starch emulsifier.

[0021] Moreover, the prepared emulsion exhibits significantly better application performance than emulsions emulsified with a single emulsifier; its self-adsorption capacity is also significantly superior to that of emulsions emulsified with a single emulsifier, and its dependence on retention aids is significantly reduced, maintaining high application efficiency even in environments with insufficient retention aids; its versatility is significantly increased, applicable to both high-calcium carbonate filled paper and packaging paper, such as coated whiteboard paper and grey-backed whiteboard paper. ASA emulsions prepared using this method can be used in various layers of different pulps, meeting on-site application requirements. Detailed Implementation

[0022] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention. Invention Overview

[0024] The traditional ASA emulsification sizing method involves diluting cationic starch or polymer emulsifier to a certain concentration, adjusting the pH, mixing it with ASA, and then using an emulsification pump to emulsify the ASA stock solution into an ASA emulsion with a certain average or median particle size through high-speed shearing. After secondary dilution, the emulsion is added to the pulp system. After papermaking, forming, and drying, the paper sheet has a certain water resistance.

[0025] This invention effectively combines the advantages of cationic starch and polymer emulsifiers, resulting in improved emulsion stability, superior low-temperature resistance, reduced dependence on retention aids, and greater versatility. Particularly in multi-sizing systems such as grey-backed white cardboard paper, a single ASA sizing system is universally applicable to all layers of pulp, with significantly improved sizing performance. The specific preparation method involves: preparing a starch solution and an amphoteric polyacrylamide (PAM) solution in a specific ratio; adding a special surfactant to adjust the pH to weakly acidic; mixing with ASA in a specific ratio; and then emulsifying at high speed in a shear mill. After adjusting to a specified particle size distribution, the mixture is diluted and added to the pulp system.

[0026] The higher the degree of substitution of cationic starch, the smaller the particle size of the emulsion and the better the adsorption of the emulsion to the fiber. However, due to technical and cost constraints, the degree of substitution of cationic starch is generally between 0.025% and 0.07%.

[0027] The present invention will be further described below with reference to the embodiments. The examples described are intended to explain the present invention and should not be construed as limiting the present invention.

[0028] Example 1:

[0029] A 3.5% cationic starch solution (with a degree of substitution of 0.034%, the same applies to all examples below) was cooled to approximately 50°C, and 175g was weighed into an emulsifying tank. The pH was adjusted to 4.0 with 10% citric acid, and 25g of ASA stock solution was added. The mixture was then subjected to high-speed shearing at 10000 RPM for 90 seconds. After shearing was stopped, an ASA emulsion concentrate was obtained (the alkenyl succinic anhydride stock solution was a mixture of 30wt% C16 alkenyl succinic anhydride and 70wt% C18 alkenyl succinic anhydride, the same applies to all examples below). The particle size and stability of the concentrate were tested using the method of Test Example 1, and its sizing degree was determined using the method of Test Example 2.

[0030] Example 2:

[0031] 175g of amphoteric PAM with an effective content of 1.5% was weighed into an emulsifying tank, and the pH was adjusted to 4.0 with 10% citric acid. 25g of ASA stock solution was added, and the mixture was sheared at 10000 RPM for 90 seconds. The shearing was then stopped to obtain an ASA emulsion concentrate. The particle size and stability of the concentrate were tested using the method of Test Example 1, and its sizing degree was determined using the method of Test Example 2 or Test Example 3.

[0032] Example 3:

[0033] Weigh 29.2 g of 3.5% cationic starch solution and 145.8 g of 1.5% amphoteric PAM solution, mix and stir thoroughly. Adjust the pH to 4.0 with 10% citric acid while stirring, and stir for 10 min to react completely. Add 25 g of ASA stock solution, and shear at 10000 RPM for 90 s. Stop shearing to obtain ASA emulsion concentrate. The particle size and stability of the concentrate are determined using the method of Test Example 1, and its sizing degree is determined using the method of Test Example 2 or Test Example 3.

[0034] Example 4:

[0035] Weigh 43.75 g of 3.5% cationic starch solution and 131.25 g of 1.5% amphoteric PAM solution, mix and stir thoroughly. Adjust the pH to 4.0 with 10% citric acid while stirring, and stir for 10 min to react completely. Add 25 g of ASA stock solution, and shear at 10000 RPM for 90 s. Stop shearing to obtain ASA emulsion concentrate. The particle size and stability of the concentrate are tested using the method of Test Example 1, and its sizing degree is determined using the method of Test Example 2.

[0036] Example 5:

[0037] Weigh 87.5g of 3.5% cationic starch solution and 87.5g of 1.5% amphoteric PAM solution, mix and stir thoroughly. Adjust the pH to 4.0 with 10% citric acid while stirring, and stir for 10 minutes to react completely. Add 25g of ASA stock solution, and shear at 10000 RPM for 90 seconds. Stop shearing to obtain ASA emulsion concentrate. The particle size and stability of the concentrate are tested using the method of Test Example 1, and its sizing degree is determined using the method of Test Example 2.

[0038] Example 6:

[0039] Weigh 131.25g of 3.5% cationic starch solution and 43.75g of 1.5% amphoteric PAM solution, mix and stir thoroughly. Adjust the pH to 4.0 with 10% citric acid while stirring, and stir for 10 minutes to react completely. Add 25g of ASA stock solution, and shear at 10000 RPM for 90 seconds. Stop shearing to obtain ASA emulsion concentrate. The particle size and stability of the concentrate are tested using the method of Test Example 1, and its sizing degree is determined using the method of Test Example 2.

[0040] Example 7:

[0041] 145.8 g of 3.5% cationic starch solution and 29.2 g of 1.5% amphoteric PAM solution were weighed and mixed thoroughly. While stirring, the pH was adjusted to 4.0 with 10% citric acid. The mixture was stirred for 10 min to allow it to react completely. Then, 25 g of ASA stock solution was added, and the mixture was subjected to high-speed shearing at 10000 RPM for 90 s. The shearing was then stopped to obtain an ASA emulsion concentrate. The particle size and stability of the concentrate were determined using the method in Example 1, and its sizing degree was determined using the method in Example 2.

[0042] Example 8:

[0043] Weigh 43.75g of 3.5% cationic starch solution and 131.25g of 1.5% amphoteric PAM solution, mix and stir until homogeneous. Adjust the pH to 3.0 with 10% citric acid while stirring, and allow to react for 10 minutes. Add 25g of ASA stock solution, and shear at 10000 RPM for 90 seconds. Stop shearing to obtain an ASA emulsion concentrate. The particle size and stability of the concentrate are tested using the method in Example 1, and its sizing degree is determined using the method in Example 2. Example 9:

[0044] Weigh 43.75 g of 3.5% cationic starch solution and 131.25 g of 1.5% amphoteric PAM solution, mix and stir thoroughly. Adjust the pH to 5.0 with 10% citric acid while stirring, and stir for 10 min to react completely. Add 25 g of ASA stock solution, and shear at 10000 RPM for 90 s. Stop shearing to obtain ASA emulsion concentrate. The particle size and stability of the concentrate are tested using the method of Test Example 1, and its sizing degree is determined using the method of Test Example 2.

[0045] Example 10:

[0046] Weigh 43.75 g of 3.5% cationic starch solution and 131.25 g of 1.5% amphoteric PAM solution, mix and stir thoroughly. Adjust the pH to 6.0 with 10% citric acid while stirring, and stir for 10 min to react completely. Add 25 g of ASA stock solution, and shear at 10000 RPM for 90 s. Stop shearing to obtain ASA emulsion concentrate. The particle size and stability of the concentrate are tested using the method of Test Example 1, and its sizing degree is determined using the method of Test Example 2.

[0047] Example 11:

[0048] Weigh 43.75 g of 3.5% cationic starch solution and 131.25 g of 1.5% amphoteric PAM solution, mix and stir thoroughly. Adjust the pH to 7.0 with 10% citric acid while stirring, and stir for 10 min to allow the mixture to react completely. Add 0.125 g of alkyl phosphate (salt) and 25 g of ASA stock solution. Shear the mixture at 10000 RPM for 90 s, then stop shearing to obtain an ASA emulsion concentrate. The particle size and stability of the concentrate were tested using the method in Example 1, and its sizing degree was determined using the method in Example 2.

[0049] Example 12:

[0050] Weigh 43.75 g of 3.5% cationic starch solution and 131.25 g of 1.5% amphoteric PAM solution, mix and stir until homogeneous. Adjust the pH to 7.0 with 10% citric acid while stirring, and stir for 10 min to allow the mixture to react fully. Add 0.125 g of fatty alcohol polyoxyethylene ether phosphate (salt) and 25 g of ASA stock solution. Shear the mixture at 10000 RPM for 90 s, then stop shearing to obtain an ASA emulsion concentrate. The particle size and stability of the concentrate were tested using the method in Example 1, and its sizing degree was determined using the method in Example 2.

[0051] Example 13:

[0052] Weigh 43.75 g of 3.5% cationic starch solution and 131.25 g of 1.5% amphoteric PAM solution, mix and stir thoroughly. Adjust the pH to 7.0 with 10% citric acid while stirring, and stir for 10 min to allow the mixture to react completely. Add 0.125 g of fatty alcohol amide phosphate and 25 g of ASA stock solution. Shear at 10000 RPM for 90 s, then stop shearing to obtain an ASA emulsion concentrate. The particle size and stability of the concentrate are determined using the method in Example 1, and its sizing degree is determined using the method in Example 2.

[0053] Example 14:

[0054] Weigh 43.75 g of 3.5% cationic starch solution and 131.25 g of 1.5% amphoteric PAM solution, mix and stir thoroughly. Adjust the pH to 7.0 with 10% citric acid while stirring, and stir for 10 min to allow the mixture to react completely. Add 0.125 g of sulfosuccinate and 25 g of ASA stock solution. Shear the mixture at 10000 RPM for 90 s, then stop shearing to obtain an ASA emulsion concentrate. The particle size and stability of the concentrate were determined using the method in Example 1, and its sizing degree was determined using the method in Example 2.

[0055] Example 15:

[0056] Weigh 43.75g of 3.5% cationic starch solution and 131.25g of 1.5% amphoteric PAM solution, mix and stir thoroughly. Adjust the pH to 7.0 with 10% citric acid while stirring, and stir for 10 minutes to allow the mixture to react completely. Add 0.025g of fatty alcohol polyoxyethylene ether phosphate and 25g of ASA stock solution. Shear the mixture at 10000 RPM for 90 seconds, then stop shearing to obtain an ASA emulsion concentrate. The particle size and stability of the concentrate were tested using the method in Example 1, and its sizing degree was determined using the method in Example 2.

[0057] Example 16:

[0058] Weigh 43.75g of 3.5% cationic starch solution and 131.25g of 1.5% amphoteric PAM solution, mix and stir until homogeneous. Adjust the pH to 7.0 with 10% citric acid while stirring, and stir for 10 min to allow the mixture to react fully. Add 0.25g of fatty alcohol polyoxyethylene ether phosphate and 25g of ASA stock solution. Shear the mixture at 10000 RPM for 90 s, then stop shearing to obtain an ASA emulsion concentrate. The particle size and stability of the concentrate are determined using the method in Example 1, and its sizing degree is determined using the method in Example 2 or Example 3.

[0059] Example 17:

[0060] Weigh 43.75g of 3.5% cationic starch solution and 131.25g of 1.5% amphoteric PAM solution, mix and stir until homogeneous. Adjust the pH to 7.0 with 10% citric acid while stirring, and stir for 10 min to allow the mixture to react fully. Add 0.375g of fatty alcohol polyoxyethylene ether phosphate and 25g of ASA stock solution. Shear the mixture at 10000 RPM for 90 s, then stop shearing to obtain an ASA emulsion concentrate. The particle size and stability of the concentrate were tested using the method in Example 1, and its sizing degree was determined using the method in Example 2.

[0061] Detection Example 1

[0062] This test example provides a laboratory evaluation method for assessing the particle size distribution and emulsion stability of ASA sizing emulsions. The test results are shown in Table 1, and the specific test parameters and methods are as follows:

[0063] 1. Particle size distribution: The particle size distribution of the emulsion concentrates prepared in Examples 1-17 above was tested using a HORIBA LA-300 particle size distribution analyzer. The D90% particle size (the particle size corresponding to the cumulative particle size distribution of a sample reaching 90%) and mean particle size were recorded.

[0064] 2. Emulsion stability: The emulsion concentrates prepared in Examples 1-17 were placed in glass bottles, and the short-term stability (particle size and emulsion state) of the emulsions (preserved at 40°C for 2 hours and at 40°C for 6 hours and at 25°C for 30 days) was tested using the particle size distribution test method of Example 1, to determine whether emulsion demulsification, flocculation or stratification occurred.

[0065] Detection Example 2

[0066] This test example provides a method for evaluating the water resistance of ASA emulsion sizing using a laboratory-simulated on-site papermaking system. The test results are shown in Table 2, and the specific test parameters and methods are as follows:

[0067] 1. Dilute the ASA concentrate 100 times with tap water (conductivity 300 μS / cm) and set aside for use.

[0068] 2. Take samples of the pulp from the on-site coated whiteboard paper machine's surface layer (cultural paper pulp system, 50% poplar chemimechanical pulp + 25% bleached sulfate hardwood pulp + 10% bleached sulfate softwood pulp + 15% office waste paper pulp, calcium carbonate filler PCC-30%), core layer (newsprint pulp system, 100% DIP pulp), and bottom layer (packaging paper pulp system, 100% OCC pulp) after flushing the pulp pump without adding ASA sizing agent, and process them according to the papermaking specifications. Weigh each layer of pulp at a rate of 100 g / m² into a beaker, add the ASA secondary dilution emulsion prepared in step ① (3.0 kg / ton pulp for the surface layer, 2.0 kg / ton pulp for the core layer, and 0.5 kg / ton pulp for the bottom layer), stir for 30 seconds, add 0.25 kg / ton pulp of Fumiao Technology retention aid VD8240, continue stirring for 60 seconds, transfer to a paper sheeter to form paper sheets, press, and dry in a 95°C paper dryer for 6 minutes, maintaining constant temperature and humidity for 24 hours.

[0069] 3. The sizing degree of the paper sample was tested using the national standard method GBT 5405-2002 "Determination of Sizing Degree of Paper (Liquid Penetration Method)".

[0070] Detection Example 3

[0071] This test example provides a laboratory-simulated on-site papermaking system for evaluating the water resistance of ASA emulsion sizing (the difference between this test example and Test Example 2 is the ratio of ASA emulsion to retention aid VD8240). The test results are shown in Table 2, and the specific test parameters and methods are as follows:

[0072] 1. Dilute the ASA concentrate 100 times with tap water (conductivity 300 μS / cm) and set aside for use.

[0073] 2. Take samples of the pulp from the on-site coated whiteboard paper machine's surface layer (cultural paper pulp system, 50% poplar chemimechanical pulp + 25% bleached sulfate hardwood pulp + 10% bleached sulfate softwood pulp + 15% office waste paper pulp, calcium carbonate filler PCC-30%), core layer (newsprint pulp system, 100% DIP pulp), and bottom layer (packaging paper pulp system, 100% OCC pulp) after flushing the pulp pump without adding ASA sizing agent, and process them according to the papermaking specifications. Weigh each layer of pulp at a rate of 100 g / m² into a beaker, add the ASA secondary dilution emulsion prepared in step ① (3.0 kg / ton pulp for the surface layer, 2.0 kg / ton pulp for the core layer, and 0.5 kg / ton pulp for the bottom layer), stir for 30 seconds, add 0.1 kg / ton pulp of Fumiao Technology retention aid VD8240, continue stirring for 60 seconds, transfer to a paper sheeter to form paper sheets, press, and dry in a 95°C paper dryer for 6 minutes, maintaining constant temperature and humidity for 24 hours.

[0074] 3. The sizing degree of the paper sample was tested using the national standard method GBT 5405-2002 "Determination of Sizing Degree of Paper (Liquid Penetration Method)".

[0075] Table 1: Particle size distribution and emulsion stability of ASA sizing emulsions obtained in Examples 1 to 17

[0076]

[0077]

[0078] Table 2: Sizing and water resistance properties of ASA sizing emulsions obtained in Examples 1 to 17

[0079]

[0080]

[0081] discuss:

[0082] As shown in Table 1, the mixtures of starch and amphoteric PAM in a specific ratio, as described in Examples 12 to 17, along with the addition of surfactants, produced emulsions that could be used as emulsifiers for ASA stock solutions. Furthermore, the stability of the resulting emulsions was significantly improved, particularly at low temperatures, where they were significantly more stable than those emulsions emulsified with pure starch. Compared to Examples 11 to 17, the addition of a specific proportion of fatty alcohol polyoxyethylene ether phosphate (salt) surfactant resulted in smaller particle sizes and better stability in the ASA stock solutions emulsified by the emulsifiers. Compared to Examples 1 and 8 to 10, the reaction products were most effective for emulsifying ASA when starch and amphoteric PAM were mixed under a weakly acidic environment, specifically at pH 4.0-6.0. In particular, the ASA emulsion dilutions prepared in Examples 16 and 17 exhibited small initial particle sizes and good stability, remaining stable for up to 30 days.

[0083] As can be seen from the data in Table 2, the versatility of the emulsions prepared using Examples 12 to 17 is significantly increased. They can be applied to both high-calcium carbonate filled paper and packaging paper, such as coated whiteboard paper and grey-backed whiteboard paper. The ASA emulsions prepared using this method can be used for different pulps in various layers, meeting the needs of on-site applications. Compared with Examples 1, 2, and 6, the application effect of the emulsions prepared using the present invention is significantly better than that of emulsions emulsified with a single emulsifier. Compared with Test Examples 2 and 3, the self-adsorption capacity of the emulsions prepared using the present invention is significantly better than that of the emulsions emulsified with a single emulsifier in the examples, and the dependence on retention aids is significantly reduced. It can still maintain a high efficiency in application even in environments with insufficient retention aids. In particular, the ASA emulsion prepared in Example 16, when applied to paper, exhibits significantly better water resistance than other examples, and the application performance of the emulsion is stable, with a significantly reduced dependence on retention aids.

[0084] In summary, the polymeric emulsion-based ASA emulsion prepared by this invention can simultaneously possess the following properties: improved stability of the ASA emulsion at low temperatures, reduced dependence on retention aids during sizing, improved ASA emulsion sizing effect, and is fully applicable to multi-pulp papermaking systems such as coated whiteboard paper and grey-backed whiteboard paper.

[0085] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for preparing an ASA paper sizing emulsion, characterized in that, ASA paper sizing emulsion, by weight, comprises the following components: 1.75 parts of a 3.5 wt% cationic starch solution; 5.25 parts of a 1.5 wt% amphoteric polyacrylamide solution; 0.01 parts of surfactant; the surfactant is fatty alcohol polyoxyethylene ether phosphate; One part of alkenyl succinic anhydride stock solution; the alkenyl succinic anhydride stock solution is a mixture of 30 wt% C16 alkenyl succinic anhydride and 70 wt% C18 alkenyl succinic anhydride; The preparation method of ASA paper sizing emulsion includes the following steps: The cationic starch solution and the amphoteric polyacrylamide solution were mixed in the above weight proportions, a surfactant was added, and the pH was adjusted to 4-6. After mixing the alkenyl succinic anhydride stock solution and the mixture according to the above-mentioned weight proportions, the mixture is sheared and emulsified in a shearing machine to adjust the D90 particle size of the sizing emulsion to be 0.5-5.0 μm and the average particle size to be 0.5-3.0 μm.

2. The method for preparing ASA paper sizing emulsion according to claim 1, characterized in that, The cationic starch is obtained by cationic etherification of one or more starches, such as corn starch, cassava starch, and potato starch.

3. The method for preparing ASA paper sizing emulsion according to claim 2, characterized in that, The degree of substitution of the cationic starch is greater than 0.025%.

4. The method for preparing ASA paper sizing emulsion according to claim 1, characterized in that, The amphoteric polyacrylamide is a copolymer of any two or more monomers selected from acrylamide, methacryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, acrylic acid and its salts, and methacrylic acid and its salts.

5. The method for preparing ASA paper sizing emulsion according to claim 4, characterized in that, The molecular weight of the amphoteric polyacrylamide is 200,000-1,000,000.

6. The method for preparing ASA paper sizing emulsion according to claim 1, characterized in that, The shearing machine rotates at 8000-12000 rpm; the emulsification time is 60-120 s.

7. An ASA paper sizing emulsion, characterized in that, It was prepared according to the preparation method of ASA paper sizing emulsion according to any one of claims 1 to 6.

8. An application of the ASA paper sizing emulsion according to claim 7 in papermaking.

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