A wet-end chemical additive, its preparation method and use

Abstract

This invention belongs to the field of new materials and discloses a wet-end chemical additive. The additive has the following characteristics: (1) it has aldehyde functional groups that can react with fibers; (2) the weight-average molecular weight of the unmodified acrylamide polymer is 30,000 to 1,000,000, and the distribution coefficient is 2 to 6; (3) the net charge of the composition is positive; (4) the particle size distribution of the particles in the composition has at least two peaks. This additive can simultaneously improve paper strength, retention and water permeability. Furthermore, this invention also provides a method for preparing and applying this wet-end chemical additive.

Description

Technical Field

[0001] This invention belongs to the field of new materials, specifically relating to a wet-end chemical additive, its preparation method, and its uses. Background Technology

[0002] In the paper industry, with the improvement of efficiency and the closed-loop white water system, some wet-end chemical additives are often used to improve production efficiency: such as increasing paper strength, improving retention in the white water cycle, and increasing dewatering efficiency to achieve the desired economic benefits. Currently, glyoxal-modified polyacrylamide polymers are widely used as strength additives. For example, CN110088398A uses glyoxal acidification of cationic polyacrylamide polymers as a paper strength additive, but its strength improvement is limited. Patent CN102408519B proposes a method to significantly improve strength and proposes a composition that is less prone to gelation and has a longer storage time. With the closed-loop papermaking system, interference from DCS in white water, diversification of paper products, and the complexity of the wet-end environment, poor suitability, reduced expected effects, and failure often occur. At the same time, some two-component compounding technologies have emerged in the industry: CN105899729B, CN105696414B, etc. mention some two-component compounding technologies to improve paper strength, but they have many problems such as complex processes, high costs, and poor adaptability to different types of paper bases. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a wet-end chemical additive that can simultaneously improve paper strength, retention, and water permeability.

[0004] In addition, the present invention also provides a method for preparing the wet-end chemical additive and its application.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] A wet-end chemical additive, wherein the additive is a composition of an acrylamide polymer modified with an aldehyde oxidizing agent; wherein the aldehyde oxidizing agent has at least two reactive aldehyde groups;

[0007] The additive has the following characteristics:

[0008] (1) It has an aldehyde functional group that can react with fibers;

[0009] (2) The weight-average molecular weight of the unmodified acrylamide polymer is 30,000 to 1,000,000, and the distribution coefficient is 2 to 6;

[0010] (3) The net charge of the composition is positive;

[0011] (4) The particle size distribution of the particles in the composition has at least two peaks; preferably, the particle size distribution of the particles in the composition is a bimodal distribution.

[0012] Implicitly, this invention excludes the presence of three or more peaks;

[0013] In this invention, the aldehyde functional group that can react with fibers refers to the presence of a certain number of aldehyde groups in the side chain of the composition, and its general structural formula is shown in Formula 1 below.

[0014]

[0015] Formula 1;

[0016] Where n refers to the number of repeating units of ethylene, which is related to the molecular weight of the acrylamide polymer that has not been modified by aldehydes;

[0017] The above (1) requires a certain ratio of aldehyde agent to amide monomer. Generally, a ratio of amide group to glyoxal of 3:1 to 12:1 can be used to obtain the target composition. Specifically, 30-80% of the glyoxal needs to react. The amount of reacted glyoxal can be detected by filtering the remaining glyoxal through a permeation membrane, or by using nuclear magnetic resonance (NMR) technology to determine the content of the above structure. Unbound by theory, C 13 NMR and H 1 NMR can characterize the above structure, but D2O and D2O can be used. 6 -DMSO is used to determine the relevant results. For example, H is used as a special case. 1 NMR analysis showed that all amide proton chemical shifts were above 7.2 ppm, while the proton shifts after acidification with glyoxal reacting with amide groups were between 5 and 6 ppm. Furthermore, the chemical shifts of the hydroxymethyl group in glyoxal due to aldehyde grafting and crosslinking were different: below 6 ppm indicated grafting, while above 6 ppm indicated crosslinking. Based on the above analysis and comparison, the content of the aforementioned structures can be estimated to be between 1% mol and 10% mol.

[0018] Preferably, the components by mass percentage are: 0-40% aldehyde agent; 60-100% unmodified acrylamide polymer.

[0019] The weight-average molecular weight of the acrylamide polymer without aldehyde modification described in (2) above is determined by a predetermined method, such as aqueous phase GPC or dynamic light scattering. In particular, the molecular weight of the composition is affected by the crosslinking or grafting of the acrylamide polymer and the aldehyde substance. Due to the requirements of feature (1), special specifications need to be made for the acrylamide polymer. As a limitation on the polymerization conditions, the weight-average molecular weight of the acrylamide polymer is preferably 100,000 to 300,000, and the dispersion index is 3 to 5.5. The above conditions can be determined by adjusting the polymerization.

[0020] The above (3) specifies that the present invention has a permanent positive charge within the operating pH range, but this does not mean that the system does not contain a certain amount of anionic components. It is sufficient to form a permanent positive charge within the operating pH range. At the same time, since the ionic structure has been formed in the acrylamide polymer, in order to achieve this, corresponding adjustments need to be made when forming the final composition to meet the characteristics of (1) to (4) mentioned above. This statement of permanent positive charge refers to maintaining the positive charge performance throughout the process rather than the quantity remaining consistent. The charge quantity of the product, i.e., charge density (PCD, eq / L), can be determined by acid-base titration. This quantity characterizes the charge status. However, since acid-base titration itself involves changes in the charge quantity, such as ionization, other methods can be used to infer its positive charge characteristics, such as osmotic pressure, electrophoresis, flow potential, and precipitation potential. Due to the requirements of characteristic (2), the PCD of the acrylamide polymer is specified to be between 0.25 and 1.2 eq / L.

[0021] The above (4) specifies that the size distribution of the colloidal particles in this invention has a bimodal distribution, which is one of the core means to achieve the purpose of this invention.

[0022] Experimental verification has shown that using colloidal particles with bimodal distribution as wet-end chemical additives has significant advantages over materials of the same material with normal distribution in terms of improving paper strength, retention, and water permeability.

[0023] In the aforementioned wet-end chemical additives, the bimodal distribution has the following characteristics:

[0024] (1) It has a first peak and a second peak;

[0025] (2) The peak particle size of the first peak and the peak particle size of the second peak are 0.05~10μm.

[0026] In the aforementioned wet-end chemical additives, the total number of particles contained in the first and second peaks accounts for more than 80% of the total number of particles in the composition.

[0027] In the aforementioned wet-end chemical additives, the total number of particles contained in the first peak and the second peak accounts for more than 90% of the total number of particles in the composition.

[0028] In the aforementioned wet-end chemical additives, the peak particle size of the first peak is 0.05~0.2μm; the peak particle size of the second peak is 0.5~3μm.

[0029] In the aforementioned wet-end chemical additives, the ratio of the total number of particles in the first peak to the total number of particles in the second peak is 1:5 to 10:1, preferably 1:5 to 8:1, more preferably 1:5 to 5:1, even more preferably 2:5 to 5:2, and even more preferably 3:5 to 5:3.

[0030] In the aforementioned wet-end chemical additives, the ester-hydrophilic value LogP of the unmodified acrylamide polymer is -0.6 to -0.9.

[0031] Due to the differences in lipophilicity and hydrophilicity of different structural units in unmodified acrylamide polymers, such as (methyl or N-substituted) acrylamide structural units, cationic structural units, and anionic structural units, stoichiometric calculations can be performed to determine the lipophilicity and hydrophilicity values ​​of acrylamide polymers with different structures. For accurate measurement, the Howard method (AtomlFragment Contribution Method for Estimating Octanol-Water Partition Coefficients. William M. Meylan, Philip H. Howard. Journal of Pharmaceutical Sciences, Volume 84, Issue 1) can be used to calculate the lipophilicity and hydrophilicity values ​​using the formula below.

[0032] LogP=

[0033] Where fi is the lipophilic / hydrophilic coefficient, ni and nj are the number of repetitions, and cj is the correction coefficient.

[0034] Data on structural units in the composition, especially in unmodified acrylamide polymers, can be obtained based on the coefficient values ​​of each structure in Table 1. For example, the esterification and hydrophilicity values ​​of acrylamide, acrylic acid, itaconic acid, and methacrylamide are listed in Table 2.

[0035] Table 1. Lipophilic and hydrophilic coefficients of the main related structures

[0036] structure coefficient fi source -COOH -0.6895 Anionic structure -COO -0.9505 Anionic structure -SO2OH -3.158 Anionic structure -SO3 -0.725 Anionic structure -C(=O)-N -0.5236 amide structure -NH2 -1.4148 cationic structure -NH -1.4962 cationic structure -N< -1.8323 cationic structure -CH3 0.5473 Main chain structure -CH2- 0.4911 Main chain structure -CH< 0.3614 Main chain structure >C< 0.2767 Main chain structure

[0037] Table 2. Examples of lipophilic and hydrophilic value calculations for some monomers

[0038]

[0039] The wet-end chemical additive of the present invention can be obtained by reacting the polymer amide group with the aldehyde agent in a stoichiometric ratio of 3:1 to 12:1.

[0040] The LogP values ​​of the raw materials involved in this invention are as follows:

[0041] Acrylamide AM: -0.8569

[0042] Methacrylamide (AAM): -0.3096

[0043] Acrylic acid AA: 0.392

[0044] Itaconic acid IA: -0.4776

[0045] Sodium methyl allyl sulfonate SMAS: 1.3949

[0046] Dimethylaminoethyl methacrylate (DMAEMA): 0.6091

[0047] Diallyl dimethyl ammonium chloride (DADMAC): -2.5892

[0048] Dimethylaminoethyl methacrylate, methyl chloride, quaternary ammonium salt (DMAEMA-BQ): -3.3914

[0049] Dimethylaminopropylacrylamide chloromethane quaternary salt DMPC: -4.4231

[0050] Dimethylaminoethyl acrylate (DM): 0.3755

[0051] N-Isopropylacrylamide (NPAM): 0.1563

[0052] N-tert-butylacrylamide (NBAM): 0.7036

[0053] N-Methylacrylamide (NAAM): -0.391

[0054] N-Ethylacrylamide (NEAM): 0.1001

[0055] N,N-Dimethylacrylamide (DMAM): -0.1798

[0056] N,N-Diethylacrylamide DEAM: 0.8024

[0057] In the above-mentioned wet-end chemical additives, the molar ratio of the amide groups to the aldehyde agent in the unmodified acrylamide polymer is 3:1 to 12:1.

[0058] In the above-mentioned wet-end chemical additives, the aldehyde agent is glyoxal or glutaraldehyde.

[0059] In the aforementioned wet-end chemical additives, the unmodified acrylamide polymer has a weight-average molecular weight of 100,000 to 300,000 and a distribution coefficient of 3 to 5.5.

[0060] 30% to 80% of the aldehydes were reacted with the unmodified acrylamide polymers.

[0061] In the aforementioned wet-end chemical additives, the unmodified acrylamide polymer comprises the following molar amounts of structural units:

[0062] Nonionic acrylamide: 75–99 parts;

[0063] Ionic monomers: 1 to 25 parts.

[0064] In the aforementioned wet-end chemical additives, the nonionic acrylamide is acrylamide, methacrylamide, N-methacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, N,N-dimethylacrylamide, or N,N-diethylacrylamide; wherein the content of acrylamide and methacrylamide is not less than 80 mol% of the total amount of nonionic acrylamide.

[0065] The ionic monomers include cationic monomers and optionally anionic monomers;

[0066] The cationic monomer is a product obtained by quaternization of ammonium salt compounds or other compounds containing tertiary amines; the cationic monomer is a quaternary ammonium salt formed from dimethyl diallyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, tetraallyl ammonium chloride, etc., dialkylaminoalkyl esters of (meth)acrylate, and dialkylaminoalkylalkyl(meth)acrylamide and their benzyl chloride or chloroalkanes.

[0067] The anionic monomer refers to an unsaturated monomer containing carboxylate, sulfonate, and phosphate groups. The anionic monomer is (meth)acrylic acid, allyl carboxylic acid, fumaric acid, maleic acid, itaconic acid, mucoaconic acid, etc., and their ammonium salts and metal salts.

[0068] Meanwhile, the present invention also discloses a method for preparing a wet-end chemical additive as described above, wherein an unmodified acrylamide polymer is reacted with an aldehyde agent to obtain a composition.

[0069] The acrylamide polymer of the present invention can be prepared by a chain reaction through a chain radical growth process. Inevitably, in the preparation of this polymer, an initiator and a solvent are required, especially a water-soluble oxidative and / or reductive initiation system, which includes a water-soluble oxidant and / or a water-soluble reductant. The water-soluble oxidant includes persulfate, hydrogen peroxide, bromate, etc., and the water-soluble reductant includes sulfite, metabisulfite, thiosulfate, etc.

[0070] More specifically, the system for preparing the above polymer is a free radical initiation system, which contains the following components:

[0071] For the sake of brevity, the components are described as follows:

[0072] Component 1 (meth)acrylamide monomer

[0073] Component 2: cationic monomers and / or anionic monomers

[0074] Component 3: Initiator;

[0075] Component 4: Water or (and) butanol, etc.

[0076] In the case of water as the reaction medium, acrylamide, ionic monomer and initiator are subjected to solution polymerization according to a certain process flow, and the reaction is carried out after heating to obtain polyacrylamide polymers.

[0077] The preferred amount of water is calculated based on a ratio of 0.2 to 0.4:1 between the total mass of the reaction raw materials and the mass of the water.

[0078] The preferred specific steps are as follows: Acrylamide, structure modifier and ionic monomer can be added individually or in combination as required. The system needs to be deoxygenated, usually by purging nitrogen; then the polymerization reaction is carried out until the reaction is completed, and the reaction yields a polyacrylamide polymer.

[0079] The preferred nitrogen purging time for deoxygenation is 10–60 min; more preferably 25–35 min; and most preferably 30 min. The components, specifically components 1, 2, 3, and 4, can be added in stages or dropwise, depending on the target product requirements.

[0080] The segmented and dropwise addition of components refers to a feeding method where, at the start of the reaction, not all raw materials are added together, but rather some or all of them are added in stages. Priority is given based on the characteristics of each component and the product structure requirements.

[0081] The reaction temperature refers to the temperature at which the polymerization reaction begins and continues until the polymerization reaction ends, and is generally preferred to be 30-95℃; more preferably 60℃-95℃.

[0082] The reaction time refers to the time from the start of the polymerization reaction to the end of the polymerization reaction, which is generally preferred to be 2 to 6 hours; more preferably 4 hours.

[0083] The preferred reaction conditions are 30-95°C for 3-5 hours; more preferably, 60-95°C for 4 hours.

[0084] Furthermore, the present invention also discloses the application of preparing papermaking additives using any of the wet-end chemical additives described above;

[0085] The papermaking additives are used to increase paper strength and improve the system retention and filtration performance in the papermaking process.

[0086] In the above applications, the amount used in the papermaking process is 0.1 to 5 wt%.

[0087] Compared with the prior art, the present invention has the following beneficial effects:

[0088] (1) The present invention provides a composition with moderate molecular weight, constant cationicity within the working pH range, and particles having at least a bimodal distribution.

[0089] (2) In paper wet-end chemistry, white water sealing leads to more DCS and higher conductivity, and ordinary reinforcing additives cannot achieve the expected effect. Similar products often cannot achieve both reinforcement and retention of water permeability. The present invention, through a special structural design, produces a product that simultaneously enhances and retains water permeability.

[0090] (3) This invention has a permanent positive charge within the pH range of papermaking operations. This ensures that the product can adhere quickly and effectively to fibers, preventing fluctuations and failures in product performance due to pH changes;

[0091] In summary, through the optimization of this invention, the resulting product has the advantage of significantly improving paper's dry and wet strength, retention, and dehydration performance. Attached Figure Description

[0092] Figure 1 This is a particle size distribution diagram of Example 10;

[0093] Figure 2 This is a particle size distribution diagram of Example 11;

[0094] Figure 3 This is a particle size distribution diagram of Example 12;

[0095] Figure 4 This is a particle size distribution diagram of Example 13;

[0096] Figure 5 This is a particle size distribution diagram of Example 14;

[0097] Figure 6 This is a particle size distribution diagram of Example 15;

[0098] Figure 7 This is a particle size distribution diagram of Example 16;

[0099] Figure 8This is a particle size distribution diagram of Example 17;

[0100] Figure 9 This is a particle size distribution diagram of Example 18;

[0101] Figure 10 The particle size distribution diagram is shown in Comparative Example 7.

[0102] Figure 11 The particle size distribution diagram is shown in Comparative Example 8.

[0103] Figure 12 The particle size distribution diagram is shown in Comparative Example 9.

[0104] Figure 13 The particle size distribution diagram is shown in Comparative Example 10.

[0105] Figure 14 This is a particle size distribution diagram of Comparative Example 11;

[0106] Figure 15 This is a particle size distribution diagram for Comparative Example 12. Detailed Implementation

[0107] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0108] Example 1

[0109] Acrylamide polymer is implemented according to the following components, wherein the parts are by weight:

[0110] According to the formula, 808.5 parts (5 mol) of diallyl dimethyl ammonium chloride and a certain amount of water / butanol (10:1 V / V, the amount of which is 4 times the total weight of all monomers) were weighed and mixed. Sulfuric acid was added until the pH reached 4 as combination 1. 6697.6 parts (94.2 mol) of acrylamide, 29.7 parts (0.3 mol) of N-ethylacrylamide, and 63.5 parts (0.5 mol) of N,N-diethylacrylamide were used as combination 2. Ammonium persulfate was prepared into a 5% wt water / butanol solution (10:1 V / V) as combination 3. Each component was purged with nitrogen to remove oxygen for half an hour. Combinations 2 and 3 were added dropwise to combination 1 at 60°C, and the reaction was carried out dropwise for 3 hours. The temperature was raised to 95°C and kept at that temperature for 1 hour to obtain the acrylamide polymer.

[0111] Since no specific requirements are specified for the specific embodiments of the present invention, the relevant performance characteristics of this embodiment are listed in the table below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0112] The difference between Examples 2-9 and Example 1 is that, except for acrylamide, the other monomer compositions are different, but the process is the same as in Example 1; the data for Examples 1-9 are shown in Table 3;

[0113] Table 3 Formulation Table Unit: mol%

[0114] Components Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 AM 94.2 93.2 93 93 92 80.50 88 88 85 AA / 0.5 / / / / / / 0 IA / / / / 1 / / 2 / SMAS / / 1 0.5 / / / / / DMAEMA / / 1 2. 2. 4.5 1. 4 5 DADMAC 5 / / 1.5 1 1 5 5 5 DMPC / 4 3 / 2 / / / / AAM / 1 1 / / 1 / / / NAAM / / / / / / 2 / / NEAM / / / / / / 2 / / NPAM 0.3 / / / / / 2 / / NBAM / 0.5 / 3 2 7 / / 3 DMAA / / 1 / / 6 / 1 2 DEAM 0.5 0.8 / / / / / / 0 LogP -0.8964 -0.8845 -0.8337 -0.7543 -0.8221 -0.6087 -0.8431 -0.8361 -0.7722 Mw / kDa 223 245 202 231 199 247 177 255 266 Distribution coefficient 4.1 4.5 4.4 5 4.9 4.8 4.5 5.3 5.2 charge density meq 0.658 0.452 0.259 0.328 0.384 0.675 0.766 0.622 1.200

[0115] Comparative Examples 1-6

[0116] The implementation process of Comparative Examples 1 to 6 is the same as that of Example 1, and the main results are listed in Table 4.

[0117] Table 4 Formulation Table Unit: mol%

[0118] Components Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 AM 88 88.5 79 84 90 89 AA / 0.5 1 / 0 / IA / / / / / 2 SMAS / / / 2 / / DMAEMA / 8 2 4 / 1 DADMAC / 3 5 0.5 8 / DMPC 5 / / / / 6 AAM / / 6 0.5 0.5 2 NAAM 1 / 5 / / / NBAM / / 2 9 1.5 / DEAA 6 / / / / / LogP -0.9120 -0.7455 -0.7206 -0.5767 -0.9247 -0.9218 Mw / kDa 245 266 189 202 255 266 Distribution coefficient 4.4 5.1 4.8 4.2 4.4 4.6 charge density meq 0.614 1.301 0.743 0.061 1.011 0.368

[0119] Examples 10-18

[0120] Weigh out the stoichiometric amount of polymer and glyoxal and carry out aldehyde conversion at pH 9.5-9.8. For process information such as reaction time and temperature, refer to Table 5.

[0121] Table 5 Reaction Parameters

[0122] Acrylamide polymer types Acrylamide polymer dosage / g Glyoxal dosage / g Reaction temperature / °C reaction time / s The ratio of glyoxal reaction Example 10 Example 1 100 20 29.2 1588 54% Example 11 Example 2 100 20 28.0 1569 56% Example 12 Example 3 100 20 28.7 1643 61% Example 13 Example 4 100 20 28.9 1594 58% Example 14 Example 5 100 20 31.1 1551 61% Example 15 Example 6 100 20 30.3 1611 55% Example 16 Example 7 100 20 30.1 1540 57% Example 17 Example 8 100 20 29.9 1621 61% Example 18 Example 9 100 20 30.5 1543 63%

[0123] Comparative Examples 7-12

[0124] Weigh out the stoichiometric amount of polymer and glyoxal and carry out aldehyde reaction at pH 9.5-9.8. For process information such as reaction time and temperature, refer to Table 6.

[0125] Table 6 Reaction Parameters

[0126] Acrylamide polymer types Acrylamide polymer dosage / g Glyoxal dosage / g Reaction temperature / °C reaction time / s The ratio of glyoxal reaction Comparative Example 7 Comparative Example 1 100 20 28.2 1623 58% Comparative Example 8 Comparative Example 2 100 20 28.4 1567 60% Comparative Example 9 Comparative Example 3 100 20 28.7 1666 62% Comparative Example 10 Comparative Example 4 100 20 29 1567 62% Comparative Example 11 Comparative Example 5 100 20 29.2 1543 64% Comparative Example 12 Comparative Example 6 100 20 30.1 1577 66%

[0127] The particle size tests described in the table above were performed using a laser particle size analyzer.

[0128] To evaluate the effect of the composition obtained in the examples, the obtained composition was added to the paper formulation as a reinforcing agent.

[0129] The paper formulation can have various compositions. Here, it is distinguished by the ratio of 70% broadleaf fiber and 30% softleaf fiber. The retention rate, filtration time, tensile index and bursting index of the finished paper are tested respectively.

[0130] The specific operation is as follows: Select softwood and hardwood pulps at a 70:30 pulp ratio, mix them, and add water at a certain concentration to prepare a 10% fiber pulp. Use a Guangdong Internesson Instruments Co., Ltd. MJ01-RFI type refiner for 5000 revolutions. After refinement, further dilute the pulp to a 1% concentration and use a Changchun Mingyue Small Testing Machine Co., Ltd. CBJ-A type fiber standard dissociator for 15000 revolutions. Then add 0.12% of the absolute solids content as reinforcement and refine for another 5000 revolutions. Use a PTA Group RK-2A type sheet-making machine to fry the sheets, accurately weighing each sheet at 80g ± 1g, to test the strength. Simultaneously, place the 1% concentration frying pulp in a Mütek... TM

[0131] Retention tests were conducted using the DFR-05 dynamic retention filtration instrument. Using unreinforced pulp as the blank sample, the performance increases of the reinforced sample compared to the blank sample are listed in Table 7 below.

[0132] The finished paper sheets were cut to a certain size. The tensile strength was tested using a WZL-C type horizontal computer tensile tester from China Building Materials Intelligent Automation Research Institute Co., Ltd.; the bursting strength was tested using a PN-BSM160F type paper bursting strength tester from Hangzhou Pinxiang Technology Co., Ltd.

[0133] The list shows the performance index improvement rate, which is defined as the performance increase rate divided by the paper weight; where the performance increase rate is the performance increase divided by the performance baseline of the blank sample. The specific formula is as follows:

[0134] Performance index growth rate % = (T1 - T0) / (T0 * W)

[0135] T1: Performance after adding reinforcing agents;

[0136] T0: Performance of the blank sample;

[0137] W: Paper weight (grammage);

[0138] Table 7 Properties of different compositions

[0139] reserve Filtration time / s Tensile index increase rate Bursting rate Does it satisfy a bimodal distribution? Particle distribution map Example 10 25.0% 41.2 18.2% 41.2% yes Figure 1 Example 11 25.6% 42.1 18.3% 46.2% yes Figure 2 Example 12 25.7% 42.4 17.9% 43.0% yes Figure 3 Example 13 24.9% 42.7 18.8% 47.0% yes Figure 4 Example 14 26.8% 42.3 18.0% 46.5% yes Figure 5 Example 15 26.2% 41.9 18.9% 44.5% yes Figure 6 Example 16 25.5% 40.8 18.2% 44.2% yes Figure 7 Example 17 26.1% 41.1 17.6% 46.2% yes Figure 8 Example 18 26.0% 42.5 19.9% 45.6% yes Figure 9 Comparative Example 7 18.2% 44.2 14.2% 40.1% no Figure 10 Comparative Example 8 19.1% 45.1 14.6% 41.2% no Figure 11 Comparative Example 9 18.5% 45.1 14.8% 42.3% no Figure 12 Comparative Example 10 19.1% 45.2 14.2% 41.9% no Figure 13 Comparative Example 11 18.8% 44.9 14.1% 39.9% no Figure 14 Comparative Example 12 17.1% 46.1 13.9% 40.1% no Figure 15

[0140] Note: The particle size distribution testing method of this invention is as follows: using the TOPSIZER laser particle size analyzer from Omec Corporation. A wet test is used, the blank is adjusted to bring the device into the test state, the refractive index of the material is 1.337, and the concentration of the test item is adjusted to 100 ppm using deionized water. The device automatically tests and saves the data.

[0141] in, Figure 1 The ratio of the number of particles in the first peak to the number of particles in the second peak is approximately 3:1; Figure 2The ratio of the number of particles in the first peak to the number of particles in the second peak is approximately 4:5; Figure 3 The ratio of the number of particles in the first peak to the number of particles in the second peak is approximately 5.8:4.2; Figure 4 The ratio of the number of particles in the first peak to the number of particles in the second peak is approximately 1:1; Figure 5 The ratio of the number of particles in the first peak to the number of particles in the second peak is approximately 3:1; Figure 8 The ratio of the number of particles in the first peak to the number of particles in the second peak is approximately 10:1.

[0142] Through the appendix of the present invention Figures 1 to 9 Therefore, the bimodal structure described in this invention is not strictly limited to having only two peaks; in actual production, the presence of a third peak is also feasible. Preferably, the two peaks satisfy their status as the dominant peaks (i.e., accounting for the majority of all particles), and the presence of a third peak has no decisive impact on product performance.

[0143] The comparison of the above cases leads to the following conclusions: whether the product exhibits a bimodal distribution is related to multiple factors, such as potential factors like charge density, molecular weight, the type of monomer used, and the polymer molecular weight distribution coefficient. The presence or absence of a bimodal distribution plays a decisive role in the performance of this invention. In Comparative Examples 7 to 12, the distribution is close to normal, but the papermaking performance shown in these comparative examples is generally inferior to that of several embodiments. The test results from the above cases demonstrate that, in this invention, the core influencing factor for the combined use of cationic acrylamide polymer and aldehyde agent is the morphology of particle distribution.

[0144] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, nor does it mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A wet-end chemical additive characterized in that, The additive is a composition of an acrylamide polymer modified with an aldehyde oxidizing agent; the aldehyde oxidizing agent has at least two reactive aldehyde groups; The composition is prepared by reacting an unmodified acrylamide polymer with an aldehyde oxidizing agent to obtain the composition. The additive has the following characteristics: (1) It has an aldehyde functional group that can react with fibers; (2) The weight-average molecular weight of the unmodified acrylamide polymer is 30,000 to 1,000,000, and the distribution coefficient is 2 to 6; (3) The net charge of the composition is positive; (4) The particle size distribution of the particles in the composition has at least two peaks, namely a first peak and a second peak; the total number of particles contained in the first peak and the second peak accounts for more than 80% of the total number of particles in the composition; the peak particle size of the first peak is 0.05~0.2μm; the peak particle size of the second peak is 0.5~3μm; The ester-to-hydrophilic value LogP of the unmodified acrylamide polymer is -0.6 to -0.9; the charge density of the unmodified acrylamide polymer is 0.25 to 1.2 eq / L.

2. The wet-end chemical additive according to claim 1, characterized in that, The particle size distribution of the particles in the composition is bimodal.

3. The wet-end chemical additive according to claim 1, characterized in that, The first and second peaks contain more than 90% of the total number of particles in the composition.

4. The wet-end chemical additive according to claim 1, characterized in that, The ratio of the total number of particles in the first peak to the total number of particles in the second peak is 1:5 to 10:

1.

5. The wet-end chemical additive according to claim 1, characterized in that, The molar ratio of amide groups to aldehydes in the unmodified acrylamide polymer is 3:1 to 12:

1. The aldehyde oxidizing agent is glyoxal or glutaraldehyde; The unmodified acrylamide polymer has a weight-average molecular weight of 100,000 to 300,000 and a distribution coefficient of 3 to 5.

5. 30% to 80% of the aldehydes were reacted with the unmodified acrylamide polymers.

6. The wet-end chemical additive according to claim 1, characterized in that, The unmodified acrylamide polymer comprises the following molar amounts of structural units: Nonionic acrylamide: 75–99 parts; Ionic monomers: 1–25 parts; The nonionic acrylamide is acrylamide, methacrylamide, N-methacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, N,N-dimethylacrylamide, or N,N-diethylacrylamide; wherein the content of acrylamide and methacrylamide is not less than 80 mol% of the total amount of nonionic acrylamide. The ionic monomers include cationic monomers and optionally anionic monomers; The cationic monomer is a product obtained by quaternization of a compound containing ammonium salts or other compounds containing tertiary amines; the cationic monomer is a quaternary ammonium salt formed from dimethyl diallyl ammonium chloride, methacryloyloxyethyltrimethyl ammonium chloride, acryloyloxyethyltrimethyl ammonium chloride, tetraallyl ammonium chloride, (meth)acrylate dialkylaminoalkyl ester, and dialkylaminoalkylalkyl(meth)acrylamide and their benzyl chloride or chloroalkanes. The anionic monomer refers to an unsaturated monomer containing carboxylate, sulfonate, and phosphate groups. The anionic monomer is (meth)acrylic acid, allyl carboxylic acid, fumaric acid, maleic acid, itaconic acid, mucoaconic acid, and their ammonium and metal salts.

7. A method for preparing a wet-end chemical additive as described in any one of claims 1 to 6, characterized in that, An unmodified acrylamide polymer is reacted with an aldehyde oxidizing agent to obtain a composition.

8. Application of papermaking additives prepared using wet-end chemical additives as described in any one of claims 1 to 6; The papermaking additives are used to increase paper strength and improve the system retention and filtration performance in the papermaking process.

9. The application according to claim 8, characterized in that, In the papermaking process, its usage is 0.1 to 5 wt%.

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