Polyelectrolyte composite for constructing papermaking filler reinforcement and papermaking method

Abstract

The invention relates to the technical field of papermaking, in particular to a polyelectrolyte compound for constructing a papermaking filler reinforcement and a papermaking method. The polyelectrolyte compound homogeneous liquid comprises a polyelectrolyte compound and a solvent, and the polyelectrolyte compound is uniformly and stably distributed in the solvent; the polyelectrolyte compound is formed by compounding anionic macromolecules and cationic macromolecules through the charge effect, the particle size of the polyelectrolyte compound is 50 nm to 50 microns, and the electrophoretic mobility is-2.0 * 10 <-8 > m < 2 > (Vs) <-1 > to-0.6 * 10 <-8 > m < 2 > (Vs) <-1 > or 0.5 * 10 <-8 > m < 2 > (Vs) <-1 > to 3.0 * 10 <-8 > m < 2 > (Vs) <-1 >. The polyelectrolyte compound can stably exist in a solution, flocculation groups obtained by flocculation of papermaking filler can resist relatively strong shearing force, the polyelectrolyte compound is particularly suitable for treating precipitated calcium carbonate (PCC) filler which is difficult to treat by a common method, and meanwhile, the binding force between the filler and fibers can be increased; therefore, the phenomena of hair falling and powder falling are relieved under the condition that high ash content is added, and the paper strength is ensured under the condition that a large amount of filler is added.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, and more particularly to a polyelectrolyte composite for constructing papermaking filler reinforcements and a papermaking method. Background Technology

[0002] Paper is a special sheet-like material composed of fibers, fine fibers, fillers, and other additives, possessing a porous network structure. In the papermaking industry, replacing some plant fiber raw materials with fillers (calcium carbonate, talc, etc.) is a widely used method to reduce production costs. The addition of fillers can increase paper whiteness and printability, but it also affects paper strength, leading to linting and dusting during printing. In papermaking with added fillers, the retention of fillers (usually calcium carbonate) in the paper's wire mesh has always been a significant challenge, as the particle size is typically 2-3 micrometers. Patent CN103038419B utilizes flocculants to pre-flocculate the filler, increasing the filler particle size from 1-2 micrometers to 40-100 micrometers, thereby improving filler retention and mitigating its impact on paper strength to some extent. While this method improves filler retention to a certain degree, linting and dusting remain significant under high filler addition conditions.

[0003] In existing technologies, the common method for filler pretreatment is to use polymeric flocculants for pre-flocculation treatment. During the interaction between the polymeric flocculant and the filler molecules, the molecular chains need to be fully extended, connecting the filler particles through a bridging mechanism to form larger flocs. For example, CN109629333A discloses a filler pretreatment method for papermaking processes, in which the filler is diluted with water and anionic sodium polyacrylate to form a suspension dispersion, a chelated titanate coupling agent is added and sheared, then a cationic composite polymeric flocculant is added and sheared, and finally a polymeric mixed flocculant is added and sheared. This process results in relatively loose flocs, which are easily dispersed into smaller flocs during shearing at a pressure screen. As the paper industry's demand for cost reduction intensifies, more paper mills are demanding higher filler ratios. However, an undeniable reality is that even after pre-flocculation treatment, the filler flocs are redispersed into smaller particles after being subjected to the strong shearing force of the paper machine system. With higher ash content, the surface strength of the paper remains low, and dusting and linting are still severe. This is a technical problem that the paper industry urgently needs to solve. Summary of the Invention

[0004] The purpose of this invention is to provide a polyelectrolyte composite for constructing paper filling reinforcements and a papermaking method. The polyelectrolyte composite of this invention is stable in solution and, compared to commonly used linear polyacrylamide flocculants (a three-dimensional structure whose surface charge can interact with filler particles in three-dimensional space), produces more stable flocs for flocculation of paper fillings. These flocs can resist strong shear forces and increase the bonding force between the filler and fibers. This alleviates lint and dusting even with high ash content and ensures paper strength even with large amounts of filler.

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

[0006] A homogeneous liquid containing a polyelectrolyte complex, the homogeneous liquid containing the polyelectrolyte complex and a solvent, wherein the polyelectrolyte complex is uniformly distributed in the solvent;

[0007] The polyelectrolyte complex is composed of anionic and cationic polymers, with a particle size of 50 nm to 50 μm and an electrophoretic mobility of -2.0 × 10⁻⁶. -8 m 2 (Vs) -1 to -0.6×10 -8 m 2 (Vs) -1 Or 0.5×10 -8 m 2 (Vs) -1 Up to 3.0×10 -8 m 2 (Vs) -1 .

[0008] Furthermore, the charge density of the anionic polymer is 0.14-6 meq / g, and the charge density of the cationic polymer is 0.05-2.5 meq / g.

[0009] Furthermore, the molecular weight of the anionic polymer ranges from 10 million to 7 million g / mol, and the molecular weight of the cationic polymer ranges from 10 million to 6 million g / mol.

[0010] Furthermore, the molecular weight of one of the two components, the anionic polymer and the cationic polymer, is greater than the molecular weight of the other component, and the content of the high molecular weight component in the homogeneous liquid of the polyelectrolyte complex is higher than the content of the low molecular weight component.

[0011] Furthermore, the intrinsic viscosity of the anionic polymer ranges from 0.1 to 16 dl / g, and the intrinsic viscosity of the cationic polymer ranges from 0.1 to 14 dl / g.

[0012] Furthermore, the cationic polymer is synthesized from a neutral monomer and a cationic monomer, wherein the neutral monomer is acrylamide, methacrylamide, or hydroxymethylacrylamide, and the cationic monomer is one or more of acryloyloxyethyltrimethylammonium chloride, diallyl dimethylammonium chloride, methacryloxyethyltrimethylammonium chloride, methacryloxyethyldimethylbenzylammonium chloride (DMBZ), and methacrylamidopropyltrimethylammonium chloride (MAPTAC).

[0013] Alternatively, the cationic polymer may be a natural cationic polymer, wherein the natural cationic polymer is one or more of cationic starch, cationic guar gum, and cationic chitosan.

[0014] Furthermore, the anionic polymer is synthesized from neutral monomers and anionic monomers.

[0015] The anionic monomer is one or more of acrylic acid, sodium acrylate, itaconic acid, methacrylic acid, sodium methacrylate, 2-acrylamide-2-methylpropanesulfonic acid, and sodium 2-acrylamide-2-methylpropanesulfonate.

[0016] Alternatively, the anionic polymer may be a natural anionic polymer, which may be one or more of anionic starch, anionic guar gum, and anionic chitosan.

[0017] Furthermore, the cationic starch has a degree of cationic substitution of 0.01 to 0.2 and a molecular weight of 1000-1000,000 g / mol;

[0018] The anionic starch has an anionic substitution degree of 0.01 to 0.3 and a molecular weight range of 20 million to 1 million g / mol.

[0019] A method for preparing a homogeneous polyelectrolyte composite liquid, the method comprising the following steps:

[0020] (1) Synthesize cationic polymers with neutral monomers and cationic monomers to obtain cationic polymer solutions; or prepare natural cationic polymer solutions;

[0021] (2) Synthesize anionic polymers with neutral monomers and anionic monomers to obtain anionic polymer solutions; or prepare natural anionic polymer solutions;

[0022] (3) Under stirring conditions, the cationic polymer solution and the anionic polymer solution are mixed and stirred for 3-5 minutes. Then the pH is adjusted to 4-9 to obtain a homogeneous polyelectrolyte complex solution.

[0023] A papermaking method includes the following steps:

[0024] The filler is mixed with the homogeneous liquid of the above-mentioned polyelectrolyte composite to obtain filler flocculents, wherein the mass ratio of polyelectrolyte composite to filler is 0.1~0.5%;

[0025] The filler flocculants are added to the pulp and mixed thoroughly. Then, the forming process, pressing process, and drying process are carried out in sequence to obtain paper.

[0026] The technical solution provided by this invention may include the following beneficial effects:

[0027] This invention enables the online generation of a stable homogeneous polyelectrolyte complex liquid for flocculation treatment of fillers by limiting the charge density, molecular weight, intrinsic viscosity, and differences between the anionic and cationic polymers. By adjusting the charge density and molecular weight of the two polymers, it can be adapted to flocculation treatment of various fillers.

[0028] The polyelectrolyte composite of this invention possesses a stable three-dimensional nanostructure, enabling it to exist stably in solution. Simultaneously, the polyelectrolyte composite exhibits a high electrophoretic mobility, ensuring the stability of the homogeneous liquid. When used for flocculation of paper fillers, this polyelectrolyte composite can resist strong shear forces while increasing the bonding force between the filler and fibers. This alleviates lint and dusting even with high ash content and ensures paper strength even with large amounts of filler added. Attached Figure Description

[0029] Figure 1 Schematic diagram of the stability of calcium carbonate filler flocs under different flocculation conditions. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the present invention.

[0031] When polyelectrolytes with different charges are mixed, they form a complex through electrostatic forces, known as a polyelectrolyte complex. When the structures of these polymers with different charges are compatible, they can form a new nanostructured homogeneous liquid, producing properties different from the original polymers, such as adsorption properties and flocculation characteristics on fibers. In previous studies, this type of polymer mixture has been proven to be a high-performance fiber reinforcing chemical, mainly due to its unique three-dimensional nanostructure, which results in higher retention rates on fibers and more interaction sites, thus leading to better reinforcing effects.

[0032] In their research, the inventors surprisingly discovered that pretreating fillers with a homogeneous liquid containing synthetic or natural polymers with different charge properties through online composite formation to create new nanostructured composites can yield shear-stable filler flocs. Because the polymers with different charge properties pre-form new nanostructured composites, these composites exhibit high flocculation capacity for fillers, significantly improving filler flocculation efficiency. Furthermore, the strong charge-force interactions between polymers within the composite nanostructure result in denser and more compact flocs after filler flocculation. Even after prolonged storage or mechanical shearing, the filler flocs remain highly stable. The nanocomposite structure exhibits more and tighter binding sites with fibers, mitigating the impact of filler addition on paper strength and reducing lint and dust shedding. Therefore, this invention provides a homogeneous liquid containing a polyelectrolyte composite, comprising a polyelectrolyte composite and a solvent, wherein the polyelectrolyte composite is uniformly distributed in the solvent.

[0033] The polyelectrolyte complex is composed of anionic and cationic polymers, with a particle size of 50 nm to 50 μm and an electrophoretic mobility of -2.0 × 10⁻⁶. -8 m 2 (Vs) -1 to -0.6×10 -8 m 2 (Vs) -1 Or 0.5×10 -8 m 2 (Vs) -1 Up to 3.0×10 -8 m 2 (Vs) -1 Preferably, the polyelectrolyte complex has a particle size of 500 nm to 5 μm and an electrophoretic mobility of -2.0 × 10⁻⁶. -8 m 2 (Vs) -1 to -1.5×10 -8 m 2 (Vs) -1 Or 0.5×10 -8 m 2 (Vs) -1 Up to 1.0×10 -8 m 2 (Vs) -1 .

[0034] The polyelectrolyte composite of this invention possesses a stable three-dimensional nanostructure, enabling it to exist stably in solution. Simultaneously, the polyelectrolyte composite exhibits a high electrophoretic mobility, ensuring the stability of the homogeneous liquid. The polyelectrolyte composite used in this invention utilizes strong intermolecular forces in the polymers, allowing the flocculated filler to resist strong shear forces and enhancing the interaction between the flocculated filler and fibers in the pulp. This increases the bonding force between the filler and fibers, thereby mitigating lint and dusting even with high ash content and ensuring paper strength even with a large amount of filler added.

[0035] In some embodiments of the present invention, the charge density of the anionic polymer is 0.14-6 meq / g, and the charge density of the cationic polymer is 0.05-2.5 meq / g. By limiting the charge densities of the two components to low to medium levels, the anionic and cationic polymers can bind together through electrostatic attraction, and the structure of the polyelectrolyte complex is controllable, which is beneficial for obtaining a homogeneous liquid. Preferably, the charge density of the anionic polymer is 1.7-2.0 meq / g, and the charge density of the cationic polymer is 1.2-1.5 meq / g.

[0036] Preferably, the molecular weight of the anionic polymer ranges from 10 million to 7 million g / mol, and the molecular weight of the cationic polymer ranges from 10 million to 6 million g / mol. More preferably, the molecular weight of the anionic polymer ranges from 1 million to 6 million g / mol, and the molecular weight of the cationic polymer ranges from 1 million to 6 million g / mol. This invention achieves structural compatibility between the two polymers by limiting their charge density and molecular weight.

[0037] For example, the molecular weight and charge density of the anionic polymer can be selected from three types: high, medium, and low, respectively, which are 6×10 6 g / mol, -1.6 meq / g; 3×10 6 g / mol, -1.4 meq / g; 1×10 6 g / mol, -6.0 meq / g;

[0038] Cationic polymers can be selected from three types based on molecular weight and charge density: high, medium, and low, with molecular weights of 6 × 10⁻⁶ and 6 × 10⁻⁶ respectively. 6 g / mol, 1.3 meq / g; 2×10 6 g / mol, 1.5 meq / g; 1×10 6 g / mol, 1.5 meq / g.

[0039] Preferably, the molecular weight of one of the two components, the anionic polymer and the cationic polymer, is greater than the molecular weight of the other component, and the content of the high molecular weight component in the homogeneous liquid of the polyelectrolyte complex is higher than the content of the low molecular weight component.

[0040] In practical applications, based on the desired structure, particle size, and charge characteristics of the polyelectrolyte composite, parameters such as the amount, degree of ionization, and molecular weight of anionic and cationic polymers are adjusted to obtain a suitable homogeneous liquid of the polyelectrolyte composite for use as a pretreatment agent for the corresponding filler.

[0041] Preferably, the intrinsic viscosity of the anionic polymer ranges from 0.1 to 16 dl / g, and the intrinsic viscosity of the cationic polymer ranges from 0.1 to 14 dl / g. More preferably, the intrinsic viscosity of the anionic polymer ranges from 3 to 15 dl / g, and the intrinsic viscosity of the cationic polymer ranges from 1.2 to 1.5 dl / g.

[0042] In one embodiment of the present invention, the cationic polymer is synthesized from a neutral monomer and a cationic monomer, wherein the neutral monomer is acrylamide, methacrylamide, or hydroxymethylacrylamide, and the cationic monomer is one or more selected from acryloyloxyethyltrimethylammonium chloride (DAC), diallyl dimethylammonium chloride (DMDAAC), methacryloxyethyltrimethylammonium chloride (DMC), methacryloxyethyldimethylbenzylammonium chloride (DMBZ), and methacrylamidopropyltrimethylammonium chloride (MAPTAC).

[0043] Alternatively, the cationic polymer may be a natural cationic polymer, wherein the natural cationic polymer is one or more of cationic starch, cationic guar gum, and cationic chitosan.

[0044] The preferred cationic monomers are N,N-dimethyldiallylammonium chloride, acryloyloxyethyltrimethylammonium chloride, or methacryloyloxyethyltrimethylammonium chloride. The cationic polymer, neutral monomer, and cationic monomer in this scheme are all soluble in water to form a solution.

[0045] In one embodiment of the present invention, the anionic polymer is synthesized from neutral monomers and anionic monomers.

[0046] The anionic monomer is one or more of acrylic acid, sodium acrylate, itaconic acid, methacrylic acid, sodium methacrylate, 2-acrylamide-2-methylpropanesulfonic acid, and sodium 2-acrylamide-2-methylpropanesulfonate.

[0047] Alternatively, the anionic polymer may be a natural anionic polymer, which may be one or more of anionic starch, anionic guar gum, and anionic chitosan.

[0048] Both the anionic polymer and the anionic monomer in this scheme are soluble in water to form a solution. The preferred anionic monomer is acrylic acid.

[0049] Preferably, the cationic starch has a cationic substitution degree of 0.01 to 0.2 and a molecular weight of 10 million to 1 million g / mol; the anionic starch has anionic substitution degree of 0.01 to 0.3 and a molecular weight range of 20 million to 1 million g / mol.

[0050] Accordingly, the present invention also provides a method for preparing a homogeneous polyelectrolyte complex liquid, the method being used to prepare the above-mentioned homogeneous polyelectrolyte complex liquid; the method includes the following steps:

[0051] (1) Synthesize cationic polymers with neutral monomers and cationic monomers to obtain cationic polymer solutions; or prepare natural cationic polymer solutions;

[0052] (2) Synthesize anionic polymers with neutral monomers and anionic monomers to obtain anionic polymer solutions; or prepare natural anionic polymer solutions;

[0053] (3) Under stirring conditions, the cationic polymer solution and the anionic polymer solution are mixed and stirred for 3-5 minutes. Then, the pH is adjusted to 4-9 to obtain a homogeneous polyelectrolyte complex solution. In the above polymer combination, one polymer has a larger molecular weight than the other, and its dosage is higher than that of the matching polymer.

[0054] Paper is manufactured using the aforementioned homogeneous polyelectrolyte composite solution. The papermaking method includes the following steps:

[0055] The filler is mixed with the homogeneous liquid of the aforementioned polyelectrolyte composite to obtain filler flocs, wherein the mass ratio of the polyelectrolyte composite to the filler is 0.1~0.5%. The filler flocs are added to pulp and mixed thoroughly, followed by forming, pressing, and drying processes to obtain paper. The filler flocs obtained after treatment with the homogeneous liquid of the polyelectrolyte composite are endowed with the ability to bind with fibers. Paper obtained by treating fillers in this way has better physical strength, higher ash content, and better printability.

[0056] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed according to conventional methods and conditions or according to the product instructions. Unless otherwise specified, the reagents are commercially available; and the performance of products from different sources does not have a significant impact.

[0057] Example Group 1: Preparation of Homogeneous Polyelectrolyte Complex

[0058] Synthesis of anionic polymers: 736 mL of water was added to a 2 L three-necked flask equipped with a condenser. In another beaker, acrylamide and acrylic acid were added sequentially and stirred until homogeneous. The pH was adjusted to 6.8-7.3 with 20% NaOH solution, and ammonium formate was added as a chain transfer agent. When the solution reached 90 °C, ammonium persulfate initiator was added dropwise. After 2 minutes of initiator addition, monomer solution was added dropwise over a period of 150 minutes. After the monomer addition was complete, ammonium persulfate initiator was added dropwise for another 10 minutes. After this addition was complete, sodium bisulfite was added dropwise for another 30 minutes. The mixture was then kept at 90 °C for one hour to obtain anionic polyacrylamide.

[0059] In the synthesis of anionic polyacrylamide, the charge characteristics of the anionic polyacrylamide can be adjusted by regulating the ratio of acrylic acid to acrylamide; the molecular weight of the anionic polyacrylamide can be adjusted by regulating the amounts of ammonium persulfate and sodium bisulfite. In this example group, acrylamide accounts for 50-99% of the total mass ratio of its reactants with anionic monomers, and the anionic acrylic monomer accounts for 1-45% of the total mass ratio of its reactants with acrylamide monomers. After free radical polymerization, an aqueous solution of anionic propylene acrylamide is obtained with a solid content of 5-10% and a viscosity of 1000-40000 cps.

[0060] Synthesis of cationic polymers:

[0061] Add 1066 g of soft water and 0.15 g of ethylenediaminetetraacetic acid to a 2 L three-necked flask equipped with a condenser. In another beaker, add acrylamide, acryloyloxyethyltrimethylammonium chloride (DAC), 38 g of water, and 0.15 g of sodium formate sequentially, and stir until homogeneous. Heat the aqueous solution in the reaction flask to 90 °C and purge with nitrogen for 20 minutes. Begin adding ammonium persulfate initiator dropwise. After 3 minutes of dropwise addition, begin adding the cationic monomer aqueous solution dropwise over 120 minutes. After the monomer addition is complete, continue adding ammonium persulfate initiator dropwise for 10 minutes. After the addition is complete, continue adding sodium metabisulfite solution dropwise for 30 minutes. After the addition is complete, maintain the temperature at 90 °C for one hour to obtain cationic polyacrylamide.

[0062] In the synthesis of cationic polyacrylamide, the charge characteristics of the cationic polyacrylamide can be adjusted by regulating the ratio of acrylamide to cationic monomers, such as acryloyloxyethyltrimethylammonium chloride (DAC), and the molecular weight can be adjusted by regulating the amounts of ammonium persulfate and sodium formate. In this example group, the mass ratio of acrylamide to the total mass of acryloyloxyethyltrimethylammonium chloride (DAC) is 55-99%, and the mass ratio of the cationic monomer DAC to the total reactants is 1-50%. After free radical polymerization, an aqueous solution of cationic acrylamide is obtained with a concentration of 5-10% and a viscosity of 1000-30000 cps.

[0063] Anionic and cationic polyacrylamide aqueous solutions were combined in a certain ratio, stirred at 300 rpm for 5 minutes, and the pH value was adjusted to obtain a homogeneous polyelectrolyte composite solution.

[0064] The formulation ratios and product data of each embodiment in this example group are shown in Table 1.

[0065] Table 1

[0066]

[0067] Comparative Example 1

[0068] Ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC) were mixed at a mass ratio of 1:1 to obtain a mixed packing material. The mixed packing material was diluted with tap water in a beaker to a solid content concentration of 10%, and stirred at 800 rpm for 1 minute to obtain a mixed packing material dispersion. The anionic polymers from Examples 1-3 were added to the mixed packing material dispersion and mixed, followed by the addition of cationic polymers and mixing to obtain a flocculant. The mass percentages of the anionic and cationic polymers in the oven-dry calcium carbonate were 0.1%, respectively.

[0069] The homogeneous polyelectrolyte composite liquid obtained in Example 1 was used to conduct flocculation experiments on calcium carbonate packing. The packing used was a 1:1 mixture of ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC). The specific procedure was as follows: the mixed packing was diluted with tap water in a beaker to a solid content concentration of 10%, and stirred at 800 rpm for 1 minute. The amount of polyelectrolyte composite to be added was calculated based on the amount of oven-dry calcium carbonate, with the polyelectrolyte composite accounting for 0.1%, 0.2%, and 0.3% of the oven-dry calcium carbonate by mass. The polyelectrolyte was slowly added and stirred for 3 minutes. The particle size of the flocculated particles was measured, as shown in Table 2.

[0070] Stability testing of filler flocs: The flocculant of Comparative Example 1 was used as the control flocculant. The flocculant obtained by mixing the 0.2% polyelectrolyte composite from Examples 1-3 with the mixed filler dispersion was used as the experimental flocculant. Both the control and experimental flocculants were stirred at 800 rpm, and the particle size distribution was tested at different time intervals to detect the change in flocculant particle size with stirring time. The results are as follows: Figure 1 As shown.

[0071] Paper sheet making experiment: The pulp (concentrated pulp, pulp concentration of 3-4%) used was obtained from the paper mill. The main components of the concentrated pulp were hardwood pulp (LBKP), softwood pulp (NBKP) and chemimechanical pulp (BCTMP). During the paper sheet making process, the pulp was diluted to a mass concentration of 0.7%, and flocculant and polymer dry powder retention aid were added in sequence. Then, the pulp with added chemical reagents was added to the sheet making machine, filtered, formed, pressed, and dried to obtain the paper sheet sample.

[0072] Strength testing of paper samples: The paper sample was cut into strips of 2cm*10cm. The tensile strength index and bursting index were tested using a tensile strength tester, as shown in Table 2. The experimental strength analysis data confirms that the pulp treated with the electrolyte complex can reduce the paper ash content by 5 percentage points without loss of strength. Clearly, the technical solution of this invention allows more filler to remain in the paper. In contrast, using polymer flocculation to treat fillers separately only increases the ash content by 3 percentage points without causing a loss of strength.

[0073] Table 2

[0074]

[0075] The homogeneous polyelectrolyte complex obtained in Example Group 1 was used to conduct flocculation experiments on milled calcium carbonate (GCC). The polyelectrolyte complex accounted for 0.2% of the dry calcium carbonate by mass. The flocculated particle size and paper sheet properties were measured, as shown in Table 3.

[0076]

[0077] Example Group 2

[0078] The anionic and cationic polyacrylamide obtained in Examples 1-3 were used. The mass ratio of the two polymers was adjusted, and the flocculation experiment and paper sheet test were performed according to Example 1. The resulting homogeneous polyelectrolyte complex solution was mixed with a light calcium carbonate (PCC) suspension, and the flocculated particle size and paper sheet performance were tested, as shown in Table 4. The mass ratio of the polyelectrolyte complex to the oven-dry calcium carbonate was 0.15% and 0.35%, respectively, which means that the amount of polyelectrolyte complex used per ton of oven-dry calcium carbonate was 1.5 kg and 3.5 kg.

[0079] Table 4

[0080]

[0081] Example Group 3

[0082] Anionic starch was mixed with the cationic polymer obtained in Example 1-1 in a certain proportion to form a stable polyelectrolyte complex homogeneous liquid, which was used for the pretreatment of the filler. The polyelectrolyte complex homogeneous liquid was added to the GCC filler suspension in a certain proportion, with the polyelectrolyte complex accounting for 0.1%, 0.2%, or 0.3% of the dry calcium carbonate by mass. The flocculent particle size and paper sheet properties were tested, as shown in Table 5.

[0083]

[0084] Example Group 4

[0085] Cationic starch was mixed with the anionic polymer obtained in Example 1-1 in a certain proportion to form a stable polyelectrolyte complex homogeneous liquid, which was used for the pretreatment of the filler. The polyelectrolyte complex homogeneous liquid was added to the PCC filler suspension in a certain proportion, with the polyelectrolyte complex accounting for 0.1%, 0.2%, or 0.3% of the dry calcium carbonate by mass. The flocculent particle size and paper sheet properties were tested, as shown in Table 6.

[0086]

[0087] Other components and operations of the polyelectrolyte composite for constructing a papermaking filler reinforcement according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here. When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the invention, both endpoints of each numerical range and any value between the two endpoints may be selected. The described performance can be achieved within the proportions specified in the invention. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by those skilled in the art to which this invention pertains.

[0088] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A homogeneous polyelectrolyte composite liquid for constructing paper filling reinforcements, characterized in that, The homogeneous liquid containing the polyelectrolyte complex comprises a polyelectrolyte complex and a solvent, wherein the polyelectrolyte complex is uniformly distributed in the solvent; The polyelectrolyte complex is composed of anionic and cationic polymers, with a particle size of 50 nm to 50 μm and an electrophoretic mobility of -2.0 × 10⁻⁶. -8 m 2 (Vs) -1 to -0.6×10 -8 m 2 (Vs) -1 Or 0.5×10 - 8 m 2 (Vs) -1 Up to 3.0×10 -8 m 2 (Vs) -1 .

2. The homogeneous polyelectrolyte composite liquid according to claim 1, characterized in that, The charge density of the anionic polymer is 0.14-6 meq / g, and the charge density of the cationic polymer is 0.05-2.5 meq / g.

3. The homogeneous polyelectrolyte composite liquid according to claim 2, characterized in that, The molecular weight of the anionic polymer ranges from 10 million to 7 million g / mol, and the molecular weight of the cationic polymer ranges from 10 million to 6 million g / mol.

4. The homogeneous polyelectrolyte composite liquid according to claim 3, characterized in that, The molecular weight of one of the two components, the anionic polymer and the cationic polymer, is greater than that of the other component, and the content of the high molecular weight component in the homogeneous liquid of the polyelectrolyte complex is higher than that of the low molecular weight component.

5. The homogeneous polyelectrolyte composite liquid according to claim 1, characterized in that, The intrinsic viscosity of the anionic polymer ranges from 0.1 to 16 dl / g, and the intrinsic viscosity of the cationic polymer ranges from 0.1 to 14 dl / g.

6. The homogeneous polyelectrolyte composite liquid according to any one of claims 1 to 5, characterized in that, The cationic polymer is synthesized from neutral monomers and cationic monomers, wherein the neutral monomers are acrylamide, methacrylamide, or hydroxymethylacrylamide, and the cationic monomers are one or more selected from acryloyloxyethyltrimethylammonium chloride, diallyl dimethylammonium chloride, methacryloxyethyltrimethylammonium chloride, methacryloxyethyldimethylbenzylammonium chloride (DMBZ), and methacrylamidopropyltrimethylammonium chloride (MAPTAC). Alternatively, the cationic polymer may be a natural cationic polymer, wherein the natural cationic polymer is one or more of cationic starch, cationic guar gum, and cationic chitosan.

7. The homogeneous polyelectrolyte composite liquid according to claim 6, characterized in that, The anionic polymer is synthesized from neutral monomers and anionic monomers. The anionic monomer is one or more of acrylic acid, sodium acrylate, itaconic acid, methacrylic acid, sodium methacrylate, 2-acrylamide-2-methylpropanesulfonic acid, and sodium 2-acrylamide-2-methylpropanesulfonate. Alternatively, the anionic polymer may be a natural anionic polymer, which may be one or more of anionic starch, anionic guar gum, and anionic chitosan.

8. The homogeneous polyelectrolyte composite liquid according to claim 7, characterized in that, The cationic starch has a degree of cationic substitution of 0.01 to 0.2 and a molecular weight of 1000-1000,000 g / mol; The anionic starch has an anionic substitution degree of 0.01 to 0.3 and a molecular weight range of 20 million to 1 million g / mol.

9. A method for preparing a homogeneous liquid of a polyelectrolyte complex, characterized in that, This method is used to prepare a homogeneous polyelectrolyte composite liquid for constructing paper filling reinforcements as described in any one of claims 1 to 8; the method includes the following steps: (1) Synthesize cationic polymers with neutral monomers and cationic monomers to obtain cationic polymer solutions; or prepare natural cationic polymer solutions; (2) Synthesize anionic polymers with neutral monomers and anionic monomers to obtain anionic polymer solutions; or prepare natural anionic polymer solutions; (3) Under stirring conditions, the cationic polymer solution and the anionic polymer solution are mixed and stirred for 3-5 minutes. Then the pH is adjusted to 4-9 to obtain a homogeneous polyelectrolyte complex solution.

10. A papermaking method, characterized in that, Includes the following steps: The filler is mixed with the homogeneous liquid of the polyelectrolyte composite according to any one of claims 1 to 8 to obtain a filler flocculent, wherein the mass ratio of the polyelectrolyte composite to the filler is 0.1% to 0.5%. The filler flocculants are added to the pulp and mixed thoroughly. Then, the forming process, pressing process, and drying process are carried out in sequence to obtain paper.

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