Paper bases and pulp molded articles strong aqueous structural resin compositions for building fiber matrices, kits and methods of making and using the same

Abstract

The application discloses a paper-based and pulp molded product strong water-based structure resin composition for constructing a fiber matrix, a kit and a preparation and application method thereof, and belongs to the technical field of papermaking wet end chemistry and pulp molding materials. In response to the global trend of replacing plastic with paper and fluorine-free control of food contact materials, the application aims at the pain point of failure of traditional chemicals in a high recycling pulp proportion and a closed water circulation high conductivity system, and constructs an acrylic polycarboxylic acid polymer and inorganic-organic dual charge buffer synergistic system. The scheme realizes the multiplication effect of physical strength such as breaking and ring pressure and the water resistance and oil resistance barrier performance by a unique crosslinking mechanism at a very low dosage, which is better than conventional enhancement technology on the market. The composition is a full water-based system and does not contain perfluorinated compounds, which ensures complete pulp recycling while giving the product excellent wet stiffness and film-forming density, and provides a green solution with high efficiency, low cost advantage and compliance for the papermaking and pulp molding industry.

Description

Strong and tough waterborne structural resin compositions, kits, and their preparation and application methods for constructing fiber matrices in paper-based and pulp molded products. Technical Field

[0001] This invention belongs to the field of papermaking wet-end chemistry and pulp molding materials technology, specifically relating to a strong and tough waterborne structural resin composition, kit, and preparation and application method of paper-based and pulp molding products used to construct fiber matrices. Background Technology

[0002] Paper-based materials and molded pulp products are widely used in packaging, transportation, and cushioning protection. Key mechanical properties typically include burst strength, ring crush resistance, tensile strength, and folding endurance. With factors such as the increasing proportion of recycled fibers, fluctuations in fine fraction load, increased conductivity due to white water accumulation, changes in the wet-end charge environment, and a narrowing sizing window, paper-based products are more prone to fluctuations in strength and quality stability. Industrial processes typically characterize the wet-end charge window using parameters such as particle charge demand (PCD) and Zeta potential, and characterize water absorption and sizing effects using indicators such as Cobb water absorption. Aqueous polymer systems based on polycarboxylic acids (PAA) can enhance fiber bonding and have the potential to improve strength and toughness. During production validation, the applicant found that this type of system exhibits window sensitivity under different wet-end charge environments and sizing windows: strength increases and water absorption remains stable within a portion of the charge window; however, water absorption increases and is accompanied by charge parameter deviations within another portion of the charge window, resulting in insufficient reproducibility.

[0003] In existing publications concerning the improvement of dry strength and control of wet end adhesion of paper and paperboard, there are disclosures on improving strength by combining anionic and cationic materials, such as EP0548960B1; there are also disclosures involving wet end chemical systems for improving the dry end strength of paper, such as US9567708B2, whose technical routes mostly involve acrylamide polymers or their derivative systems; in addition, there are also schemes that use anionic dry strength resins combined with cationic starch or with inorganic aluminum salts and cationic resins to improve strength.

[0004] Pulp molding or bamboo pulp molding products require high film-forming and curing efficiency under drying and hot pressing conditions. For example, EP3371239B1 relates to an aqueous system of polycarboxylic acid and polyol with phosphorus-containing compounds for bonding and curing fiber substrates.

[0005] On the other hand, paper-based and pulp molded products, in the areas of food contact packaging, disposable tableware, and inner trays, typically require the introduction of barrier or hydrophobic solutions to achieve oil and water resistance. Existing publicly available and industrially applied methods utilize fluorinated barrier agents for oil resistance; however, in recent years, many regions have imposed restrictions on perfluorinated and polyfluoroalkyl substances (PFAS) in food contact packaging, making it a constraint to simultaneously achieve oil and water resistance and mechanical reinforcement in non-fluorinated systems.

[0006] In the field of paper-based sustainable packaging barrier, there are published biodegradable polymer water-based dispersions and their coating application schemes. For example, CN120944505A involves a system based on polyhydroxyalkanoates (PHA). The above schemes mainly focus on barrier properties such as moisture barrier, oxygen barrier and oil resistance, but do not propose a combined approach for the synergistic improvement of strength and water absorption under the fluctuation of paper wet-end charge window and the adaptation to recycling and repulping.

[0007] The aforementioned publicly available solutions each have their own focus in terms of applicable systems, charge windows, coupling methods with sizing systems, and film-forming and curing paths during the drying or hot-pressing stages. However, in scenarios involving high-conductivity white water, increased proportion of recycled fibers, and fluctuations in fine particle composition, problems such as imbalance between strength enhancement and water absorption, narrowing of the sizing window, deviation of system charge parameters, and insufficient reproducibility are still likely to occur. Therefore, there is a need for a strong and tough waterborne structural resin composition that is more easily reproduced in variable systems across all categories of paper-based and pulp molding. This composition can be achieved through a compound design that enhances the resin with charge buffering or anchoring synergistic components and sizing-compatible or hydrophobic synergistic components, and can optionally include curing-promoting components. This allows for synergistic control of strength and water absorption without introducing PFAS-like substances or relying on starch-based film-forming binders. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a strong and tough waterborne structural resin composition, kit, and preparation and application method for paper-based and pulp molded products used to construct fiber matrices.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] This invention provides a strong and tough waterborne structural resin composition for constructing fiber matrices in paper-based and pulp molded articles. The composition is an aqueous system comprising water and solid components; the solid components, by weight, consist of the following substances:

[0011] 10 to 95 parts of waterborne polycarboxylic acid acrylate (PAA) reinforced resin, for example, 10 parts, 20 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 80 parts, 95 parts, etc.

[0012] The charge buffer or anchoring synergistic component is 0.01 to 60 parts, for example, 0.01 parts, 5 parts, 10 parts, 11 parts, 12 parts, 15 parts, 16 parts, 35 parts, 60 parts, etc., wherein the charge buffer or anchoring synergistic component includes an inorganic aluminum salt component and an organic cation immobilizing component, and the inorganic aluminum salt component and the organic cation immobilizing component coexist.

[0013] The sizing compatibility or hydrophobic synergistic component is 0 to 60 parts, for example, 0 parts, 0.1 parts, 4 parts, 5 parts, 12 parts, 18 parts, 20 parts, 30 parts, 60 parts, etc.;

[0014] Curing accelerator component: 0-30 parts, for example, 0 parts, 10 parts, 12 parts, 25 parts, 30 parts, etc.;

[0015] Additives: 0 to 20 parts, for example, 0 parts, 5 parts, 10 parts, 20 parts, etc.;

[0016] The ratio of the charge buffer or anchoring synergistic component to the carboxyl equivalent in the reinforcing resin, in terms of cationic equivalent, is 0.18 to 0.55, for example, 0.18, 0.24, 0.25, 0.30, 0.35, 0.38, 0.45, 0.48, 0.52, 0.55, etc.

[0017] The total organic fluorine (TOF) content of the composition was undetectable by combustion ion chromatography, with a method detection limit ≤5 mg / kg; the mass ratio of the inorganic aluminum salt component to the organic cation immobilizing component, based on the solid mass of the charge buffer or anchoring synergistic component, was 1:0.2–2.0, for example, 1:0.2, 1:0.5, 1:0.57, 1:0.6, 1:0.67, 1:0.875, 1:1.0, 1:2.0, etc.; the solid content of the composition was 10wt%–55wt%, for example, 10wt%, 20wt%, 25wt%, 28wt%, 30wt%, 32wt%, 35wt%, 38wt%, 55wt%, etc., and the pH value was 2.0–6.5, for example, 2.0, 3.8, 4.1, 4.2, etc. 4.3, 4.4, 4.5, 4.6, 4.8, 6.5, etc., with a viscosity of 100 mPa·s to 20000 mPa·s at 25℃, such as 100 mPa·s, 200 mPa·s, 350 mPa·s, 1600 mPa·s, 1750 mPa·s, 1800 mPa·s, 1900 mPa·s, 2000 mPa·s, 2100 mPa·s, 2200 mPa·s, 3800 mPa·s, 4500 mPa·s, 5200 mPa·s, 6500 mPa·s, 8500 mPa·s, 20000 mPa·s, etc.; the additives are selected from one or more of dispersants, defoamers, preservatives, pH buffers, stabilizers, anti-settling agents, rheology modifiers, freeze-thaw stabilizers, and bactericides.

[0018] The reinforcing resin is an aqueous polymer system containing carboxyl segments, which is polymerized from monomers including acrylic acid monomers or methacrylic acid monomers and polycarboxylic acid monomers; the acrylic acid monomers or methacrylic acid monomers are selected from one or more of acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isooctyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, glycidyl acrylate, and glycidyl methacrylate; the polycarboxylic acid monomers are selected from maleic acid, maleic anhydride, and phthalic acid. The reinforcing resin comprises one or more of the following: citralic acid, fumaric acid, maleic acid, maleic anhydride, citralic acid, citralic anhydride, methyl fumaric acid, aconitic acid, and their salts; the monomer system of the reinforcing resin includes one or more comonomers of styrene, α-methylstyrene, vinyl acetate, and ethylene; the mass fraction of the polycarboxylic acid monomer in the solid reinforcing resin is 1wt% to 35wt%, for example, 1wt%, 10wt%, 20wt%, 25wt%, 35wt%, etc.; the viscosity-average molecular weight of the reinforcing resin is 80,000 to 2,000,000, for example, 80,000, 300,000, 500,000, 2,000,000, etc.

[0019] The inorganic aluminum salt component is selected from one or more of aluminum sulfate, polyaluminum sulfate, polyaluminum chloride, polyaluminum ferric chloride, alum, aluminum chloride, basic aluminum chloride, and basic aluminum sulfate; the organic cationic immobilizer component is selected from one or more of polyamine immobilizers, polydiallyldimethylammonium chloride (Poly-DADMAC), polyethyleneimine, polyamide amine, polyethyleneimine, polyethyleneimine quaternary ammonium salt, and chitosan quaternary ammonium salt; the polyamine immobilizer includes dimethylamine-epoxychloropropane condensate, polyamine... The polyamine salt or a combination thereof; the weight-average molecular weight of the polyamine fixative is 5,000 to 5,000,000; the polydiallyldimethylammonium chloride is a homopolymer of diallyldimethylammonium chloride monomer; the weight-average molecular weight of the polydiallyldimethylammonium chloride is 5,000 to 5,000,000; based on the solid mass of the charge buffer or anchoring synergistic component, the inorganic aluminum salt sub-component accounts for 10 wt% to 90 wt%, and the organic cationic fixative sub-component accounts for 10 wt% to 90 wt%.

[0020] The sizing-compatible or hydrophobic synergistic component is selected from one or more of wax emulsions, hydrophobic polymer emulsions, hydrophobic surfactants, or their mixtures; the wax in the wax emulsion is selected from one or more of paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, Fischer-Tropsch wax, montmorillonite wax, carnauba wax, and beeswax; the film-forming polymer of the hydrophobic polymer emulsion is obtained by polymerization of one or more of the following monomers: styrene, α-methylstyrene, butadiene, ethylene, vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, methyl methacrylate, butyl methacrylate, and isooctyl methacrylate; the hydrophobic surfactant is a nonionic or anionic surfactant, selected from one or more of fatty alcohol polyoxyethylene ethers, alkyl glycosides, polyoxyethylene sorbitan fatty acid esters, alkyl sulfates, alkyl ether sulfates, α-olefin sulfonates, and alkylbenzene sulfonates; the sizing-compatible or hydrophobic synergistic component exists in the form of an emulsion or microemulsion, with an average particle size D. 50 The range is from 50nm to 2000nm, such as 50nm, 150nm, 450nm, 2000nm, etc.

[0021] The curing accelerator is selected from one or more of hypophosphite, phosphite, phosphate, binary or polyol, and metal ion complexing accelerator; the curing accelerator includes a polyol sub-component and a hypophosphite sub-component, and the mass ratio of the polyol sub-component to the hypophosphite sub-component is 1:0.05 to 5 based on the solid mass of the curing accelerator, for example, 1:0.05, 1:0.39, 1:0.5, 1:0.67, 1:5, etc.; the polyol sub-component is a polyol containing three or more hydroxyl groups, selected from one or more of glycerol, erythritol, xylitol, sorbitol, mannitol, pentaerythritol, trimethylolpropane, and sucrose; the hypophosphite sub-component is selected from one or more of sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, and ammonium hypophosphite, so that under drying or hot pressing conditions, the carboxyl groups in the reinforcing resin and the hydroxyl groups in the polyol sub-component undergo an esterification reaction to form a cross-linked structure.

[0022] This invention provides a reinforcing kit for constructing fiber matrices in paper-based and pulp molded products, comprising: a reinforcing resin packaging unit containing an acrylic polycarboxylic acid waterborne polymer reinforcing resin; and a charge buffer or anchoring synergistic component packaging unit containing a charge buffer or anchoring synergistic component. The reinforcing kit is a binary kit or a multi-component kit. When the reinforcing kit is a multi-component kit, the multi-component kit includes: a sizing-compatible or hydrophobic synergistic component packaging unit containing a sizing-compatible or hydrophobic synergistic component; or a curing-promoting component packaging unit containing a curing-promoting component; or both a sizing-compatible or hydrophobic synergistic component packaging unit and a curing-promoting component packaging unit. The reinforcing resin packaging unit and the charge buffer or anchoring synergistic component packaging unit are packaged separately or in separate areas. When either the sizing-compatible or hydrophobic synergistic component packaging unit or the curing-promoting component packaging unit is present, they are packaged separately or in separate areas from the reinforcing resin packaging unit, so that they can be applied or added in conjunction with the wet-end charge window or sizing window on-site.

[0023] The present invention provides a method for preparing the above composition, comprising the following steps:

[0024] Step 1. When the sizing compatibility or hydrophobic synergistic component is present, add the sizing compatibility or hydrophobic synergistic component to water, disperse it for 10 minutes using a high-speed disperser and stir it evenly to obtain a hydrophobic synergistic phase dispersion;

[0025] Step 2. Add the charge buffer or anchoring synergistic component to water, stir to dissolve or disperse for 20 min and record the pH value to obtain the charge buffer or anchoring synergistic phase;

[0026] Step 3. When both Step 1 and Step 2 exist, add the charge buffer or anchoring synergistic phase obtained in Step 2 to the hydrophobic synergistic phase dispersion obtained in Step 1 and stir for 10 min to obtain a mixed synergistic phase; add the reinforcing resin to the mixed synergistic phase and stir for 30 min to obtain a compatible composite dispersion system; when only Step 1 or Step 2 exists, add the reinforcing resin to the corresponding dispersion or synergistic phase and stir for 30 min to obtain a compatible composite dispersion system.

[0027] Step 4. Add curing accelerator and / or additives to the compatible composite dispersion system obtained in Step 3, add water to adjust the solid content and pH value, and filter to obtain the finished composition;

[0028] The reinforcing resin, charge buffer or anchoring synergistic component, sizing compatible or hydrophobic synergistic component, curing accelerator and additives are all pre-prepared aqueous dispersions or aqueous solutions, and no monomer polymerization reaction is carried out during the preparation process; the filtration accuracy is 80μm to 300μm, for example 80μm, 100μm, 300μm, etc.

[0029] This invention provides a method for reinforcing paper bases and pulp molded articles using the aforementioned composition, comprising one or more of the following methods:

[0030] 1) Add the pulp suspension internally;

[0031] 2) Apply to wet or semi-dry paper sheets by spraying or dipping;

[0032] 3) Apply to the paper surface by sizing press, film transfer or coating;

[0033] It is then cured under dry conditions to form a reinforced structure.

[0034] The amount added by the internal additive method is 0.5 kg / t to 30 kg / t based on oven-dry slurry, for example, 0.5 kg / t, 15 kg / t, 30 kg / t, etc.; or the amount of adhesive applied by the spraying, dipping, or coating method is 0.2 g / m² to 30 g / m², for example, 0.2 g / m², 2 g / m², 30 g / m², etc., based on solids.

[0035] When applied internally at the wet end of papermaking, the acrylic polycarboxylic acid waterborne polymer reinforcing resin is added either in the form of the composition or as a reinforcing resin packaging unit in a kit, and is applied at least twice before or after the main retention aid in the retention aid system; wherein the first application point is located before the main retention aid is added, and the second application point is located after the main retention aid is added and close to the web forming zone; the sum of the amounts added in the first and second applications accounts for 80wt% to 100wt% of the total amount of reinforcing resin added, for example, 80wt% or 100wt%; the residence time from the first application point to the main retention aid is 10s to 600s, for example, 10s or 600s, and the residence time from the second application point to web forming is 0.5s to 60s, for example, 0.5s or 60s.

[0036] During the operation of the paper machine, the particle charge demand (PCD), conductivity, and pH value of the pulp system are monitored online as process control charge parameters. Combined with the periodic sampling results of the 60-second Cobb water absorption of the finished paper, when the charge parameters deviate from the preset control window or the 60-second Cobb water absorption of the finished paper deviates from the target control range, the dosage or dosage ratio of the composition or kit is adjusted. This includes: adjusting the cationic equivalent of the charge buffer or anchoring synergistic component or its ratio to the carboxyl equivalent in the reinforcing resin, adjusting the addition amount of the sizing compatible or hydrophobic synergistic component, or adjusting the addition amount of the reinforcing resin, so that the charge parameters of the pulp system return to the preset control window and the hydrophobicity of the finished paper returns to the target control range.

[0037] When the recycled fiber content in the pulp system is ≥30wt% or the electrical conductivity is ≥2.0mS / cm:

[0038] 1) When applying in a packaged form, first add the charge buffer or anchoring synergistic component packaging unit in the package to pretreat the pulp, and then add the reinforcing resin packaging unit in the package.

[0039] 2) When applied in the form of a composition, the composition is added to the pulp system and the charge and sizing are controlled synergistically by adjusting the proportion of addition points in stages and the total amount added;

[0040] Furthermore, a retention aid system is employed, with cationic polyacrylamide (CPAM) as the main retention aid, added at a rate of 50ppm to 500ppm, such as 50ppm, 200ppm, 500ppm, etc.; the particulate retention aid is bentonite or silica sol, added at a rate of 200ppm to 2000ppm, such as 200ppm, 800ppm, 2000ppm, etc.; the system's charge parameter window is: PCD in the range of 0±100μeq / L, conductivity in the range of 2.0mS / cm to 6.0mS / cm, such as 2.0mS / cm, 3.5mS / cm, 6.0mS / cm, etc., and pH value in the range of 6.0 to 8.5, such as 6.0, 6.5, 8.5, etc.

[0041] This invention provides a method for reinforcing pulp molded articles prepared using the aforementioned composition, comprising:

[0042] Step 1. Add pulp fibers and water to a mixing tank and stir and disperse for 10 minutes. Adjust the pulp concentration to 0.1wt% to 3wt%, such as 0.1wt%, 0.3wt%, 3wt%, etc., and adjust the pH value of the pulp to 6.0 to 7.5, such as 6.0, 7.0, 7.5, etc., to obtain molding pulp.

[0043] Step 2. When using internal reinforcement, add the composition to the molding slurry obtained in Step 1 as an internal additive, and continue stirring for 5 minutes to obtain the reinforced molding slurry;

[0044] Step 3. Dehydrate the molding slurry obtained in Step 1 or the reinforcing molding slurry obtained in Step 2 in a molding die, and control the moisture content of the resulting wet blank to 10wt%~80wt% to obtain a wet blank;

[0045] Step 4. When surface reinforcement is used, the composition is diluted with water to a working solution of 0.5wt% to 25wt%, such as 0.5wt%, 5wt%, 8wt%, 25wt%, etc., and sprayed or impregnated on the wet blank obtained in step 3 to obtain a treated wet blank;

[0046] Step 5. Place the wet blank obtained in Step 3 or the processed wet blank obtained in Step 4 into the hot press of the mold for hot pressing and curing, controlling the time to 0.2 min to 30 min, for example 0.2 min, 1 min, 30 min, etc., demold, cool and take out to obtain the molded product;

[0047] The hot-press curing temperature is 90℃~220℃, such as 90℃, 180℃, 220℃, etc., and the hot-pressing pressure is 0.2mPa~10mPa, such as 0.2mPa, 5mPa, 10mPa, etc.

[0048] The present invention provides a paper-based and pulp molded article, wherein the aforementioned composition is applied during the preparation process thereof.

[0049] Compared with the prior art, the use of this invention can achieve the following significant beneficial effects:

[0050] Highly efficient fixation and environmental adaptability: This invention achieves highly efficient fixation and retention in high conductivity and complex charge environments by compounding a waterborne polymer-reinforced resin of acrylic polycarboxylic acid with charge buffers or synergistic fixation components composed of inorganic aluminum salts and organic cationic fixation components in a specific ratio. Through the synergistic effect of inorganic and organic components, it ensures rapid adsorption and provides sufficient charge buffering capacity, effectively adapting to fluctuations in the proportion of regenerated fibers and changes in system conductivity, thus solving the problem of unstable performance of traditional reinforcing agents in closed water circulation systems.

[0051] Synergistic enhancement of strength and barrier properties: The composition of this invention may include sizing-compatible or hydrophobic synergistic components (such as wax emulsions), which form an interpenetrating or interlocking structure with the reinforcing resin network, thereby improving the physical strength while giving the product excellent water resistance and sizing properties; In particular, when combined with curing-promoting components (such as polyols and hypophosphites), the esterification and crosslinking of carboxyl and hydroxyl groups are promoted under drying or hot-pressing conditions to construct a dense crosslinked reinforcing network, which significantly improves the strength retention rate (wet stiffness) of the product in humid environments and the film density at high temperatures, thus achieving a synergistic enhancement of strength and barrier properties.

[0052] Environmental safety and recyclability: The composition of this invention adopts an all-aqueous system, is free of perfluorinated or polyfluoroalkyl substances (PFAS), and has a total organic fluorine (TOF) content as low as undetectable levels, which meets the environmental protection and safety requirements for food contact materials; at the same time, the cross-linked network can be effectively dissociated through hydraulic shear and warm water immersion during the re-sizing process, ensuring the recyclability of the paper-based material and achieving a balance between high performance and environmental sustainability.

[0053] Flexible process and controllable quality: The kit design and application method of this invention, especially the dynamic feedback control strategy combining online charge (PCD, conductivity) and sizing (Cobb) parameters, enables producers to flexibly adjust the component addition ratio according to changes in the wet end environment, effectively broadening the process operation window and improving the replicability and quality stability of industrial production. Attached Figure Description

[0054] Figure 1 is a schematic diagram of the microstructure of paper-based fibers after treatment with the resin composition of the present invention.

[0055] In the figure, 1-pulp fiber; 2-acrylic acid polycarboxylic acid waterborne polymer reinforcing resin; 3-sizing compatible or hydrophobic synergistic component; 4-crosslinking structure; 5-charge buffer or anchoring synergistic component. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention. Unless otherwise stated, the raw materials used in this embodiment are commercially available industrial products or can be prepared by conventional methods. Unless otherwise specified, performance testing methods are performed according to the standards described in the invention summary section.

[0057] Figure 1 is a schematic diagram illustrating the microscopic mechanism by which the tough aqueous structural resin composition of the present invention constructs a reinforcing fiber matrix and barrier structure in a paper-based material. As shown in the figure, robust rod-like structures with rough surface textures constitute the basic pulp fiber network skeleton 1. The acrylic polycarboxylic acid aqueous polymer reinforcing resin 2 of the present invention is widely distributed in this skeleton in a continuous, smooth network form.

[0058] This network contains two key structural features: thanks to the effect of charge buffering or anchoring synergistic components in the composition, the charge buffering or anchoring synergistic components 5 on the fiber surface of the resin network form strong nodular anchoring points, achieving excellent interfacial anchoring; at the same time, under drying or hot pressing conditions, with the help of curing promoting components, chemical reactions occur between the polymer chains inside the polymer network, forming a dense cross-linked structure 4 (shown in the figure as fusion nodes between network filaments).

[0059] Furthermore, component 3, which is dispersed between the fiber skeleton and the resin network voids in the figure, corresponds to the sizing compatible or hydrophobic synergistic components (such as wax emulsions or hydrophobic polymer emulsion particles) in the composition. These components fill the pores, providing physical barrier and hydrophobic / oil-repellent properties for paper-based products. This multi-component synergistic composite microstructure simultaneously enhances the mechanical strength and barrier properties of the product.

[0060] Main reagents and raw materials:

[0061] Table 1. Main reagent and raw material names, product models and manufacturers:

[0062]

[0063] Note: Average particle size (D) of the hydrophobic synergistic component in polyethylene wax emulsion 50 The average particle size (D) of the hydrophobic synergistic component in the styrene-butyl acrylate copolymer emulsion is 450 nm. 50 The average particle size (D) is 150 nm; 50 The dynamic light scattering method was used for determination. The sample was diluted with deionized water and measured at 25°C. The measurement was repeated three times and the average value was taken. The preparation process of the reinforcing resin and composition is shown in the following examples section.

[0064] Main analytical and testing instruments:

[0065] Table 2 mainly analyzes the names, models, and manufacturers of the testing instruments:

[0066]

[0067] Main testing standards:

[0068] GB / T 10739-2023: Standard atmospheric conditions for the treatment and testing of paper, paperboard and pulp specimens;

[0069] GB / T 12914-2018: Determination of tensile strength of paper and paperboard by constant rate tensile test;

[0070] GB / T 454-2020: Determination of bursting strength of paper;

[0071] GB / T 2679.8-2016: Determination of ring crush strength of paper and paperboard;

[0072] GB / T 457-2008: Determination of folding endurance of paper and paperboard;

[0073] GB / T 1540-2002: Determination of water absorbency of paper and paperboard - Koebner method;

[0074] ISO 3783:2006: Determination of pick-resistant properties of paper and paperboard by the IGT method;

[0075] TAPPI / ANSI T 558 om-25: Contact Angle Method for Wetting and Absorption of Paper Material Surface;

[0076] TAPPI / ANSI T 559cm-22: Test for oil resistance of paper and paperboard using the KIT method;

[0077] ISO 7027-1:2016: Water quality – Determination of turbidity – Part 1: Quantitative methods;

[0078] ISO 5263-1:2004: Laboratory wet dissociation of pulp - Part 1: Dissociation of chemical pulp;

[0079] TAPPI T 275sp-23: Pulp screening using the Somerville process;

[0080] ISO 22412:2025: Dynamic light scattering (DLS) method for particle size analysis;

[0081] ISO 1628-1:2024: Determination of viscosity of dilute solutions of plastic polymers – Part 1: General rules;

[0082] EN 14582:2016: Waste characteristics, halogen and sulfur content, oxy-fuel combustion method and determination in a closed system;

[0083] GB / T 3332-2004: Determination of pulp drainage ratio (Schöber-Riegeler method, °SR);

[0084] ISO 5264-2:2011: Pulp laboratory beating - Part 2: PFI beating method.

[0085] Carboxyl equivalent of reinforcing resin: Take a sample of reinforcing resin and convert it to dry weight m (g) using the constant weight method at 105℃. Weigh 0.2000~0.5000g of dry weight m, add 50mL of deionized water to dissolve (if necessary, use a 40℃ water bath for assistance), and titrate with a standardized NaOH standard solution (c=0.1000mol / L) to pH=8.30±0.05 (pH meter endpoint determination), and record the volume of NaOH consumed V (mL); perform a blank titration with the same volume of deionized water and record V0 (mL). The carboxyl equivalent CE (mmol / g) is calculated as CE=(V-V0)×c / m (where V and V0 are in mL, c is in mol / L, and m is in g).

[0086] Cationic equivalent of charge buffer or anchoring synergistic component: Prepare the charge buffer or anchoring synergistic component to be tested as a 0.05–0.20 wt% (based on solids) aqueous solution / dispersion, and add 0.001 mol / L KCl to adjust the ionic strength (to ensure PCD signal stability). Use polyelectrolyte titration with potassium polyvinyl sulfate (PVS-K) standard titrant (0.001 N) as the titrant. Monitor the flow potential signal online using a particle charge demand analyzer. Titrate to the zero-crossing point of the signal and take the linear interpolation near the zero-crossing point to obtain the endpoint volume V (mL); use the solvent as a blank titration to obtain V0 (mL). The cation equivalent Q (mmol / g, based on solids) is calculated as Q = (V - V0) × N / m (where V and V0 are in mL, N is in mol / L, and m is in g).

[0087] The viscosity-average molecular weight (Mv) of the reinforced resin was measured using an Ubbelohde viscometer at 25 ± 0.1 °C. A 0.1 mol / L NaNO3 aqueous solution was used as the solvent to shield the charge effect. Four concentration points were prepared, for example, 0.2 g / dL, 0.4 g / dL, 0.6 g / dL, and 0.8 g / dL of the reinforced resin. The outflow time was measured, and the relative viscosity and specific viscosity were calculated. η was obtained using the Huggins extrapolation method. The Mark-Houwink parameters K and a were not directly derived from external constants. Instead, K and a were obtained by measuring η using a sodium polyacrylate (PAA-Na) molecular weight standard in the same solvent system and at the same temperature, and then by regression fitting. Specifically, K and a were obtained by linearly fitting log(η) to log(M), and then using η = K·M. v a The molecular weight (Mv) is calculated. The molecular weight points of the standards used for fitting and the correlation coefficient of the fitting should be recorded in the original record.

[0088] Solid content of the composition: determined by constant weight method at 105℃; Viscosity of the composition at 25℃: determined by rotational viscometer according to the principle of rotor and speed matching, and the rotor model, speed and shear time (stable reading ≥30s) were recorded.

[0089] Total organic fluorine (TOF, expressed as F): In this application, TOF was determined by combustion ion chromatography (CIC) and converted to F using the fluoride ion signal after combustion. The sample (solid composition or treated paper / molded article) was shredded and ground until it passed through a 0.5 mm sieve. 10–50 mg was taken and subjected to oxygen combustion at a temperature of 1000–1100 °C. The combustion products were absorbed with an alkaline absorbent (e.g., 0.01 mol / L NaOH, 10 mL). The absorbent was filtered through a 0.22 μm filter membrane and the F content was determined by ion chromatography. -A calibration curve was established using fluoride ion standard solutions (at least 5 points). After blank subtraction, the sample TOF (mg / kg, expressed as F) was converted. When it is necessary to exclude inorganic fluoride interference, another sample from the same batch can be extracted with deionized water to determine inorganic fluoride (IF), and the result can be verified using TOF=TF-IF. The method detection limit (LOD) is 5 mg / kg.

[0090] Liquid absorption at 100℃: The sample is pretreated under GB / T 10739-2023 standard atmospheric conditions for at least 24 hours. Cut the sample into 100mm × 100mm pieces (or record the actual area A, where A is in mm²), and weigh the initial mass m1. Place the sample horizontally on the surface of (100±2)℃ deionized water, ensuring the lower surface of the sample is in full contact with the hot water without overflowing the upper surface. After contact for (60±1) seconds, remove the sample and gently touch it with filter paper of the same specification to remove free water from the surface. Immediately weigh m2. The liquid absorption W (g / m²) is calculated as W = (m2 - m1) × 10⁻¹⁰. 6 / A calculation. Repeat each group 5 times and take the arithmetic mean.

[0091] General preparation process of reinforced resin aqueous solution:

[0092] The reaction apparatus is a four-port double-walled glass reactor equipped with mechanical stirring, reflux condenser, thermometer, nitrogen inlet, and constant-rate dropping interface. The effective volume of the reactor should be ≥ twice the volume of the target reaction liquid. Before the reaction begins, the reactor is purged with nitrogen for 30 minutes, and a slight positive pressure nitrogen protection is maintained during the reaction to reduce the influence of dissolved oxygen.

[0093] Step 1. Add deionized water to the reactor, control the stirring speed at 300–600 rpm, and heat to 80±2℃. Dissolve the polycarboxylic acid monomer in the water, and control the pH of the system at 2.3–2.7 to obtain the monomer aqueous phase. The total monomer mass is set to achieve a target solid content of 35–40 wt%.

[0094] Step 2. Dilute acrylic acid with deionized water to prepare an acrylic acid monomer solution with a mass fraction of 30-60 wt%. Add this solution dropwise over 120 minutes at a constant rate to the aqueous monomer phase obtained in Step 1. Simultaneously add an ammonium persulfate solution with a mass fraction of 5-15 wt% as an initiator. Maintain the temperature at 80±2℃ during the addition process and control volatilization loss through reflux condensation. After the addition is complete, continue the reaction at 80±2℃ for 2 hours to obtain the polymerization solution.

[0095] Step 3. Incubate the polymerization solution obtained in Step 2 at a warm temperature for 0.5 h, cool it down to below 40 °C, add sodium hydroxide solution to adjust the pH to 4.3-4.7, and obtain a neutralized polymerization solution.

[0096] Step 4. Add deionized water to the neutralized polymerization solution obtained in Step 3 to adjust the solid content to 35-40 wt%, and filter with a filtration accuracy of 80-300 μm to obtain an aqueous solution of reinforced resin.

[0097] Specific preparation parameters and product properties for each resin:

[0098] Aqueous solution of acrylic-maleic acid copolymer reinforced resin:

[0099] Preparation parameters: In step 1, the polycarboxylic acid monomer is maleic acid, and the monomer ratio of acrylic acid to maleic acid is 75:25; in step 2, the amount of ammonium persulfate initiator is 0.60 wt% of the total monomer mass.

[0100] Product parameters: solid content is 40wt%, viscosity-average molecular weight is 500,000.

[0101] Aqueous solution of acrylic-itaconic copolymer reinforced resin:

[0102] Preparation parameters: In step 1, the polycarboxylic acid monomer is itaconic acid, and the monomer ratio of acrylic acid to itaconic acid is 80:20. In step 2, the amount of ammonium persulfate initiator is 0.50 wt% of the total monomer mass.

[0103] Product parameters: solid content is 35wt%, viscosity-average molecular weight is 300,000.

[0104] Low viscosity-average molecular weight acrylic-maleic acid copolymer control reinforced resin aqueous solution

[0105] Preparation parameters: In step 1, the polycarboxylic acid monomer is maleic acid, and the monomer ratio of acrylic acid to maleic acid is 75:25; in step 2, the amount of ammonium persulfate initiator is increased to 2.0 wt% of the total monomer mass.

[0106] Product parameters: solid content is 40wt%, viscosity-average molecular weight is 60000.

[0107] General preparation process for strong and tough waterborne structural resin compositions:

[0108] Step 1. Add the sizing compatible or hydrophobic synergistic component to deionized water (20-30℃), disperse it for 10 minutes at 3000-6000 rpm using a high-speed disperser (match the container diameter with the disperser head diameter and record the result), and then stir it for 5 minutes at 300-600 rpm using a paddle mixer to obtain the hydrophobic synergistic phase dispersion. If it is necessary to improve the stability of the system, a dispersant can be added and its type and amount added can be recorded.

[0109] Step 2. Add the charge buffer or anchoring synergistic component to deionized water, stir / dissolve with a paddle at 300-600 rpm for 20 min and record the pH to obtain the charge buffer / anchoring synergistic phase.

[0110] Step 3. Add the reinforcing resin to the hydrophobic synergistic phase dispersion from Step 1 and / or the charge buffer / stationary synergistic phase from Step 2 according to the target ratio based on solids, and stir for 30 min to obtain a compatible composite dispersion system.

[0111] Step 4. Add curing accelerator and / or additive to the compatible composite dispersion system in Step 3, add water to adjust the solid content and adjust the pH to the target range (pH=3.5-5.5 is recommended; dilute NaOH solution can be used as the regulator), filter (80-300μm) to obtain the finished composition; no monomer polymerization reaction is carried out in the above composition preparation process.

[0112] Example:

[0113] All compositions in the examples were prepared according to the aforementioned "General Preparation Process for Strong and Tough Waterborne Structural Resin Compositions," with a filtration accuracy of 100 μm. The solid content of the compositions was determined using the constant weight method at 105°C, the pH was measured at 25°C, and the viscosity was determined using a rotational viscometer at a stable reading at 25°C. The specific formulations of each example are as follows:

[0114] Example 1:

[0115] Based on solids weight, 60 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 12 parts of charge buffer or anchoring synergistic components were added, including 8 parts of inorganic aluminum salt component and 4 parts of organic cationic anchoring component (mass ratio = 1:0.5). 4 parts of sizing compatibility or hydrophobic synergistic components were added, including 4 parts of polyethylene wax emulsion; no hydrophobic polymer emulsion was added. No curing accelerators or additives were added.

[0116] The resulting composition had a solid content of 25 wt%, a pH of 4.6, and a viscosity of 1600 mPa·s at 25°C.

[0117] Example 2:

[0118] Based on solids weight, 55 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 15 parts of charge buffer or anchoring synergistic components were added, including 8 parts of inorganic aluminum salt component and 7 parts of organic cationic anchoring component (mass ratio = 1:0.875). 12 parts of sizing-compatible or hydrophobic synergistic components were added, including 6 parts of polyethylene wax emulsion and 6 parts of styrene-butyl acrylate copolymer emulsion. No curing accelerators or additives were added.

[0119] The resulting composition had a solid content of 28 wt%, a pH of 4.4, and a viscosity of 2200 mPa·s at 25°C.

[0120] Example 3:

[0121] Based on solids weight, 45 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 12 parts of charge buffer or anchoring synergistic components were added, including 6 parts of inorganic aluminum salt sub-component and 6 parts of organic cationic anchoring sub-component (mass ratio = 1:1.0). 20 parts of sizing compatibility or hydrophobic synergistic components were added, including 12 parts of polyethylene wax emulsion and 8 parts of styrene-butyl acrylate copolymer emulsion. 10 parts of curing accelerator components were added, including 6 parts of polyol sub-component and 4 parts of hypophosphite sub-component (mass ratio = 1:0.67). No additives were added.

[0122] The resulting composition had a solid content of 30 wt%, a pH of 4.2, and a viscosity of 3800 mPa·s at 25°C.

[0123] Example 4:

[0124] Based on solids by weight, 80 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 16 parts of charge buffer or anchoring synergistic components were added, including 10 parts of inorganic aluminum salt component and 6 parts of organic cationic anchoring component (mass ratio = 1:0.6). 5 parts of sizing compatibility or hydrophobic synergistic components were added, all in the form of polyethylene wax emulsion. No curing accelerators or additives were added.

[0125] The resulting composition had a solid content of 35 wt%, a pH of 4.5, and a viscosity of 4500 mPa·s at 25°C.

[0126] Example 5:

[0127] Based on solids weight, 40 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 11 parts of charge buffer or anchoring synergistic components were added, including 7 parts of inorganic aluminum salt sub-component and 4 parts of organic cationic anchoring sub-component (mass ratio = 1:0.57). 18 parts of sizing compatibility or hydrophobic synergistic components were added, all in the form of polyethylene wax emulsion. 25 parts of curing accelerator components were added, including 18 parts of polyol sub-component and 7 parts of hypophosphite sub-component (mass ratio 1:0.39). No additives were added.

[0128] The resulting composition had a solid content of 32 wt%, a pH of 4.1, and a viscosity of 5200 mPa·s at 25°C.

[0129] Example 6:

[0130] Based on solids weight, 20 parts of acrylic-itaconic copolymer reinforced resin (P(AA-IA), viscosity-average molecular weight 300,000) were used. 5 parts of charge buffer or anchoring synergistic component were added, including 3 parts of inorganic aluminum salt component and 2 parts of organic cationic anchoring component (mass ratio = 1:0.67). 30 parts of sizing compatibility or hydrophobic synergistic component were added, including 15 parts of polyethylene wax emulsion and 15 parts of styrene-butyl acrylate copolymer emulsion. 12 parts of curing accelerator component were added, including 8 parts of polyol component and 4 parts of hypophosphite component (mass ratio 1:0.5). No additives were added.

[0131] The resulting composition had a solid content of 25 wt%, a pH of 4.3, and a viscosity of 2000 mPa·s at 25°C.

[0132] Example 7:

[0133] Based on solids by weight, 10 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 60 parts of charge buffer or anchoring synergistic components were added, including 40 parts of inorganic aluminum salt component and 20 parts of organic cationic anchoring component (mass ratio = 1:0.5). No sizing compatibility or hydrophobic synergistic components, curing accelerators, or additives were added.

[0134] The resulting composition had a solid content of 20 wt%, a pH of 3.8, and a viscosity of 200 mPa·s at 25°C.

[0135] Example 8:

[0136] Based on solids by weight, 95 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 0.01 parts of charge buffer or anchoring synergist were added, including 0.005 parts of inorganic aluminum salt component and 0.005 parts of organic cationic fixative component (mass ratio = 1:1.0). 0.1 parts of sizing compatibility or hydrophobic synergist were added, all in the form of polyethylene wax emulsion. No curing accelerators or additives were added.

[0137] The resulting composition had a solid content of 38 wt%, a pH of 4.8, and a viscosity of 6500 mPa·s at 25°C.

[0138] Example 9:

[0139] Based on solids by weight, 60 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 2 million) were used. 12 parts of charge buffer or anchoring synergistic components were added, including 8 parts of inorganic aluminum salt component and 4 parts of organic cationic anchoring component (mass ratio = 1:0.5). 4 parts of sizing compatibility or hydrophobic synergistic components were added, all in the form of polyethylene wax emulsion. No curing accelerators or additives were added.

[0140] The resulting composition had a solid content of 25 wt%, a pH of 4.5, and a viscosity of 8500 mPa·s at 25°C.

[0141] Example 10:

[0142] Based on solids by weight, 60 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 80,000) were used. 12 parts of charge buffer or anchoring synergistic components were added, including 8 parts of inorganic aluminum salt component and 4 parts of organic cationic anchoring component (mass ratio = 1:0.5). 4 parts of sizing compatibility or hydrophobic synergistic components were added, all in the form of polyethylene wax emulsion. No curing accelerators or additives were added.

[0143] The resulting composition had a solid content of 25 wt%, a pH of 4.6, and a viscosity of 350 mPa·s at 25°C.

[0144] Example 11:

[0145] Based on solids weight, 50 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 10 parts of charge buffer or anchoring synergist were added, including 6.6 parts of inorganic aluminum salt component and 3.4 parts of organic cationic fixative component (mass ratio = 1:0.5). 5 parts of sizing compatibility or hydrophobic synergist were added, all in the form of polyethylene wax emulsion. 10 parts of curing accelerator were added, including 9.5 parts of polyol component and 0.5 parts of hypophosphite component (mass ratio = 1:0.05). No additives were added.

[0146] The resulting composition had a solid content of 30 wt%, a pH of 4.3, and a viscosity of 1800 mPa·s at 25°C.

[0147] Example 12:

[0148] Based on solids by weight, 50 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 10 parts of charge buffer or anchoring synergist were added, including 6.6 parts of inorganic aluminum salt component and 3.4 parts of organic cationic fixative component (mass ratio = 1:0.5). 5 parts of sizing compatibility or hydrophobic synergist were added, all in the form of polyethylene wax emulsion. 10 parts of curing accelerator were added, including 1.67 parts of polyol component and 8.33 parts of hypophosphite component (mass ratio = 1:5.0). No additives were added.

[0149] The resulting composition had a solid content of 30 wt%, a pH of 4.1, and a viscosity of 1750 mPa·s at 25°C.

[0150] Example 13:

[0151] Based on solids by weight, 55 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 10 parts of charge buffer or anchoring synergistic component were added, including 8.3 parts of inorganic aluminum salt component and 1.7 parts of organic cationic anchoring component (mass ratio = 1:0.2). 5 parts of sizing compatibility or hydrophobic synergistic component were added, all in the form of polyethylene wax emulsion. No curing accelerators or additives were added.

[0152] The resulting composition had a solid content of 28 wt%, a pH of 4.2, and a viscosity of 1900 mPa·s at 25°C.

[0153] Example 14:

[0154] Based on solids weight, 55 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 12 parts of charge buffer or anchoring synergistic components were added, including 4 parts of inorganic aluminum salt component and 8 parts of organic cationic anchoring component (mass ratio = 1:2.0). 5 parts of sizing compatibility or hydrophobic synergistic components were added, all in the form of polyethylene wax emulsion. No curing accelerators or additives were added.

[0155] The resulting composition had a solid content of 28 wt%, a pH of 4.8, and a viscosity of 2100 mPa·s at 25°C.

[0156] Table 3. Formulation composition of the examples (by solid mass):

[0157]

[0158] Note: Charge buffer or anchoring synergistic components: including inorganic aluminum salt sub-components and organic cationic anchoring sub-components; Sizing compatible or hydrophobic synergistic components: including wax emulsions and hydrophobic polymer emulsions; Curing accelerator components: including polyol sub-components and hypophosphite sub-components, etc.

[0159] Comparative example:

[0160] Each comparative example system was prepared according to the control process or general procedure; the solid content, pH, viscosity, and parameter determination methods of the compositions were the same as those in the examples. The following are the specific formulations and key differences of each comparative example:

[0161] Comparative Example 1 (Resin Only):

[0162] Based on solids weight, only 60 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. No charge buffers or anchoring synergists, sizing compatibility or hydrophobic synergists, curing accelerators, or additives were added.

[0163] Comparative Example 2 (Wax only):

[0164] Based on solids weight, 60 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 4 parts of sizing compatibility or hydrophobic synergistic component (polyethylene wax emulsion) were added. No charge buffering or setting synergistic components, curing accelerators, or additives were added.

[0165] Comparative Example 3 (without organic fixation):

[0166] Based on solids weight, 60 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 12 parts of charge buffer or anchoring synergist were added, but all were divided into inorganic aluminum salt components (12 parts), with 0 parts of organic cationic anchoring components. No sizing compatibility or hydrophobic synergist, curing accelerator, or additives were added.

[0167] Comparative Example 4 (Blank):

[0168] Blank control system. Under the same basic chemical system, no reinforcing resin, charge buffer or setting synergist, sizing compatible or hydrophobic synergist, or curing accelerator were added.

[0169] Comparative Example 5 (extremely low aluminum / organic ratio):

[0170] Based on solids weight, 60 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 11 parts of charge buffer or anchoring synergistic components were added, including 10 parts of inorganic aluminum salt component and 1 part of organic cationic anchoring component (mass ratio = 1:0.1). 4 parts of sizing compatibility or hydrophobic synergistic components (polyethylene wax emulsion) were added. No curing accelerators or additives were added.

[0171] Comparative Example 6 (extremely high aluminum / organic ratio):

[0172] Based on solids weight, 60 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 16 parts of charge buffer or anchoring synergistic components were added, including 4 parts of inorganic aluminum salt component and 12 parts of organic cationic anchoring component (mass ratio = 1:3.0). 4 parts of sizing compatibility or hydrophobic synergistic component (polyethylene wax emulsion) were added. No curing accelerators or additives were added.

[0173] Comparative Example 7 (Equivalent ratio too low):

[0174] Based on solids weight, 80 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 10 parts of charge buffer or anchoring synergistic component were added, including 8 parts of inorganic aluminum salt component and 2 parts of organic cationic anchoring component. The cationic / carboxyl equivalent ratio was controlled at 0.12 (slightly low). 4 parts of sizing compatibility or hydrophobic synergistic component (polyethylene wax emulsion) were added. No curing accelerators or additives were added.

[0175] Comparative Example 8 (Equivalent Ratio Too High):

[0176] Based on solids weight, 40 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 35 parts of charge buffer or anchoring synergistic components were added, including 20 parts of inorganic aluminum salt component and 15 parts of organic cationic immobilizer component. The cationic / carboxyl equivalent ratio was controlled at 0.70 (slightly high). 4 parts of sizing compatibility or hydrophobic synergistic component (polyethylene wax emulsion) were added. No curing accelerators or additives were added.

[0177] Comparative Example 9 (low molecular weight):

[0178] Based on solids weight, 60 parts of low viscosity-average molecular weight acrylic-maleic acid copolymer control reinforced resin (Mv=60000) were used. 12 parts of charge buffer or anchoring synergistic component were added, including 8 parts of inorganic aluminum salt component and 4 parts of organic cationic anchoring component (mass ratio = 1:0.5). 4 parts of sizing compatibility or hydrophobic synergistic component (polyethylene wax emulsion) were added. No curing accelerators or additives were added.

[0179] Comparative Example 10 (Molecular weight too high):

[0180] Based on solids by weight, 60 parts of acrylic-maleic acid copolymer reinforced resin (Mv = 2.5 million) were used. 12 parts of charge buffer or anchoring synergistic component were added, including 8 parts of inorganic aluminum salt component and 4 parts of organic cationic anchoring component (mass ratio = 1:0.5). 4 parts of sizing compatibility or hydrophobic synergistic component (polyethylene wax emulsion) were added. No curing accelerators or additives were added.

[0181] Comparative Example 11 (Cure Ratio Imbalance):

[0182] Based on solids weight, 50 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 10 parts of charge buffer or fixing synergist (inorganic:organic = 1:0.5) were added. 5 parts of sizing compatibility or hydrophobic synergist (polyethylene wax emulsion) were added. 10 parts of curing accelerator were added, including 1.1 parts of polyol sub-component and 8.9 parts of hypophosphite sub-component (mass ratio = 1:8.0, hypophosphite in excess). No additives were added.

[0183] Comparative Example 12 (excess hydrophobic agent):

[0184] Based on solids weight, 45 parts of acrylic-maleic acid copolymer reinforced resin (P(AA-MA), viscosity-average molecular weight 500,000) were used. 12 parts of charge buffer or fixing synergist (inorganic:organic = 1:1.0) were added. 80 parts of sizing compatibility or hydrophobic synergist (polyethylene wax emulsion, in very high amounts) were added. No curing accelerators or additives were added.

[0185] Table 4 Comparative Example Formulation Composition (by solid mass parts):

[0186]

[0187] Note: Charge buffer or anchoring synergistic components: including inorganic aluminum salt sub-components and organic cationic anchoring sub-components; Sizing compatible or hydrophobic synergistic components: including wax emulsions and hydrophobic polymer emulsions; Curing accelerator components: including polyol sub-components and hypophosphite sub-components, etc.

[0188] Application example:

[0189] Application Example 1: Application of high-strength corrugated base paper wet end filling.

[0190] Experimental Description: This experiment aims to simulate the corrugated base paper production environment under a high-conductivity closed-loop water system and evaluate the effects of different resin compositions on the physical strength and wet-end chemical environment of the finished paper. 100% OCC (used corrugated cardboard box) waste pulp was used as raw material. After dissociation using a standard desiccant, the freeness was controlled at 35°SR. To simulate the harsh water quality of an industrial site, calcium chloride and sodium sulfate were added to the pulp to adjust the conductivity of the white water system to 3.5 mS / cm and the pH to 6.5. A two-component retention aid system was used. The main retention aid was cationic polyacrylamide (CPAM, molecular weight 12 million), added at a fixed amount of 200 ppm; the particulate retention aid was silica sol (40 wt% colloidal silica), added at a fixed amount of 800 ppm (based on the commercial weight of silica sol), added 5 seconds after the addition of CPAM. The total addition amount of the reinforcing resin composition (Examples 1-14 and Comparative Examples 1-12) was set at 1.5 wt% (based on oven-dry pulp). The addition process employed a staged addition method: 80% of the total composition was added to the pulp 60 seconds before the addition of CPAM (front stage), and the remaining 20% ​​was added 10 seconds after the addition of CPAM and before the wire bonding process (back stage). Papermaking was carried out on a Rapid-Köthen papermaking machine, with a target basis weight control of 120 g / m². The wet paper sheets were pressed to 45% dryness and then dried at 105°C for 3 minutes. All paper samples were equilibrated at 23°C and 50% RH for 24 hours, and then their physical properties and wet-end parameters were tested according to the standards listed in the "Main Test Standards" section of this specification. Test indicators included ring crush index, bursting strength index, tensile index, and 60-second Cobb absorbance. 60 The rate of change of wet particulate charge demand (PCD) relative to the blank control (Comparative Example 4) and the turbidity of white water.

[0191] PCD was determined using a particle charge demand analyzer combined with polyelectrolyte titration, and the results are expressed in μeq / L; the rate of change of PCD is calculated as (PCD... 样品 -PCD 空白 ) / PCD 空白 Calculate by 100% and record PCD synchronously in the original record. 空白 With PCD 样品 The absolute value. During the operation of the paper machine, PCD, conductivity, and pH are used as online process control parameters, with preset control windows of: PCD = 0 ± 100 μeq / L, conductivity = 2.0~6.0 mS / cm, pH = 6.0~8.5; and the finished paper Cobb... 60 The target control range is used as a feedback indicator for adhesive application. When PCD deviates from the control window or Cobb... 60When deviations from the target range, adjust the dosage or ratio of the composition / kit according to the following rules: increase or decrease the dosage of the charge buffer or anchoring synergist to adjust the cationic equivalent, or adjust its ratio to the carboxyl equivalent in the reinforcing resin; simultaneously, according to Cobb 60 The deviation can be adjusted by increasing or decreasing the amount of sizing compatible or hydrophobic synergistic components, and if necessary, by adjusting the amount of reinforcing resin added, so that the charge parameters return to the preset control window and the hydrophobicity of the paper returns to the target control range.

[0192] Table 5. Test results of corrugated base paper properties and wet end parameters in Examples 1-14:

[0193]

[0194] Table 6. Test results of properties and wet end parameters of corrugated base paper in Comparative Examples 1-12:

[0195]

[0196] Analysis: The experimental data show that the retention efficiency and reinforcing effect of this resin composition in complex wet-end environments are closely related. Examples 1-14 all exhibit excellent performance. Among them, Examples 3, 5, and 11, which introduce curing accelerators, achieve high ring pressure indices (8.7-9.2 N·m / g) while maintaining low white water turbidity (155-165 NTU), indicating that the system not only has high retention but also effectively aggregates fine fibers. Example 8, due to its highest content of effective resin components, has the strongest fiber binding ability, achieving a ring pressure index of 9.5 N·m / g. However, its PCD change rate is relatively large, which has a certain impact on the charge balance of the system. In contrast, the comparative examples, Comparative Examples 1 and 2, lack effective charge buffering / stabilizing components, prevent the anion exchange resin from effectively adsorbing onto the fiber surface, resulting in white water turbidity as high as 320 NTU and 280 NTU, respectively, significantly reducing the reinforcing effect. Comparative Examples 6 and 8, due to an imbalance in the cation / carboxyl ratio, resulted in excessive charge reversal or poor flocculation, leading to drastic changes in PCD and poor production stability. Of particular note is Comparative Example 10, which, despite using a high molecular weight resin, did not translate into a strength advantage (ring compression only 7.2 N·m / g). Significant uneven floc formation was observed in the experiment, confirming the dispersion limitations of excessively high molecular weight resins in wet-end applications. Although Comparative Example 12 had the lowest Cobb value (25 g / m²), excessive wax severely hindered hydrogen bonding between fibers, resulting in a strength index only slightly higher than the control group (Comparative Example 4). This further confirms the importance of balancing hydrophobic and reinforcing components.

[0197] Application Example 2: Spraying and hot pressing of molded pulp tableware.

[0198] Experimental Description: This experiment focuses on investigating the application performance of the resin composition in the hot pressing process of pulp molded products, particularly the synergistic improvement of reinforcement and barrier properties. Sugarcane bagasse pulp and bleached bamboo pulp, after being decomposed by a standard decomposer, were mixed at a mass ratio of 70:30. The mixture was then beaten using a PFI beater, and the freeness (°SR) was measured according to GB / T 3332-2004, controlling the freeness at 40°SR. Pulp fibers and water were added to a mixing tank and stirred for 10 minutes to achieve a pulp concentration of 0.3 wt% and adjust the pH to 7.0. Standard tableware wet blanks were prepared using vacuum filtration molding: the vacuum degree was set to -0.08 MPa, the forming and filtration time was 30 s, the forming mold mesh was a stainless steel mesh (100 mesh), and the moisture content of the wet blank was 65% (mass fraction). The composition of Example 3 was prepared as a working fluid with a solid content of 5 wt% (diluted with deionized water, and the solid content was verified by constant weight at 105°C). It was uniformly sprayed onto the surface of a wet blank using a spraying device. The spray gun nozzle diameter was 1.0 mm, the atomizing air pressure was 0.20 MPa, the spray gun distance was 20 cm, the spraying speed was 10 cm / s, and two passes were made. The coating amount was 2 g / m² based on dry solids. The surface area A (m²) of the wet blank was recorded, and the mass difference Δm (g) before and after spraying was measured. The coating amount (dry solids, g / m²) was calculated and verified as Δm × working fluid solid content / A. Immediately after spraying, the wet blank was placed in a hot press mold with a diamond-patterned surface and hot-pressed at 180°C and 5 MPa for 60 seconds to obtain a pulp molded sheet.

[0199] Table 7. Performance test results of pulp molded products from Examples 1-14:

[0200]

[0201] Table 8. Performance test results of pulp molded products from Comparative Examples 1-12:

[0202]

[0203] Analysis: Experimental results show that the hot-press curing process significantly amplifies the effect of the crosslinking components in the formulation. Examples 3, 5, 11, and 12 contain polyols and hypophosphite, which undergo efficient esterification and crosslinking reactions at 180°C, forming a dense network structure. This not only significantly improves tensile strength (all exceeding 45 MPa), but more importantly, it significantly reduces water absorption at 100°C (120-130 g / m²), indicating excellent heat penetration resistance. Example 5, due to its higher polyol content, imparts better flexibility to the product, achieving a folding resistance of 35 times, far exceeding other groups. Comparative Example 4, serving as a blank control, exhibits extremely poor performance and fails to meet usage requirements. Comparative Examples 1 and 3, lacking hydrophobic components, have high liquid absorption and low oil resistance. Although Comparative Example 10 could be sprayed, the resin molecular weight was too large, resulting in poor atomization and poor leveling during the short hot-pressing process. This led to insufficient micro-density of the coating, and the tensile strength (35.5 MPa) and oil resistance (grade 3) did not reach the ideal levels. Comparative Example 12 again demonstrated the negative impact of excessive hydrophobic agent. Although the water and oil resistance indicators were acceptable, the tensile strength (32.0 MPa) and flexural strength (10 times) were close to the blank sample, indicating that the excessive wax layer damaged the bonding force between fibers, causing the product to become brittle and severely impairing its mechanical strength.

[0204] Application Example 3: Gluing, pressing, or coating application on the surface of whiteboard paper.

[0205] Experimental Description: This experiment aims to evaluate the rheological adaptability and film-forming properties of the compositions in sizing or coating processes on paper surfaces. Unsizing coated white board paper with a basis weight of 250 g / m² was used as the substrate. All compositions from the examples and comparative examples were diluted with deionized water to a solid content of 8 wt% to prepare sizing working solutions. If the system viscosity was found to be too high, resulting in a gel-like consistency or preventing normal flow during preparation, it was deemed unsuitable. Surface sizing was performed using a laboratory coating / film transfer machine (K ControlCoater K202), with a No. 12 wire rod and a coating speed set to 6 m / min. The dry mass m0 of the paper sample before coating and the dry mass m1 after coating and drying were weighed and the sample area A was recorded. The sizing amount (g / m²) was calculated and controlled to be 1.5 g / m² based on the formula (m1-m0) / A. The coated paper samples were directly placed in a 105°C forced-air drying oven for 2 minutes to dry and mature. After cooling, the surface strength (IGT pickup speed, using medium viscosity oil), 60-second Cobb water absorption (Cobb60), and water droplet contact angle (200 ms) were measured. The water droplets were deionized water with a drop volume of 3.0 μL. The arithmetic mean of the measurements was taken five times at different locations for each sample.

[0206] Table 9. Surface sizing performance test results for Examples 1-14:

[0207]

[0208] Table 10: Test results of surface sizing performance of comparative examples 1-12:

[0209]

[0210] Note: Comparative Example 10 has no data because the resin molecular weight is too high, and the viscosity is extremely high when prepared as an 8wt% working solution, making it impossible to coat normally.

[0211] Analysis: Surface sizing processes require the working solution to have good rheological properties to ensure uniform coating, and also require the formation of a high-strength film after drying. The results of the examples show that the formulation system of this invention can well meet these requirements. The cross-linking formulations of Examples 3, 5, and 11, after curing, formed a cross-linking network, significantly improving surface strength, with an IGT pick-up speed exceeding 2.1 m / s and a Cobb value as low as 22-24 g / m², exhibiting excellent water-resistant printing performance. Example 8, with its high content of reinforcing resin, although slightly less hydrophobic (Cobb = 31 g / m²), has extremely high surface strength (2.10 m / s), making it suitable for applications requiring high strength. The results of Comparative Example 10 have important reverse verification significance: because its resin viscosity-average molecular weight is as high as 2.5 million, the viscosity of the solution at an 8% concentration exceeds the operating limit of the coating machine, making film formation impossible. This proves the necessity of controlling the upper limit of molecular weight for surface sizing adaptability. Comparative Example 12 again revealed the problem of "excessive wax and low strength." Although the contact angle reached 96°, the IGT speed was only 1.45 m / s, close to the blank sample coated with water (Comparative Example 4). This easily leads to powder and lint problems during printing. In addition, Comparative Example 11, due to improper curing accelerator ratio (insufficient crosslinking agent), failed to significantly improve surface strength and water resistance as in the examples, demonstrating the crucial importance of the synergistic ratio of each component.

[0212] Application Example 4: Maintaining the strength of corrugated base paper under high humidity conditions.

[0213] Experimental Description: Paper-based materials are highly susceptible to moisture absorption and softening under high humidity conditions such as cold chain logistics, leading to packaging collapse. This experiment aims to evaluate the effect of various compositions on improving the wet stability of paper. The test samples were taken from the corrugated base paper prepared in Application Example 1. First, the ring crush index (RCT) of each sample was measured under standard atmospheric conditions (23°C, 50% RH). std Subsequently, parallel samples from the same batch were placed in a constant temperature and humidity chamber, with environmental conditions set at 38℃ and 90% RH, and treated for 24 hours to simulate an extreme humid environment. Immediately after removal, their high humidity ring pressure index (RCT) was measured. wet The formula for calculating the high humidity ring pressure retention rate is: Retention rate = (RCT) wet / RCT std )× 100%.

[0214] Table 11 Results of High Humidity Strength Retention Rate Tests in Examples 1-14:

[0215]

[0216] Table 12 Results of High Humidity Strength Retention Rate Test for Comparative Examples 1-12:

[0217]

[0218] Analysis: In high humidity environments, water molecules can penetrate the amorphous regions of fibers, disrupting hydrogen bonds. Experimental results show that the chemical modification strategy of this invention can effectively resist this process. Example 5 exhibited the highest retention rate of 74.1%, ranking first among all samples. This is attributed to the high proportion of polyols and hypophosphites in its formulation forming a high-density ester cross-linked structure throughout the fiber matrix during the drying process. This covalent bond is insensitive to water molecules, effectively limiting fiber hygroscopic swelling and relative slippage. Examples 3 and 11 also performed well, with retention rates exceeding 66%. In contrast, the retention rates of Comparative Examples 1-10 were generally around 50%, not significantly different from the blank sample (Comparative Example 4, 47.7%), indicating that resin systems relying solely on physical adsorption or hydrogen bond enhancement will fail under extremely high humidity conditions. Although Comparative Example 11 contained crosslinking components, the low catalyst (hypophosphite) content (polyol:hypophosphite = 1:0.05) resulted in insufficient reaction activation energy, leading to low crosslinking density and an inability to form an effective rigid network. Its retention rate (53.5%) was significantly lower than that of Example 11 with optimized formulation (66.8%). This result profoundly reveals the decisive role of precise proportioning of each sub-component in the curing accelerator in achieving moisture resistance.

[0219] Application Example 5: Evaluation of repulping and sieve residue.

[0220] Experimental Description: The recyclability of paper-based materials is their core advantage over plastics. This experiment, referencing the TAPPIT 275 standard, evaluates the ease of repulping paper samples treated with different resin compositions. 30 grams (octane dry weight) of each paper sample prepared in Application Example 1 were torn into 25mm × 25mm pieces and soaked in 2 liters of 40°C warm water. Dissociation was performed using a standard laboratory dissociation machine at 30,000 revolutions per minute. The dissociated pulp was then screened using a sieve with a sieve gap width of 0.15mm. Undissociated pulp residue (flaky material) retained on the sieve was collected, dried, weighed, and the residue rate was calculated. According to industry standards, a residue rate ≤ 1.0% is considered acceptable, indicating that the paper can be recycled using conventional equipment.

[0221] Table 13 Results of re-slurry performance tests in Examples 1-14:

[0222]

[0223] Table 14 Results of re-slurry performance tests for Comparative Examples 1-12:

[0224]

[0225] Analysis: Experimental data show that all embodiments (1-14) of the present invention provide strong and tough properties without sacrificing the recyclability of the paper. Even in embodiment 5, which has a high crosslinking density, the sieve residue rate of 0.85% is still below the 1.0% threshold. This indicates that the ester bond crosslinking network constructed in this invention can be broken down and separated under mechanical shear and hydraulic action, unlike some wet-strength resins (such as PAE) that cause permanent "difficult-to-dissociate" problems. However, Comparative Example 12 had a sieve residue rate as high as 1.20%, which was deemed unacceptable. This is because the formulation contains a very high proportion of wax emulsion (80 parts). During the paper drying process, a large amount of hydrophobic wax coats the fibers and fills the pores, forming a hydrophobic barrier that is difficult to wet with water and mechanically disperse. This not only hinders the reswelling of the fibers but also causes the pulp residue to exist in the form of hydrophobic clumps. The sieve residue rate of Comparative Example 11 (0.95%) is close to the critical value, presumably due to the resin forming an insoluble gel locally due to an imbalance in the formulation. These results suggest that when designing highly water-resistant paper-based materials, the amount of hydrophobic components must be precisely balanced. The formulation range of this invention successfully achieves a balance between performance and environmental protection.

[0226] Application Example 6: Detection of total organic fluorine (TOF).

[0227] Experimental Description: To verify the performance of the product of this invention under fluorine-free requirements, the total organic fluorine (TOF) content of the solid compositions of Examples 1-14 and Comparative Examples 1-12 (composed samples were ground after removing moisture at 105°C) was determined, and the pulp molded products prepared in Example 2 were sampled and compared. The detection method employed combustion ion chromatography (CIC). The sample was pulverized and burned at high temperature; the generated fluorine-containing gas was absorbed by an alkaline solution, and the fluoride ion concentration in the absorption liquid was then determined by ion chromatography and converted into the total organic fluorine content of the sample. The limit of detection (LOD) for this method was 5 mg / kg.

[0228] Table 15 Results of total organic fluorine detection in Examples 1-14:

[0229]

[0230] Table 16 Results of total organic fluorine content in Comparative Examples 1-12:

[0231]

[0232] Analysis: The test results consistently show that, in both the examples and comparative examples, the total organic fluorine content is below the method detection limit (5 mg / kg). This result is completely consistent with the technical route design of this invention: that is, by combining an acrylic polycarboxylic acid polymer network, an inorganic / organic binary anchoring system, and a non-fluorinated hydrophobic synergistic component, the traditional pulp molding industry's reliance on fluorinated oil-repellent agents to achieve oil and water resistance is replaced. This proves that the resin composition provided by this invention is a truly fluorine-free solution.

[0233] Experimental Results and Analysis:

[0234] This invention provides a strong and tough waterborne structural resin composition for constructing fiber matrices. Through a specific blending of acrylic polycarboxylic acid reinforcing resin, charge buffering or anchoring synergistic components, sizing-compatible or hydrophobic synergistic components, and curing-promoting components, significant synergistic effects are achieved in terms of adaptability to complex wet-end environments, improved physical strength, barrier properties, and environmental friendliness. Based on the experimental data from Application Examples 1 to 6, the experimental results of the technical solution of this invention are analyzed in detail below:

[0235] Analysis of charge management and wet-end adaptation mechanisms:

[0236] Data from Application Example 1 shows that in a closed white water circulation system with a high conductivity of 3.5 mS / cm and the presence of anionic interfering substances, relying solely on traditional anion exchange resins such as Comparative Example 1 or physical adsorption such as Comparative Example 2 cannot achieve effective retention, resulting in high white water turbidity (>280 NTU) and a large PCD change rate, indicating significant resin loss or drastic charge fluctuations. The binary charge buffer or anchoring synergistic component of "inorganic aluminum salt and organic cation" introduced in this invention plays a crucial role. The inorganic aluminum salt provides rapid charge neutralization and primary flocculation, while the organic cationic polymer provides a wider charge buffer window and long-chain bridging effect. Examples 1-14 show that when the mass ratio of the two is controlled at 1:0.2–2.0 and the cation to carboxyl equivalent ratio is in the range of 0.18–0.55, the white water turbidity is significantly reduced to 150–180 NTU, and the PCD change rate is controlled within ±20%. The comparison shows that when the organic component is too low, as in Comparative Example 5, or too high, as in Comparative Example 6, or when the equivalence ratio is unbalanced, as in Comparative Examples 7 and 8, it is impossible to simultaneously achieve retention rate and system stability, thus confirming the necessity of binary synergy and a specific equivalence ratio.

[0237] Synergistic Construction Analysis of Toughness and Barrier:

[0238] Traditional papermaking chemicals often present a trade-off between reinforcement and hydrophobicity. Comparative Example 12 shows that while excessive addition of hydrophobic components, i.e., wax emulsions, can reduce water absorption (Cobb value 25 g / m²), it severely disrupts hydrogen bonding between fibers, leading to a significant decrease in ring crush index and tensile strength. This invention achieves an "interpenetrating network" structure by introducing appropriate amounts of nanoscale sizing-compatible or hydrophobic synergistic components into the reinforcing resin network. The formulations in Examples 3, 5, and 11, while maintaining high strength (ring crush index > 8.5 N·m / g and pulp molding tensile strength > 45 MPa), achieve excellent barrier properties (Cobb value < 30 g / m² and KIT oil resistance rating of 9 to 10). This indicates that, under specific formulations, hydrophobic particles fill the micropores of the fiber and resin network, providing physical barrier function without disrupting key fiber bonding nodes.

[0239] The contribution of curing and crosslinking to moisture and heat resistance:

[0240] Application Example 4, regarding high-humidity strength retention, and Application Example 2, regarding pulp molding hot pressing, highlight the role of the curing-promoting component. Under high-temperature drying or hot pressing conditions, the polyol and carboxyl groups in the reinforcing resin undergo esterification under hypophosphite catalysis, forming a water-resistant covalent cross-linked structure. Example 5, after optimizing the polyol to hypophosphite ratio, achieved a ring compression retention rate as high as 74.1% under 90% RH high humidity conditions, and the pulp molded product exhibited a low hot water absorption of only 130 g / m² at 100°C. In contrast, the comparative example lacking cross-linking components or with an imbalanced catalyst ratio in Comparative Example 11 only achieved a high-humidity retention rate of around 50%. This confirms that the esterification cross-linking network is the core mechanism for resisting moisture erosion and maintaining wet rigidity.

[0241] Trend analysis of the impact of key component content and ratio on performance:

[0242] Based on the data points from the examples and comparative examples, the impact of changes in each key parameter on the experimental results shows the following trends:

[0243] Reinforcing the resin molecular weight: As the viscosity-average molecular weight of the resin increases from 60,000 to 500,000, the fiber bonding strength gradually improves. However, when the molecular weight is too high, reaching 2.5 million (as in Comparative Example 10), the limited distribution of molecular chains on the fiber surface and poor permeability lead to uneven micro-flocculation, a decrease in strength, and a serious impact on the rheological properties of the surface coating. Therefore, 80,000 to 2 million is an effective range that balances reinforcement and process adaptability.

[0244] The ratio of charge buffering or anchoring synergistic components, i.e., the ratio of inorganic to organic components: As the proportion of organic cationic components increases, from the pure inorganic component in Comparative Example 3 to the high organic component in Comparative Example 6, the shear retention capacity of the system first increases and then decreases. The optimal synergistic effect occurs in the mass ratio range of 1:0.2 to 2.0, at which point the charge neutralization of inorganic salts and the bridging and anchoring of organic polymers reach the optimal balance.

[0245] Addition amount of sizing compatible or hydrophobic synergistic components: As the amount of wax emulsion or hydrophobic polymer emulsion added increases, the water absorption of the paper, i.e., the Cobb value, shows a monotonically decreasing trend, that is, the hydrophobicity increases; however, physical strengths such as burst strength and ring crush test show a trend of first stabilizing and then decreasing sharply. The optimal balance window between strength and hydrophobicity can be obtained in the range of 0.1 to 60 parts, especially in the range of 4 to 30 parts.

[0246] Catalyst ratio in the curing accelerator: With a fixed polyol content, the crosslinking efficiency first increases and then decreases with the increase of the hypophosphite ratio. When the mass ratio of polyol to hypophosphite is in the range of 1:0.05 to 5, the catalytic efficiency is relatively high; too low a ratio leads to insufficient reaction kinetics, as in Comparative Example 11, while too high a ratio may cause salting out or side reactions, affecting the network density.

[0247] Environmental and sustainability assessment:

[0248] Application Examples 5 and 6 confirm that, despite the introduction of chemical crosslinking, the residue rate of all samples from the embodiments of the present invention under standard warm water dissociation conditions was <1.0%, meeting the requirements for repulping and recycling. Simultaneously, total organic fluorine (TOF) was undetectable in all formulations, completely resolving the environmental pain point of relying on fluorinated anti-oil agents in the pulp molding industry.

[0249] In summary, this invention has successfully solved the adaptability problem of traditional paper-based reinforcing agents in complex wet end environments through the precise regulation and synergistic effect of multiple components, and has overcome the technical bottleneck of the difficulty in achieving both strength and barrier properties under fluorine-free conditions.

[0250] Those skilled in the art should understand that the above embodiments are merely exemplary and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the technical solutions of the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A strong and tough waterborne structural resin composition for constructing fiber matrices in paper-based and pulp molded articles, characterized in that, The composition is an aqueous system, comprising water and solid components; Based on solid mass, the solid component comprises the following substances: 10-95 parts of acrylic polycarboxylic acid waterborne polymer reinforcing resin; 0.01-60 parts of charge buffer or anchoring synergistic component, wherein the charge buffer or anchoring synergistic component includes an inorganic aluminum salt component and an organic cationic fixative component, and the inorganic aluminum salt component and the organic cationic fixative component coexist; 0-60 parts of sizing compatibility or hydrophobic synergistic component; 0.1-30 parts of curing accelerator component; and 0-20 parts of additives; the ratio of the charge buffer or anchoring synergistic component to the carboxyl equivalent in the reinforcing resin, based on cationic equivalent, is 0.18-0.55; based on the solid mass of the charge buffer or anchoring synergistic component, the mass ratio of the inorganic aluminum salt component to the organic cationic fixative component is 1:

0. 0.2~2.0; the viscosity-average molecular weight of the reinforcing resin is 80,000~2,000,000; the curing accelerator component includes a polyol sub-component and a hypophosphite sub-component, and the mass ratio of the polyol sub-component to the hypophosphite sub-component is 1:0.05~5 based on the solid mass of the curing accelerator component; the polyol sub-component is a polyol containing 3 or more hydroxyl groups, selected from one or more of glycerol, erythritol, xylitol, sorbitol, mannitol, pentaerythritol, trimethylolpropane, and sucrose; the hypophosphite sub-component is selected from one or more of sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, and ammonium hypophosphite, such that under drying or hot pressing conditions, the carboxyl groups in the reinforcing resin and the hydroxyl groups in the polyol sub-component undergo an esterification reaction to form a cross-linked structure.

2. The composition according to claim 1, characterized in that, The total organic fluorine content of the composition was not detected by combustion ion chromatography, with a method detection limit ≤5 mg / kg; the solid content of the composition was 10 wt% to 55 wt%, the pH value was 2.0 to 6.5, and the viscosity at 25°C was 100 mPa·s to 20000 mPa·s; the additives were selected from one or more of dispersants, defoamers, preservatives, pH buffers, stabilizers, antisettling agents, rheology modifiers, freeze-thaw stabilizers, and bactericides.

3. The composition according to claim 1, characterized in that, The reinforcing resin is an aqueous polymer system containing carboxyl segments, which is polymerized from monomers including acrylic monomers or methacrylic monomers and polycarboxylic acid monomers; the acrylic monomers or methacrylic monomers are selected from one or more of acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isooctyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, glycidyl acrylate, and glycidyl methacrylate; the polycarboxylic acid monomers are selected from one or more of maleic acid, maleic anhydride, itaconic acid, fumaric acid, maleic anhydride, citraconic acid, citraconic anhydride, methyl fumaric acid, aconitic acid, and their salts; the monomer system of the reinforcing resin includes one or more comonomers of styrene, α-methylstyrene, vinyl acetate, and ethylene; the mass fraction of the polycarboxylic acid monomers in the solid reinforcing resin is 1wt% to 35wt%.

4. The composition according to claim 1, characterized in that, The inorganic aluminum salt component is selected from one or more of aluminum sulfate, polyaluminum sulfate, polyaluminum chloride, polyaluminum ferric chloride, alum, aluminum chloride, basic aluminum chloride, and basic aluminum sulfate; the organic cationic fixative component is selected from one or more of polyamine fixatives, polydiallyldimethylammonium chloride, polyethyleneimine, polyamide amine, polyethyleneamine, polyethyleneamine quaternary ammonium salt, and chitosan quaternary ammonium salt; the polyamine fixative includes dimethylamine-epoxychloropropane condensate, polyamine quaternary ammonium salt, or a combination of both; the weight-average molecular weight of the polyamine fixative is 5,000 to 5,000,000; the weight-average molecular weight of the polydiallyldimethylammonium chloride is 5,000 to 5,000,000; the polydiallyldimethylammonium chloride is a homopolymer of diallyldimethylammonium chloride monomer; based on the solid mass of the charge buffer or fixation synergistic component, the inorganic aluminum salt component accounts for 10 wt% to 90 wt%, and the organic cationic fixative component accounts for 10 wt% to 90 wt%.

5. The composition according to claim 1, characterized in that, The sizing-compatible or hydrophobic synergistic component is selected from one or more of wax emulsions, hydrophobic polymer emulsions, hydrophobic surfactants, or their mixtures; the wax in the wax emulsion is selected from one or more of paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, Fischer-Tropsch wax, montmorillonite wax, carnauba wax, and beeswax; the film-forming polymer of the hydrophobic polymer emulsion is obtained by polymerization of one or more of the following monomers: styrene, α-methylstyrene, butadiene, ethylene, vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, methyl methacrylate, butyl methacrylate, and isooctyl methacrylate; the hydrophobic surfactant is a nonionic or anionic surfactant, selected from one or more of fatty alcohol polyoxyethylene ethers, alkyl glycosides, polyoxyethylene sorbitan fatty acid esters, alkyl sulfates, alkyl ether sulfates, α-olefin sulfonates, and alkylbenzene sulfonates; the sizing-compatible or hydrophobic synergistic component exists in the form of an emulsion or microemulsion, with an average particle size D. 50 The range is 50nm to 2000nm.

6. A reinforcing kit for constructing fiber matrices in paper-based and pulp molded articles, characterized in that, The kit is used to provide the composition of claim 1, comprising: the reinforcing kit is a multi-component kit; the multi-component kit includes: a reinforcing resin packaging unit containing an acrylic polycarboxylic acid aqueous polymer reinforcing resin; a charge buffer or anchoring synergistic component packaging unit containing a charge buffer or anchoring synergistic component; a curing accelerator packaging unit containing a curing accelerator component; when the sizing-compatible or hydrophobic synergistic component is present, the multi-component kit further includes: a sizing-compatible or hydrophobic synergistic component packaging unit containing a sizing-compatible or hydrophobic synergistic component; wherein the reinforcing resin packaging unit is separately packaged or partitioned from the charge buffer or anchoring synergistic component packaging unit, and the curing accelerator component packaging unit is separately packaged or partitioned from the reinforcing resin packaging unit; and when the sizing-compatible or hydrophobic synergistic component packaging unit is present, the sizing-compatible or hydrophobic synergistic component packaging unit is separately packaged or partitioned from the reinforcing resin packaging unit.

7. A method for preparing the composition according to claim 1, characterized in that, The process includes the following steps: Step 1. When the sizing-compatible or hydrophobic synergistic component is present, add the sizing-compatible or hydrophobic synergistic component to water, disperse it using a high-speed disperser for 10 minutes and stir until homogeneous to obtain a hydrophobic synergistic phase dispersion; Step 2. Add the charge buffer or anchoring synergistic component to water, stir to dissolve or disperse for 20 minutes and record the pH value to obtain a charge buffer or anchoring synergistic phase; Step 3. When both Step 1 and Step 2 are present, add the charge buffer or anchoring synergistic phase obtained in Step 2 to the hydrophobic synergistic phase dispersion obtained in Step 1 and stir for 10 minutes to obtain a mixed synergistic phase; add the reinforcing resin to the mixed synergistic phase and stir for 30 minutes to obtain a compatible composite dispersion system; when only Step 2 is present, add the reinforcing resin to the corresponding charge buffer or anchoring synergistic phase and stir for 30 minutes to obtain a compatible composite dispersion system; Step 4. Add the curing accelerator to the compatible composite dispersion system obtained in Step 3, add water to adjust the solid content and pH value, and filter to obtain the finished composition; The reinforcing resin, charge buffer or anchoring synergistic component, sizing compatible or hydrophobic synergistic component, and curing accelerator component are all pre-prepared aqueous dispersions or aqueous solutions, and no monomer polymerization reaction is carried out during the preparation process; the filtration accuracy is 80μm to 300μm.

8. A method for reinforcing paper-based and pulp molded articles, characterized in that, The composition of claim 1 is used in one or more of the following ways: 1) adding the pulp suspension internally; 2) applying it to a wet or semi-dry paper sheet by spraying or impregnation; 3) applying it to the surface of the paper sheet by sizing press, film transfer or coating. The pulp is cured under drying conditions to form a reinforced structure. Specifically, the method for preparing the reinforced pulp molded product includes: Step 1. Adding pulp fibers and water to a mixing tank and stirring for 10 minutes, adjusting the pulp concentration to 0.1wt%–3wt%, and adjusting the pH value of the pulp to 6.0–7.5 to obtain a molding pulp; Step 2. When using internal reinforcement, adding the composition to the molding pulp obtained in Step 1 as an internal additive, and continuing to stir for 5 minutes to obtain a reinforced molding pulp; Step 3. Molding the molding pulp obtained in Step 1 or the reinforced molding pulp obtained in Step 2 in a molding die. Dehydrate the wet blank and control the moisture content of the resulting wet blank to 10wt%~80wt% to obtain a wet blank; Step 4. When surface reinforcement is used, dilute the composition with water to a working solution of 0.5wt%~25wt%, and spray or impregnate the wet blank obtained in step 3 to obtain a treated wet blank; Step 5. Place the wet blank obtained in step 3 or the treated wet blank obtained in step 4 into a hot press of a mold for hot pressing and curing, control the time to 0.2min~30min, demold and cool to obtain a molded product; wherein the hot pressing curing temperature is 90℃~220℃, and the hot pressing pressure is 0.2MPa~10MPa.

9. The enhancement method according to claim 8, characterized in that, The amount added by the internal additive method is 0.5 kg / t to 30 kg / t based on oven-dry paste; or the amount of adhesive applied by the spraying, dipping, or coating methods is 0.2 g / m² to 30 g / m², based on solids.

10. The enhancement method according to claim 8, characterized in that, When applied internally at the wet end of papermaking, the acrylic polycarboxylic acid waterborne polymer reinforcing resin is added either in the form of the composition or as a reinforcing resin packaging unit in a kit, and is applied at least twice before or after the main retention aid in the retention aid system; wherein the first application point is located before the main retention aid is added, and the second application point is located after the main retention aid is added and close to the web forming zone; the sum of the amounts added in the first and second applications accounts for 80wt% to 100wt% of the total amount of reinforcing resin added; the residence time from the first application point to the main retention aid is 10s to 600s, and the residence time from the second application point to web forming is 0.5s to 60s.

11. The enhancement method according to claim 10, characterized in that, During the operation of the paper machine, the particle charge requirement, conductivity, and pH value of the pulp system are monitored online as process control charge parameters. Combined with the periodic sampling results of the 60-second Cobb water absorption of the finished paper, when the charge parameters deviate from the preset control window or the 60-second Cobb water absorption of the finished paper deviates from the target control range, the dosage or ratio of the composition or kit is adjusted. This includes: adjusting the cationic equivalent of the charge buffer or anchoring synergistic component or its ratio to the carboxyl equivalent in the reinforcing resin, adjusting the addition amount of the sizing compatible or hydrophobic synergistic component, or adjusting the addition amount of the reinforcing resin, so that the charge parameters of the pulp system return to the preset control window and the hydrophobicity of the finished paper returns to the target control range.

12. The enhancement method according to claim 10, characterized in that, When the recycled fiber content in the pulp system is ≥30wt% or the conductivity is ≥2.0mS / cm: 1) When applied in a package, first add the charge buffer or anchoring synergistic component packaging unit in the package to pre-treat the pulp, and then add the reinforcing resin packaging unit in the package; 2) When applied in a composition form, add the composition to the pulp system and adjust the segmented addition ratio and total addition amount to achieve synergistic control of charge and sizing; and use a retention aid system, with the main retention aid being cationic polyacrylamide, added at a rate of 50ppm to 500ppm, and the particulate retention aid being bentonite or silica sol, added at a rate of 200ppm to 2000ppm; the system charge parameter window is: particulate charge requirement of 0±100μeq / L, conductivity of 2.0mS / cm to 6.0mS / cm, and pH value of 6.0 to 8.

5.

13. A paper-based and pulp molded article, characterized in that, The composition of claim 1 is applied during its preparation.

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