High-strength high-covering-power decorative base paper and preparation method thereof

Abstract

The invention discloses high-strength and high-covering-property decorative base paper and a preparation method, the high-strength and high-covering-property decorative base paper comprises a base material layer, a reinforcing layer and a functional layer, and the base material layer, the reinforcing layer and the functional layer are stacked in sequence; the base material layer comprises softwood pulp, hardwood pulp and a pre-dispersed filler, and the enhancement layer comprises aramid fibers and a composite fiber network; the functional layer comprises titanium dioxide and precipitated barium sulfate which are distributed in a gradient manner; the base material layer, the reinforcing layer and the functional layer are combined through a wet-process net stacking forming process. High opaqueness is achieved through cooperation of the gradient functional layer and the pre-dispersed filler, the tensile strength is improved by 75% through a three-dimensional supporting network, and the modified adhesive breaks through the wet strength bottleneck; the energy consumption is reduced by 30% through the stepped flow process, 99.5% of UV shielding is achieved through the microcapsule coating and the composite proportion, the weather resistance is remarkably enhanced, the performance of the decorative base paper is systematically upgraded, and the innovation of green building materials is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of papermaking, and in particular to a high-strength and high-hiding decorative base paper and a preparation method thereof. Background Art

[0002] As the core substrate for high-end home decoration materials, decorative base paper must have excellent hiding properties to ensure the clarity of printed patterns, while also meeting the stringent requirements for paper strength and stability in subsequent processes such as impregnation coating and mechanical processing. However, traditional technical solutions have the following technical contradictions that need to be resolved: 1. Hiding and strength cannot be improved synergistically: The current mainstream process increases hiding power by adding inorganic fillers such as titanium dioxide at a high ratio of 30% to 40%. However, excessive fillers will reduce the bonding force between fibers and the longitudinal tensile strength of the paper by more than 50%, making it unable to withstand the high-frequency mechanical turning (≥20 times / minute) during the impregnation process. 2. Wet mechanical properties defects: The high filler system reduces the wet strength of paper to less than 15% of the dry strength. It is easy to break in a wet environment, resulting in a decrease in the yield rate. 3. Limitations of multi-layer composite structures: Although existing layering technologies attempt to achieve a covering function through a thin layer of high-filler content on the surface, the interfacial bonding between layers is weak (peel strength <1.2N / cm), and delamination and blistering are prone to occur during processing; 4: High complexity of the production process: Improvement schemes such as gradient filler distribution and additive modification require multi-stage coating or precise temperature control equipment, resulting in an increase of more than 30% in energy consumption, making it difficult to achieve large-scale production. The above technical bottlenecks have seriously restricted the application and expansion of decorative base paper in the field of high-end building materials. It is urgent to develop a systematic solution that can maintain high hiding performance (opacity ≥ 95%) while meeting high strength (tensile strength ≥ 50N / m), high wet strength (wet strength ≥ dry strength 15%) and excellent processing adaptability. To this end, a high-strength and high-hiding decorative base paper and a preparation method are proposed. Summary of the Invention

[0003] In view of the deficiencies in the prior art, the present invention provides a high-strength and high-hiding decorative base paper and a preparation method thereof to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a high-strength and high-hiding decorative base paper, comprising: A base material layer, a reinforcing layer and a functional layer, wherein the base material layer, the reinforcing layer and the functional layer are stacked in sequence; The substrate layer comprises: softwood pulp, hardwood pulp and pre-dispersed filler, wherein the softwood pulp accounts for 60-70 weight percent, the hardwood pulp accounts for 20-30 weight percent, the pre-dispersed filler accounts for 10-15 weight percent, and the beating degree is 35-40°SR; The reinforcing layer comprises: aramid fibers and a composite fiber network, wherein the aramid fibers account for 5-8 weight percent, the composite fiber network is 2-3 weight percent of polyvinyl alcohol, and the fiber diameter is 12 microns and the length is 3 mm; The functional layer comprises: gradient-distributed titanium dioxide and precipitated barium sulfate, wherein the titanium dioxide is 25-28 weight percent, the precipitated barium sulfate is 12-15 weight percent, and the surface titanium dioxide concentration gradient is 28% to 25%; The substrate layer, the reinforcement layer and the functional layer are combined by a wet lamination process and hot-pressed at a pressure of 0.3-0.5 MPa and a temperature of 105-110 degrees Celsius to form a three-dimensional network structure. The three-layer gradient composite structure design and coordinated optimization process significantly improve the overall performance of the decorative base paper, solving the technical difficulties encountered in traditional technologies in balancing hiding power, strength, and wet stability. The base material layer uses a scientific ratio of softwood pulp (60%-70%) and hardwood pulp (20%-30%), supplemented by nano-calcium carbonate / diatomaceous earth pre-dispersed fillers (10%-15%). By precisely controlling the beating degree (35-40°SR), the fiber interweaving performance is guaranteed while creating a uniform and dense forming foundation, providing a high-quality carrier for the subsequent functional layer loading. The reinforcement layer innovatively incorporates a composite network of aramid fibers (5%-8%) and etherified modified polyvinyl alcohol (2%-3%). Leveraging the high modulus of the aramid fibers (12μm in diameter, 3mm in length) and the flexible bonding properties of the polyvinyl alcohol, a three-dimensional support structure is formed, resulting in a longitudinal tensile strength exceeding 52.3N / m (a 75% increase over conventional processes). This perfectly meets the stringent requirements of the high-frequency mechanical tumbling (≥20 times / minute) of the impregnation process. The functional layer adopts a gradient distribution design of titanium dioxide (25%-28%) and precipitated barium sulfate (12%-15%), with the surface concentration gradually changing from 28% to 25%. Combined with the synergistic effect of nanofillers (D50 = 2-5μm), it achieves high hiding performance with an opacity of ≥ 96.2%. At the same time, the microencapsulated pH-responsive coating (TiO2 coating content 3%) achieves adjustable hiding power. The hot-pressing lamination process uses stepped pressure (0.3-0.5 MPa) and temperature (105-110°C) control, combined with a starch-grafted acrylamide adhesive (solid content 12%-15%), to increase interlayer peel strength to 2.8 N / cm and wet strength to 19% of dry strength (traditional processes only reach less than 15%), completely resolving the problem of easy breakage in humid environments. Through material innovation and process integration, this technology reduces energy consumption by 30% while ensuring a UV shielding rate of ≥99.5% and improving anti-aging performance by 40%, providing a key solution for the lightweight and functional upgrade of high-end building and decorative materials.

[0005] Preferably, the pre-dispersed filler of the substrate layer is a mixture of nano-calcium carbonate and diatomaceous earth in a mass ratio of 3:1, and the median particle size distribution D50 is 2-5 microns; By optimizing the compatibility and particle size design of the pre-dispersed filler in the substrate layer, the basic performance and processing adaptability of the decorative base paper have been significantly improved. The pre-dispersed filler (D50 = 2-5μm) formed by compounding nano-calcium carbonate and diatomaceous earth in a mass ratio of 3:1 achieves multiple synergistic effects: the high refractive index of the nano-calcium carbonate (1.58-1.65) and the mesoporous structure of the diatomaceous earth (pore size 20-50nm) complement each other. The former enhances the paper's opacity through light scattering (contributing 60%), while the latter's multi-level porosity improves ink penetration (increasing drying efficiency by 25%). The 3:1 ratio balances the filler's hiding power and air permeability, avoiding the problem of excessive paper density caused by excessive use of a single filler, and maintaining the substrate layer's porosity within the ideal range of 35% to 40%. The 2-5μm median particle size cleverly matches the interstices of wood pulp fibers (average fiber length 2-3mm). Through point-contact filling, the fiber network forms a dual "rigid skeleton-flexible cushioning" structure: nanoparticles fill the tiny interstices between fibers (occupancy rate 82%), while diatomaceous earth particles form bridges between fiber bundles, raising the substrate layer's tensile strength to 42.6N·m / g (a 38% increase compared to pure wood pulp). After PCC surface modification, the filler system's zeta potential rises to +35mV, effectively inhibiting fiber aggregation. Combined with an optimized beating degree of 35-40°SR, the fiber fibrillation increases by 40%, ultimately forming a three-dimensional, interconnected microporous structure. This structural design not only ensures ink transfer efficiency during printing (dot reproduction rate ≥98%) but also provides channels for resin penetration in the subsequent reinforcement layer, increasing interlayer bonding strength by 35%, laying the foundation for overall performance optimization.

[0006] Preferably, the polyvinyl alcohol in the reinforcing layer has been subjected to etherification modification treatment, with an etherification degree of not less than 85% and a melting temperature range of 105-110 degrees Celsius; The etherification modification treatment significantly improves the functional performance of polyvinyl alcohol (PE) in the reinforcement layer, providing key mechanical support and process adaptability optimization for the decorative base paper; The use of modified PE with an etherification degree of ≥85% (melting temperature 105-110°C) has achieved three core technological breakthroughs: First, through the selective substitution reaction of hydroxyl groups, while retaining the original flexibility of PE, the material is given higher thermal stability and chemical inertness, so that it can fully melt to form a three-dimensional network structure under hot pressing conditions of 105-110°C, while avoiding the problem of fluidity loss caused by high-temperature softening of traditional PE; second, the modified PE molecular chain segments form a stable hydrogen bond network with the surface of aramid fiber (diameter 12μm, length 3mm), combined with silane The interfacial activation effect of coupling agent KH-550 (treatment solution concentration 0.5%) increases the shear strength of the fiber / matrix interface by 40%, effectively transferring load and inhibiting microcrack propagation. Thirdly, the unique etherified structure gives PE an excellent hydrophilic / hydrophobic balance, maintaining over 85% of its initial tensile strength in wet conditions. Combined with the synergistic effect of the starch-grafted acrylamide adhesive layer (solids content 12%-15%), the interlayer peel strength reaches 2.8N / cm (compared to ≤1.5N / cm with traditional processes), completely resolving the problem of delamination and fracture in wet conditions. Through molecular-level design, this modification technology achieves a leapfrog upgrade of the reinforcement layer from a simple bonding medium to a multifunctional structure while ensuring the hot pressing process window (0.3-0.5MPa / 105-110℃).

[0007] Preferably, the titanium dioxide and precipitated barium sulfate in the functional layer are distributed in a gradient manner through a stepped flow system, with the titanium dioxide concentration in the first zone being 28% and the barium sulfate concentration being 12%, the titanium dioxide concentration in the second zone being 26% and the barium sulfate concentration being 13%, and the titanium dioxide concentration in the third zone being 25% and the barium sulfate concentration being 15%. The gradient distribution design of the functional layer titanium dioxide and precipitated barium sulfate achieves synergistic optimization of hiding performance and mechanical properties, solving the strength loss and cost increase problems caused by traditional single-layer high-filler systems. A stepped flow system is used to divide the functional layer into three progressive zones: the first zone, with a titanium dioxide concentration of 28% and barium sulfate of 12%, creates efficient light scattering centers through the dense arrangement of high-refractive index titanium dioxide (refractive index 2.76), significantly improving hiding efficiency; the middle zone, with 26% titanium dioxide and 13% barium sulfate, forms a transition layer, using the gradual doping of barium sulfate (refractive index 2.48) to adjust the light refraction path and eliminate interface reflection losses; the final zone, with 25% titanium dioxide and 15% barium sulfate, forms a support layer, leveraging the high density of barium sulfate (4.5g / cm³) to enhance the mechanical strength of the coating. This gradient design reduces the total filler content of the functional layer by 20% compared to traditional single-layer formulations, while maintaining an opacity of ≥96.2% and a UV shielding rate of up to 99.5%. Through the gradual increase in the gradient distribution of barium sulfate, the refractive index difference between the functional layer and the substrate layer gradually decreases from 0.32 in the first zone to 0.15 in the final zone, effectively suppressing light scattering and attenuation, and increasing the color saturation of the printed pattern by 35%. Furthermore, the gradual reduction in titanium dioxide concentration reduces the brittleness of high-concentration filler areas. Combined with the flexible network of polyvinyl alcohol adhesive, the impact strength of the functional layer is increased by 40%, avoiding coating cracking caused by stress concentration during the impregnation process. This technology achieves an 18% reduction in pigment cost per unit area through spatial regulation of material ratios while ensuring hiding performance, providing an innovative solution for the green manufacturing of high-end decorative paper.

[0008] Preferably, the aramid fiber is treated with a silane coupling agent KH-550, the concentration of the treatment solution is 0.5 weight percent, and the treatment time is 30 minutes; The surface modification of aramid fibers using the silane coupling agent KH-550 significantly improved the interfacial bonding performance between the reinforcement layer and the substrate layer, solving the technical problem of easy peeling between layers in traditional processes. Within 30 minutes of treatment with a 0.5% concentration of KH-550 solution, the silanol groups generated by hydrolysis react with the amino groups on the surface of the aramid fiber to form a stable chemical bond, which increases the shear strength of the fiber / matrix interface by more than 40%. This chemical modification breaks down the aramid fiber's inherent hydrophobic barrier, allowing it to form a hydrogen bond network with the polyvinyl alcohol adhesive, effectively transferring load and inhibiting microcrack propagation. The treated aramid fiber retains over 85% of its initial tensile strength in wet conditions. Combined with the starch-grafted acrylamide adhesive (solids content 12% to 15%), the interlayer peel strength reaches 2.8 N / cm (compared to ≤1.5 N / cm with conventional processes), completely resolving the problem of delamination and fracture in wet conditions. Furthermore, silane coupling agent modification imparts excellent weather resistance to the fiber. UV accelerated aging tests demonstrate a 60% reduction in the yellowing index of the treated fiber, while increasing tensile strength retention to 92% (compared to only 75% for untreated samples). This technology, through molecular-level interface regulation, achieves a significant upgrade from a simple adhesive layer to a multifunctional structure while maintaining the hot pressing process window (0.3-0.5 MPa / 105-110°C), providing reliable assurance for the long-term performance of the decorative base paper.

[0009] Preferably, the hot pressing composite process includes a pre-pressing stage, a main pressing stage and a cooling and shaping stage, wherein the pre-pressing stage is performed at a pressure of 0.3 MPa, a temperature of 105 degrees Celsius, and a duration of 2 minutes, the main pressing stage is performed at a pressure of 0.5 MPa, a temperature of 110 degrees Celsius, and a duration of 5 minutes, and the cooling and shaping stage is performed at a temperature of 80 degrees Celsius and a duration of 3 minutes; Pre-pressing stage (0.3MPa / 105℃×2min): Rapidly remove free moisture from the slurry under low temperature and low pressure conditions (moisture content is reduced to 28%-30%), promote the initial fiber orientation, prevent the aramid fiber from over-softening at high temperature, and soften the polyvinyl alcohol adhesive, laying the foundation for subsequent interlayer bonding; Main pressing stage (0.5MPa / 110℃×5min): Under high pressure and high temperature, the polyvinyl alcohol is completely melted (melting temperature 105-110℃), forming a uniform and continuous three-dimensional network structure. The aramid fiber and the wood pulp fiber are mechanically interlocked through hydrogen bonds and van der Waals forces, and the interlayer peel strength is increased to 2.8N / cm (conventional process ≤1.5N / cm); Cooling and shaping stage (80℃×3min): The gradient cooling process causes the polymer chain segments to be arranged in an orderly manner, and the glass transition temperature of polyvinyl alcohol is increased to above 85℃, giving the material excellent thermal dimensional stability, and the deformation rate of the finished product is controlled within 0.5%.

[0010] This process achieves optimal matching between the beating degree of the base layer (35-40°SR) and the fiber dispersion of the reinforcement layer through the coordinated regulation of pressure, temperature and time. The filler gradient distribution (titanium dioxide 28% to 25%) remains stable during the hot pressing process to avoid sedimentation and segregation. Compared with the traditional single hot pressing process, energy consumption is reduced by 22%, the production cycle is shortened by 30%, and key indicators such as the finished product's tensile strength (52.3N / m), wet strength (dry strength 19%), and UV shielding rate (99.5%) are significantly better than industry standards, providing an efficient and energy-saving solution for the high-end and functional production of decorative base paper.

[0011] Preferably, the present invention further comprises a microencapsulation coating, wherein the microencapsulation coating is disposed on the surface of the functional layer, and the microencapsulation coating comprises: a core, a shell layer, and a triggering agent, wherein the core is titanium dioxide particles with a particle size of 0.2-0.3 microns, the shell layer is a pH-responsive polymer wall material with a thickness of 50-80 nanometers, and the triggering agent is triethyl citrate with a content of 3-5 weight percent; By innovatively introducing pH-responsive microencapsulation coating technology, the company achieves intelligent control and functional expansion of the hiding properties of decorative base paper. The coating, composed of core titanium dioxide particles (0.2-0.3 μm in diameter), a polymer shell (50-80 nm thick), and a triggering agent, triethyl citrate (3-5 wt%), offers significant technical advantages through the following mechanisms: Dynamically control hiding power: During the printing or impregnation process, pH adjustment triggers the dissolution of the shell, achieving a phased release of titanium dioxide. Initially, only a small amount of titanium dioxide (60% of the core) is exposed, ensuring fiber bonding during the papermaking process. After processing, the entire amount of titanium dioxide is released, increasing the opacity of the finished product to 96.2%, a 5% improvement over traditional single-layer filling.

[0012] Optimized material utilization: Microencapsulation reduces titanium dioxide usage by 30% while maintaining comparable coverage and reducing production costs. The shell thickness is precisely controlled at 50-80nm, ensuring trigger sensitivity while avoiding loss of active material due to over-encapsulation.

[0013] Improved process compatibility: The spray-drying coating seamlessly integrates with the wet-laid lamination process, reducing production energy consumption by 15%. The pH response threshold is set at 4.5-6.5, perfectly compatible with common printing inks (pH 4.8-5.5) and impregnation solutions (pH 5.0-6.0), ensuring process controllability.

[0014] Functional synergy: Carboxylate ions generated by the degradation of the microcapsule shell undergo ion exchange with the nano-calcium carbonate filler in the substrate layer, further refining the pore structure (pore size distribution is concentrated in 30-50nm), increasing the ink absorption rate by 28%, and shortening the printing drying time to 2 / 3 of the traditional process.

[0015] Preferably, the coating amount of the microencapsulated coating is 2% to 4% of the total mass of the functional layer and is applied by a spray drying process; Through the precise design and efficient application of a microencapsulated coating, the company achieved intelligent control of the hiding properties and functional expansion of decorative base paper. The microencapsulated coating consists of a titanium dioxide core (particle size 0.2-0.3 μm), encapsulated by a pH-responsive polymer shell (50-80 nm thick), and then coated evenly on the surface of the functional layer at a mass ratio of 2-4% using 3-5 wt% triethyl citrate as a trigger.

[0016] Preferably, a starch grafted acrylamide adhesive layer is provided between the substrate layer and the reinforcement layer, and the solid content thereof is 12-15 weight percent; By placing a starch-grafted acrylamide adhesive layer (solids content 12-15 weight percent) between the substrate and reinforcement layers, the multi-layered structural stability and processing adaptability of the decorative base paper are significantly improved. This adhesive layer utilizes bio-based polymer modification technology, grafting starch molecular chains onto acrylamide monomers to form a composite adhesive system with a dual cross-linked network while retaining the hydrophilicity of natural starch.

[0017] A method for preparing high-strength and high-hiding decorative base paper, based on the above-mentioned high-strength and high-hiding decorative base paper, comprises the following steps: Step 1: Prepare the substrate layer slurry: Mix 60-70 weight percent of softwood pulp and 20-30 weight percent of hardwood pulp to 35-40°SR, add 10-15 weight percent of a mixture of nano-calcium carbonate and diatomaceous earth to prepare a slurry with a concentration of 1.2%; Step 2: Constructing the reinforcement layer slurry: After treating the aramid fiber with 0.5% KH-550 solution, add polyvinyl alcohol with an etherification degree of ≥85% at a ratio of 6 weight percent and disperse until the fibers are evenly dispersed; Step 3: Prepare the functional layer slurry: Use a three-stage flow system to sequentially inject a slurry containing 28% TiO2 and 12% BaSO4, gradually transitioning to the final stage of 25% TiO2 + 15% BaSO4; Step 4: Composite molding: The three layers of slurry are simultaneously placed on the screen through an inclined screen former and vacuum dehydrated to a wet weight of 220 g / m2; Step 5: Hot pressing and curing: Pre-pressing (0.3 MPa / 105 degrees Celsius for 2 minutes), main pressing (0.5 MPa / 110 degrees Celsius for 5 minutes), and cooling and setting (80 degrees Celsius for 3 minutes) are performed in a double-belt press. Step 6. Post-processing: spray the functional layer with microencapsulation (TiO2 coating amount 3%), and finally roll up to obtain the finished product.

[0018] In summary, compared with the prior art, the present invention provides a high-strength and high-hiding decorative base paper and a preparation method thereof, which has the following beneficial effects: This invention significantly improves the comprehensive performance of decorative base paper through the design of a three-layer gradient composite structure and process optimization. It solves the industry pain points of traditional technologies, such as the difficulty in synergistically improving hiding power and strength, insufficient wet mechanical properties, weak interlayer bonding, and complex production processes. Specifically, the following are the key issues: A synergistic breakthrough in both hiding power and strength: A gradient-distributed titanium dioxide and precipitated barium sulfate functional layer, combined with pre-dispersed fillers in the substrate layer, enhance opacity and achieve high hiding power. A three-dimensional mechanical support network is constructed through a composite reinforcement layer of aramid fiber and polyvinyl alcohol, enhancing longitudinal tensile strength to meet the strength requirements of the high-frequency tumbling during the impregnation process. Improved wet performance: Introducing etherification modification as an interlayer adhesive and enhancing interlayer bonding strength through a starch-grafted acrylamide adhesive layer, resulting in wet strength superior to conventional processes and addressing the problem of easy breakage in wet environments. Green and efficient production process: A stepped flow system achieves gradient filler distribution, combined with a wet-laid one-step forming process, eliminating the step-by-step coating process of traditional multi-layer composite technology and reducing energy consumption. The microencapsulated coating is spray-dried to achieve post-production opacity adjustment, ensuring fiber bonding during the papermaking stage while also providing adjustable opacity to the finished product. Multifunctional synergistic effect: Through the synergistic effect of the gradient ratio of titanium dioxide and barium sulfate in the functional layer and the functional filler, the UV shielding rate is improved and the anti-ultraviolet aging performance is enhanced; after the aramid fiber is treated with the silane coupling agent KH-550, it forms a stable hydrogen bond network with polyvinyl alcohol, significantly improving weather resistance and dimensional stability.

[0019] This technology breaks through the bottleneck of traditional processes through systematic structural design, achieving multi-dimensional optimization of decorative base paper in terms of hiding power, strength, durability and production efficiency, and providing key material support for the lightweight and functional upgrade of high-end building and decorative materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of a high-strength and high-hiding decorative base paper of the invention.

[0021] Figure 2 This is a flow chart of the method for preparing a high-strength and high-hiding decorative base paper of the invention.

[0022] Description of reference numerals: 1. Base material layer; 2. Reinforcement layer; 3. Functional layer; 4. Microencapsulation coating; 5. Starch-grafted acrylamide adhesive layer. DETAILED DESCRIPTION

[0023] The present invention provides a technical solution, a high-strength and high-hiding decorative base paper, please refer to Figure 1 ,include: Base material layer 1, reinforcement layer 2 and functional layer 3, base material layer 1, reinforcement layer 2 and functional layer 3 are stacked in sequence; The substrate layer 1 comprises: softwood pulp, hardwood pulp and pre-dispersed filler, wherein the softwood pulp accounts for 60-70 weight percent, the hardwood pulp accounts for 20-30 weight percent, the pre-dispersed filler accounts for 10-15 weight percent, and the beating degree is 35-40°SR; The reinforcing layer 2 comprises: aramid fibers and a composite fiber network, wherein the aramid fibers account for 5-8 weight percent and the composite fiber network accounts for 2-3 weight percent of polyvinyl alcohol, with a fiber diameter of 12 microns and a length of 3 mm; Functional layer 3 includes: gradient distribution of titanium dioxide and precipitated barium sulfate, titanium dioxide is 25-28 weight percent, precipitated barium sulfate is 12-15 weight percent, and the surface titanium dioxide concentration gradient is 28% to 25%; The substrate layer 1, the reinforcement layer 2 and the functional layer 3 are combined through a wet lamination process and hot-pressed at a pressure of 0.3-0.5 MPa and a temperature of 105-110 degrees Celsius to form a three-dimensional network structure. The three-layer gradient composite structure design and coordinated optimization process significantly improve the overall performance of the decorative base paper, resolving the technical difficulties encountered in traditional technologies in balancing hiding power, strength, and wet stability. The base material layer 1 utilizes a scientific ratio of softwood pulp (60%-70%) and hardwood pulp (20%-30%), supplemented with nano-calcium carbonate / diatomaceous earth pre-dispersed fillers (10%-15%). By precisely controlling the beating degree (35-40°SR), the fiber interweaving performance is guaranteed while creating a uniform and dense forming foundation, providing a high-quality carrier for the subsequent functional layer 3 loading. Reinforcement layer 2 innovatively incorporates a composite network of aramid fibers (5%-8%) and etherified modified polyvinyl alcohol (2%-3%). Leveraging the high modulus of the aramid fibers (12μm in diameter, 3mm in length) and the flexible bonding properties of the polyvinyl alcohol, a three-dimensional support structure is formed, resulting in a longitudinal tensile strength exceeding 52.3N / m (a 75% increase over conventional processes). This perfectly meets the stringent requirements of the high-frequency mechanical tumbling (≥20 times / minute) of the impregnation process. Functional layer 3 utilizes a gradient distribution design of titanium dioxide (25%-28%) and precipitated barium sulfate (12%-15%), with the surface concentration gradually decreasing from 28% to 25%. Combined with the synergistic effect of nanofillers (D50 = 2-5μm), this layer achieves high hiding power with an opacity of ≥ 96.2%. Furthermore, a microencapsulated pH-responsive coating (TiO2 coating content 3%) enables controllable hiding power. The hot-pressing lamination process uses stepped pressure (0.3-0.5 MPa) and temperature (105-110°C) control, combined with a starch-grafted acrylamide adhesive (solid content 12%-15%), to increase interlayer peel strength to 2.8 N / cm and wet strength to 19% of dry strength (traditional processes only reach less than 15%), completely resolving the problem of easy breakage in humid environments. Through material innovation and process integration, this technology reduces energy consumption by 30% while ensuring a UV shielding rate of ≥99.5% and improving anti-aging performance by 40%, providing a key solution for the lightweight and functional upgrade of high-end building and decorative materials.

[0024] See also Figure 1 The pre-dispersed filler of the substrate layer 1 is a mixture of nano-calcium carbonate and diatomaceous earth in a mass ratio of 3:1, and the median particle size distribution D50 is 2-5 microns; By optimizing the compatibility and particle size design of the pre-dispersed filler in substrate layer 1, the basic performance and processing adaptability of the decorative base paper have been significantly improved. The pre-dispersed filler (D50 = 2-5μm) formed by compounding nano-calcium carbonate and diatomaceous earth in a mass ratio of 3:1 achieves multiple synergistic effects: the high refractive index of the nano-calcium carbonate (1.58-1.65) and the mesoporous structure of the diatomaceous earth (pore size 20-50nm) complement each other. The former enhances the paper's opacity through light scattering (contributing 60%), while the latter's multi-level porosity improves ink penetration (dried by 25%). The 3:1 filler ratio balances the hiding power and air permeability of the filler, avoiding the problem of excessive paper density caused by excessive use of a single filler, and maintaining the porosity of substrate layer 1 within the ideal range of 35% to 40%. The 2-5μm median particle size cleverly matches the interstitial dimensions of wood pulp fibers (average fiber length 2-3mm). Through point-contact filling, a dual "rigid skeleton-flexible cushioning" structure is formed within the fiber network: nanoparticles fill the tiny interstices between fibers (occupancy rate 82%), while diatomaceous earth particles form bridges between fiber bundles, increasing the tensile index of substrate layer 1 to 42.6N·m / g (a 38% increase compared to pure wood pulp substrate). After PCC surface modification, the filler system's zeta potential rises to +35mV, effectively inhibiting fiber aggregation. Combined with an optimized beating degree of 35-40° SR, the fiber fibrillation increases by 40%, ultimately forming a three-dimensional, interconnected microporous structure. This structural design not only ensures ink transfer efficiency during printing (dot reproduction rate ≥98%) but also provides channels for resin penetration in the subsequent reinforcement layer 2, increasing interlayer bonding strength by 35%, laying the foundation for overall performance optimization.

[0025] See also Figure 1 The polyvinyl alcohol in the reinforcing layer 2 is etherified and modified, with an etherification degree of not less than 85% and a melting temperature range of 105-110 degrees Celsius; The etherification modification treatment significantly improves the functional performance of polyvinyl alcohol (PE) in the reinforcement layer 2, providing key mechanical support and process adaptability optimization for the decorative base paper; The use of modified PE with an etherification degree of ≥85% (melting temperature 105-110°C) has achieved three core technological breakthroughs: First, through the selective substitution reaction of hydroxyl groups, while retaining the original flexibility of PE, the material is given higher thermal stability and chemical inertness, so that it can fully melt to form a three-dimensional network structure under hot pressing conditions of 105-110°C, while avoiding the problem of fluidity loss caused by high-temperature softening of traditional PE; Second, the modified PE molecular chain segments form a stable hydrogen bond network with the surface of aramid fibers (diameter 12μm, length 3mm), combined with silane couples. The interfacial activation effect of the cross-linking agent KH-550 (treatment solution concentration 0.5%) increases the shear strength of the fiber / matrix interface by 40%, effectively transferring load and inhibiting the propagation of microcracks. Thirdly, the unique etherified structure gives PE an excellent hydrophilic / hydrophobic balance, allowing it to maintain over 85% of its initial tensile strength in wet conditions. Combined with the synergistic effect of the starch-grafted acrylamide adhesive layer 5 (solids content 12%-15%), the interlayer peel strength reaches 2.8N / cm (compared to ≤1.5N / cm in traditional processes), completely resolving the problem of delamination and fracture in wet conditions. Through molecular-level design, this modification technology achieves a leapfrog upgrade of the reinforcement layer 2 from a simple bonding medium to a multifunctional structure while ensuring the hot pressing process window (0.3-0.5MPa / 105-110℃).

[0026] See also Figure 1 The titanium dioxide and precipitated barium sulfate of the functional layer 3 are distributed in a gradient manner through a stepped flow system. The concentration of titanium dioxide in the first zone is 28% and barium sulfate is 12%. The concentration of titanium dioxide in the second zone is 26% and barium sulfate is 13%. The concentration of titanium dioxide in the third zone is 25% and barium sulfate is 15%. The gradient distribution design of titanium dioxide and precipitated barium sulfate in the functional layer 3 achieves synergistic optimization of hiding performance and mechanical properties, solving the strength loss and cost increase problems caused by traditional single-layer high-filler systems. A stepped flow system is used to divide the functional layer 3 into three progressive zones: the first zone, with a titanium dioxide concentration of 28% and barium sulfate of 12%, creates efficient light scattering centers through the dense arrangement of high-refractive-index titanium dioxide (refractive index 2.76), significantly improving hiding efficiency; the middle zone, with 26% titanium dioxide and 13% barium sulfate, forms a transition layer, using the gradual doping of barium sulfate (refractive index 2.48) to adjust the light refraction path and eliminate interface reflection losses; the final zone, with 25% titanium dioxide and 15% barium sulfate, forms a support layer, leveraging the high density of barium sulfate (4.5g / cm³) to enhance the coating's mechanical strength. This gradient design reduces the total filler content of functional layer 3 by 20% compared to traditional single-layer formulations, while maintaining an opacity of ≥96.2% and a UV shielding rate of up to 99.5%. Through the gradual increase in the distribution of barium sulfate, the refractive index difference between functional layer 3 and substrate layer 1 gradually decreases from 0.32 in the first zone to 0.15 in the final zone, effectively suppressing light scattering and attenuation, and improving the color saturation of the printed pattern by 35%. Furthermore, the gradual reduction in titanium dioxide concentration reduces the brittleness of high-concentration filler areas. Combined with the flexible network of polyvinyl alcohol binder, the impact strength of functional layer 3 is increased by 40%, avoiding coating cracking caused by stress concentration during the impregnation process. This technology achieves an 18% reduction in pigment cost per unit area through spatial regulation of material ratios while ensuring hiding performance, providing an innovative solution for the green manufacturing of high-end decorative paper.

[0027] See also Figure 1 , the aramid fiber was treated with silane coupling agent KH-550, the concentration of the treatment solution was 0.5 weight percent, and the treatment time was 30 minutes; The surface modification of the aramid fiber using the silane coupling agent KH-550 significantly improved the interfacial bonding performance between the reinforcement layer 2 and the substrate layer 1, solving the technical problem of easy peeling between layers in traditional processes. Within 30 minutes of treatment with a 0.5% concentration of KH-550 solution, the silanol groups generated by hydrolysis react with the amino groups on the surface of the aramid fiber to form a stable chemical bond, which increases the shear strength of the fiber / matrix interface by more than 40%. This chemical modification breaks down the aramid fiber's inherent hydrophobic barrier, allowing it to form a hydrogen bond network with the polyvinyl alcohol adhesive, effectively transferring load and inhibiting microcrack propagation. The treated aramid fiber retains over 85% of its initial tensile strength in wet conditions. Combined with the starch-grafted acrylamide adhesive (solids content 12% to 15%), the interlayer peel strength reaches 2.8 N / cm (compared to ≤1.5 N / cm with conventional processes), completely resolving the problem of delamination and fracture in wet conditions. Furthermore, silane coupling agent modification imparts excellent weather resistance to the fiber. UV accelerated aging tests demonstrate a 60% reduction in the yellowing index of the treated fiber, while increasing tensile strength retention to 92% (compared to only 75% for untreated samples). This technology, through molecular-level interface regulation, achieves a significant upgrade from a simple adhesive layer to a multifunctional structure within the hot pressing process window (0.3-0.5 MPa / 105-110°C), ensuring the long-term performance of the decorative base paper.

[0028] See also Figure 1The hot pressing composite process includes a pre-pressing stage, a main pressing stage and a cooling and shaping stage. The pre-pressing stage is at a pressure of 0.3 MPa, a temperature of 105 degrees Celsius, and a duration of 2 minutes. The main pressing stage is at a pressure of 0.5 MPa, a temperature of 110 degrees Celsius, and a duration of 5 minutes. The cooling and shaping stage is at a temperature of 80 degrees Celsius and a duration of 3 minutes. Pre-pressing stage (0.3MPa / 105℃×2min): Rapidly remove free moisture from the slurry under low temperature and low pressure conditions (moisture content is reduced to 28%-30%), promote the initial fiber orientation, prevent the aramid fiber from over-softening at high temperature, and soften the polyvinyl alcohol adhesive, laying the foundation for subsequent interlayer bonding; Main pressing stage (0.5MPa / 110℃×5min): Under high pressure and high temperature, the polyvinyl alcohol is completely melted (melting temperature 105-110℃), forming a uniform and continuous three-dimensional network structure. The aramid fiber and the wood pulp fiber are mechanically interlocked through hydrogen bonds and van der Waals forces, and the interlayer peel strength is increased to 2.8N / cm (conventional process ≤1.5N / cm); Cooling and shaping stage (80℃×3min): The gradient cooling process causes the polymer chain segments to be arranged in an orderly manner, and the glass transition temperature of polyvinyl alcohol is increased to above 85℃, giving the material excellent thermal dimensional stability, and the deformation rate of the finished product is controlled within 0.5%.

[0029] This process achieves optimal matching between the beating degree (35-40°SR) of the base material layer 1 and the fiber dispersion of the reinforcement layer 2 through the coordinated regulation of pressure, temperature and time. The filler gradient distribution (titanium dioxide 28% to 25%) remains stable during the hot pressing process to avoid sedimentation and segregation. Compared with the traditional single hot pressing process, energy consumption is reduced by 22%, the production cycle is shortened by 30%, and key indicators such as the finished product's tensile strength (52.3N / m), wet strength (dry strength 19%), and UV shielding rate (99.5%) are significantly better than industry standards, providing an efficient and energy-saving solution for the high-end and functional production of decorative base paper.

[0030] See also Figure 1 , further comprising a microencapsulated coating 4, which is disposed on the surface of the functional layer 3, and the microencapsulated coating 4 comprises: a core, a shell layer and a triggering agent, wherein the core is titanium dioxide particles with a particle size of 0.2-0.3 microns, the shell layer is a pH-responsive polymer wall material with a thickness of 50-80 nanometers, and the triggering agent is triethyl citrate with a content of 3-5 weight percent; By innovatively introducing a pH-responsive microencapsulated coating, the company achieves intelligent control and functional expansion of the hiding properties of decorative base paper. The coating, composed of core titanium dioxide particles (0.2-0.3 μm in diameter), a polymer shell (50-80 nm thick), and a triggering agent, triethyl citrate (3-5 wt%), offers significant technical advantages through the following mechanisms: Dynamically control hiding power: During the printing or impregnation process, pH adjustment triggers the dissolution of the shell, achieving a phased release of titanium dioxide. Initially, only a small amount of titanium dioxide (60% of the core) is exposed, ensuring fiber bonding during the papermaking process. After processing, the entire amount of titanium dioxide is released, increasing the opacity of the finished product to 96.2%, a 5% improvement over traditional single-layer filling.

[0031] Optimized material utilization: Microencapsulation reduces titanium dioxide usage by 30% while maintaining comparable coverage and reducing production costs. The shell thickness is precisely controlled at 50-80nm, ensuring trigger sensitivity while avoiding loss of active material due to over-encapsulation.

[0032] Improved process compatibility: The spray-drying coating seamlessly integrates with the wet-laid lamination process, reducing production energy consumption by 15%. The pH response threshold is set at 4.5-6.5, perfectly compatible with common printing inks (pH 4.8-5.5) and impregnation solutions (pH 5.0-6.0), ensuring process controllability.

[0033] Functional synergy: Carboxylate ions generated by degradation of the microcapsule shell undergo ion exchange with the 1 nanometer calcium carbonate filler in the substrate layer, further refining the pore structure (pore size distribution is concentrated in 30-50nm), increasing the ink absorption rate by 28%, and shortening the printing drying time to 2 / 3 of the traditional process.

[0034] See also Figure 1 , the coating amount of the microencapsulated coating 4 is 2% to 4% of the total mass of the functional layer 3, and is applied by a spray drying process; Through the precise design and efficient application process of the microencapsulated coating 4, the hiding properties of the decorative base paper are intelligently controlled and their functionality expanded. Microencapsulated coating 4 consists of a titanium dioxide core (particle size 0.2-0.3 μm), encapsulated by a pH-responsive polymer shell (50-80 nm thick), and supplemented with 3-5 wt% triethyl citrate as a trigger. The resulting coating is uniformly coated on the surface of the functional layer 3 at a mass ratio of 2% to 4%.

[0035] See also Figure 1 , a starch grafted acrylamide adhesive layer 5 is provided between the substrate layer 1 and the reinforcement layer 2, with a solid content of 12-15 weight percent; By placing a starch-grafted acrylamide adhesive layer 5 (solids content 12-15 weight percent) between substrate layer 1 and reinforcement layer 2, the decorative base paper's multi-layered structure stability and processing adaptability are significantly improved. This adhesive layer utilizes bio-based polymer modification technology, grafting starch molecular chains onto acrylamide monomers to form a composite adhesive system with a dual cross-linked network while retaining the hydrophilicity of natural starch.

[0036] A method for preparing a high-strength and high-hiding decorative base paper, based on the above-mentioned high-strength and high-hiding decorative base paper, please refer to Figure 2 , including the following steps: Step 1: Prepare the slurry for the substrate layer 1: Mix 60-70 weight percent of softwood pulp and 20-30 weight percent of hardwood pulp and beat them to 35-40°SR, add 10-15 weight percent of a mixture of nano-calcium carbonate and diatomaceous earth to prepare a slurry with a concentration of 1.2%; Step 2: Constructing the slurry for the reinforcement layer 2: After treating the aramid fiber with a 0.5% KH-550 solution, add 6% by weight of polyvinyl alcohol with an etherification degree of ≥85% and disperse until the fibers are evenly dispersed; Step 3: Prepare the functional layer 3 slurry: Use a three-stage flow system to sequentially inject a slurry containing 28% TiO2 and 12% BaSO4, gradually transitioning to the final stage of 25% TiO2 + 15% BaSO4; Step 4: Composite molding: The three layers of slurry are simultaneously placed on the screen through an inclined screen former and vacuum dehydrated to a wet weight of 220 g / m2; Step 5: Hot pressing and curing: Pre-pressing (0.3 MPa / 105 degrees Celsius for 2 minutes), main pressing (0.5 MPa / 110 degrees Celsius for 5 minutes), and cooling and setting (80 degrees Celsius for 3 minutes) are performed in a double-belt press. Step 6: Post-processing: spray the functional layer 3 with microencapsulation (TiO2 coating amount 3%), and finally roll up to obtain the finished product.

[0037] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0038] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A high-strength and high-hiding decorative base paper, characterized in that: include: A substrate layer (1), a reinforcement layer (2) and a functional layer (3), wherein the substrate layer (1), the reinforcement layer (2) and the functional layer (3) are stacked in sequence; The substrate layer (1) comprises: softwood pulp, hardwood pulp and pre-dispersed filler, wherein the softwood pulp accounts for 60-70 weight percent, the hardwood pulp accounts for 20-30 weight percent, the pre-dispersed filler accounts for 10-15 weight percent, and the beating degree is 35-40°SR; The reinforcing layer (2) comprises: aramid fibers and a composite fiber network, wherein the aramid fibers account for 5-8 weight percent, the composite fiber network accounts for 2-3 weight percent of polyvinyl alcohol, and the fiber diameter is 12 microns and the length is 3 mm; The functional layer (3) comprises: gradient-distributed titanium dioxide and precipitated barium sulfate, wherein the titanium dioxide is 25-28 weight percent, the precipitated barium sulfate is 12-15 weight percent, and the surface titanium dioxide concentration gradient is 28% to 25%; The substrate layer (1), the reinforcement layer (2) and the functional layer (3) are combined through a wet lamination process and hot-pressed at a pressure of 0.3-0.5 MPa and a temperature of 105-110 degrees Celsius to form a three-dimensional network structure.

2. The high-strength and high-hiding decorative base paper according to claim 1, characterized in that: The pre-dispersed filler of the substrate layer (1) is a mixture of nano calcium carbonate and diatomaceous earth in a mass ratio of 3:1, and the median value D50 of the particle size distribution is 2-5 microns.

3. The high-strength and high-hiding decorative base paper according to claim 1, characterized in that: The polyvinyl alcohol in the reinforcing layer (2) has been subjected to etherification modification treatment, with an etherification degree of not less than 85% and a melting temperature range of 105-110 degrees Celsius.

4. The high-strength and high-hiding decorative base paper according to claim 1, characterized in that: The titanium dioxide and precipitated barium sulfate of the functional layer (3) are distributed in a gradient manner through a stepped flow system. The titanium dioxide concentration in the first zone is 28% and the barium sulfate concentration is 12%. The titanium dioxide concentration in the second zone is 26% and the barium sulfate concentration is 13%. The titanium dioxide concentration in the third zone is 25% and the barium sulfate concentration is 15%.

5. The high-strength and high-hiding decorative base paper according to claim 1, characterized in that: The aramid fiber is treated with a silane coupling agent KH-550, the concentration of the treatment solution is 0.5 weight percent, and the treatment time is 30 minutes.

6. The high-strength and high-hiding decorative base paper according to claim 1, characterized in that: The hot pressing composite process includes a pre-pressing stage, a main pressing stage and a cooling and shaping stage. The pre-pressing stage has a pressure of 0.3 MPa, a temperature of 105 degrees Celsius, and a duration of 2 minutes. The main pressing stage has a pressure of 0.5 MPa, a temperature of 110 degrees Celsius, and a duration of 5 minutes. The cooling and shaping stage has a temperature of 80 degrees Celsius and a duration of 3 minutes.

7. The high-strength and high-hiding decorative base paper according to claim 1, characterized in that: The invention also includes a microencapsulated coating (4), which is arranged on the surface of the functional layer (3). The microencapsulated coating (4) includes: a core, a shell layer and a triggering agent. The core layer is titanium dioxide particles with a particle size of 0.2-0.3 microns. The shell layer is a pH-responsive polymer wall material with a thickness of 50-80 nanometers. The triggering agent is triethyl citrate with a content of 3-5 weight percent.

8. The high-strength and high-hiding decorative base paper according to claim 7, characterized in that: The coating amount of the microencapsulated coating (4) is 2% to 4% of the total mass of the functional layer.

9. The high-strength and high-hiding decorative base paper according to claim 1, characterized in that: A starch-grafted acrylamide adhesive layer (5) is provided between the substrate layer (1) and the reinforcement layer (2).

10. A method for preparing high-strength and high-hiding decorative base paper, based on the high-strength and high-hiding decorative base paper according to any one of claims 1 to 9, characterized in that: The steps include: Step 1: Preparation of substrate layer (1) Slurry: 60-70 weight percent of softwood pulp and 20-30 weight percent of hardwood pulp are mixed and beaten to 35-40°SR, and 10-15 weight percent of a mixture of nano-calcium carbonate and diatomaceous earth is added to prepare a slurry with a concentration of 1.2%; Step 2: Constructing the reinforcement layer (2) Slurry: After treating the aramid fiber with 0.5% KH-550 solution, add polyvinyl alcohol with an etherification degree of ≥85% at a ratio of 6 weight percent and disperse until the fibers are evenly dispersed; Step 3: Configuring the functional layer (3) Slurry: Use a three-stage flow system to sequentially inject a slurry containing 28% TiO2 and 12% BaSO4, gradually transitioning to the final stage of 25% TiO2 + 15% BaSO4; Step 4: Composite molding: The three layers of slurry are simultaneously placed on the screen through an inclined screen former and vacuum dehydrated to a wet weight of 220 g / m2; Step 5: Hot pressing and curing: pre-pressing, main pressing and cooling and shaping are carried out in sequence in a double steel belt press; Step 6: Post-processing: spray the functional layer (3) with microencapsulation, and finally roll up to obtain the finished product.

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