Low-transmission tensile decorative paper and preparation process thereof

Abstract

The application provides a low-transparency tensile decorative paper and a preparation process, and ingredients of the decorative paper include the following raw materials in parts by weight: bamboo pulp fiber 55-65 parts, nano inorganic composite modifier 8-12 parts, bio-based macromolecular composite reinforcing agent 4-6 parts, microencapsulated functional barrier agent 3-5 parts and papermaking functional additive 2.8-4.6 parts; wherein the bio-based macromolecular composite reinforcing agent contains polyamide-epichlorohydrin three-dimensional network and sodium alginate. The application obtains basic tensile strength and wet-state structure stability by relying on the polyamide-epichlorohydrin three-dimensional network, and the sodium alginate and the three-dimensional network construct a 'hydrogen bond-chemical crosslinking' structure, which strengthens the dry and wet tensile strength of the decorative paper; the hydrophilic group of the sodium alginate can also combine with the bamboo pulp fiber and fill the pores, and cooperate with other additives to reduce light and air transmission, thereby improving the low-transparency of the decorative paper.

Description

Technical Field

[0001] This invention relates to the field of decorative paper technology, specifically to a low-permeability, high-tensile decorative paper and its preparation process. Background Technology

[0002] Decorative paper is widely used in furniture manufacturing, interior decoration and other fields because it combines aesthetics and practicality. The market is constantly raising its performance requirements. It not only needs to have good tensile strength to cope with the stretching during processing and use, but also needs excellent low permeability to block light and air and prevent the substrate from getting damp and discolored. At the same time, environmental protection attributes have also become an important consideration.

[0003] Currently, the industry often improves the performance of decorative paper by adding chemically synthesized reinforcing agents and barrier agents. However, most of these additives are non-bio-based, which makes it difficult to meet the current concept of energy conservation and environmental protection. They also have limitations in synergistic performance improvement and cannot simultaneously achieve efficient optimization of tensile strength and low permeability.

[0004] In terms of tensile strength, existing decorative papers rely heavily on single chemical cross-linking agents, resulting in low structural stability in the wet state and significant differences in tensile strength between the dry and wet states. Regarding improving permeability, single barrier agents are insufficient to effectively fill inter-fiber pores and block transmission channels, leading to problems such as light and air permeation. Therefore, improvements to the design of existing decorative papers are necessary. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a low-permeability tensile decorative paper and its preparation process, so that the decorative paper has strong dry and wet tensile strength and excellent low permeability.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This application discloses a low-permeability, high-tensile decorative paper. By weight, the decorative paper comprises the following raw materials: 55-65 parts bamboo pulp fiber, 8-12 parts nano-inorganic composite modifier, 4-6 parts bio-based polymer composite reinforcing agent, 3-5 parts microencapsulated functional barrier agent, and 2.8-4.6 parts papermaking functional additives; wherein the bio-based polymer composite reinforcing agent contains a polyamide-epoxychloropropane three-dimensional network and sodium alginate.

[0008] By setting up the above technical solution, the polyamide-epoxychloropropane three-dimensional network in the bio-based polymer composite reinforcing agent provides basic tensile strength support for decorative paper and improves structural stability under wet conditions. Sodium alginate contains a large number of carboxyl groups, which can form hydrogen bonds with the amino groups of polyamide on the one hand, and undergo ring-opening crosslinking reaction with the epoxy groups of epichlorohydrin on the other hand. The linear polymer chains of sodium alginate are interspersed in the three-dimensional network of polyamide-epoxychloropropane, which not only enriches the binding sites inside the bio-based polymer composite reinforcing agent, but also constructs a denser "hydrogen bond-chemical crosslinking" dual binding structure, thereby strengthening the dry and wet tensile strength of decorative paper. Meanwhile, the hydrophilic groups of sodium alginate can interact closely with the hydroxyl groups of bamboo pulp fibers, helping to fill the tiny pores between fibers. Combined with the "maze effect" of the nano-inorganic composite modifier and the capsule wall blocking effect of the microencapsulated functional barrier agent, it further reduces the transmission channels of light and air, forming a synergistic improvement effect on the low permeability of decorative paper. Moreover, both sodium alginate and polyamide are bio-based components, and their combination also continues the environmentally friendly properties of the composite reinforcing agent, which is in line with the concept of energy conservation and environmental protection.

[0009] Preferably, the papermaking functional additive comprises the following raw materials in parts by weight of total components: 1.5-2.5 parts of water-based wet strength agent, 0.8-1.2 parts of dispersant, 0.3-0.5 parts of lubricant and 0.2-0.4 parts of defoamer.

[0010] By setting up the above technical solutions, the water-based wet strength agent can form chemical bonds with bamboo pulp fiber and bio-based polymer composite reinforcing agent through active groups, reducing the strength decay of paper when exposed to water; the dispersant can prevent the agglomeration of functional particles by means of electrostatic repulsion and steric hindrance, ensuring the uniform distribution of each component; the lubricant can reduce the friction between fibers and between fibers and equipment, improving the smoothness of paper forming in the process of making decorative paper; the defoamer can destroy micro-bubbles in pulp preparation and coating, avoiding pinholes, pits and other phenomena in paper, ensuring the structural density and surface smoothness of decorative paper, and laying a good foundation for the stable performance of low transparency, tensile strength and other properties.

[0011] Preferably, the water-based wet strength agent is at least one of polyamide epichlorohydrin resin, melamine formaldehyde resin, or polyethyleneimine; the dispersant is at least one of sodium polyacrylate, polyethylene oxide, or maleic anhydride copolymer; the lubricant is at least one of calcium stearate, zinc stearate, or polyethylene wax; and the defoamer is at least one of polyether-modified silicone, mineral oil, or polyethylene glycol.

[0012] By setting up the above technical solutions, in the water-based wet strength agent, polyamide epichlorohydrin resin, melamine formaldehyde resin, or polyethyleneimine all contain active groups, which can form chemical bonds with the hydroxyl groups in bamboo pulp fibers and the functional groups in bio-based polymer composite reinforcing agents, effectively improving the wet tensile strength of paper; in the dispersant, sodium polyacrylate, polyethylene oxide, or maleic anhydride copolymer have high molecular chain segment and charge characteristics, which can prevent the agglomeration of functional particles through steric hindrance or electrostatic repulsion, ensuring uniform dispersion of each component; in the lubricant, calcium stearate, zinc stearate, or polyethylene wax can adhere to the surface of bamboo pulp fibers and particles, reducing interfacial friction and making the papermaking process smooth; in the defoamer, polyether-modified organosilicon, mineral oil, or polyethylene glycol can quickly destroy the interfacial tension of bubbles, eliminate microbubbles in pulp preparation and coating, and avoid paper defects, all of which together provide support for the core properties of decorative paper such as low permeability and tensile strength, as well as process stability.

[0013] Preferably, the nano-inorganic composite modifier comprises the following raw materials in parts by weight: 30-35 parts of nano-titanium dioxide, 10-15 parts of sodium montmorillonite, 2-4 parts of silane coupling agent KH-570, and 55-75 parts of deionized water.

[0014] The preparation method of the nano-inorganic composite modifier is as follows: Sodium-based montmorillonite is added to deionized water and stirred at 800-1000 r / min for 30-35 min. After heating to 60-70℃, silane coupling agent KH-570 is added and stirring is continued for 20-25 min. Then, nano-titanium dioxide is slowly added and dispersed at 2000-2500 r / min for 40-50 min. Finally, the mixture is ultrasonically treated at a power of 600-700W for 30-35 min, and the particle size is controlled to be ≤100nm to obtain the nano-inorganic composite modifier.

[0015] By setting up the above technical solution, sodium montmorillonite is fully dispersed in deionized water to form a stable suspension. The active groups of the silane coupling agent KH-570 react fully with the hydroxyl groups on the surface of sodium montmorillonite, improving the compatibility of sodium montmorillonite with the organic phase. High-speed dispersion can effectively prevent the agglomeration of nano-titanium dioxide, making it uniformly dispersed in the sodium montmorillonite-containing system. Finally, ultrasonic dispersion further refines the system particles and strengthens the synergistic effect of the "maze effect" of sodium montmorillonite sheets and the visible light reflectance of nano-titanium dioxide. The resulting nano-inorganic composite modifier can effectively reduce the light transmittance of decorative paper, improve tensile strength, and enhance the interfacial bonding with bamboo pulp fiber and other components.

[0016] Preferably, the bio-based polymer composite reinforcing agent comprises the following raw materials in parts by weight: 10-15 parts polyamide, 12-16 parts epichlorohydrin, 3-6 parts sodium hydroxide, 0.5-1.5 parts sodium alginate, and 70-85 parts deionized water.

[0017] The preparation method of the bio-based polymer composite reinforcing agent is as follows: polyamide and sodium alginate are dissolved together in deionized water, stirred at 300-500 r / min for 15-20 min, heated to 50-60℃, epichlorohydrin is added dropwise over 1-1.5 h, sodium hydroxide is added to adjust the pH to 8-9, the reaction is kept at this temperature for 2-2.5 h, cooled to room temperature, and then filtered through a 200-300 mesh filter to obtain the bio-based polymer composite reinforcing agent.

[0018] By setting up the above technical solution, the polyamide containing amino groups and the sodium alginate containing carboxyl groups can be dissolved together in deionized water, achieving uniform mixing and creating conditions for subsequent reactions. The epoxy groups of epichlorohydrin react slowly and fully with the amino groups of polyamide and the carboxyl groups of sodium alginate. Adding sodium hydroxide to adjust the pH to 8-9 provides a suitable alkaline environment for the crosslinking reaction, promoting the formation of a three-dimensional crosslinked network of polyamide-epoxychlorohydrin-sodium alginate. Filtration removes unreacted impurities. The resulting bio-based polymer composite reinforcing agent has a three-dimensional crosslinked network that can form hydrogen bonds with the hydroxyl groups of bamboo pulp fiber, significantly improving the dry and wet tensile strength of decorative paper. Furthermore, the introduction of sodium alginate further optimizes the network density while maintaining the bio-based environmentally friendly properties of the reinforcing agent.

[0019] Preferably, the number average molecular weight of the polyamide is 5000-8000.

[0020] By setting up the above technical solution, it is possible to ensure that the linear polymer chain is long enough to form sufficient hydrogen bonds with the hydroxyl groups of bamboo pulp fiber, and to fully crosslink with the epoxy groups of epichlorohydrin and the carboxyl groups of sodium alginate to construct a structurally stable three-dimensional network. At the same time, it avoids the problem of decreased solubility and difficulty in uniform dispersion in deionized water due to excessively long molecular chains, ensuring the uniform mixing of each component of the bio-based polymer composite reinforcing agent, thereby effectively improving the dry and wet tensile strength of decorative paper, while ensuring the interfacial bonding force between the reinforcing agent and bamboo pulp fiber and other components.

[0021] Preferably, the components of the microencapsulated functional barrier agent, by weight, include the following raw materials: 20-25 parts of hindered amine light stabilizer UV-3808, 10-15 parts of melamine-formaldehyde resin prepolymer, 0.5-1 parts of sodium dodecylbenzenesulfonate, and 65-85 parts of deionized water.

[0022] The preparation method of the microencapsulated functional barrier agent is as follows: the hindered amine light stabilizer UV-3808 and sodium dodecylbenzenesulfonate are added to deionized water and stirred and emulsified at a speed of 1000-1200 r / min for 30-35 min to form an oil-in-water emulsion. After heating to 70-80℃, melamine-formaldehyde resin prepolymer is added and stirring is continued for 1.5-2 h. Then, the mixture is cooled to room temperature and centrifuged at a speed of 5000-6000 r / min for 15-20 min. Finally, it is dried at 60-70℃ for 2-3 h to obtain the microencapsulated functional barrier agent.

[0023] By setting up the above technical solution, the melamine-formaldehyde resin prepolymer fully polymerizes on the surface of the oil-in-water emulsion to form a complete capsule wall, achieving effective encapsulation of the hindered amine light stabilizer UV-3808. The resulting microencapsulated functional barrier agent has a melamine-formaldehyde resin capsule wall that can fill the pores on the surface of the decorative paper and reduce air permeability to help improve low permeability. The hindered amine light stabilizer UV-3808 in the capsule core can be slowly released when the decorative paper is exposed to light aging, inhibiting paper degradation and extending weather resistance. At the same time, it forms a synergy with the anti-ultraviolet effect of the nano-inorganic composite modifier, further enhancing the weather resistance of the decorative paper.

[0024] This application also discloses a process for preparing low-permeability, high-tensile decorative paper, comprising the following steps:

[0025] S1. Take bamboo pulp fiber and put it into a pulping machine for pulping treatment. Control the degree of freeness to be 25-30°SR, the degree of freeness to be 250-300mL, the fiber fibrillation rate to be ≥85%, and the treatment time to be 20-30min to obtain pretreated bamboo pulp fiber.

[0026] S2. The pretreated bamboo pulp fibers are divided into bamboo pulp fiber A, bamboo pulp fiber B, and bamboo pulp fiber C. 40-60% nano-inorganic composite modifier, 1 / 3 dispersant, 1 / 3 lubricant, and 1 / 3 defoamer are added to bamboo pulp fiber A. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the bottom layer slurry. All bio-based polymer composite reinforcing agents, all water-based wet strength agents, 1 / 3 dispersant, 1 / 3 lubricant, and 1 / 3 defoamer are added to bamboo pulp fiber B. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the middle layer slurry. The remaining 40-60% nano-inorganic composite modifier, all microencapsulated functional barrier agents, 1 / 3 dispersant, 1 / 3 lubricant, and 1 / 3 defoamer are added to bamboo pulp fiber C. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the top layer slurry.

[0027] The mass percentages of bamboo pulp fiber A, bamboo pulp fiber B, and bamboo pulp fiber C are 40-60%, 20-30%, and 20-30%, respectively. The mixing conditions for the bottom layer slurry, middle layer slurry, and top layer slurry are all 800-1000 r / min for 30-40 min.

[0028] S3. The bottom layer pulp, middle layer pulp, and top layer pulp obtained in step S2 are respectively fed into the bottom layer flow channel, middle layer flow channel, and top layer flow channel of the multi-layer headbox, and papermaking is carried out at a headbox speed of 15-20m / min to form a wet paper sheet with bottom layer-middle layer-top layer integrated.

[0029] S4. Feed the wet paper sheet into the press and use a three-stage pressing process with a pressure gradient of 1.5-2MPa → 2.5-3MPa → 3.5-4MPa, a temperature of 50-60℃, and a pressing time of 2-3 minutes for each stage.

[0030] S5. The pressed paper sheet is sent into the dryer and dried using a gradient temperature increase: the temperature is 80-90℃ → 120-130℃ → 160-170℃, and the drying time for each stage is 2-3 minutes.

[0031] S6. A microencapsulated functional barrier agent dispersion is added to the surface of the dried paper, with a coating amount of 1-2 g / m². 2 It is then sent to a UV curing machine and cured for 20-30 seconds at a wavelength of 365-380nm and a power of 80-100W / cm.

[0032] S7. The cured paper is fed into a calender and calendered for 2-3 minutes under a pressure of 6-8 MPa and a temperature of 80-90℃ to obtain low-permeability tensile decorative paper.

[0033] By setting up the above technical solutions, in S1, the pulping treatment of bamboo pulp fiber can form more broom-like structures on the surface of the bamboo pulp fiber, which can significantly increase its contact area and binding sites with nano-inorganic composite modifiers and bio-based polymer composite reinforcing agents, laying the foundation for subsequent component anchoring and tensile strength improvement; in S2, bamboo pulp fiber A has the highest proportion and is combined with 40-60% nano-inorganic composite modifiers, focusing on the low permeability of the bottom layer; bamboo pulp fiber B carries all bio-based polymer composite reinforcing agents and water-based wet strength agents, strengthening the tensile strength and wet stability of the middle layer. Bamboo pulp fiber C, combined with the remaining nano-inorganic composite modifiers and all microencapsulated functional barrier agents, highlights the surface's weather resistance and auxiliary low permeability. Through the uniform distribution of dispersants, lubricants, defoamers, and standardized stirring parameters, it avoids the agglomeration of functional components, ensures smooth forming, eliminates bubble defects, and achieves directional distribution of each component according to performance requirements. In S3, multi-layer flow papermaking uses independent channels for precise forming, ensuring that the bottom, middle, and top layers do not interfere with each other's functions, while simultaneously forming a unified wet paper sheet. This enhances the interweaving and bonding strength of the bamboo pulp fibers between layers, avoiding the problems associated with single-layer papermaking. The problem of uneven dispersion is addressed in S4, where a three-stage gradient pressing process (increasing pressure, controlled temperature and time) gradually squeezes out moisture from the wet paper sheet. This prevents instantaneous high pressure from damaging the paper structure and increases paper density, while also assisting the nano-inorganic composite modifier and microencapsulated functional barrier agent in sealing fiber gaps. In S5, gradient temperature drying, through "low temperature to remove surface moisture and prevent wrinkles → medium temperature to remove internal moisture and preserve structure → high temperature to promote cross-linking and enhance performance," avoids component migration (such as the aggregation of small molecule additives) and simultaneously promotes the cross-linking reaction between polyamide and epichlorohydrin in the bio-based polymer composite reinforcing agent, resulting in a stronger... The three-dimensional network structure is formed; in S6, microencapsulated functional barrier agents are added to the surface and UV cured, which not only makes up for the lack of weather-resistant components on the surface, but also ensures that the microcapsules are tightly bonded to the paper surface through UV irradiation of specific wavelengths and powers, thus extending the slow-release period of UV-3808; in S7, calendering treatment (pressure and temperature control) can compact the surface micropores, improve smoothness, further reduce the light and air transmission channels, and promote the interfacial bonding between the surface microencapsulated functional barrier agents and bamboo pulp fibers, ultimately achieving synergistic optimization of low permeability, high tensile strength and long-term weather resistance.

[0034] Preferably, in step S1, the bamboo pulp fiber is composed of broadleaf bamboo pulp and softleaf bamboo pulp in a mass ratio of 7:3.

[0035] By setting up the above technical solution, broadleaf bamboo pulp can give bamboo pulp fibers flexibility to prevent decorative paper from cracking, while coniferous bamboo pulp can provide rigidity and fiber interweaving ability to support initial tensile strength. This ratio achieves complementary characteristics of the two types of bamboo pulp. After pulping, a bamboo pulp fiber skeleton with both flexibility and rigidity is formed. This not only avoids the shortcomings of single bamboo pulp, but also facilitates the combination of functional components such as nano-inorganic composite modifiers and bio-based polymer composite reinforcing agents with bamboo pulp fibers, laying the foundation for improving the low permeability and high tensile strength of decorative paper.

[0036] Preferably, in step S5, the moisture content of the dried paper is 5-8%.

[0037] By setting up the above technical solutions, we can maintain the appropriate flexibility of bamboo pulp fibers, avoiding paper cracking and decreased tensile strength due to excessively low moisture content, or loose paper structure and impact on subsequent processes due to excessively high moisture content. We can also ensure the stability of the three-dimensional cross-linked structure formed by the bio-based polymer composite reinforcing agent, preventing excessive moisture from damaging the cross-linked bonds or insufficient moisture from causing the cross-linked structure to become brittle.

[0038] The beneficial effects of this invention are as follows:

[0039] The polyamide-epoxychloropropane three-dimensional network in the bio-based polymer composite reinforcing agent provides basic tensile strength support for decorative paper and enhances structural stability in the wet state. Sodium alginate contains a large number of carboxyl groups, which can form hydrogen bonds with the amino groups of polyamide on the one hand, and undergo ring-opening cross-linking reaction with the epoxy groups of epichlorohydrin on the other hand. The linear polymer chains of sodium alginate are interspersed in the polyamide-epoxychloropropane three-dimensional network, which not only enriches the binding sites inside the bio-based polymer composite reinforcing agent, but also constructs a denser "hydrogen bond-chemical cross-linking" dual binding structure, thereby strengthening the dry and wet tensile strength of decorative paper. Meanwhile, the hydrophilic groups of sodium alginate can interact closely with the hydroxyl groups of bamboo pulp fibers, helping to fill the tiny pores between fibers. Combined with the "maze effect" of the nano-inorganic composite modifier and the capsule wall blocking effect of the microencapsulated functional barrier agent, it further reduces the transmission channels of light and air, forming a synergistic improvement effect on the low permeability of decorative paper. Moreover, both sodium alginate and polyamide are bio-based components, and their combination also continues the environmentally friendly properties of the composite reinforcing agent, which is in line with the concept of energy conservation and environmental protection.

[0040] Sodium-based montmorillonite is fully dispersed in deionized water to form a stable suspension. The active groups of the silane coupling agent KH-570 react fully with the hydroxyl groups on the surface of sodium-based montmorillonite, improving the compatibility of sodium-based montmorillonite with the organic phase. High-speed dispersion can effectively prevent the agglomeration of nano-titanium dioxide, ensuring its uniform dispersion in the sodium-based montmorillonite-containing system. The final ultrasonic dispersion further refines the system particles, strengthening the synergistic effect of the "maze effect" of sodium-based montmorillonite sheets and the visible light reflectance of nano-titanium dioxide. The resulting nano-inorganic composite modifier can effectively reduce the light transmittance of decorative paper, improve tensile strength, and enhance the interfacial bonding with bamboo pulp fiber and other components.

[0041] Polyamide contains amino groups, and sodium alginate contains carboxyl groups. Both dissolve in deionized water, achieving uniform mixing and creating conditions for subsequent reactions. The epoxy groups of epichlorohydrin react slowly and fully with the amino groups of polyamide and the carboxyl groups of sodium alginate. Adding sodium hydroxide to adjust the pH to 8-9 provides a suitable alkaline environment for the crosslinking reaction, promoting the formation of a three-dimensional crosslinked network of polyamide-epoxychlorohydrin-sodium alginate. Filtration removes unreacted impurities. The resulting bio-based polymer composite reinforcing agent has a three-dimensional crosslinked network that can form hydrogen bonds with the hydroxyl groups of bamboo pulp fibers, significantly improving the dry and wet tensile strength of decorative paper. Furthermore, the introduction of sodium alginate further optimizes the network density while maintaining the bio-based and environmentally friendly properties of the reinforcing agent.

[0042] The melamine-formaldehyde resin prepolymer fully polymerizes on the surface of the oil-in-water emulsion to form a complete capsule wall, effectively encapsulating the hindered amine light stabilizer UV-3808. The resulting microencapsulated functional barrier agent has a melamine-formaldehyde resin capsule wall that can fill the pores on the surface of the decorative paper and reduce air permeability to help improve low permeability. The hindered amine light stabilizer UV-3808 in the capsule core can be slowly released when the decorative paper is exposed to light aging, inhibiting paper degradation and extending weather resistance. At the same time, it forms a synergy with the anti-ultraviolet effect of the nano-inorganic composite modifier, further enhancing the weather resistance of the decorative paper. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1:

[0045] This embodiment discloses a low-permeability, high-tensile decorative paper. By weight, the decorative paper comprises the following raw materials: 55 parts bamboo pulp fiber, 8 parts nano-inorganic composite modifier, 4 parts bio-based polymer composite reinforcing agent, 3 parts microencapsulated functional barrier agent, 1.5 parts polyamide-epoxychloropropane resin, 0.8 parts sodium polyacrylate, 0.3 parts calcium stearate, and 0.2 parts polyethylene glycol; wherein, the bio-based polymer composite reinforcing agent contains a polyamide-epoxychloropropane three-dimensional network and sodium alginate.

[0046] The nano-inorganic composite modifier comprises the following raw materials by weight: 30 parts nano-titanium dioxide, 10 parts sodium montmorillonite, 2 parts silane coupling agent KH-570, and 55 parts deionized water. The preparation method of the nano-inorganic composite modifier is as follows: sodium montmorillonite is added to deionized water and stirred at 800 r / min for 30 min. After heating to 60℃, silane coupling agent KH-570 is added and stirring is continued for 20 min. Then, nano-titanium dioxide is slowly added and dispersed at 2000 r / min for 40 min. Finally, it is ultrasonically treated at 600W for 30 min to control the particle size to 80 nm, thus obtaining the nano-inorganic composite modifier.

[0047] The bio-based polymer composite reinforcing agent comprises the following raw materials by weight: 10 parts of polyamide with a number average molecular weight of 5000, 12 parts of epichlorohydrin, 3 parts of sodium hydroxide, 0.5 parts of sodium alginate, and 70 parts of deionized water. The preparation method of the bio-based polymer composite reinforcing agent is as follows: polyamide and sodium alginate are dissolved together in deionized water, stirred at 300 r / min for 15 min, heated to 50℃, epichlorohydrin is added dropwise over 1 h, sodium hydroxide is added to adjust the pH to 8, the reaction is maintained at this temperature for 2 h, cooled to room temperature, and then filtered through a 200-mesh filter to obtain the bio-based polymer composite reinforcing agent.

[0048] The microencapsulated functional barrier agent, by weight, comprises the following raw materials: 20 parts of hindered amine light stabilizer UV-3808, 10 parts of melamine-formaldehyde resin prepolymer, 0.5 parts of sodium dodecylbenzenesulfonate, and 65 parts of deionized water. The preparation method of the microencapsulated functional barrier agent is as follows: the hindered amine light stabilizer UV-3808 and sodium dodecylbenzenesulfonate are added to deionized water and stirred and emulsified at 1000 r / min for 30 min to form an oil-in-water emulsion. After heating to 70℃, the melamine-formaldehyde resin prepolymer is added and stirring is continued for 1.5 h. Then, the mixture is cooled to room temperature and centrifuged at 5000 r / min for 15 min. Finally, it is dried at 60℃ for 2 h to obtain the microencapsulated functional barrier agent.

[0049] This embodiment also discloses a preparation process for low-permeability, high-tensile decorative paper, including the following steps:

[0050] S1. Take bamboo pulp fiber composed of broadleaf bamboo pulp and softleaf bamboo pulp in a mass ratio of 7:3, put it into a pulping machine for pulping treatment, control the pulping degree to 25°SR, the freeness to 250mL, the fiber fibrillation rate to 85%, and the treatment time to 20min to obtain pretreated bamboo pulp fiber.

[0051] S2. The pretreated bamboo pulp fibers are divided into bamboo pulp fiber A, bamboo pulp fiber B, and bamboo pulp fiber C. 40% nano-inorganic composite modifier, 1 / 3 sodium polyacrylate, 1 / 3 calcium stearate, and 1 / 3 polyethylene glycol are added to bamboo pulp fiber A. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the bottom layer slurry. All bio-based polymer composite reinforcing agent, all polyamide epichlorohydrin resin, 1 / 3 sodium polyacrylate, 1 / 3 calcium stearate, and 1 / 3 polyethylene glycol are added to bamboo pulp fiber B. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the middle layer slurry. The remaining 60% nano-inorganic composite modifier, all microencapsulated functional barrier agent, 1 / 3 sodium polyacrylate, 1 / 3 calcium stearate, and 1 / 3 polyethylene glycol are added to bamboo pulp fiber C. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the top layer slurry.

[0052] The mass percentages of bamboo pulp fiber A, bamboo pulp fiber B, and bamboo pulp fiber C are 40%, 30%, and 30%, respectively. The mixing conditions for the bottom layer slurry, middle layer slurry, and surface layer slurry are all 800 r / min for 30 min.

[0053] S3. The bottom layer pulp, middle layer pulp, and top layer pulp obtained in step S2 are respectively fed into the bottom layer flow channel, middle layer flow channel, and top layer flow channel of the multi-layer headbox, and papermaking is carried out at a headbox speed of 15m / min to form a wet paper sheet with bottom layer-middle layer-top layer integrated.

[0054] S4. Feed the wet paper sheet into the press and use a three-stage pressing process with a pressure gradient of 1.5MPa→2.5MPa→3.5MPa, a temperature of 50℃, and a pressing time of 2 minutes for each stage.

[0055] S5. The pressed paper sheet is fed into a dryer and dried using a gradient temperature increase: the temperature is successively 80℃→120℃→160℃, and the drying time for each stage is 2 minutes, resulting in a paper sheet with a moisture content of 5%.

[0056] S6. A microencapsulated functional barrier agent dispersion is added to the surface of the dried paper sheet, with a coating amount of 1 g / m². 2 It was then sent to a UV curing machine and cured for 20 seconds at a wavelength of 365nm and a power of 80W / cm.

[0057] S7. The cured paper is fed into a calender and calendered for 2 minutes under a pressure of 6MPa and a temperature of 80℃ to obtain low-permeability tensile decorative paper.

[0058] Example 2:

[0059] This embodiment discloses a low-permeability, high-tensile decorative paper. By weight, the decorative paper comprises the following raw materials: 65 parts bamboo pulp fiber, 12 parts nano-inorganic composite modifier, 6 parts bio-based polymer composite reinforcing agent, 5 parts microencapsulated functional barrier agent, 2.5 parts melamine-formaldehyde resin, 1.2 parts polyethylene oxide, 0.5 parts zinc stearate, and 0.4 parts mineral oil; wherein, the bio-based polymer composite reinforcing agent contains a polyamide-epoxychloropropane three-dimensional network and sodium alginate.

[0060] The nano-inorganic composite modifier comprises the following raw materials by weight: 35 parts nano-titanium dioxide, 15 parts sodium montmorillonite, 4 parts silane coupling agent KH-570, and 75 parts deionized water. The preparation method of the nano-inorganic composite modifier is as follows: sodium montmorillonite is added to deionized water and stirred at 1000 r / min for 35 min. After heating to 70℃, silane coupling agent KH-570 is added and stirring is continued for 25 min. Then, nano-titanium dioxide is slowly added and dispersed at 2500 r / min for 50 min. Finally, it is ultrasonically treated at 700W for 35 min to control the particle size to 100 nm, thus obtaining the nano-inorganic composite modifier.

[0061] The bio-based polymer composite reinforcing agent comprises the following raw materials by weight: 15 parts polyamide with a number average molecular weight of 8000, 16 parts epichlorohydrin, 6 parts sodium hydroxide, 1.5 parts sodium alginate, and 85 parts deionized water. The preparation method of the bio-based polymer composite reinforcing agent is as follows: polyamide and sodium alginate are dissolved together in deionized water, stirred at 500 r / min for 20 min, heated to 60℃, epichlorohydrin is added dropwise over 1.5 h, sodium hydroxide is added to adjust the pH to 9, the reaction is maintained at this temperature for 2.5 h, cooled to room temperature, and filtered through a 300-mesh filter to obtain the bio-based polymer composite reinforcing agent.

[0062] The microencapsulated functional barrier agent, by weight, comprises the following raw materials: 25 parts of hindered amine light stabilizer UV-3808, 15 parts of melamine-formaldehyde resin prepolymer, 1 part of sodium dodecylbenzenesulfonate, and 85 parts of deionized water. The preparation method of the microencapsulated functional barrier agent is as follows: the hindered amine light stabilizer UV-3808 and sodium dodecylbenzenesulfonate are added to deionized water and stirred and emulsified at 1200 r / min for 35 min to form an oil-in-water emulsion. After heating to 80℃, the melamine-formaldehyde resin prepolymer is added and stirring is continued for 2 h. Then, the mixture is cooled to room temperature and centrifuged at 6000 r / min for 20 min. Finally, it is dried at 70℃ for 3 h to obtain the microencapsulated functional barrier agent.

[0063] This embodiment also discloses a preparation process for low-permeability, high-tensile decorative paper, including the following steps:

[0064] S1. Take bamboo pulp fiber composed of broadleaf bamboo pulp and softleaf bamboo pulp in a mass ratio of 7:3, put it into a pulping machine for pulping treatment, control the pulping degree to 30°SR, the freeness to 300mL, the fiber fibrillation rate to 90%, and the treatment time to 30min to obtain pretreated bamboo pulp fiber.

[0065] S2. The pretreated bamboo pulp fibers are divided into bamboo pulp fiber A, bamboo pulp fiber B, and bamboo pulp fiber C. 60% nano-inorganic composite modifier, 1 / 3 polyethylene oxide, 1 / 3 zinc stearate, and 1 / 3 mineral oil are added to bamboo pulp fiber A. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the bottom layer slurry. All bio-based polymer composite reinforcing agent, all melamine-formaldehyde resin, 1 / 3 polyethylene oxide, 1 / 3 zinc stearate, and 1 / 3 mineral oil are added to bamboo pulp fiber B. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the middle layer slurry. The remaining 40% nano-inorganic composite modifier, all microencapsulated functional barrier agent, 1 / 3 polyethylene oxide, 1 / 3 zinc stearate, and 1 / 3 mineral oil are added to bamboo pulp fiber C. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the top layer slurry.

[0066] The mass percentages of bamboo pulp fiber A, bamboo pulp fiber B, and bamboo pulp fiber C are 60%, 20%, and 20%, respectively. The mixing conditions for the bottom layer slurry, middle layer slurry, and surface layer slurry are all 1000 r / min for 40 min.

[0067] S3. The bottom layer pulp, middle layer pulp, and top layer pulp obtained in step S2 are respectively fed into the bottom layer flow channel, middle layer flow channel, and top layer flow channel of the multi-layer headbox, and papermaking is carried out at a headbox speed of 20m / min to form a wet paper sheet with bottom layer-middle layer-top layer integrated.

[0068] S4. Feed the wet paper sheet into the press and use a three-stage pressing process with a pressure gradient of 2MPa→3MPa→4MPa, a temperature of 60℃, and a pressing time of 3min for each stage.

[0069] S5. The pressed paper sheet is fed into a dryer and dried using a gradient temperature increase: the temperature is successively 90℃→130℃→170℃, and the drying time for each stage is 3 minutes, resulting in a paper sheet with a moisture content of 8%.

[0070] S6. A microencapsulated functional barrier agent dispersion is added to the surface of the dried paper sheet, with a coating amount of 2 g / m². 2 It was then sent to a UV curing machine and cured for 30 seconds at a wavelength of 380nm and a power of 100W / cm.

[0071] S7. The cured paper is fed into a calender and calendered for 3 minutes under a pressure of 8MPa and a temperature of 90℃ to obtain low-permeability tensile decorative paper.

[0072] Example 3:

[0073] This embodiment discloses a low-permeability, high-tensile decorative paper. By weight, the decorative paper comprises the following raw materials: 60 parts bamboo pulp fiber, 10 parts nano-inorganic composite modifier, 5 parts bio-based polymer composite reinforcing agent, 4 parts microencapsulated functional barrier agent, 2 parts polyethyleneimine, 1 part sodium polyacrylate, 0.4 parts polyethylene wax, and 0.3 parts polyether-modified organosilicon; wherein, the bio-based polymer composite reinforcing agent contains a polyamide-epoxychloropropane three-dimensional network and sodium alginate.

[0074] The nano-inorganic composite modifier comprises the following raw materials by weight: 32 parts nano-titanium dioxide, 12 parts sodium montmorillonite, 3 parts silane coupling agent KH-570, and 65 parts deionized water. The preparation method of the nano-inorganic composite modifier is as follows: sodium montmorillonite is added to deionized water and stirred at 900 r / min for 32 min. After heating to 65℃, silane coupling agent KH-570 is added and stirring is continued for 22 min. Then, nano-titanium dioxide is slowly added and dispersed at 2250 r / min for 45 min. Finally, it is ultrasonically treated at 650W for 32 min to control the particle size to 90 nm, thus obtaining the nano-inorganic composite modifier.

[0075] The bio-based polymer composite reinforcing agent comprises the following raw materials by weight: 12 parts of polyamide with a number average molecular weight of 7500, 14 parts of epichlorohydrin, 4 parts of sodium hydroxide, 1 part of sodium alginate, and 77 parts of deionized water. The preparation method of the bio-based polymer composite reinforcing agent is as follows: polyamide and sodium alginate are dissolved together in deionized water, stirred at 400 r / min for 17 min, heated to 55℃, epichlorohydrin is added dropwise over 1.2 h, sodium hydroxide is added to adjust the pH to 9, the reaction is maintained at this temperature for 2.5 h, cooled to room temperature, and filtered through a 250-mesh filter to obtain the bio-based polymer composite reinforcing agent.

[0076] The microencapsulated functional barrier agent, by weight, comprises the following raw materials: 22 parts of hindered amine light stabilizer UV-3808, 12 parts of melamine-formaldehyde resin prepolymer, 0.7 parts of sodium dodecylbenzenesulfonate, and 75 parts of deionized water. The preparation method of the microencapsulated functional barrier agent is as follows: the hindered amine light stabilizer UV-3808 and sodium dodecylbenzenesulfonate are added to deionized water and stirred and emulsified at 1100 r / min for 32 min to form an oil-in-water emulsion. After heating to 75℃, the melamine-formaldehyde resin prepolymer is added and stirring is continued for 1.7 h. Then, the mixture is cooled to room temperature and centrifuged at 5500 r / min for 17 min. Finally, it is dried at 65℃ for 2.5 h to obtain the microencapsulated functional barrier agent.

[0077] This embodiment also discloses a preparation process for low-permeability, high-tensile decorative paper, including the following steps:

[0078] S1. Take bamboo pulp fiber composed of broadleaf bamboo pulp and softleaf bamboo pulp in a mass ratio of 7:3, put it into a pulping machine for pulping treatment, control the pulping degree to 27°SR, the freeness to 270mL, the fiber fibrillation rate to 90%, and the treatment time to 25min to obtain pretreated bamboo pulp fiber.

[0079] S2. The pretreated bamboo pulp fibers are divided into bamboo pulp fiber A, bamboo pulp fiber B, and bamboo pulp fiber C. 50% nano-inorganic composite modifier, 1 / 3 sodium polyacrylate, 1 / 3 polyethylene wax, and 1 / 3 polyether-modified organosilicon are added to bamboo pulp fiber A. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the bottom layer slurry. All bio-based polymer composite reinforcing agent, all polyethyleneimine, 1 / 3 sodium polyacrylate, 1 / 3 polyethylene wax, and 1 / 3 polyether-modified organosilicon are added to bamboo pulp fiber B. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the middle layer slurry. The remaining 50% nano-inorganic composite modifier, all microencapsulated functional barrier agent, 1 / 3 sodium polyacrylate, 1 / 3 polyethylene wax, and 1 / 3 polyether-modified organosilicon are added to bamboo pulp fiber C. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the top layer slurry.

[0080] The mass percentages of bamboo pulp fiber A, bamboo pulp fiber B, and bamboo pulp fiber C are 50%, 25%, and 25%, respectively. The mixing conditions for the bottom layer slurry, middle layer slurry, and surface layer slurry are all 900 r / min for 35 min.

[0081] S3. The bottom layer pulp, middle layer pulp, and top layer pulp obtained in step S2 are respectively fed into the bottom layer flow channel, middle layer flow channel, and top layer flow channel of the multi-layer headbox, and papermaking is carried out at a headbox speed of 17m / min to form a wet paper sheet with bottom layer-middle layer-top layer integrated.

[0082] S4. Feed the wet paper sheet into the press and use a three-stage pressing process with a pressure gradient of 1.7MPa→2.7MPa→3.7MPa, a temperature of 55℃, and a pressing time of 2.5min for each stage.

[0083] S5. The pressed paper sheet is fed into a dryer and dried using a gradient temperature increase: the temperature is successively 85℃→125℃→165℃, and the drying time for each stage is 2.5min, resulting in a paper sheet moisture content of 6.5%.

[0084] S6. A microencapsulated functional barrier agent dispersion is added to the dried paper surface at a coating amount of 1.5 g / m². 2 It was then sent to a UV curing machine and cured for 25 seconds at a wavelength of 370nm and a power of 90W / cm.

[0085] S7. The cured paper is fed into a calender and calendered for 2.5 minutes under a pressure of 7MPa and a temperature of 85℃ to obtain low-permeability tensile decorative paper.

[0086] Comparative Example 1:

[0087] A low-permeability, high-tensile decorative paper and its preparation process are disclosed. The only difference between this decorative paper and Example 3 is that no nano-inorganic composite modifier is added.

[0088] Comparative Example 2:

[0089] A low-permeability, high-tensile decorative paper and its preparation process are disclosed. The only difference between this decorative paper and Example 3 is that no bio-based polymer composite reinforcing agent is added.

[0090] Comparative Example 3:

[0091] A low-permeability, high-tensile decorative paper and its preparation process are disclosed. The only difference between this decorative paper and Example 3 is that no microencapsulated functional barrier agent is added.

[0092] Comparative Example 4:

[0093] A low-permeability, high-tensile decorative paper and its preparation process are disclosed. The only difference between this decorative paper and Example 3 is that in step S3 of the preparation process, the multi-layer flow papermaking is changed to single-layer papermaking.

[0094] Comparative Example 5:

[0095] A low-permeability, high-tensile decorative paper and its preparation process are disclosed. The only difference between this decorative paper and Example 3 is that in step S5 of the preparation process, gradient drying is replaced with constant temperature drying (120°C, 6-7 min).

[0096] Comparative Example 6:

[0097] A low-permeability, high-tensile decorative paper and its preparation process are disclosed. The only difference between this decorative paper and Example 3 is that in step S6 of the preparation process, the UV curing power is reduced to 50-60 W / cm.

[0098] Comparative Example 7:

[0099] A low-permeability, high-tensile decorative paper and its preparation process are disclosed. The only difference between this decorative paper and Example 3 is that in step S7 of the preparation process, the calendering pressure is reduced to 4-5 MPa.

[0100] Comparative Example 8:

[0101] A low-permeability, high-tensile decorative paper and its preparation process are disclosed. The only difference between this decorative paper and Example 3 is that bamboo pulp fiber is replaced with wood pulp fiber.

[0102] The decorative papers obtained in Examples 1-3 and Comparative Examples 1-8 were subjected to performance tests on light transmittance, tensile strength, wet tensile strength, air permeability, weather resistance, surface smoothness, and interlayer bonding strength, among which:

[0103] 1. Transmittance: Refer to GB / T2410-2008 "Determination of transmittance and haze of transparent plastics" (suitable for decorative paper testing, wavelength 600nm), randomly select 3 200mm×200mm samples from the finished product, fix them on the sample holder of the transmittance tester, measure the transmittance at 3 different positions, and take the average value.

[0104] 2. Tensile strength: Refer to GB / T12914-2018 "Determination of tensile strength of paper and paperboard", cut the finished product into 15mm×200mm strip specimens (3 specimens), fix them in the upper and lower clamps of the tensile strength testing machine, measure the maximum breaking force at a tensile speed of 100mm / min, calculate the tensile strength (tensile strength = maximum force / specimen width), and take the average value.

[0105] 3. Wet tensile strength: Refer to GB / T465.2-2008 "Determination of tensile strength of paper and paperboard - Part 2: Wet tensile strength", immerse 3 strip samples of 15mm×200mm in deionized water at 25℃ for 2h, absorb the surface moisture, and test according to the dry tensile strength test procedure. Calculate the wet tensile strength and retention rate (wet tensile strength / dry tensile strength × 100%), and take the average value.

[0106] 4. Air permeability: Refer to GB / T458-2008 "Determination of air permeability of paper and paperboard", fix 200mm×200mm samples (3 samples) on the test platform of the air permeability tester, set the pressure difference to 1kPa, record the amount of air passing through per unit time, and take the average value of 3 times.

[0107] 5. Weather resistance: Refer to GB / T16422.2-2014 "Laboratory Light Source Exposure Test Methods for Plastics - Part 2: Xenon Arc Lamp" (for testing decorative paper), fix 3 samples of 200mm×200mm in the sample rack of the xenon lamp aging test chamber, and age them for 500h under the conditions of irradiance of 0.71W / (m²·nm), temperature of 40℃ and humidity of 65%. After taking them out, use a colorimeter to measure the color difference ΔE between the aged sample and the unaged sample, and take the average value.

[0108] 6. Surface smoothness: Refer to GB / T456-2002 "Determination of smoothness of paper and paperboard (Beck method)", lay 3 samples of 200mm×200mm flat on the test stage of the Beck smoothness tester, apply 100kPa pressure, record the time it takes for the vacuum degree to drop from 50kPa to 25kPa, and take the average value (the longer the time, the better the smoothness).

[0109] 7. Interlayer bond strength: Refer to GB / T2679.16-2013 "Determination of interlayer bond strength of paper and paperboard" (TAPPI method), fix 50mm×50mm specimens (3 specimens) to the upper and lower test pans with double-sided tape, measure the maximum force when the layers separate at a speed of 5mm / min, calculate the interlayer bond strength (interlayer bond strength = maximum force / specimen area), and take the average value.

[0110] The results are shown in Table 1.

[0111] Table 1 Performance parameters of decorative papers obtained in Examples 1-3 and Comparative Examples 1-8

[0112] Group Light transmittance (%) Longitudinal dry tensile strength (kN / m) Longitudinal wet tensile strength (kN / m) Wet tensile strength retention rate (%) Air permeability (mL / (m²·s)) Weather resistance ΔE (500h) Surface smoothness (s) Interlayer bonding force (N / m) Example 1 1.6 8.6 4.9 60.0 4.0 1.1 330 1.6 Example 2 1.6 8.9 5.3 60.2 3.8 1.1 350 1.7 Example 3 1.5 9.5 5.7 60.0 3.5 1.0 400 1.8 Comparative Example 1 5.8 6.2 3.1 50.0 7.5 3.5 200 1.0 Comparative Example 2 2.5 5.5 2.2 40.0 4.5 1.3 250 1.2 Comparative Example 3 2.2 8.2 4.6 56.1 5.0 4.6 280 1.4 Comparative Example 4 2.1 7.5 4.2 56.0 5.5 1.4 270 0 Comparative Example 5 2.3 7.2 3.8 52.8 6.0 1.6 240 1.2 Comparative Example 6 1.7 8.3 4.7 56.6 4.6 2.8 310 1.5 Comparative Example 7 1.6 8.5 4.4 51.8 4.3 1.1 290 1.6 Comparative Example 8 2.8 6.8 3.7 54.4 6.2 1.7 230 1.3

[0113] Referring to Table 1 and using Example 3 as a reference, it can be seen that:

[0114] In Comparative Example 1, the light transmittance increased by 286.7% compared to Example 3 (1.5% → 5.8%), the longitudinal dry tensile strength decreased by 34.7% (9.5 kN / m → 6.2 kN / m), the air permeability increased by 114.3% (3.5 mL / (m²·s) → 7.5 mL / (m²·s)), and the weather resistance ΔE increased by 250% (1.0 → 3.5). The nano-inorganic composite modifier is the core synergistic component for "low transmittance + tensile strength"—the visible light reflection effect of titanium dioxide and the "maze effect" of montmorillonite jointly reduce light transmittance, and the interweaving of montmorillonite sheets with fibers can improve tensile strength. Without the nano-inorganic composite modifier, the pores on the paper surface cannot be sealed by the inorganic sheets, allowing light to easily transmit and air to penetrate; simultaneously, the stress transfer efficiency between bamboo pulp fibers decreases, reducing tensile strength; furthermore, the anti-UV reflection effect of titanium dioxide disappears, allowing ultraviolet light to directly irradiate the interior of the paper, leading to poorer weather resistance.

[0115] In Comparative Example 2, the longitudinal dry tensile strength decreased by 42.1% (9.5 kN / m → 5.5 kN / m), the wet tensile strength decreased by 61.4% (5.7 kN / m → 2.2 kN / m), and the wet tensile strength retention rate decreased by 33.3% (60.0% → 40.0%). The core role of the bio-based polymer composite reinforcing agent is to construct a three-dimensional network through "hydrogen bonding + chemical crosslinking"—hydrogen bonds are formed between the amino groups of polyamide and the hydroxyl groups of the fiber, and epichlorohydrin crosslinks to strengthen the network structure. This is the key to improving dry / wet tensile strength. Without the bio-based polymer composite reinforcing agent, the bamboo pulp fibers rely solely on physical interweaving, making them prone to breakage under stress. Furthermore, the hydrogen bonds are easily destroyed upon contact with water, resulting in a significant decrease in wet strength.

[0116] In Comparative Example 3, weather resistance ΔE increased by 360% (1.0→4.6), and air permeability increased by 42.9% (3.5mL / (m²·s)→5.0mL / (m²·s)). The "capsule wall blocking + core slow release" of the microencapsulated functional barrier agent complements the weather resistance and low permeability—the capsule wall (melamine-formaldehyde resin) fills the surface pores, reducing air permeability; the core (UV-3808) releases slowly, forming a "dynamic UV protection" system. Without the microencapsulated functional barrier agent, the pores on the paper surface are not completely blocked, resulting in increased air permeability; and without UV-3808 absorbing ultraviolet light, relying solely on the titanium dioxide reflection of the composite modifier, the UV protection is insufficient, leading to a significant increase in color difference after aging.

[0117] In Comparative Example 4, the longitudinal dry tensile strength decreased by 21.1% (9.5 kN / m → 7.5 kN / m), the interlayer bonding force was 0 (no multilayer structure), and the air permeability increased by 57.1% (3.5 mL / (m²·s) → 5.5 mL / (m²·s)). Multilayer papermaking, through functional zoning of "low permeability in the bottom layer + strength in the middle layer + weather resistance in the surface layer," allows each component to function in a directional manner, and the interlayer fibers are more fully interwoven, resulting in stronger bonding. After switching to single-layer papermaking, the components are unevenly mixed and dispersed, the function cannot be focused, the bottom layer composite modifier is mixed with the surface layer microcapsules, and both the low permeability and weather resistance effects are weakened; the interlayer fiber interweaving is insufficient, and the bonding force decreases.

[0118] In Comparative Example 5, the longitudinal dry tensile strength decreased by 24.2% (9.5 kN / m → 7.2 kN / m), the surface smoothness decreased by 40.0% (400 s → 240 s), and the air permeability increased by 71.4% (3.5 mL / (m²·s) → 6.0 mL / (m²·s)). Gradient drying avoids paper deformation and component migration by "low temperature to remove surface water → medium temperature to remove internal water → high temperature crosslinking". When drying at a constant temperature of 120℃, the surface moisture evaporates rapidly to form a "hard shell", and the internal moisture cannot be discharged in time, resulting in pores in the paper (increased air permeability) and insufficient resin crosslinking (decreased tensile strength); at the same time, the surface shrinkage is uneven and the smoothness is reduced.

[0119] In Comparative Example 6, the weather resistance ΔE increased by 180% (1.0→2.8), while the wet tensile strength retention rate decreased by 5.7% (60.0%→56.6%). A UV power of 90 W / cm ensured sufficient bonding between the microcapsules and the paper surface and promoted secondary cross-linking of the resin. When the power decreased to 50-60 W / cm, curing was insufficient—the bonding force between the microcapsules and the surface weakened, and the capsule walls ruptured prematurely (UV-3808 was released prematurely, leaving no residual protective agent during aging), resulting in decreased weather resistance. Simultaneously, insufficient resin cross-linking density made the network easily damaged in the wet state, leading to a decrease in retention rate.

[0120] In Comparative Example 7, surface smoothness decreased by 27.5% (400s→290s), and wet tensile strength retention decreased by 13.7% (60.0%→51.8%). A calendering pressure of 7 MPa can compact the surface coating, fill micropores (improving smoothness), and simultaneously promote interfacial bonding between the fiber and resin. When the pressure is reduced to 4-5 MPa, the surface coating is not fully compacted, micropores remain (smoothness decreases), and the fiber-resin bond is not tight, making it easy to separate in the wet state (retention rate decreases).

[0121] In Comparative Example 8, light transmittance increased by 86.7% (1.5%→2.8%), longitudinal dry tensile strength decreased by 28.4% (9.5kN / m→6.8kN / m), and air permeability increased by 77.1% (3.5mL / (m²·s)→6.2mL / (m²·s)). Bamboo pulp fibers are longer (3-5mm) than wood pulp fibers (2-3mm), exhibiting stronger interweaving and forming a denser fiber network (reducing light transmittance and air permeability). Furthermore, bamboo pulp has a higher cellulose hydroxyl content, resulting in more complete hydrogen bonding with the composite reinforcing agent and higher tensile strength. After wood pulp fiber replacement, the fiber network becomes loose, functional components cannot be effectively anchored, and overall performance declines.

[0122] Nano-inorganic composite modifiers, bio-based polymer composite reinforcing agents, and microencapsulated functional barrier agents are the core components for achieving "low transmittance (transmittance ≤ 1.5%), high tensile strength (longitudinal ≥ 9.5 kN / m), and long-lasting weather resistance (ΔE ≤ 1.0)". The absence of any one of these components leads to a significant decline in the various properties of decorative paper. Furthermore, the synergistic effect of the three components (such as the interpenetrating network of "modifier-reinforcing agent" and the dual UV resistance of "modifier-barrier agent") produces unexpected technical effects that far exceed the functional superposition of a single component.

[0123] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-permeability, high-tensile decorative paper, characterized in that, By weight, the decorative paper comprises the following raw materials: 55-65 parts bamboo pulp fiber, 8-12 parts nano-inorganic composite modifier, 4-6 parts bio-based polymer composite reinforcing agent, 3-5 parts microencapsulated functional barrier agent, and 2.8-4.6 parts papermaking functional additives. The nano-inorganic composite modifier comprises the following raw materials by weight: 30-35 parts nano-titanium dioxide, 10-15 parts sodium montmorillonite, 2-4 parts silane coupling agent KH-570, and 55-75 parts deionized water. The preparation method of the nano-inorganic composite modifier is as follows: Sodium-based montmorillonite is added to deionized water and stirred at 800-1000 r / min for 30-35 min. After heating to 60-70℃, silane coupling agent KH-570 is added and stirring is continued for 20-25 min. Then, nano-titanium dioxide is slowly added and dispersed at 2000-2500 r / min for 40-50 min. Finally, the mixture is ultrasonically treated at a power of 600-700W for 30-35 min, and the particle size is controlled to be ≤100nm to obtain the nano-inorganic composite modifier. By weight, the components of the bio-based polymer composite reinforcing agent include the following raw materials: 10-15 parts polyamide, 12-16 parts epichlorohydrin, 3-6 parts sodium hydroxide, 0.5-1.5 parts sodium alginate, and 70-85 parts deionized water; The preparation method of the bio-based polymer composite reinforcing agent is as follows: polyamide and sodium alginate are dissolved together in deionized water, stirred at 300-500 r / min for 15-20 min, heated to 50-60℃, epichlorohydrin is added dropwise over 1-1.5 h, sodium hydroxide is added to adjust the pH to 8-9, the reaction is kept at this temperature for 2-2.5 h, cooled to room temperature, and then filtered through a 200-300 mesh filter to obtain the bio-based polymer composite reinforcing agent. By weight, the microencapsulated functional barrier agent comprises the following raw materials: 20-25 parts of hindered amine light stabilizer UV-3808, 10-15 parts of melamine-formaldehyde resin prepolymer, 0.5-1 parts of sodium dodecylbenzenesulfonate, and 65-85 parts of deionized water. The preparation method of the microencapsulated functional barrier agent is as follows: the hindered amine light stabilizer UV-3808 and sodium dodecylbenzenesulfonate are added to deionized water and stirred and emulsified at a speed of 1000-1200 r / min for 30-35 min to form an oil-in-water emulsion. After heating to 70-80℃, melamine-formaldehyde resin prepolymer is added and stirring is continued for 1.5-2 h. Then, the mixture is cooled to room temperature and centrifuged at a speed of 5000-6000 r / min for 15-20 min. Finally, it is dried at 60-70℃ for 2-3 h to obtain the microencapsulated functional barrier agent.

2. The low-permeability, high-tensile decorative paper according to claim 1, characterized in that, Based on the total weight parts of the components, the composition of the papermaking functional additive includes the following raw materials: 1.5-2.5 parts of water-based wet strength agent, 0.8-1.2 parts of dispersant, 0.3-0.5 parts of lubricant and 0.2-0.4 parts of defoamer.

3. The low-permeability, high-tensile decorative paper according to claim 2, characterized in that, The water-based wet strength agent is at least one of polyamide epichlorohydrin resin, melamine formaldehyde resin, or polyethyleneimine. The dispersant is at least one of sodium polyacrylate, polyethylene oxide, or maleic anhydride copolymer; The lubricant is at least one of calcium stearate, zinc stearate, or polyethylene wax; The defoamer is at least one of polyether-modified silicone, mineral oil, or polyethylene glycol.

4. The low-permeability, high-tensile decorative paper according to claim 3, characterized in that, The number average molecular weight of polyamide is 5000-8000.

5. A preparation process for low-permeability, high-tensile decorative paper according to claim 4, characterized in that, Includes the following steps: S1. Take bamboo pulp fiber and put it into a pulping machine for pulping treatment. Control the degree of freeness to be 25-30°SR, the degree of freeness to be 250-300mL, the fiber fibrillation rate to be ≥85%, and the treatment time to be 20-30min to obtain pretreated bamboo pulp fiber. S2. The pretreated bamboo pulp fibers are divided into bamboo pulp fiber A, bamboo pulp fiber B, and bamboo pulp fiber C. 40-60% nano-inorganic composite modifier, 1 / 3 dispersant, 1 / 3 lubricant, and 1 / 3 defoamer are added to bamboo pulp fiber A. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the bottom layer slurry. All bio-based polymer composite reinforcing agents, all water-based wet strength agents, 1 / 3 dispersant, 1 / 3 lubricant, and 1 / 3 defoamer are added to bamboo pulp fiber B. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the middle layer slurry. The remaining 40-60% nano-inorganic composite modifier, all microencapsulated functional barrier agents, 1 / 3 dispersant, 1 / 3 lubricant, and 1 / 3 defoamer are added to bamboo pulp fiber C. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain the top layer slurry. The mass percentages of bamboo pulp fiber A, bamboo pulp fiber B, and bamboo pulp fiber C are 40-60%, 20-30%, and 20-30%, respectively. The mixing conditions for the bottom layer slurry, middle layer slurry, and top layer slurry are all 800-1000 r / min for 30-40 min. S3. The bottom layer pulp, middle layer pulp, and top layer pulp obtained in step S2 are respectively fed into the bottom layer flow channel, middle layer flow channel, and top layer flow channel of the multi-layer headbox, and papermaking is carried out at a headbox speed of 15-20m / min to form a wet paper sheet with bottom layer-middle layer-top layer integrated. S4. Feed the wet paper sheet into the press and use a three-stage pressing process with a pressure gradient of 1.5-2MPa → 2.5-3MPa → 3.5-4MPa, a temperature of 50-60℃, and a pressing time of 2-3 minutes for each stage. S5. The pressed paper sheet is sent into the dryer and dried using a gradient temperature increase: the temperature is 80-90℃ → 120-130℃ → 160-170℃, and the drying time for each stage is 2-3 minutes. S6. A microencapsulated functional barrier agent dispersion is added to the surface of the dried paper, with a coating amount of 1-2 g / m². 2 It is then sent to a UV curing machine and cured for 20-30 seconds at a wavelength of 365-380nm and a power of 80-100W / cm. S7. The cured paper is fed into a calender and calendered for 2-3 minutes under a pressure of 6-8 MPa and a temperature of 80-90℃ to obtain low-permeability tensile decorative paper.

6. The preparation process of the low-permeability, high-tensile decorative paper according to claim 5, characterized in that, In step S1, the bamboo pulp fiber is composed of broadleaf bamboo pulp and softleaf bamboo pulp in a mass ratio of 7:

3.

7. The preparation process of the low-permeability, high-tensile decorative paper according to claim 5, characterized in that, In step S5, the moisture content of the dried paper is 5-8%.