Environment-friendly high-elastic instant soluble degradable non-woven fabric and production process thereof

Abstract

The invention discloses an environment-friendly high-elastic instant soluble degradable non-woven fabric and a production process thereof, and relates to the technical field of advanced materials, the environment-friendly high-elastic instant soluble degradable non-woven fabric comprises a first fiber web layer, a mixed cellulose core layer, a viscose fiber skeleton layer and a second fiber web layer which are compounded in sequence, all the layers are bonded through a cross-linked degradable unsaturated polyester emulsion, and the production process comprises a fiber pretreatment step, a mixing I step, a mixing II step, a dipping treatment step, a composite stacking step and a drying and curing step. The materials used in the invention can be synergistically biodegraded under specific environmental conditions, and can comprehensively balance the contradiction among the strength, high elasticity, dispersion property and degradability of the non-woven fabric product, thereby improving the use experience of the product and improving the environmental protection property of the non-woven fabric product.

Description

Technical Field

[0001] This invention relates to the field of advanced materials technology, specifically to environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric and its production process. Background Technology

[0002] Nonwoven fabric is a type of fabric made by forming polymer chips, short fibers, and long filaments into a web through airflow or mechanical means, and then reinforcing it through hydroentangling, needle punching, and hot rolling. It has advantages such as breathability and flexibility and is widely used in nursing, clothing, medical fields, and especially in the manufacture of common household items such as disinfectant wipes or face towels.

[0003] Since washable nonwoven fabrics are typically used or stored in a wet state, certain requirements are placed on the material's strength and water retention. Nonwoven fabrics prepared using traditional methods often use plant fibers and chitin fibers as biodegradable fiber materials. However, these materials do not provide a pleasant rubbing feel against human skin, are uncomfortable, and can easily irritate the skin, affecting the user experience.

[0004] In existing technologies, nonwoven fabrics made from raw materials such as polylactic acid have high biodegradability, but poor elasticity and water retention, which can easily cause blockages in toilets and pipes, making them difficult to flush quickly and affecting the user experience. Flushing nonwoven fabrics made from PP / PE hybrid structures or laminated composite materials have improved flushability, but the materials have poor water retention and mostly rely on non-degradable chemical adhesives or hot melt adhesives for lamination, making it impossible to achieve full degradation. Their core material degrades slowly, still burdening the environment and failing to meet the needs of high-end hygiene products.

[0005] Regarding the above-mentioned technical solutions, existing washable nonwoven fabric products are difficult to fully degrade, which can easily cause pollution and damage to the soil environment, resulting in poor environmental performance. Summary of the Invention

[0006] The purpose of this invention is to provide an environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric and its production process, so as to solve the problems mentioned in the background art.

[0007] Firstly, the present invention provides an environmentally friendly, highly elastic, rapidly dissolving, and biodegradable nonwoven fabric, achieving the invention's objective through the following technical solution: An environmentally friendly, high-elasticity, fast-dissolving, and biodegradable nonwoven fabric comprises, in sequence, a first fiber web layer comprising 10-20% by weight, a mixed cellulose core layer comprising 50-80% by weight, a viscose fiber skeleton layer comprising 5-20% by weight, and the remainder being a second fiber web layer. The mixed cellulose core layer comprises 70-90% wood pulp short fibers and the remainder being biodegradable fibers by weight. The viscose fiber skeleton layer is composed of viscose fiber filaments. The first fiber web layer is composed of biodegradable fibers. The second fiber web layer comprises biodegradable fibers. The first fiber web layer, the mixed cellulose core layer, the viscose fiber skeleton layer, and the second fiber web layer are bonded together by a biodegradable unsaturated polyester emulsion.

[0008] By adopting the above technical solution, the mixed cellulose core layer constitutes the main weight component of the nonwoven fabric product. Wood pulp short fibers account for a significant proportion of this core layer. These fibers are hydrophilic and easily disintegrate under water flow, providing the product with a certain thickness, as well as high liquid absorption and rapid dissolution. The first and second fiber web layers, as outer layers, provide surface smoothness, a soft touch, and increased strength. Made of biodegradable fibers, they enhance the overall environmental friendliness of the product. A viscose fiber skeleton layer composed of continuous filaments forms an internal reinforcing network, significantly improving the nonwoven fabric's longitudinal and transverse tensile strength, tear resistance, and deformation recovery ability—i.e., high elasticity—thereby reducing its stress during wet use. The probability of accidental breakage or excessive elongation during the process is reduced. Each layer is bonded by a biodegradable unsaturated polyester emulsion. After curing, this adhesive can form continuous and strong chemical bonds at the interface of each layer, realizing the effective transfer of stress between different layers. Compared with traditional physical entanglement or non-degradable chemical adhesives, the emulsion itself is biodegradable and will not form permanent chemical pollution. After the product's service life ends, the materials used can undergo biodegradation under specific environmental conditions, eventually transforming into water, carbon dioxide, and biomass, achieving full-component environmental friendliness. Through the independent and synergistic effects of each functional layer, the contradiction between the strength, high elasticity, washability, and degradability of nonwoven products can be comprehensively balanced, improving the environmental friendliness of nonwoven products.

[0009] Optionally, the biodegradable unsaturated polyester emulsion is prepared by mixing one or more of the following: water-based unsaturated polyester resin, starch, and cellulose nanofibers.

[0010] By adopting the above technical solutions, water-based unsaturated polyester resin can provide certain adhesive strength and film-forming properties. Its water-based nature indicates that the emission of volatile organic compounds is reduced during the production process, meeting green environmental protection requirements. Starch, as a natural polysaccharide, is an inexpensive bio-based filler that can partially replace synthetic resins. It is easily decomposed by microorganisms, reducing the carbon footprint. Furthermore, starch molecules are rich in hydroxyl groups, which can form hydrogen bonds with the fiber surface to enhance adhesion, and can also undergo physical or weak chemical reactions with unsaturated polyester to improve the internal structure between adhesive layers. Cellulose nanofibers have a high specific surface area and can form a micro-nanofiber network in the adhesive matrix, playing a reinforcing and toughening role, improving the strength and water resistance of the adhesive layer. At the same time, cellulose nanofibers have good chemical similarity and compatibility with matrix fibers such as wood pulp and viscose, and can deeply penetrate into the fiber network to improve bonding strength. Therefore, by limiting the biodegradable resin to not containing polyester emulsion, it is no longer a simple connecting medium, but can combine strength, bonding, and rapid degradation, thereby improving the user experience and environmental friendliness of the product.

[0011] Optionally, the biodegradable fiber includes, but is not limited to, one or more combinations of biodegradable unsaturated polyester fiber, polylactic acid fiber, and polyhydroxyalkanoate, wherein the basis weight of the biodegradable fiber is 10-35 g / m².

[0012] By adopting the above technical solutions, biodegradable fibers made from synthetic or bio-based resins can generally provide higher strength, wear resistance and better dimensional stability, making up for the shortcomings of pure cellulose products in mechanical properties. Different types of biodegradable fibers have different degradation rates and triggering conditions, such as compost, soil, seawater, etc., and can be formulated according to the expected service life of the product and the waste treatment environment, thereby achieving controllability of degradation conditions. If the fiber basis weight is too low, the fiber web will be too thin, and its effect as a reinforcing layer and functional surface layer will be insignificant, failing to effectively bear stress and provide a good user experience. If the basis weight is too high, the product may become too stiff and less flexible. At the same time, because synthetic fibers are generally less hydrophilic than wood pulp, an excessively thick layer will hinder the rapid penetration and diffusion of water, thus delaying the dissolution process of the core layer. This basis weight range allows the first and second fiber web layers to form a dense and flexible film-like structure, providing a smooth and comfortable surface while effectively protecting the internal core and skeleton layers. It can evenly distribute stress under external force, improving the product's high elasticity and durability. At the same time, this thickness ensures that water molecules can quickly pass through and reach the hydrophilic core layer, triggering a rapid disintegration process, thus improving the environmental friendliness of nonwoven products.

[0013] Optionally, the mass fraction of short wood pulp fibers in the mixed cellulose core layer gradually increases from one surface to the other, while the mass fraction of biodegradable fibers gradually decreases accordingly.

[0014] By adopting the above technical solution, the side with a gradually increasing proportion of short wood pulp fibers will correspondingly have enhanced water absorption and dispersibility under water flow. The side with a higher proportion of biodegradable fibers will have relatively higher toughness, water retention, and durability. When this gradient core layer is placed in a composite structure, it can be oriented and stacked as needed, thereby achieving a smooth transition in unidirectional liquid guiding performance. At the same time, the continuous change in composition reduces stress concentration at the interfaces of different materials, allowing stress to be smoothly transferred to high-strength areas when the material is stretched, reducing the risk of interface delamination and damage, and further enhancing the product's elasticity and durability. In addition, different types of... Biodegradable fibers have different degradation rates and triggering conditions. By precisely adjusting the ratio of different types of biodegradable fibers to wood pulp short fibers, nonwoven products can have different degradation rates and triggering conditions during degradation, thereby achieving controllability of degradation behavior. For example, if the side with high wood pulp content faces the inside of the product and the side with high biodegradable fiber content is used as the contact surface, the liquid can be quickly drawn from the contact surface and guided to the more absorbent inner core layer. This allows the product to preferentially dissolve or biodecompose from the inside after use, promoting the disintegration of the overall structure, reducing the probability of inconsistent overall product dispersion and decomposition rates, and thus improving the environmental friendliness of nonwoven products.

[0015] Optionally, the second fiber web layer further includes wood pulp short fibers, wherein the mass ratio of the biodegradable fibers to the wood pulp short fibers is 1:0.6 to 1, and the second fiber web layer is obtained by wet web formation or hydroentangling reinforcement of the biodegradable fibers and wood pulp short fibers.

[0016] By adopting the above technical solution, the surface of a single biodegradable synthetic fiber may be relatively hydrophobic. However, by introducing a certain proportion of short wood pulp fibers, the hydrophilicity of this layer is significantly improved. This is beneficial for the product during use, such as when used as a wiping cloth, as it can quickly absorb liquids. It also facilitates the rapid penetration of water when washed away, promoting the disintegration of the overall structure. While maintaining a certain surface strength, it improves hydrophilicity and a soft touch. In addition, since the main components of the wood pulp fiber and the core layer are the same, through wet web forming or hydroentangling reinforcement processes, the wood pulp fibers in the second fiber web layer can interweave and entangle with the fibers on the surface of the core layer. Combined with the action of biodegradable adhesives, this forms a region that transitions from the surface layer to the core layer in terms of composition and structure, enhancing the interlayer bonding strength, reducing the risk of delamination, and making the product more robust and durable.

[0017] Secondly, the present invention provides a production process for environmentally friendly, high-elasticity, fast-dissolving, and biodegradable nonwoven fabrics. Using the environmentally friendly, high-elasticity, fast-dissolving, and biodegradable nonwoven fabrics described in the first aspect, the invention achieves its objective through the following technical solutions: The production process for environmentally friendly, high-elasticity, fast-dissolving, and biodegradable nonwoven fabrics includes the following steps: Fiber pretreatment steps: short wood pulp fibers are subjected to disc milling to control the wood pulp concentration at 3-5%; biodegradable fibers are subjected to milling under pressure of 0.2-0.3 MPa to cause them to absorb water and deform under pressure; and viscose fiber filaments are spun to obtain viscose fiber skeleton layer. Mixing Step I: The pretreated wood pulp short fibers and biodegradable fibers are fed into the pulp distributor according to the ratio, so that the pulp is combined on the forming mesh and hydroentangled to obtain the first fiber web layer and the second fiber web layer. Mixing Step II: The pretreated wood pulp short fibers and biodegradable fibers are fed into the pulp distributor according to the ratio, so that the pulp is combined on the forming wire and hydroentangled to obtain the mixed cellulose core layer; Composite lamination steps: The first fiber web layer, the mixed cellulose core layer, the viscose fiber skeleton layer and the second fiber web layer are laminated in sequence, and a biodegradable unsaturated polyester resin emulsion is uniformly sprayed between the layers. Drying and curing steps: The biodegradable unsaturated polyester resin emulsion is cross-linked and cured by low-temperature hot air drying or ultraviolet irradiation, bonding the layers into a whole to obtain an environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric.

[0018] By employing the above technical solutions, the short wood pulp fibers are subjected to disc milling treatment, which breaks them down into fine fibers, exposing more hydroxyl groups and fiber hairs. This enhances their entanglement ability during hydroentangling and their hydrogen bond strength with other fibers. The biodegradable fibers are then subjected to pressure milling treatment, which disrupts their smooth surface structure, making them more prone to deformation in a wet state and creating a tight mechanical interlock with the cellulose fibers. This facilitates the formation of a uniform and stable fiber web. A strategy of separate forming and recombining is adopted, allowing independent control of the first and second fiber web layers and the mixed cellulose core layer, based on the functional requirements of each layer, such as the softness and delicacy of the surface layer or the rapid liquid absorption of the core layer. By optimizing fiber ratio, basis weight, or uniformity, and using a spray-applied biodegradable unsaturated polyester emulsion for interlayer bonding, the adhesive is evenly and thinly distributed, reducing the probability of localized over-hardening or pore blockage. Low-temperature or ultraviolet methods are used to ensure the adhesive fully cross-links to form a high-strength network while reducing high-temperature damage to cellulose fibers and heat-sensitive biodegradable fibers, thus improving the natural elasticity and degradation performance of the fibers. Through the independent and synergistic effects of each functional layer, the contradictions between the strength, high elasticity, washability, and degradability of nonwoven products can be comprehensively balanced, thereby improving the environmental friendliness of nonwoven products.

[0019] Optionally, the mixing II step is further updated as follows: the pretreated wood pulp short fibers are made into a first pulp suspension with a concentration of 0.5% to 1.5%, and the biodegradable fibers are made into a second pulp suspension with a concentration of 0.5% to 1.5%. The first pulp suspension and the second pulp suspension are continuously fed into the pulp distributor through the first valve and the second valve, respectively. The opening of the first valve gradually increases linearly from one side of the forming mesh to the other side, and the opening of the second valve gradually decreases linearly from one side of the forming mesh to the other side, so that the two pulps merge and overlap on the forming mesh, and a mixed cellulose core layer is obtained by hydroentanglement.

[0020] By employing the above technical solution, and by preparing and combining two different pulp suspensions, precise control of fiber structure distribution is achieved. Dynamic linear control of the opening of the two valves ensures that, in the transverse direction of the forming mesh, the amount of wood pulp fibers deposited per unit area continuously increases from one side to the other, while the amount of biodegradable fibers correspondingly decreases. When these two pulps with opposite concentration gradients are combined and superimposed on the forming mesh, they form a transition zone with continuously changing composition in the thickness direction of the core layer under the shear force of the water flow and the interweaving effect of the fibers themselves, rather than a clear interface. This gradient structure eliminates internal stress concentration that may be caused by abrupt changes in material properties, allowing stress to be smoothly transferred to areas of lower strength when the material is subjected to bending or tension. The high-grade gradient core layer enhances the integrity and durability of the core layer and achieves a directional transition in performance, such as a gradual change in hydrophilicity and dispersibility from one side to the other. This creates conditions for the product to achieve functions such as one-way liquid guidance. The gradient core layer produced by this method has a structure closer to natural materials, improves the natural elasticity of the fibers, and exhibits superior and more stable performance. By precisely adjusting the ratio of different types of biodegradable fibers to wood pulp short fibers, nonwoven products can have different degradation rates and triggering conditions during degradation, thereby achieving controllability of degradation behavior. This allows the product to preferentially dissolve or biodegrade from the inside after use, promoting the disintegration of the overall structure, reducing the probability of inconsistent overall product dispersion and decomposition rates, and thus improving the environmental friendliness of nonwoven products.

[0021] Optionally, the mixing II step is further updated as follows: the pretreated wood pulp short fibers and biodegradable fibers are fed into a pulper and made into multiple fiber webs with different fiber ratios by wet web forming or air-laid web forming process. The proportion of wood pulp short fibers gradually decreases and the proportion of biodegradable fibers gradually increases among the multiple fiber webs. They are sequentially merged and stacked on the forming web to obtain a multi-layer fiber web, and then hydroentangled to obtain a mixed cellulose core layer.

[0022] By adopting the above technical solution and preparing multiple fiber webs with fixed but different fiber ratios, the performance of each single-layer structure can be stably and precisely controlled. This layered stacking strategy is relatively easier to implement and control. By setting a rule that the proportion of wood pulp gradually decreases and the proportion of biodegradable fiber gradually increases among multiple fiber webs, these fiber webs with different ratios are laid up in sequence and hydroentangled. The water needle piercing action can force the fibers between different layers to migrate longitudinally, interpenetrate and entangle with each other, so that at the interface of each layer, the fibers are no longer simply stacked, thus blurring the boundaries between layers. The multilayer structure after hydroentanglement can also achieve a smooth transition of mechanical properties and hydrophilic and hydrophobic properties. The process is relatively simple, has low requirements for equipment precision, and is easier to modify and implement on existing production lines.

[0023] Optionally, in the fiber pretreatment step, the viscose fiber filaments are spun to obtain a viscose fiber skeleton layer. Specifically, 20-60mm viscose fiber filaments are twisted and then woven into a yarn mesh structure or oriented web to obtain a viscose fiber skeleton layer.

[0024] By adopting the above technical solutions, simple filament bundles, due to their smooth surface, have limited bonding force with short fiber webs. Twisting transforms continuous viscose filaments into a spatial structure capable of bonding with other fiber web layers, increasing the cohesion between filaments and the overall yarn density. This improves the tensile strength and stiffness of the filaments as reinforcement, enabling them to more effectively bear and distribute loads. Further weaving them into a mesh structure allows for penetration and entanglement by the short fibers of the upper and lower layers after lamination, forming a mechanical interlock that firmly anchors the skeleton layer within the matrix. Furthermore, directional web laying, such as laying the yarns at specific angles, enhances fiber orientation according to the desired anisotropic properties of the final product, providing a primary load-bearing structure, significantly suppressing material deformation, improving the product's high elasticity, and simultaneously enhancing its liquid absorption and washout properties, thereby improving the environmental friendliness of nonwoven fabric products.

[0025] Optionally, an impregnation step may be included between the mixing II step and the composite lamination step: the mixed cellulose core layer is impregnated in a mixed solution containing cellulase and lipase, and then dried at low temperature.

[0026] By adopting the above technical solutions, cellulase specifically catalyzes the hydrolysis of amorphous regions on the surface of cellulose fibers, slightly etching the fiber surface and adjusting roughness and specific surface area. Lipase can hydrolyze residual lipids or certain biodegradable oils on the fiber surface, playing a role in purifying and activating the surface. The fiber surface after enzyme treatment provides more anchoring points for subsequent adhesive spraying. The exposed active groups such as hydroxyl groups can form stronger hydrogen bonds with the polar groups in the adhesive, improving the strength of the core layer and other layers bonded by the adhesive and reducing the risk of delamination during use. In addition, since the enzyme treatment is an aqueous phase reaction carried out under mild conditions and dried at low temperature, the overall damage to the fiber is reduced, which is in line with the principles of green chemistry, reduces the environmental burden, and thus improves the environmental friendliness of nonwoven products.

[0027] Compared with the prior art, the beneficial effects of the present invention are: 1. The mixed cellulose core layer constitutes the main weight component of the nonwoven fabric product. Wood pulp short fibers make up a significant portion of this core layer. These fibers are hydrophilic and easily disintegrate under water flow, providing the product with a certain thickness, as well as good liquid absorption and rapid dissolution. The first and second fiber web layers, as the outer layers, provide surface smoothness, a soft touch, and increased strength. Made of biodegradable fibers, they enhance the overall environmental friendliness of the product. A viscose fiber skeleton layer composed of continuous filaments forms an internal reinforcing network, significantly improving the nonwoven fabric's longitudinal and transverse tensile strength, tear resistance, and deformation recovery ability—i.e., high elasticity—thereby reducing its resistance in a wet state. The probability of accidental breakage or excessive elongation during use is reduced. Each layer is bonded by a biodegradable unsaturated polyester emulsion. After curing, this adhesive can form continuous and strong chemical bonds at the interface of each layer. Compared with traditional physical entanglement or non-degradable chemical adhesives, the emulsion itself is biodegradable and will not form permanent chemical pollution. After the product has been used for a period of time, the materials used can undergo biodegradation under specific environmental conditions, eventually transforming into water, carbon dioxide and biomass, achieving full environmental friendliness. Through the independent and synergistic effects of each functional layer, the contradiction between the strength, high elasticity, washability and degradability of nonwoven products can be comprehensively balanced, thus improving the environmental friendliness of nonwoven products.

[0028] 2. Biodegradable fibers typically offer higher strength, abrasion resistance, and better dimensional stability, compensating for the shortcomings of pure cellulose products in terms of mechanical properties. Different types of biodegradable fibers have different degradation rates and triggering conditions, such as composting, soil, and seawater. They can be formulated according to the expected service life of the product and the waste disposal environment to achieve controllability of degradation conditions. If the fiber basis weight is too low, the fiber web will be too thin, and its effect as a reinforcing layer and functional surface layer will be insignificant, failing to effectively bear stress and provide a good user experience. If the basis weight is too high, the product may become too stiff and less flexible. At the same time, because synthetic fibers are generally less hydrophilic than wood pulp, an excessively thick layer will hinder the rapid penetration and diffusion of water, thus delaying the dissolution process of the core layer. This basis weight range allows the first and second fiber web layers to form a dense and flexible film-like structure, providing a smooth and comfortable surface while effectively protecting the internal core and skeleton layers. It can evenly distribute stress under external force, improving the product's high elasticity and durability. At the same time, this thickness ensures that water molecules can quickly pass through and reach the hydrophilic core layer, triggering a rapid disintegration process, thus improving the environmental friendliness of nonwoven products.

[0029] 3. As the proportion of short wood pulp fibers gradually increases, its water absorption and dispersibility under water flow gradually improve. Conversely, a higher proportion of biodegradable fibers results in higher toughness, water retention, and durability. When this gradient core layer is placed in a composite structure, it can be oriented and stacked as needed, achieving a smooth transition in unidirectional liquid guiding properties. Simultaneously, the continuous variation in composition reduces stress concentration at different material interfaces, minimizing the risk of interfacial delamination and damage, further enhancing the product's elasticity and durability. Furthermore, different types of biodegradable fibers have different degradation rates and triggering conditions. By precisely adjusting the ratio of different types of biodegradable fibers to wood pulp short fibers, nonwoven products can have different degradation rates and triggering conditions during degradation, thus achieving controllability of degradation behavior. For example, if the side with higher wood pulp content faces the inside of the product and the side with higher biodegradable fiber content is used as the contact surface, liquid can be quickly drawn from the contact surface and guided to the more absorbent inner core layer. This allows the product to preferentially dissolve or biodecompose from the inside after use, promoting the disintegration of the overall structure, reducing the probability of inconsistent overall product dispersion and decomposition rates, and thus improving the environmental friendliness of nonwoven products.

[0030] 4. The wood pulp short fibers are disc-milled to break them down into finer fibers, exposing more hydroxyl groups and fiber hairs. This enhances their entanglement ability during hydroentangling and their hydrogen bond strength with other fibers. The biodegradable fibers are pressure-milled to disrupt their smooth surface structure, making them more prone to deformation in a wet state and creating a tight mechanical interlock with the cellulose fibers. This facilitates the formation of a uniform and stable fiber web. A separate forming and then compounding strategy is employed, using a spraying method with biodegradable unsaturated polyester emulsion for interlayer bonding. This ensures a uniform, thin-layer distribution of the adhesive, reducing the probability of localized over-hardening or pore blockage. Low-temperature or ultraviolet methods are used to ensure the adhesive fully cross-links to form a high-strength network while minimizing high-temperature damage to the cellulose fibers and heat-sensitive biodegradable fibers. This improves the fibers' natural elasticity and degradation performance. Through the independent and synergistic effects of each functional layer, a comprehensive balance can be struck between the strength, high elasticity, shock resistance, and biodegradability of the nonwoven fabric product, thus improving its environmental friendliness.

[0031] 5. By preparing and combining two different pulp suspensions, precise control of fiber structure distribution is achieved. Dynamic linear control of the opening of two valves ensures that the amount of wood pulp fibers deposited per unit area continuously increases from one side to the other in the transverse direction of the forming mesh, while the amount of biodegradable fibers decreases accordingly. When these two pulps with opposite concentration gradients are combined and superimposed on the forming mesh, they form a transition zone with continuously changing composition in the thickness direction of the core layer under the shear force of the water flow and the interweaving effect of the fibers themselves. This eliminates internal stress concentration that may be caused by abrupt changes in material properties, allowing stress to be smoothly transferred to areas of higher strength when the material is subjected to bending or tension. This method enhances the integrity and durability of the core layer and achieves a directional transition in performance, such as a gradual change in hydrophilicity and dispersibility from one side to the other. This creates conditions for the product to achieve functions such as one-way liquid guidance. The gradient core layer produced by this method improves the natural elasticity of the fiber, resulting in superior and more stable performance. By precisely adjusting the ratio of different types of biodegradable fibers to wood pulp short fibers, nonwoven products can have different degradation rates and triggering conditions during degradation, thereby achieving controllability of degradation behavior. This allows the product to preferentially dissolve or biodegrade from the inside after use, promoting the disintegration of the overall structure and reducing the probability of inconsistent overall product dispersion and decomposition rates, thus improving the environmental friendliness of nonwoven products. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 This is a system block diagram of the production process of environmentally friendly, high-elasticity, fast-dissolving, and biodegradable nonwoven fabric according to Embodiment 1 of the present invention; Figure 2 This is a system block diagram of the production process of environmentally friendly, high-elasticity, fast-dissolving, and biodegradable nonwoven fabric according to Embodiment 2 of the present invention. Detailed Implementation

[0033] The following will be based on embodiments of the present invention. Figure 1 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] The environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric proposed in this invention comprises, in sequence, a first fiber web layer comprising 10-20% by weight, a mixed cellulose core layer comprising 50-80% by weight, a viscose fiber skeleton layer comprising 5-20% by weight, and the remainder being a second fiber web layer.

[0035] The first fiber web layer is a biodegradable fiber, and the mixed cellulose core layer includes 70-90% wood pulp short fibers by weight and the remainder being biodegradable fibers. The mass fraction of wood pulp short fibers in the mixed cellulose core layer gradually increases from 60% to 90% from one surface to the other, either linearly or non-linearly, while the mass fraction of biodegradable fibers gradually decreases accordingly, thereby forming a continuous component gradient structure within the mixed cellulose core layer.

[0036] The mixed cellulose core layer constitutes the main weight component of the nonwoven fabric product, giving it a certain thickness, liquid absorption capacity, and rapid dissolution. As the proportion of short wood pulp fibers gradually increases, its water absorption and dispersibility gradually improve; conversely, the side with a higher proportion of biodegradable fibers exhibits relatively higher water retention and durability. This gradient structure can be oriented and stacked according to requirements, achieving a transition in unidirectional liquid-guiding properties. Simultaneously, the change in composition reduces stress concentration, minimizes the risk of interfacial delamination, and enhances the product's elasticity and durability.

[0037] Furthermore, different types of biodegradable fibers have different degradation rates and triggering conditions. By precisely adjusting the ratio of different types of biodegradable fibers to wood pulp short fibers, nonwoven products can have different degradation rates and triggering conditions during degradation, thereby achieving controllability of degradation behavior. For example, if the side with a high wood pulp content faces the inside of the product and the side with a high biodegradable fiber content is used as the contact surface, the liquid can be quickly drawn from the contact surface and guided to the more absorbent inner core layer. This allows the product to preferentially dissolve or biodecompose from the inside after use, promoting the disintegration of the overall structure, reducing the probability of inconsistent overall product dispersion and decomposition rates, and thus improving the environmental friendliness of nonwoven products.

[0038] The viscose fiber skeleton layer is viscose fiber filament, and the second fiber web layer includes biodegradable fibers and wood pulp short fibers. The mass ratio of the biodegradable fibers to the wood pulp short fibers is 1:0.6 to 1. The second fiber web layer is made by wet web formation or hydroentangling of biodegradable fibers and wood pulp short fibers.

[0039] By constructing a viscose fiber skeleton layer from continuous filaments, the longitudinal and transverse tensile strength, tear resistance, and high elasticity of the nonwoven fabric are significantly improved. While the surface of a single biodegradable synthetic fiber may be relatively hydrophobic, the introduction of a certain proportion of short wood pulp fibers significantly enhances the hydrophilicity of this layer. This allows the product to quickly absorb liquids during use and also facilitates rapid water penetration during rinsing, promoting the disintegration of the overall structure. While maintaining a certain surface strength, this improves hydrophilicity and a soft touch. Furthermore, since the wood pulp fibers are the same main component as the core layer, through wet web forming or hydroentangling reinforcement processes, the wood pulp fibers in the second fiber web layer can interweave and entangle with the fibers on the core layer surface. Combined with the action of biodegradable adhesives, this forms a transitional region in composition and structure from the surface layer to the core layer, enhancing interlayer bonding strength, reducing the risk of delamination, and making the product more robust and durable.

[0040] The first fiber web layer, the mixed cellulose core layer, the viscose fiber skeleton layer, and the second fiber web layer are bonded together by a water-based biodegradable unsaturated polyester emulsion that has been UV-cured or thermally crosslinked. The biodegradable unsaturated polyester emulsion partially penetrates into the interior of each fiber web to form an interpenetrating network structure, thereby achieving a high degree of bonding between the layers.

[0041] Each layer is bonded together with a biodegradable unsaturated polyester emulsion. After curing, this adhesive forms a continuous and strong chemical bond at the interface of each layer, enabling effective stress transfer between different layers. At the end of the product's service life, the materials used can biodegrade synergistically under specific environmental conditions, improving environmental friendliness. Through the independent and synergistic effects of each functional layer, the contradiction between the strength, high elasticity, shock resistance and degradability of nonwoven products can be comprehensively balanced, thus improving the environmental friendliness of nonwoven products.

[0042] The biodegradable unsaturated polyester emulsion is prepared by mixing one or more of the following: including but not limited to water-based unsaturated polyester resin, starch, and cellulose nanofibers. The wood pulp staple fiber is preferably hardwood pulp staple fiber. The biodegradable fiber is prepared by hot air rolling or spunbonding processes, including but not limited to one or more of the following: biodegradable unsaturated polyester fiber, viscose fiber, polylactic acid fiber, polyhydroxyalkanoate, and polybutylene adipate / terephthalate fiber. The biodegradable fiber has a basis weight of 10–35 g / m².

[0043] Waterborne unsaturated polyester resins can provide certain adhesive strength and film-forming properties. Their waterborne characteristics meet green and environmental protection requirements. Starch can partially replace synthetic resins, reduce carbon footprint, and improve the internal structure between adhesive layers. Cellulose nanofibers have a high specific surface area and can play a reinforcing and toughening role in the adhesive matrix, improving the strength and water resistance of the adhesive layer. Cellulose nanofibers have good chemical similarity and compatibility, which can improve bonding force. By limiting the biodegradable polyester emulsion, it can combine strength, bonding and rapid degradation, thereby improving the user experience and environmental friendliness of the product.

[0044] Biodegradable fibers made from bio-based resins typically offer higher strength, abrasion resistance, and better dimensional stability. Different types of biodegradable fibers have different degradation rates and triggering conditions, such as composting, soil, and seawater. They can be formulated according to the product's expected lifespan and waste disposal environment to achieve controllability of degradation conditions. If the fiber basis weight is too low, the fiber web will be too thin, and its effect as a reinforcing layer and functional surface layer will be insignificant, failing to effectively bear stress and provide a good user experience. If the basis weight is too high, the product may become too stiff and less flexible. At the same time, because synthetic fibers are generally less hydrophilic than wood pulp, an excessively thick layer will hinder the rapid penetration and diffusion of water, thus delaying the dissolution process of the core layer. This basis weight range allows the first and second fiber web layers to form a dense and flexible film-like structure, providing a smooth and comfortable surface while effectively protecting the internal core and skeleton layers. It can evenly distribute stress under external force, improving the product's high elasticity and durability. At the same time, this thickness ensures that water molecules can quickly pass through and reach the hydrophilic core layer, triggering a rapid disintegration process, thus improving the environmental friendliness of nonwoven products.

[0045] Example 1: This example discloses a production process for environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric, referring to... Figure 1 It includes fiber pretreatment steps, mixing step I, mixing step II, composite lamination step, and drying and curing steps.

[0046] Fiber pretreatment steps: short wood pulp fibers are subjected to disc milling to control the wood pulp concentration at 3-5%. Biodegradable fibers are subjected to milling under pressure of 0.2-0.3 MPa to cause them to absorb water and deform under pressure. 20-60 mm viscose fiber filaments are twisted and woven into a yarn mesh structure to obtain the viscose fiber skeleton layer.

[0047] Mixing Step I: The pretreated wood pulp short fibers and biodegradable fibers are fed into the pulp distributor according to the ratio, so that the pulp is combined on the forming net and hydroentangled to obtain the first fiber web layer and the second fiber web layer.

[0048] Mixing Step II: Pretreated wood pulp short fibers and biodegradable fibers are fed into a pulp distributor according to a specified ratio, allowing the pulp to converge on a forming mesh and undergo hydroentanglement to obtain a mixed cellulose core layer. The pretreated wood pulp short fibers are prepared into a first pulp suspension with a concentration of 0.5% to 1.5%, and the biodegradable fibers are prepared into a second pulp suspension with a concentration of 0.5% to 1.5%. The first and second pulp suspensions are continuously fed into the pulp distributor through a first valve and a second valve, respectively. The opening of the first valve gradually increases linearly from one side of the forming mesh to the other, while the opening of the second valve gradually decreases linearly from one side of the forming mesh to the other, allowing the two pulps to converge and overlap on the forming mesh and undergo hydroentanglement to obtain a mixed cellulose core layer.

[0049] Composite lamination steps: The first fiber web layer, the mixed cellulose core layer, the viscose fiber skeleton layer and the second fiber web layer are laminated in sequence, and a biodegradable unsaturated polyester resin emulsion is evenly sprayed between the layers.

[0050] Drying and curing steps: The biodegradable unsaturated polyester resin emulsion is cross-linked and cured by low-temperature hot air drying at 50-60℃ or ultraviolet irradiation, bonding the layers into a whole to obtain an environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric.

[0051] The implementation principle of the environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric in this embodiment is as follows: The short wood pulp fibers are disc-milled to break them down into finer fibers, exposing more hydroxyl groups and fiber hairs. This enhances their entanglement ability during hydroentangling and their hydrogen bonding with other fibers. The biodegradable fibers are pressure-milled to disrupt their smooth surface structure, making them more prone to deformation in a wet state and creating a tight mechanical interlock with the cellulose fibers. This facilitates the formation of a uniform and stable fiber web. A strategy of separate forming and recombining is adopted, allowing for independent control of the first and second fiber web layers and the mixed cellulose core layer. Based on the functional requirements of each layer, such as the softness and delicacy of the surface layer or the rapid liquid absorption and dispersion of the core layer, the fiber ratio, basis weight, or uniformity are optimized.

[0052] Interlayer bonding is achieved by spraying biodegradable unsaturated polyester emulsion, ensuring uniform and thin-layer distribution of the adhesive and reducing the probability of localized over-hardening or pore blockage. Low-temperature or ultraviolet light methods are used to fully cross-link the adhesive, forming a high-strength network while reducing high-temperature damage to cellulose fibers and heat-sensitive biodegradable fibers. This improves the natural elasticity and degradation performance of the fibers. Through the independent and synergistic effects of each functional layer, the contradictions between the strength, high elasticity, washability, and biodegradability of nonwoven products can be comprehensively balanced, thereby improving the environmental friendliness of nonwoven products.

[0053] The surface of the long filament bundle is smooth, and its bonding force with the short fiber web is limited. Twisting it transforms the continuous viscose filament into a spatial structure that can combine with other fiber web layers, thereby improving its tensile strength and stiffness as a reinforcement, enabling it to more effectively bear and distribute loads. Further weaving it into a yarn-like structure allows it to be penetrated and entangled by the short fibers of the upper and lower layers after lamination, making the skeleton layer firmly embedded in the matrix. By using directional web laying, such as laying the yarns at a specific angle, the orientation of the fibers can be enhanced according to the anisotropic properties required by the final product, providing the main load-bearing structure, improving the high elasticity of the product, and improving the product's liquid absorption and washout properties, thereby improving the environmental friendliness of the nonwoven fabric product.

[0054] By preparing and combining two different pulp suspensions, precise control of fiber structure distribution is achieved. Dynamic linear control of the opening of two valves ensures that the number of wood pulp fibers deposited per unit area in the transverse direction of the forming mesh continuously increases from one side to the other, while the amount of biodegradable fibers deposited decreases accordingly. When these two pulps with opposite concentration gradients are combined and superimposed on the forming mesh, a transition zone with continuously changing composition is formed in the thickness direction of the core layer under the shear force of the water flow and the interweaving of fibers. This reduces the potential internal stress concentration and allows the stress to be smoothly transferred to the area with higher strength when the material is subjected to bending or stretching, thereby improving the integrity and durability of the core layer.

[0055] For example, the gradual change in hydrophilicity and dispersibility from one side to the other creates conditions for the product to achieve functions such as one-way liquid guidance. The gradient core layer produced by this method has a structure closer to natural materials, improves the natural elasticity of the fiber, and has better and more stable performance. By precisely adjusting the ratio of different types of biodegradable fibers to wood pulp short fibers, nonwoven products can have different degradation rates and triggering conditions during degradation, thereby achieving controllability of degradation behavior. This allows the product to preferentially dissolve or biodecompose from the inside after use, promoting the disintegration of the overall structure, reducing the probability of inconsistent overall product dispersion speed and decomposition speed, and thus improving the environmental friendliness of nonwoven products.

[0056] Example 2: This example discloses a production process for environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric, referring to... Figure 2 It includes fiber pretreatment steps, mixing step I, mixing step II, impregnation step, composite lamination step, and drying and curing step.

[0057] Fiber pretreatment steps: short wood pulp fibers are subjected to disc milling to control the wood pulp concentration at 3-5%. Biodegradable fibers are subjected to milling under pressure of 0.2-0.3 MPa to cause them to absorb water and deform under pressure. Viscose fiber filaments of 20-60 mm are twisted and laid in a directional manner to obtain a viscose fiber skeleton layer.

[0058] Mixing Step I: The pretreated wood pulp short fibers and biodegradable fibers are fed into the pulp distributor according to the ratio, so that the pulp is combined on the forming net and hydroentangled to obtain the first fiber web layer and the second fiber web layer.

[0059] Mixing Step II: The pretreated wood pulp short fibers and biodegradable fibers are fed into a pulper and made into multiple fiber webs with different fiber ratios through wet web forming or air-laid web forming processes. The proportion of wood pulp short fibers gradually decreases and the proportion of biodegradable fibers gradually increases among the multiple fiber webs. They are sequentially merged and stacked on the forming web to obtain a multi-layer fiber web, and then hydroentangled to obtain a mixed cellulose core layer.

[0060] Impregnation process: The mixed cellulose core layer is impregnated in a mixed solution containing cellulase and lipase, treated at 40-50°C for 10-30 minutes, and then dried at low temperature.

[0061] Composite lamination steps: The first fiber web layer, the mixed cellulose core layer, the viscose fiber skeleton layer and the second fiber web layer are laminated in sequence, and a biodegradable unsaturated polyester resin emulsion is evenly sprayed between the layers.

[0062] Drying and curing steps: The biodegradable unsaturated polyester resin emulsion is cross-linked and cured by low-temperature hot air drying or ultraviolet irradiation, bonding the layers into a whole to obtain an environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric.

[0063] The implementation principle of the environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric production process in this embodiment is as follows: Short wood pulp fibers are subjected to disc milling treatment to enhance their entanglement ability and hydrogen bonding force. Biodegradable fibers undergo pressure milling treatment to facilitate deformation in a wet state, promoting the formation of a uniform and stable fiber web. A strategy of separate forming and then compounding is employed to regulate the first and second fiber web layers and the mixed cellulose core layer, optimizing fiber ratios, basis weight, and uniformity according to the functional requirements of each layer. Interlayer bonding is achieved by spraying biodegradable unsaturated polyester emulsion, ensuring a uniform, thin layer distribution of the adhesive. Low-temperature or ultraviolet light treatments allow the adhesive to fully cross-link, forming a high-strength network and improving the fiber's natural elasticity and biodegradability. Through the independent and synergistic effects of each functional layer, a comprehensive balance is achieved between the strength, high elasticity, shock resistance, and biodegradability of the nonwoven fabric product, thus improving its environmental friendliness.

[0064] By preparing multiple fiber webs with fixed but different fiber ratios, the performance of each single-layer structure can be precisely controlled. This layered stacking strategy is relatively easier to implement and control. By setting a rule that the proportion of wood pulp gradually decreases and the proportion of biodegradable fiber gradually increases among multiple fiber webs, these fiber webs with different ratios are laid up in sequence and hydroentangled. The water needle piercing action can force the fibers between different layers to migrate longitudinally, interpenetrate and entangle with each other, so that at the interface of each layer, the fibers are no longer simply stacked, thus blurring the boundaries between layers. The multilayer structure after hydroentanglement can also achieve a smooth transition of mechanical properties and hydrophilic and hydrophobic properties. The process is relatively simple, has low requirements for equipment precision, and is easier to modify and implement on existing production lines.

[0065] Cellulase specifically catalyzes the hydrolysis of amorphous regions on the surface of cellulose fibers, slightly etching the fiber surface and adjusting roughness and specific surface area. Lipase can hydrolyze residual lipids or certain biodegradable oils on the fiber surface, purifying and activating the surface. The fiber surface after enzyme treatment provides more anchoring points for subsequent adhesive coating. The exposed active groups such as hydroxyl groups can form stronger hydrogen bonds with the polar groups in the adhesive, improving the bonding strength between the core layer and other layers through the adhesive and reducing the risk of delamination during use. In addition, since the enzyme treatment is an aqueous phase reaction carried out under mild conditions and dried at low temperature, the overall damage to the fiber is reduced, which conforms to the principles of green chemistry, reduces the environmental burden, and thus improves the environmental friendliness of nonwoven products.

[0066] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric, characterized by: The environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric comprises, in sequence, a first fiber web layer comprising 10-20% by weight, a mixed cellulose core layer comprising 50-80% by weight, a viscose fiber skeleton layer comprising 5-20% by weight, and the remainder being a second fiber web layer. The mixed cellulose core layer comprises 70-90% wood pulp short fibers and the remainder being biodegradable fibers by weight. The viscose fiber skeleton layer is composed of viscose fiber filaments. The first fiber web layer is composed of biodegradable fibers. The second fiber web layer comprises biodegradable fibers. The first fiber web layer, the mixed cellulose core layer, the viscose fiber skeleton layer, and the second fiber web layer are bonded together by a biodegradable unsaturated polyester emulsion.

2. The environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric according to claim 1, characterized in that: The biodegradable unsaturated polyester emulsion is prepared by mixing one or more of the following: water-based unsaturated polyester resin, starch, and cellulose nanofibers.

3. The environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric according to claim 1, characterized in that: The biodegradable fiber includes, but is not limited to, one or more of biodegradable unsaturated polyester fiber, polylactic acid fiber, and polyhydroxyalkanoate, and the basis weight of the biodegradable fiber is 10-35 g / m².

4. The environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric according to claim 1, characterized in that: The mass fraction of short wood pulp fibers in the mixed cellulose core layer gradually increases from one surface to the other, while the mass fraction of biodegradable fibers gradually decreases accordingly.

5. The environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric according to claim 1, characterized in that: The second fiber web layer also includes wood pulp short fibers, and the mass ratio of the biodegradable fibers to the wood pulp short fibers is 1:0.6 to 1. The second fiber web layer is made by wet web formation or hydroentangling reinforcement of biodegradable fibers and wood pulp short fibers.

6. A production process for environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric, using the environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric as described in any one of claims 1-5, characterized in that... Includes the following steps: Fiber pretreatment steps: short wood pulp fibers are subjected to disc milling to control the wood pulp concentration at 3-5%; biodegradable fibers are subjected to milling under pressure of 0.2-0.3 MPa to cause them to absorb water and deform under pressure; and viscose fiber filaments are spun to obtain viscose fiber skeleton layer. Mixing Step I: The pretreated wood pulp short fibers and biodegradable fibers are fed into the pulp distributor according to the ratio, so that the pulp is combined on the forming mesh and hydroentangled to obtain the first fiber web layer and the second fiber web layer. Mixing Step II: The pretreated wood pulp short fibers and biodegradable fibers are fed into the pulp distributor according to the ratio, so that the pulp is combined on the forming wire and hydroentangled to obtain the mixed cellulose core layer; Composite lamination steps: The first fiber web layer, the mixed cellulose core layer, the viscose fiber skeleton layer and the second fiber web layer are laminated in sequence, and a biodegradable unsaturated polyester resin emulsion is uniformly sprayed between the layers. Drying and curing steps: The biodegradable unsaturated polyester resin emulsion is cross-linked and cured by low-temperature hot air drying or ultraviolet irradiation, bonding the layers into a whole to obtain an environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric.

7. The environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric production process according to claim 6, characterized in that: The mixing II step is further updated as follows: the pretreated wood pulp short fibers are made into a first pulp suspension with a concentration of 0.5% to 1.5%, and the biodegradable fibers are made into a second pulp suspension with a concentration of 0.5% to 1.5%. The first and second pulp suspensions are continuously fed into the pulp distributor through the first and second valves, respectively. The opening of the first valve gradually increases linearly from one side of the forming mesh to the other side, and the opening of the second valve gradually decreases linearly from one side of the forming mesh to the other side, so that the two pulps merge and overlap on the forming mesh, and are hydroentangled to obtain a mixed cellulose core layer.

8. The environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric production process according to claim 6, characterized in that: The mixing II step is further updated as follows: the pretreated wood pulp short fibers and biodegradable fibers are fed into a pulper and made into multiple fiber webs with different fiber ratios by wet web forming or air-laid web forming process. The proportion of wood pulp short fibers gradually decreases and the proportion of biodegradable fibers gradually increases among the multiple fiber webs. They are sequentially merged and stacked on the forming web to obtain a multi-layer fiber web, and then hydroentangled to obtain a mixed cellulose core layer.

9. The environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric production process according to claim 6, characterized in that: In the fiber pretreatment step, the viscose fiber filaments are spun to obtain a viscose fiber skeleton layer. Specifically, 20-60mm viscose fiber filaments are twisted and then woven into a yarn mesh structure or oriented web to obtain a viscose fiber skeleton layer.

10. The environmentally friendly, high-elasticity, fast-dissolving, biodegradable nonwoven fabric production process according to claim 6, characterized in that: The mixing II step and the composite lamination step also include an impregnation treatment step: the mixed cellulose core layer is impregnated in a mixed solution containing cellulase and lipase, and then dried at low temperature.

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