A SAP non-continuous application type absorbent substrate and a method for manufacturing the same

Abstract

The application discloses a SAP non-continuous application type absorbing base material and a preparation method thereof, and belongs to the technical field of absorbing materials of sanitary products. The absorbing base material comprises at least two fiber absorbing layers which are arranged in a stack mode, and a SAP layer arranged between the two adjacent fiber absorbing layers; the SAP layer is distributed in a non-continuous mode between the fiber absorbing layers, and the SAP layers between different layers are distributed in a staggered mode in a vertical projection direction. The SAP non-continuous application and the staggered distribution between layers are used, so that the SAP does not form a dense whole sol gel barrier layer after water absorption and expansion, liquid infiltration channels are ensured to be unobstructed during multiple absorption, and the secondary absorption speed can reach 3.0-3.5s; meanwhile, the thickness of the base material can be controlled to be less than 1mm under the premise of ensuring high SAP addition, and the synergy and unity of high absorption and ultra-thin are realized. The application can be widely applied to products such as sanitary pads, sanitary napkins, paper diapers and nursing pads.

Description

Technical Field

[0001] This invention relates to the field of personal hygiene absorbent care products, specifically to an SAP discontinuous application type absorbent substrate and its preparation method. Background Technology

[0002] The core of personal hygiene absorbent care products is the absorbent component, whose core function is to achieve "absorption + locking" of liquid excretions (such as menstrual blood, urine, etc.). "Absorption" is the basic function, requiring the material to have a high absorption rate and absorption capacity to reduce the time the liquid stays on the product surface and reduce the risk of horizontal leakage and surface residue. "Locking" is an added-value function, requiring the material to minimize liquid backflow under pressure to keep the surface dry.

[0003] Currently, the mainstream absorbent material solution for commercially available absorbent care products is a combination of "fluff pulp + SAP". Fluff pulp is a natural plant fiber material, characterized by rapid liquid wetting and strong instantaneous absorption capacity, undertaking rapid absorption and temporary liquid storage functions in the initial stage of liquid contact with the absorbent component; however, its absorption rate is relatively low (approximately 15-20 times) and it lacks water-locking ability, making it prone to leakage under pressure. SAP (Super Absorbent Polymer) is an acrylic superabsorbent polymer with a water absorption rate of 300-500 times and excellent water-locking properties, but its absorption rate is relatively slow. The combination of the two achieves complementary performance and is recognized as the preferred absorbent material system in the field.

[0004] With consumers increasingly demanding thinner and lighter absorbent products, the thickness of absorbent substrates is continuously decreasing, objectively requiring an increase in the proportion of SAP added to absorbent materials to maintain or improve the total absorption capacity. To overcome the limitations of the SAP addition ratio in traditional mixed web laying methods, the industry generally adopts a "sandwich" interlayer application process, which involves uniformly applying SAP in a continuous planar manner between the upper and lower fiber webs. While this process can achieve a high proportion of SAP addition, it also gives rise to several technical problems that urgently need to be solved:

[0005] 1. SAP expands in volume and forms a viscous substance upon contact with liquid. When a continuous layer of SAP absorbs water, the particles bond together to form a dense sol-gel barrier layer. This barrier layer significantly reduces the rate of liquid penetration after the initial absorption. When the product encounters a second or subsequent liquid pulse (such as the surge during sanitary napkin use or multiple urinations in diapers), liquid penetration is hindered, and the liquid remains on the product surface for a longer period. This not only increases the risk of side leakage but also creates conditions for microbial growth, potentially harming the user's health.

[0006] 2. The sol layer formed after SAP absorbs water has extremely low wet strength and a significantly reduced coefficient of friction. When subjected to external forces during product use, this layer is prone to slippage or SAP particles to clump together, leading to structural damage to the absorbent material and further deterioration of its absorption performance.

[0007] 3. Insufficient overall wet strength of the absorbent substrate. The fibers of the fluff pulp are only bonded by physical entanglement and pressure, lacking a stable fixed structure; the poor wet strength of SAP itself and the further weakening of the bonding force between fibers with increased addition amount result in low strength of the absorbent substrate in a wet state, making the product prone to delamination, clumping and other phenomena during use, seriously affecting user experience and product reliability.

[0008] 4. The ultra-thin absorbent substrate made to achieve high absorbency is usually quite dense, resulting in an overall stiff substrate. For users with different crotch widths, this can create a noticeable physical presence, reducing comfort.

[0009] To address the aforementioned issues, the industry has attempted to adjust the mixing ratio of fluff pulp and SAP, and optimize the layered structure, but none of these methods have fundamentally solved the core problem of forming a sol layer through continuous planar application of SAP, nor have they achieved a synergistic balance between high SAP addition, ultra-thinness, high absorption performance, and high wet strength.

[0010] In summary, with absorbent products continuously trending towards thinner profiles and higher absorbency, effectively improving the multiple absorption rate and wet strength of the absorbent substrate while ensuring high SAP (Super Absorbent Polymer) content, and maintaining a soft and comfortable user experience, has become a pressing technical challenge in this field. To address this, the applicant, through beneficial exploration and research, has found a solution to the aforementioned problems, and the technical solution described below arose from this context. Summary of the Invention

[0011] One of the technical problems to be solved by the present invention is to provide an SAP discontinuous application type absorbent substrate that addresses the shortcomings of the prior art, effectively improves the multiple absorption speed and wet strength of the absorbent substrate, and also takes into account the soft and comfortable user experience.

[0012] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned SAP discontinuous application type absorbent substrate.

[0013] As a first aspect of the present invention, an SAP discontinuous application type absorbent substrate includes:

[0014] At least two fiber absorption layers are stacked; and

[0015] The SAP layer is disposed between two adjacent fiber absorption layers. The SAP layer is distributed discontinuously between the fiber absorption layers, and the SAP layers located between different layers are staggered in the vertical projection direction.

[0016] In a preferred embodiment of the present invention, the raw material of the fiber absorbent layer is one of plant fiber, a mixture of plant fiber and chemical fiber, or a mixture of plant fiber, chemical fiber and SAP.

[0017] In a preferred embodiment of the present invention, the plant fiber is selected from at least one of fluff pulp, board pulp, cotton fiber, bamboo fiber or viscose fiber; the chemical fiber is selected from at least one of PE / PP staple fiber, PE / PET staple fiber or EVA staple fiber.

[0018] In a preferred embodiment of the present invention, the discontinuous distribution of the SAP layer is a combination of multiple spaced linear application areas, multiple spaced independent point application areas, or a combination of linear and point distributions.

[0019] In a preferred embodiment of the present invention, when the SAP layer is distributed linearly, the application width of the SAP layer is 3-5 mm, and the interval between adjacent linear SAP layers is 8-10 mm; when the SAP layer is distributed dot-like, the diameter of a single point of the SAP layer is 2-3 mm, and the distance between adjacent dot-like SAP layers is 5-6 mm; the amount of SAP added between single layers is 5-7 gsm.

[0020] In a preferred embodiment of the present invention, a wet strength reinforcing mesh is provided between adjacent fiber absorption layers.

[0021] In a preferred embodiment of the present invention, the wet strength reinforcing mesh is one of PP mesh, PET mesh, PE / PP spunbond nonwoven fabric or hot air nonwoven fabric, and the basis weight of the wet strength reinforcing mesh is 8-10 gsm.

[0022] In a preferred embodiment of the present invention, the surface of the absorbent substrate is provided with a flow channel along its longitudinal direction.

[0023] In a preferred embodiment of the present invention, the guide channel is a triangular guide channel or an arc-shaped guide channel, and is provided on one side or both sides; the outer width of the guide channel is 0.8 to 1 mm, the depth is 30% to 50% of the thickness of the absorbent substrate, and the channel spacing is 4 to 5 mm.

[0024] In a preferred embodiment of the present invention, the total basis weight of the absorbent substrate is 60-160 gsm and the thickness is ≤1 mm.

[0025] In a preferred embodiment of the present invention, the fiber absorbent layer has a three-layer structure, including a surface absorbent layer, an intermediate absorbent layer, and a bottom absorbent layer; the surface absorbent layer and the bottom absorbent layer have the same raw material composition, while the intermediate absorbent layer has a different raw material composition from the surface absorbent layer and the bottom absorbent layer.

[0026] In a preferred embodiment of the present invention, the surface absorbent layer and the bottom absorbent layer are a mixture of plant fibers and chemical fibers, wherein the mass percentage of plant fibers is 75% to 80%, the mass percentage of chemical fibers is 20% to 25%, and the basis weight is 30 to 38 gsm; the intermediate absorbent layer is a mixture of plant fibers and SAP, wherein the mass percentage of plant fibers is 80% to 85%, the mass percentage of SAP is 15% to 20%, and the basis weight is 50 to 60 gsm.

[0027] As a second aspect of the present invention, a method for preparing the above-mentioned SAP discontinuous application type absorbent substrate includes the following steps:

[0028] Step S10: Prepare plant fiber, chemical fiber, and SAP according to the preset composition of the fiber absorption layer, and set aside.

[0029] Step S20: After mixing and dispersing the pre-set raw materials, at least two fiber absorption layers are formed by air-laid web or mechanical web laying process;

[0030] Step S30: Using an SAP discontinuous application device, SAP layers are discontinuously applied between adjacent fiber absorption layers in a preset pattern, ensuring that the SAP layers of different layers are staggered in the vertical projection direction.

[0031] Step S40: Stack the layers in sequence and fix them together by hot pressing or chemical bonding.

[0032] Step S50: After the composite fixed substrate is shaped, it is cut to the required specifications to obtain the finished product.

[0033] In a preferred embodiment of the present invention, the SAP discontinuous application device includes a storage bin, a conveying pipeline and an application nozzle, wherein the application nozzle is a linear nozzle or a dot nozzle, and the nozzle spacing and output rate are adjustable.

[0034] In a preferred embodiment of the present invention, in step S40, the hot pressing is performed by hot melt fiber bonding or direct hot pressing roller bonding, and the hot pressing pressure is 0.3-0.5 MPa; the chemical bonding is performed by acrylic water-based adhesive, and the spraying method is dot spraying or mist spraying.

[0035] In a preferred embodiment of the present invention, step S40 further includes laying a wet strength reinforcing mesh between adjacent fiber absorbent layers before interlayer lamination.

[0036] In a preferred embodiment of the present invention, after step S40 and before step S50, a step of pressing a guide groove on the surface of the composite substrate along its longitudinal direction using a heated pressure roller is further included.

[0037] In a preferred embodiment of the present invention, the preparation method employs a one-step online molding process or an offline composite molding process.

[0038] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0039] 1. Significantly improves the rate of multiple absorptions. This invention employs a discontinuous application method of SAP, with different SAP layers staggered in the vertical projection direction. After SAP absorbs water and swells, it does not form a dense sol barrier layer; the perforated fiber areas between layers always retain channels for liquid infiltration. The secondary absorption rate can reach 3.0–3.5 seconds, effectively reducing the liquid residence time on the surface and lowering the risk of side leakage and surface residue.

[0040] 2. Achieving a synergistic balance between high absorbency and ultra-thinness. This invention ensures a high SAP addition rate (5-7 gsm per layer) while keeping the total thickness of the absorbent substrate within 1 mm, achieving a water absorption ratio of 80-90 times, thus overcoming the technical limitation of "thickness is required for absorption" in traditional methods.

[0041] 3. Significantly improves wet strength and prevents clumping and delamination. This invention forms a skeletal support by setting a wet strength reinforcing mesh between the fiber absorption layers. After absorbing water, the tensile strength can reach 1.8-2.0 N / 15 mm, effectively solving industry pain points such as interlayer slippage, clumping, and delamination.

[0042] 4. Balancing softness and fluid flow. The substrate surface of this invention features longitudinally spaced flow channels, utilizing a hinge effect to enhance softness in the CD direction and reduce stiffness. Simultaneously, the flow channels guide the liquid longitudinally, synergistically enhancing the absorption rate in conjunction with the discontinuous distribution of SAP.

[0043] 5. Safe and environmentally friendly raw materials with a wide range of applications. This invention uses plant fibers (fluff pulp, board pulp, cotton fiber, bamboo fiber, viscose fiber, etc.) as the main raw materials, which are safe and environmentally friendly; the total weight can be flexibly adjusted within the range of 60-160 gsm, making it fully compatible with products such as panty liners, sanitary napkins, diapers, and nursing pads.

[0044] 6. The preparation method is compatible with existing production lines, resulting in low modification costs. This invention only requires replacing the traditional continuous surface application device with a non-continuous SAP application device. The remaining processes are highly compatible with existing processes, and can be used for one-step online molding or offline composite molding. The modification cost is low, and it is easy to promote on a large scale. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a cross-sectional structural schematic diagram of Example 1 of the SAP discontinuous application type absorbent substrate of the present invention.

[0047] Figure 2 This is a schematic diagram of the structure of Example 1 of the SAP discontinuous application type absorbent substrate of the present invention after liquid absorption.

[0048] Figure 3 This is a schematic diagram of the surface of Embodiment 1 of the SAP discontinuous application type absorbent substrate of the present invention.

[0049] Figure 4 This is a side view of Example 1 of the SAP discontinuous application type absorbent substrate of the present invention.

[0050] Figure 5 This is a cross-sectional structural schematic diagram of Example 2 of the SAP discontinuous application type absorbent substrate of the present invention.

[0051] Figure 6 This is a schematic diagram of the structure of Example 2 of the SAP discontinuous application type absorbent substrate of the present invention after liquid absorption.

[0052] Figure 7 This is a cross-sectional structural schematic diagram of Example 3 of the SAP discontinuous application type absorbent substrate of the present invention.

[0053] Figure 8 This is a schematic diagram of the structure of Example 3 of the SAP discontinuous application type absorbent substrate of the present invention after liquid absorption.

[0054] Figure 9 This is a schematic diagram of the surface of Example 3 of the SAP discontinuous application type absorbent substrate of the present invention.

[0055] Figure 10 This is a side view of Example 3 of the SAP discontinuous application type absorbent substrate of the present invention.

[0056] Figure 11 These are various schematic diagrams illustrating the discontinuous distribution of SAP in the SAP discontinuous application type absorbent substrate of the present invention. Detailed Implementation

[0057] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0058] Example 1

[0059] This embodiment provides an SAP discontinuous application type absorbent substrate with a total basis weight of 150 gsm and a thickness of 0.8 mm, which can be applied to sanitary napkin products.

[0060] See Figure 1 In this embodiment, the SAP discontinuous application type absorbent substrate has a three-layer structure, including a surface absorbent layer 110, an intermediate absorbent layer 120, and a bottom absorbent layer 130. SAP layers are discontinuously applied between adjacent fiber absorbent layers, and the SAP layers in different layers are staggered in the vertical projection direction. The surface absorbent layer 110 and the bottom absorbent layer 130 have the same raw material composition, while the intermediate absorbent layer 120 has a different raw material composition.

[0061] The specific composition and parameters of each layer are as follows:

[0062] The surface absorbent layer 110 is a mixture of fluff pulp (75%) and PE / PP short fibers (25%), with a basis weight of 38 gsm;

[0063] The intermediate absorbent layer 120 is made of a mixture of fluff pulp (80%) and SAP (20%) with a basis weight of 60 gsm;

[0064] The bottom absorbent layer 130 is a mixture of fluff pulp (75%) and PE / PP short fibers (25%), with a basis weight of 38 gsm;

[0065] The first SAP layer 210 (between the surface absorber layer 110 and the intermediate absorber layer 120) adopts a linear discontinuous distribution, with an application width of 5 mm, a spacing of 10 mm between adjacent linear SAP layers, and an SAP addition amount of 7 gsm.

[0066] The second SAP layer 220 (between the intermediate absorber layer 120 and the bottom absorber layer 130) adopts a linear discontinuous distribution, with an application width of 5 mm, an interval of 10 mm between adjacent linear SAP layers, an SAP addition amount of 7 gsm, and is staggered from the first SAP layer 210 in the vertical projection direction.

[0067] The function of the aforementioned discontinuous distribution and interlayer staggered arrangement of SAP is that, after the SAP absorbs water and expands, each distribution unit remains independent and will not connect to form a dense, monolithic sol barrier layer. Figure 2As shown, the fiber absorption layer region between adjacent SAP layers remains continuous, providing a continuous infiltration channel for the second and even multiple liquid pulses. This effectively avoids the problem of a significant decrease in secondary and tertiary absorption rates caused by the sol layer blockage in traditional continuous planar application methods.

[0068] This embodiment also includes a wet strength reinforcing mesh 300 between the surface absorbent layer 110 and the intermediate absorbent layer 120. The reinforcing mesh 300 is made of 10gsm PE / PP spunbond nonwoven fabric. The function of the reinforcing mesh 300 is to form a skeletal support structure in the absorbent substrate, significantly improving the overall wet strength of the substrate in both dry and water-absorbing states, and effectively preventing interlayer slippage, SAP clumping, and delamination due to stress during product use.

[0069] See Figure 3 and Figure 4 The surface of the absorbent substrate has triangular flow channels 101 arranged along its longitudinal direction (MD direction). The flow channels 101 are arranged on one side, with an outer opening width of 1mm, a depth of 40% of the substrate thickness, and a channel spacing of 5mm. The function of the flow channels 101 is twofold: firstly, to significantly improve the flexibility of the substrate in the CD direction by utilizing the hinge effect, reducing the stiffness caused by the dense molding of the ultra-thin substrate and improving user comfort; secondly, to utilize the difference in the diffusion rate of the liquid along the channels to guide the liquid longitudinally, accelerating the diffusion rate of the liquid along the substrate surface, thus forming a synergistic effect with the discontinuous distribution structure of SAP.

[0070] The SAP discontinuous application type absorbent substrate of this embodiment is prepared according to the following steps:

[0071] Step S10: Raw material preparation. Prepare fluff pulp, PE / PP staple fiber, SAP, and 10gsm PE / PP spunbond nonwoven reinforcing mesh according to the above proportions, and set aside.

[0072] Step S20: Preparation of fiber absorbent layer. The raw materials (fluff pulp and PE / PP short fibers) of the surface absorbent layer and the bottom absorbent layer are mixed and dispersed separately, and then processed into 38gsm fiber layers by air-laid web process; the raw materials (fluff pulp and SAP) of the middle absorbent layer are mixed and dispersed, and then processed into 60gsm fiber layers by air-laid web process.

[0073] Step S30: Discontinuous SAP Application. A discontinuous SAP application device is used, which includes a storage bin, a delivery pipeline, and linear application nozzles. The nozzle spacing and output rate are adjustable. SAP layers are applied discontinuously in a linear pattern on the lower surface of the surface absorption layer and the upper and lower surfaces of the intermediate absorption layer, respectively. The application width is 5 mm, and the interval is 10 mm, ensuring that the first SAP layer 210 and the second SAP layer 220 are staggered in the vertical projection direction. This step achieves discontinuous SAP distribution through a specialized application device to ensure gaps between each SAP distribution unit, thereby maintaining the unobstructed liquid infiltration channels during subsequent liquid absorption.

[0074] Step S40: Interlayer bonding. The wet strength reinforcing mesh 300 is laid between the surface absorbent layer 110 and the intermediate absorbent layer 120. The layers are then stacked sequentially and fixed interlayer by hot pressing. Hot-pressing uses hot-melt fiber bonding, and the hot-pressing pressure is 0.3 MPa.

[0075] Step S50: Forming of the guide groove. Using a heated roller at 120℃, triangular longitudinal guide grooves 101 are pressed into the surface of the laminated substrate along the MD direction. The outer width is 1mm, the depth is 40% of the substrate thickness, and the groove spacing is 5mm.

[0076] Step S60: Shaping and Cutting. After the pressed substrate is shaped, it is cut to the required specifications for sanitary napkins to obtain the finished product.

[0077] The performance of the absorbent substrate prepared in this embodiment was tested, and the results are shown in Table 1.

[0078] Table 1. Performance test results of product in Example 1

[0079]

[0080] Example 2

[0081] This embodiment provides an SAP discontinuous application type absorbent substrate with a total basis weight of 70 gsm and a thickness of 0.5 mm, which can be applied to pad products.

[0082] See Figure 5 The SAP discontinuous application type absorbent substrate of this embodiment includes two fiber absorbent layers stacked together, with an SAP layer discontinuously applied between adjacent fiber absorbent layers.

[0083] The specific composition and parameters of each layer are as follows:

[0084] The surface absorbent layer 110a is made of fluff pulp with a basis weight of 35 gsm.

[0085] The bottom absorbent layer 130a is made of fluff pulp with a basis weight of 35 gsm.

[0086] SAP layer 200a (between surface absorber layer 110a and bottom absorber layer 130a) adopts a dotted discontinuous distribution, with a single dot diameter of 3mm, a dot spacing of 6mm between adjacent dotted SAP layers, and an SAP addition amount of 6gsm.

[0087] The point-like, discontinuous distribution of SAP ensures that individual SAP points, after absorbing water and swelling, are not interconnected horizontally. The fiber regions between adjacent points remain open, providing continuous downward and lateral diffusion channels for the liquid, thus ensuring stable secondary and tertiary absorption rates. Figure 6 As shown. This structure is particularly suitable for thin and light products, enabling rapid and repeated absorption even at low weight.

[0088] This embodiment does not include a wet strength reinforcing mesh. An arc-shaped flow channel is formed on the surface of the absorbent substrate along its longitudinal direction (MD direction). The flow channel is formed on one side, with an outer opening width of 0.8 mm, a depth of 30% of the substrate thickness, and a channel spacing of 4 mm.

[0089] The SAP discontinuous application type absorbent substrate of this embodiment is prepared according to the following steps:

[0090] Step S10: Raw material preparation. Prepare the fluff pulp and SAP according to the above proportions, and set aside.

[0091] Step S20: Preparation of fiber absorbent layer. The fluff pulp is mixed and dispersed, and then two 35gsm fiber absorbent layers are prepared by mechanical web laying process.

[0092] Step S30: Discontinuous SAP application. A discontinuous SAP application device is used, which includes a storage bin, a conveying pipe, and point application nozzles. A layer of SAP is applied discontinuously in a point pattern between the two fiber absorbent layers, with each point having a diameter of 3 mm and a spacing of 6 mm.

[0093] Step S40: Interlayer lamination. The layers are stacked sequentially and fixed together using chemical bonding. The chemical bonding uses an acrylic water-based adhesive, applied via a mist spraying method.

[0094] Step S50: Forming of the guide groove. Using a heated roller at 100℃, an arc-shaped longitudinal guide groove is pressed into the surface of the laminated substrate along the MD direction. The outer width is 0.8mm, the depth is 30% of the substrate thickness, and the groove spacing is 4mm.

[0095] Step S60: Shaping and Cutting. After the pressed substrate is shaped, it is cut to the required specifications of the pad to obtain the finished product.

[0096] The performance of the absorbent substrate prepared in this embodiment was tested, and the results are shown in Table 2.

[0097] Table 2. Product performance test results for Example 2

[0098]

[0099] This product is designed to meet the lightweight absorption needs of panty liners.

[0100] Example 3

[0101] This embodiment provides an SAP discontinuous application type absorbent substrate with a total basis weight of 160 gsm and a thickness of 0.9 mm, which can be applied to diaper products.

[0102] See Figure 7 In this embodiment, the SAP discontinuous application type absorbent substrate has a three-layer structure, including a surface absorbent layer 110b, an intermediate absorbent layer 120b, and a bottom absorbent layer 130b. SAP layers are discontinuously applied between adjacent fiber absorbent layers, and the SAP layers of different layers are staggered in the vertical projection direction. The surface absorbent layer 110b and the bottom absorbent layer 130b have the same raw material composition, while the intermediate absorbent layer 120b has a different raw material composition.

[0103] The specific composition and parameters of each layer are as follows:

[0104] The surface absorbent layer 110b is made of a mixture of bamboo fiber (80%) and PET short fiber (20%), with a basis weight of 35 gsm.

[0105] The intermediate absorbent layer 120b is made of a mixture of bamboo fiber (85%) and SAP (15%), with a basis weight of 55 gsm.

[0106] The bottom absorbent layer 130b is made of a mixture of bamboo fiber (80%) and PET short fiber (20%), with a basis weight of 35 gsm;

[0107] The first SAP layer 210b (between the surface absorber layer 110b and the intermediate absorber layer 120b) adopts a linear discontinuous distribution, with an application width of 4 mm, a spacing of 9 mm between adjacent linear SAP layers, and an SAP addition amount of 6 gsm.

[0108] The second SAP layer 220b (between the intermediate absorber layer 120b and the bottom absorber layer 130b) adopts a dotted discontinuous distribution with a single dot diameter of 2.5mm, a dot spacing of 5.5mm between adjacent dotted SAP layers, an SAP addition amount of 6gsm, and is staggered from the first SAP layer 210b in the vertical projection direction.

[0109] In this embodiment, the linear distribution pattern on the surface layer creates a wider liquid interception surface in the upper layer, improving the initial absorption efficiency; the dotted distribution pattern on the bottom layer leaves more fiber gaps in the lower layer, increasing the rate of downward liquid diffusion. The staggered distribution of the two SAP layers further disperses the expansion stress, avoiding unevenness caused by excessive local SAP concentration, and keeping the substrate surface flat after absorption.

[0110] This embodiment also includes a wet strength reinforcing mesh 300b between the intermediate absorbent layer 120b and the bottom absorbent layer 130b. The reinforcing mesh 300b is made of 8gsm PP mesh. See also Figure 9 and Figure 10 The surface of the absorbent substrate is provided with triangular guide grooves 101b along its longitudinal direction (MD direction). The guide grooves 101b are provided on both sides, with an outer opening width of 1mm, a depth of 50% of the substrate thickness, and a groove spacing of 5mm.

[0111] The SAP discontinuous application type absorbent substrate of this embodiment is prepared according to the following steps:

[0112] Step S10: Raw material preparation. Prepare bamboo fiber, PET staple fiber, SAP, and 8gsm PP mesh reinforcement according to the above proportions, and set aside.

[0113] Step S20: Preparation of fiber absorption layer. The raw materials (bamboo fiber and PET short fiber) of the surface absorption layer and the bottom absorption layer are mixed and dispersed separately, and then processed into 35gsm fiber layers by air-laid web process; the raw materials (bamboo fiber and SAP) of the middle absorption layer are mixed and dispersed, and then processed into 55gsm fiber layers by air-laid web process.

[0114] Step S30: Discontinuous SAP application. A discontinuous SAP application device is used, which includes a storage bin 10, a conveying pipe 11, and a combined application nozzle 12 (a combination of linear nozzles and dot nozzles). A SAP layer (4 mm wide, 9 mm spaced) is discontinuously applied in a linear pattern between the surface absorption layer and the intermediate absorption layer. A SAP layer (2.5 mm in diameter, 5.5 mm spaced) is discontinuously applied in a dot pattern between the intermediate absorption layer and the bottom absorption layer, ensuring that the first SAP layer 210b and the second SAP layer 220b are staggered in the vertical projection direction.

[0115] Step S40: Interlayer bonding. The wet strength reinforcing mesh 300b is laid between the intermediate absorbent layer 120b and the bottom absorbent layer 130b. The layers are then stacked sequentially and fixed interlayer by hot pressing. Hot pressing is performed using a hot press roller for direct bonding, with a pressing pressure of 0.5 MPa.

[0116] Step S50: Forming of the guide groove. Using a heated roller at 130℃, double-sided triangular longitudinal guide grooves 101b are pressed into the surface of the laminated substrate along the MD direction. The outer width is 1mm, the depth is 50% of the substrate thickness, and the groove spacing is 5mm.

[0117] Step S60: Shaping and Cutting. After the pressed substrate is shaped, it is cut to the required specifications for diapers to obtain the finished product.

[0118] The performance of the absorbent substrate prepared in this embodiment was tested, and the results are shown in Table 3.

[0119] Table 3. Performance test results of product in Example 3

[0120]

[0121] The product in this embodiment is adapted to the high absorbency and high moisture strength requirements of diapers.

[0122] In addition to the embodiments described above, the present invention may also employ the following alternative solutions:

[0123] (i) In addition to fluff pulp and bamboo fiber, plant fibers may also include one or more of board pulp, cotton fiber, or viscose fiber; in addition to PE / PP staple fiber and PET staple fiber, chemical fibers may also include EVA staple fiber. The raw materials for the fiber absorbent layer may be plant fibers used alone, a mixture of plant fibers and chemical fibers, or a mixture of plant fibers, chemical fibers, and SAP. All of the above fibers have good hydrophilicity and liquid conductivity, which can ensure that liquids can quickly pass through the fiber layer to reach the SAP distribution area.

[0124] (ii) In addition to linear and dotted distributions, the discontinuous distribution of the SAP layer can also adopt a combination of linear and dotted distributions. See [link to relevant documentation]. Figure 11 The figure shows several schematic diagrams of discontinuous SAP distribution. For linear distribution, the application width can be selected as 3–5 mm, and the interval between adjacent linear SAP layers as 8–10 mm; for point distribution, the single-point diameter can be selected as 2–3 mm, and the spacing between adjacent point SAP layers as 5–6 mm; the amount of SAP added between single layers can be selected as 5–7 gsm. Experimental verification of the above intervals and addition ranges ensures that a sufficient fiber gap is maintained between adjacent SAP distribution units, guaranteeing both the amount of SAP added and the absorption rate, while also ensuring the unobstructed flow of the rapid liquid infiltration channels.

[0125] (III) In addition to PE / PP spunbond nonwoven fabric and PP mesh, PET mesh or hot-air nonwoven fabric can also be used for wet strength reinforcement mesh, with a basis weight of 8-10 gsm. The reinforcement mesh can be selectively set between adjacent fiber absorption layers according to product requirements. Its function is to provide additional skeleton support for the absorbent substrate and improve wet strength.

[0126] (iv) In addition to triangular and arc-shaped longitudinal grooves, other shapes can also be used for the flow guide channels; they can be set on one side or both sides. The outer width of the flow guide channel can be selected in the range of 0.8 to 1 mm, the depth can be selected in the range of 30% to 50% of the substrate thickness, and the groove spacing can be selected in the range of 4 to 5 mm. The above parameter range has been experimentally verified to provide sufficient hinge effect to improve flexibility while ensuring the structural integrity of the substrate, and at the same time achieve effective longitudinal guidance of liquid.

[0127] (v) In addition to hot pressing (hot melt fiber bonding or direct hot pressing with hot rollers, hot pressing pressure 0.3-0.5MPa), chemical bonding (acrylic ester water-based adhesive, dot spraying or mist spraying) can also be used for interlayer fixing. Both fixing methods can achieve reliable bonding between layers, ensuring the integrity and structural stability of the absorbent substrate.

[0128] (vi) The molding process can adopt a one-step online molding process or an offline composite molding process. Both molding methods are compatible with existing hygiene products and material production lines. Only an additional SAP discontinuous application device and heated roller are required. The modification cost is low and it is easy to promote and implement on a large scale.

[0129] (vii) The total weight and thickness of the absorbent substrate can be adjusted within the range of 60 to 160 gsm according to product requirements, and the thickness can be controlled within 1 mm, fully adapting to the application needs of panty liners, sanitary napkins, diapers and nursing pads in multiple scenarios.

[0130] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An SAP discontinuous application type absorbent substrate, characterized in that, include: At least two fiber absorption layers are stacked together; as well as The SAP layer is disposed between two adjacent fiber absorption layers. The SAP layer is distributed discontinuously between the fiber absorption layers, and the SAP layers located between different layers are staggered in the vertical projection direction.

2. The SAP discontinuous application type absorbent substrate according to claim 1, characterized in that, The raw material of the fiber absorbent layer is one of plant fiber, a mixture of plant fiber and chemical fiber, or a mixture of plant fiber, chemical fiber and SAP.

3. The SAP discontinuous application type absorbent substrate according to claim 2, characterized in that, The plant fiber is selected from at least one of fluff pulp, board pulp, cotton fiber, bamboo fiber, or viscose fiber; the chemical fiber is selected from at least one of PE / PP staple fiber, PE / PET staple fiber, or EVA staple fiber.

4. The SAP discontinuous application type absorbent substrate according to claim 1, characterized in that, The discontinuous distribution of the SAP layer can be multiple spaced linear application areas, multiple spaced independent point application areas, or a combination of linear and point distributions.

5. The SAP discontinuous application type absorbent substrate according to claim 4, characterized in that, When distributed linearly, the application width of the SAP layer is 3-5 mm, and the interval between adjacent linear SAP layers is 8-10 mm; when distributed dottedly, the diameter of a single point of the SAP layer is 2-3 mm, and the distance between adjacent dotted SAP layers is 5-6 mm; the amount of SAP added between single layers is 5-7 gsm.

6. The SAP discontinuous application type absorbent substrate according to claim 1, characterized in that, A wet strength reinforcing mesh is provided between adjacent fiber absorption layers.

7. The SAP discontinuous application type absorbent substrate according to claim 6, characterized in that, The wet strength reinforcing mesh is one of PP mesh, PET mesh, PE / PP spunbond nonwoven fabric or hot air nonwoven fabric, and the basis weight of the wet strength reinforcing mesh is 8-10 gsm.

8. The SAP discontinuous application type absorbent substrate according to claim 1, characterized in that, The surface of the absorbent substrate is provided with a flow channel along its longitudinal direction.

9. The SAP discontinuous application type absorbent substrate according to claim 8, characterized in that, The guide channel is a triangular guide channel or an arc-shaped guide channel, and can be set on one side or both sides; the outer width of the guide channel is 0.8 to 1 mm, the depth is 30% to 50% of the thickness of the absorbent substrate, and the channel spacing is 4 to 5 mm.

10. The SAP discontinuous application type absorbent substrate according to claim 1, characterized in that, The total basis weight of the absorbent substrate is 60-160 gsm, and the thickness is ≤1 mm.

11. The SAP discontinuous application type absorbent substrate according to any one of claims 1 to 10, characterized in that, The fiber absorbent layer has a three-layer structure, including a surface absorbent layer, an intermediate absorbent layer, and a bottom absorbent layer; the surface absorbent layer and the bottom absorbent layer have the same raw material composition, while the intermediate absorbent layer has a different raw material composition than the surface absorbent layer and the bottom absorbent layer.

12. The SAP discontinuous application type absorbent substrate according to claim 11, characterized in that, The top and bottom absorbent layers are mixtures of plant fibers and chemical fibers, wherein the mass percentage of plant fibers is 75%–80%, the mass percentage of chemical fibers is 20%–25%, and the basis weight is 30–38 gsm; the middle absorbent layer is a mixture of plant fibers and SAP, wherein the mass percentage of plant fibers is 80%–85%, the mass percentage of SAP is 15%–20%, and the basis weight is 50–60 gsm.

13. A method for preparing a SAP discontinuous application type absorbent substrate as described in any one of claims 1 to 12, characterized in that, Includes the following steps: Step S10: Prepare plant fiber, chemical fiber, and SAP according to the preset composition of the fiber absorption layer, and set aside. Step S20: After mixing and dispersing the pre-set raw materials, at least two fiber absorption layers are formed by air-laid web or mechanical web laying process; Step S30: Using an SAP discontinuous application device, SAP layers are discontinuously applied between adjacent fiber absorption layers in a preset pattern, ensuring that the SAP layers of different layers are staggered in the vertical projection direction. Step S40: Stack the layers in sequence and fix them together by hot pressing or chemical bonding. Step S50: After the composite fixed substrate is shaped, it is cut to the required specifications to obtain the finished product.

14. The preparation method according to claim 13, characterized in that, The SAP discontinuous application device includes a storage bin, a conveying pipeline, and an application nozzle. The application nozzle is a linear nozzle or a dot nozzle, and the nozzle spacing and output rate are adjustable.

15. The preparation method according to claim 13, characterized in that, In step S40, the hot pressing is performed using hot melt fiber bonding or direct hot pressing roller bonding, with a hot pressing pressure of 0.3 to 0.5 MPa; the chemical bonding is performed using acrylic water-based adhesive, and the spraying method is dot spraying or mist spraying.

16. The preparation method according to claim 13, characterized in that, In step S40, before interlayer lamination, a step of laying a wet strength reinforcing mesh between adjacent fiber absorbent layers is also included.

17. The preparation method according to claim 13, characterized in that, After step S40 and before step S50, the method further includes pressing guide grooves on the surface of the composite substrate along its longitudinal direction using heated rollers.

18. The preparation method according to any one of claims 13 to 17, characterized in that, The preparation method employs a one-step online molding process or an offline composite molding process.

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