DESC:FIELD OF THE INVENTION:
The present invention relates to an absorbent article, and more particularly to an absorbent article with a slit core design.

BACKGROUND OF THE INVENTION:
Absorbent hygiene products indeed play a significant role in the personal care and hygiene market. They are designed to absorb bodily fluids and maintain hygiene, catering to various needs across different age groups and situations. These products include items like diapers for infants and adults, sanitary napkins, tampons, incontinence and nursing pads.
The absorbent quality of an absorbent article is based on fluid acquisition, fluid distribution, fluid retention and leakage prevention. The ability to attract and absorb fluid away from the skin is important for keeping the wearer dry and comfortable. This is usually achieved through materials like superabsorbent polymers (SAP) that can hold many times their weight in liquid. Once absorbed, the fluid needs to be distributed quickly and evenly throughout the absorbent core of the article. This helps prevent localized saturation and ensures maximum use of the absorbent capacity.
After absorption and distribution, the article is required to maintain a dry feel against the skin. This is achieved by the design of the absorbent core and possibly additional layers that provide a barrier between the wet absorbent and the skin. Further, effective absorbent articles include features to prevent leakage, such as elastic barriers or leg cuffs in diapers, or wing designs in sanitary pads. These features help contain the absorbed fluid and prevent it from leaking onto clothing.
The absorbent core is crucial in absorbent articles. The design of the polymer matrix within the absorbent core serves to optimize its performance. The strategic placement of fast-absorbing polymers (such as superabsorbent polymers) closer to the top layer of the core to quickly draw fluid away from the surface; and the slow absorbing polymers deeper within the core to manage fluid distribution; helps in even distribution of the absorbed fluid throughout the core. A typical absorbent article generally includes a liquid-pervious topsheet, a liquid-impervious backsheet and an absorbent assembly disposed between the topsheet and the backsheet.
The US patent application US2017079858A1 to Willhaus Keith Richard and others describes an absorbent article having an absorbent core with at least two longitudinally extending curved channels, carded nonwoven layer as topsheet or acquisition layer under the topsheet. However, as these channels are inwardly curved (concave) towards the longitudinal axis, there is a possibility of saturation of fluid in central part from both the front and back extremities.
The US patent application US2011152813A1 to Ellingson Daniel Lee describes an absorbent article having an absorbent core including a first absorbent portion, a second absorbent portion, and a channel portion extending the entire length of the absorbent core. The channels placed along the entire length of the article, however, causes the liquid to be distributed till both the front and back extremities leading to discomfort.
There is a need for an absorbent article incorporating an absorbent core with a slit design that promotes rapid and uniform distribution of liquid throughout the absorbent area, enhancing the user comfort and improving the functional performance of the article.

SUMMARY OF THE INVENTION:
The present invention relates to an absorbent article with a slit core design that provides improved fluid acquisition, distribution, and retention while reducing surface rewet and leakage.
In one aspect, the absorbent article includes a liquid-permeable and breathable top layer forming the skin-contacting surface, an acquisition and distribution layer positioned beneath the top layer to laterally disperse fluid, and an absorbent core disposed below the acquisition and distribution layer. The absorbent core incorporates longitudinally extending slits arranged in a funnel-shaped configuration, with a wider spacing at a front region and a narrower spacing at a rear region, thereby promoting directional fluid flow and more uniform utilization of absorbent capacity. The absorbent core is encapsulated within a core wrap that maintains integrity and alignment of the absorbent material, while a liquid-impermeable bottom layer provides leakage protection.
The top layer is formed from hydrophilic spunbonded nonwoven fabric, melt blown or carded fabrics, viscose-polyester blends, biodegradable nonwovens such as PLA, or perforated films. The acquisition and distribution layer is formed from chemically bonded or air-laid nonwoven structures, thermally bonded or carded nonwovens, or fiber blends including rayon or viscose.
The absorbent core includes fluff pulp, cellulosic fibers, superabsorbent polymers (SAP), tissue-SAP composites, or nonwoven SAP matrices, with SAP content ranging between 25–50% by weight. The core wrap is constructed from cellulose tissue or lightweight air-laid nonwoven, while the bottom layer may comprise a breathable microporous film, optionally laminated with a nonwoven outer sheet to impart a textile-like feel. At least one of the top or bottom layers may be biodegradable, for example PLA or PBAT.
The slits of the absorbent core may extend over 10% to 95% of its longitudinal length, with a depth of approximately 3–5 mm. In certain embodiments, the spacing between the slits at the front end is at least 50 mm, while the spacing at the rear end is not greater than 30 mm.
In another aspect, a method is provided for preparing the absorbent article. The method includes a preprocessing cycle for formation of each functional layer, followed by an assembly cycle in which the layers are sequentially aligned and integrated. The top layer is treated to exhibit a hydrophilicity gradient; the absorbent core is provided with funnel-shaped longitudinal slits; the acquisition and distribution layer is patterned with density gradients aligned to the slit geometry; and the core wrap is bonded along slit paths to maintain channel integrity.
A bottom layer is formed from breathable microporous film laminated with nonwoven. The assembly cycle includes sequential lamination of all layers, bonding by ultrasonic or thermal methods, incorporation of elastic elements and closure systems, and contouring of the article into an ergonomic shape with softened peripheral edges for wearer comfort.
In yet another aspect, the invention provides alternative methods for incorporating longitudinal slits in the absorbent core, including die cutting, laser cutting, embossing and bonding, water jet cutting, or perforation with subsequent expansion.
Through these structural limitations and method, the absorbent article achieves faster fluid acquisition, enhanced distribution, lower rewet, and improved comfort, while enabling efficient material utilization and sustainable manufacturing.

BRIEF DESCRIPTION OF DRAWINGS:
The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,
FIG. 1 depicts an exploded view of the layers of an absorbent article in accordance with the present invention;
FIG. 2 demonstrates a top view of an absorbent article in newborn infant size in accordance with the present invention; and
FIG. 3 demonstrates a 3 - dimensional view of the absorbent article in accordance with the present invention.

DESCRIPTION OF THE INVENTION:
References in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
References in the specification to “preferred embodiment” means that a particular feature, structure, characteristic, or function described in detail thereby omitting known constructions and functions for clear description of the present invention.
The foregoing description of specific embodiments of the present invention has been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed and obviously many modifications and variations are possible in light of the above teaching.
The present invention discloses an absorbent article that has an absorbent core with engraved long narrow cut slits below the top layer of the absorbent article that facilitates better distribution and quick absorption of liquid in the entire absorbent area.
Referring to FIGURES 1, 2 and 3, an absorbent article with slit core design 100, hereinafter referred to as absorbent article 100 in accordance with the present invention is described. The absorbent article 100 includes a top layer 105, a bottom layer 110 and an absorbent core 115 positioned between the top 105 and bottom layers 110. The absorbent article 100 further includes an acquisition distribution layer (ADL) 120 and a core wrap 125. The acquisition and distribution layer 120 is disposed between the top layer 105 and the absorbent core 115, and the absorbent core 115 is encapsulated within a core wrap 125 that maintains structural integrity during use.
The top layer 105 of the absorbent article 100 defines a surface layer that is in contact with the user’s skin. In one embodiment, the top layer 105 is a permeable and breathable layer that allows fluids to pass through easily into the absorbent core 115 beneath. The acquisition distribution layer 120 of the absorbent article 100 is positioned immediately beneath the top layer 105. Immediately beneath the top layer 105, the acquisition and distribution layer 120 is configured to receive incoming liquid and disperse it laterally across a broader area. The absorbent core 115, disposed below the acquisition and distribution layer 120, is configured to capture and retain the liquid distributed by the ADL 120. Accordingly, the acquisition distribution layer 120 receives liquid from the top layer and facilitates its dispersal over a broader surface area and reduces localized saturation. The absorbent core 115 retains and stores the liquid distributed by the acquisition distribution layer 120.
In this one embodiment, the absorbent core 115 is elongated and generally rectangular, extending in a longitudinal direction 130 along its length and a transverse direction 135 along its width. The absorbent core 115 includes a pair of elongated slits 140 extending generally along the longitudinal direction 130. In the embodiment shown, two slits 140 are formed in parallel relation, each extending substantially along the length of the absorbent core 115. The spacing between the slits 140 varies such that the slits are positioned farther apart at a front region of the absorbent core 115 and progressively closer together toward a rear region, thereby defining a funnel-like geometry that promotes directed liquid movement within the core.
The absorbent core 115 is enclosed within the core wrap 125. The core wrap 125 maintains the integrity and position of the absorbent material during use. The bottom layer 110 is positioned immediately beneath the absorbent core 115 wrapped in the core wrap 125. The bottom layer 110 forms the lowermost layer of the absorbent article 100 and acts as a liquid-impermeable barrier to prevent leakage to the outside environment.
The top layer 105 is a permeable layer prepared from materials selected from hydrophilic spunbonded non-woven fabrics, spunbonded meltblown spunbonded non-woven fabric, viscose polyester blend nonwoven fabric, polylactic acid or other biodegradable nonwoven fabrics, perforated films and the like. In certain embodiments, the top layer 105 is optionally embossed or perforated to facilitate directional liquid movement and to minimize rewetting.
In a preferred embodiment, the top layer 105 is prepared from hydrophilic spunbonded non-woven fabric made from polypropylene, with a basis weight of approximately 15-25 gsm. The fabric is subjected to hydrophilic surface treatment to significantly increase its wettability, and to ensure rapid transfer of liquid from the surface to the acquisition distribution layer 120 and subsequently into the absorbent core 115.
In accordance with alternate embodiments, the top layer 105 is prepared either from spunbonded - melt blown - spunbonded (SMS) nonwoven fabric that provides enhanced strength and barrier properties; or from viscose polyester blend nonwoven fabric that provides higher softness and improved liquid handling; or from polylactic acid (PLA) or other biodegradable nonwoven fabrics that provide environmentally sustainable options; or air-through bonded or thermally bonded nonwoven fabrics that provide tailored porosity and softness profiles.
The acquisition distribution layer 120 is positioned between the top layer 105 and the absorbent core 115; and facilitates rapid fluid acquisition by quickly drawing liquid away from the top layer to reduce the surface wetness. The acquisition distribution layer 120 is made from materials selected from chemically bonded or air laid nonwoven fabric, thermal bonded or carded nonwoven fabric, synthetic fiber blends with rayon or viscose, air laid pulp sheets and the like.
In accordance with the preferred embodiment, the acquisition distribution layer 120 is prepared from high loft chemically bonded or air laid nonwoven fabric with a basis weight of approximately 10 - 50 gsm. It contains = 80% synthetic fibers (for example, polyester, PET) that facilitate resilience under repeated wetting and promote lateral liquid distribution. The material enables creation of a density gradient, that complements the funnel-shaped slit pattern of the absorbent core 115 and ensures efficient and uniform fluid spreading across the surface of the absorbent core 115.
In accordance with alternate embodiments, the acquisition distribution layer 120 is prepared either from thermal bonded or carded nonwoven fabric that provide customized pore size distribution for controlled fluid flow; or from synthetic fiber blends with rayon or viscose that provide improved absorbency and softness; or from air laid pulp sheets that provide a sustainable cellulose rich option.
The absorbent core 115 is typically made of materials selected from fluff pulp, cellulosic fibers, superabsorbent polymers, tissue-SAP composites, air laid absorbent sheets with embedded SAP, nonwoven SAP matrices and the like.
In accordance with the preferred embodiment, the absorbent core 115 is prepared from a composite of cellulose fluff pulp (basis weight approximately 100-250 gsm) and superabsorbent polymer (SAP) 30 - 50% by weight. The fluff pulp provides structural integrity and wicking capability, and the SAP enables high absorbent capacity and fluid retention.
In accordance with alternate embodiments, the absorbent core 115 is prepared either from tissue-SAP composites with controlled SAP placement that provides uniform performance; or from air laid absorbent sheets with embedded SAP that provides excellent distribution; or from nonwoven-SAP matrices that provides uniform swelling and maintain core stability.
The core wrap 125 is prepared from cellulose tissue or lightweight air laid nonwoven material. The absorbent core 115 is wrapped in a permeable core wrap substrate that is adhered along slit paths to maintain the longitudinal channels.
In accordance with the preferred embodiment, the core wrap 125 is prepared from cellulose tissue or lightweight air laid nonwoven material having approximately 10 - 15 gsm.
The bottom layer 110 placed below the core wrap encapsulated absorbent core, prevents fluid from leaking out of the absorbent article 100. The bottom layer 110 is a waterproof or moisture-resistant layer prepared from materials selected from breathable, microporous polyethylene (PE) film, microporous polypropylene (PP) films, polypropylene films, breathable laminates, laminated composites combining nonwoven and film layers, biodegradable films, and the like.
In accordance with the preferred embodiment, the bottom layer 110 is prepared from a breathable, microporous polyethylene (PE) film, laminated with a nonwoven outer layer that imparts a textile-like feel, having a basic weight of approximately 20-30 gsm. The inner surface of the PE film is corona-treated to enable adhesion during assembly and prevent delamination during use. It further enables moisture vapor transmission while being impermeable to liquids.
In accordance with alternate embodiments, the bottom layer 110 is either prepared from microporous polypropylene (PP) films that offer high mechanical strength; or from laminated composites that combine nonwoven and film layers for providing improved breathability and feel; or from biodegradable films (for example, PLA or PBAT) that provide a sustainable option.
Now a method 200 of preparation of the absorbent article 100 in accordance with the present invention is described. The method of preparation of the absorbent article, herein after referred to as ‘the method 200’ includes a series of technically optimized steps for preprocessing and assembly of the absorbent article 100 such that the article 100 exhibits superior liquid distribution performance, reduced rewetting, and enhanced user comfort.
The method 200 includes a first preprocessing cycle 205 and a second assembly cycle 210. The first preprocessing cycle 205 includes several steps of preparation of the layers of the absorbent article 100 for further assembly. The first preprocessing cycle 205 includes steps of top layer formation 205A, absorbent core formation 205B, acquisition and distribution layer formation 205C, core wrap formation 205D and bottom layer formation 205E.
In a first step 205A of top layer formation, a skin-contacting top layer 105 is prepared from hydrophilic spunbonded nonwoven fabric. The material is engineered with a hydrophilicity gradient such that the surface fibers are plasma treated or chemically treated to exhibit higher wettability than the inner fibers. The gradient promotes unidirectional liquid transport toward the absorbent core 110, and minimizes rewetting and maintains a dry surface.
In a second step 205B of absorbent core formation, unique slit shaped channels or slits 140 are introduced into the absorbent core 115. The longitudinal slits 140 are configured in a funnel-shaped pattern such that the slits 140 are wider apart at the front end and narrower at the rear, covering approximately 10 - 95% of the longitudinal length of the core. The funnel shaped pattern enables directing the liquid toward the rear end while maintaining containment and fit. The slits 140 are configured to be substantially free of absorbent material, facilitating efficient fluid channeling and capillary action.
In a third step 205C of acquisition and distribution layer formation, the acquisition and distribution layer (ADL) 120 is patterned to align with the funnel-shaped slit configuration of the absorbent core 115. The acquisition and distribution layer (ADL) 120 is configured to have differential density zones such that the layer is denser in the front and more open toward the rear. This optimizes liquid wicking and distribution efficiency. The acquisition and distribution layer (ADL) 120 is composed predominantly (=80% by weight) of synthetic fibers and is thermally point-bonded to maintain structural resilience through repeated wetting cycles.
In a fourth step 205D of core wrap formation, the absorbent core 115 is encapsulated within a permeable core wrap 125 typically formed from cellulose tissue or air laid nonwoven material. The top and bottom layers of the core wrap 125 are bonded along the slits 140 to maintain the longitudinal channels during use. An appropriate adhesive is selectively applied to immobilize the superabsorbent polymer (SAP) of the absorbent core 115 within the designated region. This ensures preserving the structural integrity of the absorbent core 115 and prevents the migration of the absorbent core 115 during production, handling, and use.
In a fifth step 205E of bottom layer formation, the bottom layer 110 is constructed from breathable microporous polyethylene (PE) film and laminated with a nonwoven outer layer to impart a textile-like feel. The PE film is corona-treated on its inner face to enhance adhesion of the glue lines during assembly. The bottom layer is prepared such that it enables optimal moisture vapor transmission rate while remaining impermeable to liquids.
Next, the second assembly cycle 210 includes steps of article assembly 210A, article sealing 210B, and profiling and contouring 210C. In a sixth step of article assembly 210A; the top layer 105, the acquisition and distribution layer (ADL) 120, the core wrap 125 encapsulated absorbent core 115, and the bottom layer 110 are assembled sequentially. The assembly is performed using assembly equipment, such as an automated assembly system or the like, capable of achieving the required alignment and integration. The automated assembly system equipped with optical registration precisely aligns the embossing of the top layer 105 with the longitudinal slits 140 of the absorbent core 115.
In a seventh step of article sealing 210B, the sequentially assembled layers are bonded to preserve the integrity of the slit pattern. The bonding is carried out using methods selected from ultrasonic bonding, thermal bonding and the like. Further, elastic elements, leg cuffs, and closure components are incorporated in the article as per the requirement to improve fit and wearability.
In an eighth step of profiling and contouring 210C, the assembled and bonded layered web is die-cut into ergonomically contoured absorbent article 100 configured as per the requirement for infant or adult use. The margins are precisely defined to reduce leakage risk. Further, waistbands, stretch panels, and closure systems (mechanical or adhesive) are affixed as per the requirement. The peripheral edges of the absorbent article 100 are treated to provide a soft finish and minimize skin irritation during wear.
Now a method of incorporation of longitudinal slits 140 in the absorbent core 115 in accordance with the present invention is described. The slits 140 are incorporated in the absorbent core 115 by methods selected from but not limited to die cutting, laser cutting, embossing and bonding, water jet cutting, perforation and expansion, and the like.
In the process of incorporation of longitudinal slits 140 by die cutting, an absorbent core 115 including homogeneous mixture of cellulose fluff pulp and superabsorbent polymer (SAP) is prepared with uniform basis weight and thickness and subjected to a rotary die-cutting station for slit formation. The rotary die is precision-calibrated to produces longitudinal slits 140 of controlled width and depth in a funnel-shaped pattern. Accordingly, the slits are wider at the front and narrower at the rear, and extend across approximately 10% - 95% of the longitudinal length of the absorbent core 115.
The slit formation using die cutting is achieved without substantial SAP displacement, by maintaining both channel openness and core integrity. In the next step after cutting, the absorbent core 115 is encapsulated in a permeable core wrap 125 (e.g., cellulose tissue or air laid nonwoven), with its top and bottom layers adhered along the slits 140 to preserve the channel geometry during manufacture, handling, and use.
In the process of incorporation of longitudinal slits 140 by laser cutting, the absorbent core 115 including homogeneous mixture of cellulose fluff pulp and superabsorbent polymer (SAP) is subjected to precision-controlled laser cutting system. The laser cutting system selectively vaporizes the designated slit regions of the absorbent core 115 and produces clean, continuous longitudinal slits 140 with minimal mechanical disruption to adjacent structures. Laser cutting offers advantage of high patterning accuracy and compatibility with the complex slit geometry.
In the process of incorporation of longitudinal slits 140 by embossing and bonding, the absorbent core 115 including homogeneous mixture of cellulose fluff pulp and superabsorbent polymer (SAP) is subjected to heated, patterned compression rollers. The rollers engage the absorbent core 115 along predetermined longitudinal paths to compress and thermally bond the material to form low-absorbency channels that functionally emulate slits 140. Embossing and bonding maintains material continuity and provides fluid-directing channels within the absorbent structure.
In the process of incorporation of longitudinal slits 140 by water jet cutting, the absorbent core 115 including homogeneous mixture of cellulose fluff pulp and superabsorbent polymer (SAP) is subjected to high-pressure water jets. The water jets directed along predetermined longitudinal paths of the absorbent core 115 cut through the material to form slits 140. Water jet cutting enables contactless cutting with minimal mechanical stress to the surrounding structure.
In the process of incorporation of longitudinal slits 140 by perforation and expansion, the absorbent core 115 including homogeneous mixture of cellulose fluff pulp and superabsorbent polymer (SAP) is initially perforated in a staggered pattern and subsequently subjected to controlled longitudinal stretching. This causes the perforations to open into aligned, longitudinally extending channels or slits. Perforation and expansion facilitate continuous production and is adaptable for slit geometries.
In accordance with the preferred embodiment of the present invention, the absorbent article 100 in newborn infant size is preferably 295 mm in length. The length of the absorbent core 115 is preferably 280 mm along the longitudinal direction 130. The breadth of the absorbent core 115 is preferably 100 mm along the transverse direction 135.
The length of the slits 140 is 160 mm, leaving a gap of 50 mm at the front end of the absorbent core 115 and 70 mm at the rear end of the absorbent core 115 along the longitudinal direction 130. The depth of the slits 130 is 3-5mm. The distance between the two slits 140 towards the front end of the absorbent core 115 is 70 mm, whereas the distance between the two slits 130 at the rear end is 25 mm.

EXAMPLES:
Only a few examples and implementations are disclosed. Variations, modifications, and enhancements to the described examples and implementations and other implementations can be made based on what is disclosed.
Examples are set forth herein below and are illustrative of different amounts and types of reactants and reaction conditions that can be utilized in practicing the disclosure. It will be apparent, however, that the disclosure can be practiced with other amounts and types of reactants and reaction conditions than those used in the examples, and the resulting devices various different properties and uses in accordance with the disclosure above and as pointed out hereinafter.

EXAMPLE 1: SLIT DIMENSIONS OF THE ABSORBENT ARTICLE IN VARIOUS ARTICLE SIZES
Table 1 below provides the dimensions of the slits 140 in proportion to the absorbent core 115 for various sizes of the absorbent article 100.
Sr. no. Size of absorbent article Length of Absorbent article Length of Absorbent core Breadth of Absorbent core Length of slits Gap at front end of absorbent core along longitudinal direction Gap at rear end of absorbent core along longitudinal direction Distance between two slits at front end of absorbent core Distance between two slits at rear end of absorbent core
1 Newborn 295 mm 280 mm 100 mm 160 mm 50 mm 70 mm 70 mm 25 mm
2 Small 325 mm 310 mm 110 mm 180 mm 50 mm 80 mm 70 mm 25 mm
3 Medium 375 mm 360 mm 110 mm 210 mm 60 mm 90 mm 70 mm 25 mm
4 Large 415 mm 400 mm 110 mm 230 mm 65 mm 105 mm 70 mm 25 mm
5 Extra Large 445 mm 430 mm 110 mm 245 mm 70 mm 115 mm 70 mm 25 mm
6 Double ExtraLarge 445 mm 430 mm 110 mm 245 mm 70 mm 115 mm 70 mm 25 mm
Table 1: Details of dimensions of various sizes of the absorbent article

EXAMPLE 2: ABSORBENT ARTICLE AND THE MATERIAL OF THE LAYERS
Table 2 below provides the details of the primary material employed for each functional layer of the absorbent article 100.
Sr. no. Layer Primary Material Specification
1. Top Layer Hydrophilic spun bonded polypropylene nonwoven 15-25 gsm
2. Acquisition Distribution Layer Chemically bonded or air laid nonwoven 10-50 gsm, = 80% PET
3. Absorbent core Fluff pulp + SAP wrapped in cellulose tissue or air laid nonwoven 10-15 gsm
4. Core wrap Cellulose tissue or lightweight air laid nonwoven 10-15 gsm
5. Bottom layer Breathable PE film laminated with nonwoven 20-30 gsm
Table 2: Primary materials employed for each functional layer of the absorbent article

EXAMPLE 3: DEMONSTRATION OF IMPROVED ABSORPTIVE CAPACITY AND LIQUID DISTRIBUTION OF THE ABSORBENT ARTICLE COMPARED TO MARKET PRODUCTS
To evaluate the technical efficacy of the absorbent article 100, a comparative laboratory testing was conducted against a leading commercially brand. The tests were performed under controlled conditions in accordance with the standard test protocol IS 17509:2021, prescribing the procedures for assessing absorption performance and rewetting characteristics of disposable absorbent articles.
Test Parameters and methodology
A. Sample Sizes:
Medium and Large
B. Tested Parameters:
1. Speed of absorption (time taken to absorb successive gushes of fluid)
2. Rewet value (amount of fluid returned to surface under standard pressure)
C. Procedure:
1. Three successive fluid gushes were applied at defined intervals.
2. The time required for each gush to be completely absorbed was recorded.
3. Rewet was measured as the weight of moisture transferred back to a filter paper under pressure after full absorption.
Experimental Results
Size: Medium
Test Parameter Slit Core Design Leading Commercial Brand % Improvement
Speed of Absorption - 1st Gush (sec) 10 15 33% faster
Speed of Absorption -2nd Gush (sec) 30 52 42% faster
Speed of Absorption - 3rd Gush (sec) 68 83 18% faster
Rewet Value (gm) 0.76 2.40 68% lower

Size: Large
Test Parameter Slit Core Design Leading Commercial Brand % Improvement
Speed of Absorption - 1st Gush (sec) 18 33 45% faster
Speed of Absorption - 2nd Gush (sec) 32 57 44% faster
Speed of Absorption - 3rd Gush (sec) 74 86 14% faster
Rewet Value (gm) 0.89 2.14 58% lower

Observations
1. The absorbent article with slit core design 100 absorbed liquid significantly faster, with improvements of up to ~45% in absorption time compared to the leading commercial brand.
2. The slit channels effectively guided liquid longitudinally and laterally, reducing pooling and promoting even distribution across the core.
3. The rewet value, an indicator of surface dryness and user comfort, was reduced by 58-68%, confirming superior retention within the core and minimal fluid return to the surface.
4. The funnel-shaped pattern of the slits contributed to these benefits by directing fluid from the front (higher loading zone) to the rear, improving overall utilization of the absorbent material.

EXAMPLE 4: EXPERIMENTAL DATA DEMONSTRATING REDUCED WETNESS AND ENHANCED DRYNESS COMPARED TO MARKET PRODUCTS
Comparative laboratory tests were conducted to assess the surface wetness and dryness performance of the absorbent article 100 with slit core design against a leading commercial brand. The evaluation was carried out under controlled conditions in accordance with IS 17509:2021, the standard protocol for testing disposable absorbent articles.
Test Parameters and Methodology
Objective: To quantify and compare the residual surface moisture (rewet) after absorption, which correlates directly with user-perceived dryness.
Sample Sizes: Medium and Large
Procedure:
1. Three successive fluid gushes were introduced into each product at defined intervals.
2. After full absorption of each gush, a standard weight and filter paper were placed on the product surface.
3. The amount of fluid transferred to the filter paper was recorded as the rewet value (grams) - lower values indicate enhanced surface dryness.
Experimental Results: Rewet Values
Size: Medium
Test Parameter Slit Core Design Leading Commercial Brand % Improvement
Rewet Value (gm) 0.76 2.40 68% reduction

Size: Large
Test Parameter Slit Core Design Leading Commercial Brand % Improvement
Rewet Value (gm) 0.89 2.14 58% reduction

Observations
1. The slit core design demonstrated a rewet value reduction of approximately 58-68% compared to the leading commercial brand.
2. This significant reduction in surface wetness is attributable to: The longitudinal slits, which facilitate rapid downward fluid movement away from the top layer. The funnel-shaped slit pattern, which distributes fluid effectively throughout the absorbent core and prevents localized saturation. The enhanced capillary action of the slits, which promotes deeper SAP capture and locks fluid away from the surface.
The absorbent article with slit core design 100 of the present invention is industrially applicable in the manufacture of disposable hygiene products such as infant diapers, adult incontinence pads, sanitary napkins, and nursing pads. The present invention is implementable on high-speed absorbent article production lines using conventional converting machinery with minimal adaptation. The absorbent article with the slit core design 100 advantageously promotes rapid fluid absorption across the entire absorbent area. Parallel slits positioned on the opposite sides of the absorbent core, with a narrower front configuration and a broader rear configuration, enable even fluid distribution throughout the core. This structure reduces residual wetness, enhances dryness, and provides a snug, body-conforming fit in products such as diapers, ultimately improving wearer comfort.
The funnel-shaped longitudinal slit channels, precisely die-cut into the SAP-loaded fluff core and aligned with top layer embossing, create a synergistic structure that optimizes fluid dynamics beyond conventional designs. The integrity of the slits is preserved through targeted bonding of the core wrap along the slit paths, that ensures open, functional channels throughout the product’s lifecycle. Further, coordinated optimization of the top layer, acquisition/distribution layer (ADL), and slit core geometry enhances longitudinal fluid transport, reduces rewetting, and improves wearer comfort.
The slit core design improves liquid distribution and retention, enabling more efficient use of SAP and fluff pulp. This allows for reduced absorbent material usage while maintaining or enhancing performance, leading to cost savings. Further, seamless manufacturing via rotary die-cutting with thermal bonding, without the need for adhesives, reduces both material and processing costs.
The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others, skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated.
It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the scope of the present invention.
,CLAIMS:We claim:
1. An absorbent article with slit core design 100 comprising:
a top layer 105 being the surface layer in contact with the user’s skin such that the top layer being permeable and breathable allowing the fluids to pass through easily;
an acquisition distribution layer 120 being positioned immediately beneath the top layer 105 such that the acquisition distribution layer 120 receiving fluid from the top layer 105, facilitating its dispersal over a broader surface area and reducing localized saturation;
an absorbent core 115 being disposed below the acquisition distribution layer such that the absorbent core 115 retaining the liquid distributed by the acquisition distribution layer 120 and the absorbent core 115 housing long engraved slits 140 along its longitudinal direction 130;
a core wrap 125 encapsulating the absorbent core 115, such that the core wrap 125 maintaining the integrity and position of the absorbent material during use; and
a bottom layer 110, the bottom layer being the lowermost layer of the absorbent article 100, acting as a liquid-impermeable barrier for preventing leakage to the outside environment.

2. The absorbent article with slit core design 100 as claimed in Claim 1, wherein the absorbent core 115 is an elongated rectangular structure having a longitudinal direction 130 along its length and a transverse direction 135 along its breadth, the absorbent core 115 including at least two longitudinally extending slits 140 arranged substantially parallel or converging toward one another such that the spacing between the slits 140 is greater at a front region and smaller at a rear region, thereby defining a funnel-shaped configuration within the absorbent core 115.
3. The absorbent article with slit core design 100 as claimed in Claim 1, wherein the top layer 105 being prepared from materials selected from hydrophilic spunbonded non-woven fabrics, spunbond meltblown spunbond non-woven fabric, viscose polyester blend nonwoven fabric, polylactic acid or other biodegradable nonwoven fabrics, perforated films; and the top layer 105 being optionally embossed or perforated facilitating directional liquid movement and minimizing rewetting.
4. The absorbent article with slit core design 100 as claimed in Claim 1, wherein the acquisition distribution layer 120 being prepared from materials selected from chemically bonded or air laid nonwoven fabric, thermal bonded or carded nonwoven fabric, synthetic fiber blends with rayon or viscose, air laid pulp sheets; such that the acquisition distribution layer 120 facilitating rapid fluid acquisition by quickly drawing liquid away from the top layer for reducing surface wetness.
5. The absorbent article with slit core design 100 as claimed in Claim 1, wherein the absorbent core 115 being prepared from materials selected from fluff pulp, cellulosic fibers, superabsorbent polymers, tissue-SAP composites, air laid absorbent sheets with embedded SAP, nonwoven SAP matrices.
6. The absorbent article with slit core design 100 as claimed in Claim 1, wherein the core wrap 125 being prepared from cellulose tissue or lightweight air laid nonwoven material.
7. The absorbent article with slit core design 100 as claimed in Claim 1, wherein the bottom layer 110 being prepared from materials selected from breathable, microporous polyethylene (PE) film, microporous polypropylene (PP) films, polypropylene films, breathable laminates, laminated composites combining nonwoven and film layers, biodegradable films.
8. The absorbent article of claim 1, wherein the slits 140 being extend between about 10% and about 95% of the longitudinal length of the absorbent core 115.
9. The absorbent article of claim 1, wherein the slits 140 including a depth of about 3 mm to about 5 mm.
10. The absorbent article of claim 1, wherein the spacing between the slits 140 at the front end of the absorbent core 115 being at least 50 mm and the spacing at the rear end being not greater than 30 mm.
11. The absorbent article of claim 1, wherein the absorbent core 115 including 25–50% by weight of superabsorbent polymer.
12. The absorbent article of claim 1, wherein the bottom layer 110 being a breathable microporous film laminated with a nonwoven outer sheet to provide a textile-like feel.
13. The absorbent article of claim 1, wherein at least one of the top layer 105 or bottom layer 110 being biodegradable, selected from polylactic acid (PLA) or polybutylene adipate terephthalate (PBAT).
14. A method 200 of preparation of the absorbent article 100 as claimed in claim 1, including a first preprocessing cycle 205 and a second assembly cycle 210,
such that the first preprocessing cycle 205 including:
a) a first step 205A of top layer formation wherein a skin-contacting top layer 105 being prepared from hydrophilic spunbonded nonwoven fabric such that the material being engineered with a hydrophilicity gradient by treating the surface fibers with plasma treatment or chemically treatment for exhibiting higher wettability than the inner fibers;
b) a second step 205B of absorbent core formation wherein longitudinal slits 140 being configured into the absorbent core 115 in a funnel-shaped pattern such that the slits 140 being wider apart at the front end and narrower at the rear, covering approximately 10 - 95% of the longitudinal length of the core, and the funnel shaped pattern directing the liquid toward the rear end while maintaining containment and fit;
c) a third step 205C of acquisition and distribution layer formation wherein the acquisition and distribution layer (ADL) 120 being patterned to align with the funnel-shaped slit configuration of the absorbent core 115, the ADL 120 being configured to have differential density zones such that the layer being denser in the front and more open toward the rear;
d) a fourth step 205D of core wrap formation wherein the absorbent core 115 being encapsulated within a permeable core wrap 125 formed from cellulose tissue or air laid nonwoven material, the top and bottom layers of the core wrap 125 being bonded along the slits 140 for maintaining the longitudinal channels during use, and selectively applying adhesive for immobilizing the superabsorbent polymer (SAP) of the absorbent core 115 within the designated region;
e) a fifth step 205E of bottom layer formation wherein the bottom layer 110 being constructed from breathable microporous polyethylene (PE) film and being laminated with a nonwoven outer layer for imparting a textile-like feel, the PE film being corona-treated on its inner face to enhance adhesion of the glue lines during assembly; and
the second assembly cycle 210 including
f) a sixth step of article assembly 210A wherein the top layer 105, the acquisition and distribution layer (ADL) 120, the core wrap 125 encapsulated absorbent core 115, and the bottom layer 110 being assembled sequentially using an assembly system capable of achieving required alignment and integration, and the assembly system being equipped with optical registration for precisely aligning the embossing of the top layer 105 with the longitudinal slits 140 of the absorbent core 115;
g) a seventh step of article sealing 210B, wherein the sequentially assembled layers being bonded for preserving the integrity of the slit pattern such that the bonding being carried out using methods selected from ultrasonic bonding, thermal bonding, and elastic elements, leg cuffs, and closure components being incorporated in the article; and
h) an eighth step of profiling and contouring 210C, wherein the assembled and bonded layered web being die-cut into ergonomically contoured absorbent article 100 configured as per the requirement for infant or adult use; the margins being precisely defined to reduce leakage risk; waistbands, stretch panels, and closure systems (mechanical or adhesive) being affixed; and the peripheral edges of the absorbent article 100 being treated for providing a soft finish and minimizing skin irritation during wear.
15. A method of incorporation of longitudinal slits 140 in the absorbent core 115 of the absorbent article 100 as claimed in claim 1, wherein the slits 140 being incorporated in the absorbent core 115 by methods selected from die cutting, laser cutting, embossing and bonding, water jet cutting, perforation and expansion.

Dated this 17th day of August 2024.

For SWARA BABY PRODUCTS PRIVATE LIMITED

Mahurkar Anand Gopalkrishna
IN/PA-1862
(Agent for Applicant)