Multilayer absorbent substrate and absorbent article incorporating same

Abstract

Multilayer substrates having an excellent combination of tensile strength and water treatment characteristics are disclosed. The substrate can be produced according to a foam forming process. The binder fibers are strategically positioned in the outer layer while minimizing the inner layer to create an absorbent structure capable of receiving a large amount of liquid and expanding unlimitedly.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application 63 / 431,409, filed on December 9, 2022, which is hereby incorporated by reference in its entirety. Background Art

[0003] There are many different types of nonwoven materials that are designed to have different functions. In many embodiments, the nonwoven materials are designed to have liquid handling characteristics. These nonwoven materials can be used in absorbent articles to absorb fluids.

[0004] Absorbent articles, also known as personal care products, such as diapers, diaper pants, training pants, adult incontinence products, and feminine care products, can include a variety of substrates. For example, an absorbent article can include an absorbent structure, a nonwoven material, and a film. These layers are positioned relative to each other such that fluids contacting the absorbent article can be quickly drawn into and contained within the absorbent structure, thereby keeping the wearer feeling dry.

[0005] The absorbent structure can contain superabsorbent materials. Superabsorbent materials can be configured in the form of particles that include fibers and are typically used in substrates to increase the absorption capacity.

[0006] One problem in designing absorbent articles is the ability to produce an absorbent structure containing superabsorbent materials that are soft, flexible, strong, thin, and have good absorption characteristics. For example, an absorbent structure made only of superabsorbent materials does not have the strength or a consolidated substrate that is easy to handle. Thus, in the past, various different fibers have been incorporated into the absorbent structure, including binder fibers. Binder fibers can increase the strength and integrity of the absorbent structure, but can impede absorbent performance. For example, binder fibers can have hydrophobic characteristics and can create a binding network that can resist or slow down volume expansion as the absorbent structure swells upon contact with a fluid, reducing the available void volume of the absorbent structure. Accordingly, there is a current need for an improved absorbent structure that has a balance of strength and absorbent characteristics. Summary of the Invention

[0007] The present disclosure generally relates to multi-layer liquid absorbent substrates having a combination of excellent absorbent characteristics and excellent physical strength characteristics. The present disclosure also relates to all different types of absorbent articles incorporating the liquid absorbent substrate. The substrate can be manufactured by a foam forming process.

[0008] In one aspect, for example, the present disclosure relates to a multi-layer substrate that includes a first layer containing binder fibers. The substrate further includes a second layer containing a superabsorbent material. According to the present disclosure, the multi-layer substrate has a tensile strength greater than about 1,000 grams-force per 3 inches in one direction and exhibits a 30-second AUL test result greater than about 10 g / g. For example, the multi-layer substrate can have a tensile strength greater than about 1,500 grams-force per 3 inches in at least one direction, such as greater than about 2,000 grams-force per 3 inches, such as greater than about 3,000 grams-force per 3 inches, such as greater than about 3,500 grams-force per 3 inches, such as greater than about 4,000 grams-force per 3 inches, such as greater than about 4,500 grams-force per 3 inches, such as greater than about 5,000 grams-force per 3 inches, such as greater than about 5,500 grams-force per 3 inches, such as greater than about 6,000 grams-force per 3 inches, such as greater than about 6,500 grams-force per 3 inches, such as greater than about 7,000 grams-force per 3 inches, such as greater than about 7,500 grams-force per 3 inches, such as greater than about 8,000 grams-force per 3 inches, such as greater than about 8,500 grams-force per 3 inches, such as greater than about 9,000 grams-force per 3 inches, such as greater than about 9,500 grams-force per 3 inches, such as greater than about 10,000 grams-force per 3 inches, and generally less than about 20,000 grams-force per 3 inches. The normalized tensile strength can be greater than about 333 grams-force per inch, such as greater than about 500 grams-force per inch, such as greater than about 700 grams-force per inch, such as greater than about 1,000 grams-force per inch, such as greater than about 1,200 grams-force per inch, such as greater than about 1,300 grams-force per inch, such as greater than about 1,500 grams-force per inch, such as greater than about 2,000 grams-force per inch, such as greater than about 2,500 grams-force per inch, such as greater than about 3,000 grams-force per inch, and generally less than about 10,000 grams-force per inch, such as less than about 7,000 grams-force per inch.

[0009] The multi-layer substrate can exhibit a 30-second AUL test result greater than about 11 g / g, such as greater than about 12 g / g, such as greater than about 13 g / g, such as greater than about 14 g / g, such as greater than about 15 g / g, such as greater than about 16 g / g, such as greater than about 17 g / g, such as greater than about 18 g / g, and less than about 30 g / g. The multi-layer substrate can also exhibit an area-normalized saturation capacity greater than about 0.25 g / cm 2 , such as greater than about 0.5 g / cm 2 , about 0.8 g / cm 2 , such as greater than about 1.0 g, such as greater than about 1.2 g, such as greater than about 1.5 g / cm 2 , and less than about 2.5 g / cm 2 .

[0010] As described above, the second layer contains a superabsorbent material. In one aspect, the second layer contains little or no binder fibers. For example, the binder fibers may be present in an amount less than about 20 wt%, such as less than about 8 wt%, such as less than about 5 wt%, such as less than about 4 wt%, such as less than about 3 wt%, such as less than about 2 wt%, such as less than about 1 wt% in the second layer. In one aspect, the amount of binder fibers contained in the second layer is less than about 5 wt% based on the total amount of fibers contained in the second layer.

[0011] The second layer may contain an amount greater than about 20 wt%, such as greater than about 30 wt%, such as greater than about 40 wt%, such as greater than about 50 wt%, such as greater than about 60 wt%, such as greater than about 70 wt%, such as greater than about 80 wt%, such as greater than about 90 wt%, such as greater than about 95 wt% of the superabsorbent material. The second layer may contain an amount less than about 100 wt%, such as less than about 90 wt%, such as less than about 80 wt%, such as less than about 70 wt% of the superabsorbent material. The second layer may also contain various different types of fibers. For example, the second layer may contain pulp fibers, such as crosslinked pulp fibers, non-crosslinked pulp fibers, or mixtures thereof, synthetic polymer fibers, such as polyester fibers, or mixtures thereof. The basis weight of the second layer may be greater than about 200 gsm, such as greater than about 250 gsm, such as greater than about 300 gsm, such as greater than about 350 gsm and less than about 800 gsm, such as less than about 600 gsm.

[0012] In another aspect, the first layer of the multi-layer substrate may contain a relatively large amount of binder fibers compared to the second layer. For example, the first layer may contain an amount greater than about 20 wt%, such as greater than about 30 wt%, such as greater than about 40 wt%, such as greater than about 50 wt%, and up to 100 wt%, such as less than about 80 wt%, such as less than about 70 wt% of the binder fibers. The binder fibers may include bicomponent fibers having a core polymer and a sheath polymer. The sheath polymer may have a lower melting temperature, which causes the binder fibers to bond to other binder fibers or other materials contained in the substrate when heated. In one aspect, the binder fibers include a core polymer made of a polyester polymer and a sheath polymer made of a polyethylene polymer. In addition to the binder fibers, the first layer may also contain pulp fibers (including crosslinked pulp fibers), synthetic polymer fibers (such as polyester fibers), and mixtures thereof. In one aspect, the first layer contains an amount less than about 2 wt% of the superabsorbent material and / or may be free of the superabsorbent material.

[0013] The first layer may have a basis weight of from about 10 gsm to about 100 gsm, including all 1 gsm increments therebetween. In one aspect, the first layer has a basis weight greater than about 35 gsm, such as greater than about 40 gsm, such as greater than about 45 gsm, such as greater than about 50 gsm, and less than about 100 gsm, such as less than about 90 gsm, such as less than about 80 gsm. In this embodiment, the first layer may contain from about 20 wt% to about 80 wt% of binder fibers and may be combined with synthetic polymer fibers.

[0014] In another aspect, the first layer may have a basis weight less than about 35 gsm, such as less than about 30 gsm, such as less than about 25 gsm, such as less than about 20 gsm, and greater than about 10 gsm, such as greater than about 15 gsm, such as greater than about 20 gsm. In this embodiment, the first layer may contain from about 10 wt% to about 80 wt% of binder fibers. The binder fibers may be combined with pulp fibers (including crosslinked pulp fibers). The first layer may optionally contain polymer synthetic fibers.

[0015] In one embodiment, the multi-layer substrate may optionally include a third layer. The second absorbent layer may be positioned between the first layer and the third layer. In one aspect, the first layer may form a top outer layer that is configured to face the wearer when incorporated into an absorbent article. In another aspect, the third layer may form a bottom outer layer. In one aspect, the third layer may include any suitable layer capable of preventing the superabsorbent material from escaping the multi-layer substrate from the second layer. For example, the third layer may have a basis weight of from about 5 gsm to about 50 gsm, including all 1 gsm increments therebetween. For example, the third layer may have a basis weight greater than about 10 gsm, such as greater than about 15 gsm, and less than about 50 gsm, such as less than about 40 gsm, such as less than about 30 gsm, such as less than about 25 gsm, such as less than about 20 gsm. The third layer may contain binder fibers alone or in combination with pulp fibers and / or synthetic polymer fibers. The pulp fibers may optionally include crosslinked pulp fibers. In one aspect, the binder fibers may have a size less than about 6 denier, such as less than about 4 denier, such as less than about 2.5 denier, such as less than about 2 denier, such as less than about 1.5 denier, and greater than about 0.3 denier.

[0016] The present disclosure also relates to an absorbent article incorporating a multi-layer substrate as described above. For example, the absorbent article may include a fluid-permeable liner, an outer cover, and an absorbent core that contains the multi-layer substrate of the present disclosure positioned between the liner and the outer cover. In one aspect, the absorbent article may include a diaper or child's pants, including training pants. Alternatively, the absorbent article may include an adult incontinence product.

[0017] Other features and aspects of the present disclosure are discussed in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present disclosure, which is to be made comprehensive and enabling, is set forth more specifically in the remainder of the specification and with reference to the drawings, in which:

[0019] Figure 1A is a side plan view of an exemplary multi-layer absorbent material including three layers according to an embodiment of the present disclosure;

[0020] Figure 1B is a side plan view of an exemplary multi-layer absorbent material including two layers according to another embodiment of the present disclosure;

[0021] Figure 2 is a process schematic of an exemplary apparatus and associated method for forming a multi-layer absorbent material;

[0022] Figure 3 is a detailed view of a headbox, headbox input, and resulting stock from the Figure 2 headbox;

[0023] Figure 4 is a side plan view of an alternative apparatus and associated method that can be used to form a multi-layer absorbent material;

[0024] Figure 5 is a perspective view of an exemplary rig for performing the Absorbency Under Load (AUL) test described herein; and

[0025] Figure 6 is Figure 5 a perspective view of a plastic platen weight inserted into the AUL cylinder shown.

[0026] Figure 7 is a perspective view of an exemplary rig for performing the Fluid Ingress Under Pressure (FIUP) test described herein, with the lid open.

[0027] Figure 8 is Figure 7 a perspective view of the exemplary rig with the lid closed.

[0028] The repeated use of reference numerals in the specification and drawings is intended to represent the same or analogous features or elements of the invention.

[0029] Definitions

[0030] As used herein, the term "foam-formed product" means a product formed from a suspension comprising a mixture of solids, liquids, and dispersed gas bubbles.

[0031] As used herein, the term "foam forming process" means a process for manufacturing a product involving a suspension of a mixture including solids, liquids, and dispersed gas bubbles.

[0032] As used herein, the term "foaming fluid" means any one or more known fluids that are compatible with other components in a foam forming process. Suitable foaming fluids include, but are not limited to, water.

[0033] As used herein, the term "foam half-life" means the time elapsed until half of the initial foamed foam material reverts to liquid water.

[0034] As used herein, the term "layer" refers to a structure that provides a substrate region in the height direction of a substrate composed of similar components and structure.

[0035] As used herein, the term "nonwoven web" refers to a web having a structure of individual fibers or threads that are interlayered but not in an identifiable pattern (such as in a knitted web).

[0036] As used herein, unless otherwise expressly specified, when used in relation to material composition, the terms "percentage", "%", "weight percentage", or "weight %" each refer to the amount of a component as a percentage by weight of the total amount, unless otherwise expressly indicated.

[0037] The term "absorbent article" as used herein refers to an article that is intended or adapted to be placed adjacent to or near the body of a wearer (i.e., adjacent to the body) to absorb and contain various liquid, solid, and semi-solid exudates discharged from the body. Examples include, but are not limited to, diapers, diaper pants, training pants, youth pants, swimsuits, feminine hygiene products (including, but not limited to, menstrual pads or pants), incontinence products, medical garments, surgical pads, and bandages, among others.

[0038] As used herein, the term "superabsorbent material" refers to a water-swellable, water-insoluble organic or inorganic material, including superabsorbent polymers and superabsorbent polymer compositions that are capable of absorbing at least about 10 times, or at least about 15 times, or at least about 25 times their weight in an aqueous solution containing 0.9 weight % sodium chloride under the most favorable conditions.

[0039] As used herein, the term "longitudinal direction" refers to the direction of travel of the forming surface on which fibers are deposited during the formation of a nonwoven web.

[0040] As used herein, the term "transverse direction" refers to the direction perpendicular to the longitudinal direction and the height direction as defined above.

[0041] As used herein, the term "pulp" refers to fibers from natural sources such as woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto, milkweed, straw, jute, hemp, and bagasse. Pulp fibers can include hardwood fibers, softwood fibers, and mixtures thereof.

[0042] As used herein, the term "average fiber length" refers to the average length of fibers, fiber bundles, and / or fibrous materials determined by measurement using microscopy techniques. A sample of at least 20 randomly selected fibers is separated from a liquid suspension of the fibers. The fibers are placed on a microscope slide that has been prepared to suspend the fibers in water. A coloring dye is added to the suspended fibers to color the cellulose-containing fibers so that they can be distinguished or separated from synthetic fibers. The slide is placed under a Fisher Stereomaster II microscope - S19642 / S19643 series. Twenty fibers in the sample are measured at 20X linear magnification using a 0 - 20 mil scale, and the average length, minimum and maximum lengths, and deviation or coefficient of variation are calculated. In some cases, the average fiber length will be calculated as the weighted average length of the fibers (e.g., fibers, fiber bundles, fibrous materials), which is determined by equipment such as the Kajaani Fiber Analyzer model FS - 200 obtained from Kajaani Oy Electronics, Kajaani, Finland. According to standard test procedures, the sample is treated with an impregnating solution to ensure the absence of fiber bundles or debris. Each sample is decomposed in hot water and diluted to a suspension of approximately 0.001%. When tested using standard Kajaani fiber analysis test procedures, test samples of approximately 50 ml to 100 ml each are drawn from the diluted suspension. The weighted average fiber length can be an arithmetic mean, a length-weighted mean, or a weight-weighted mean, and can be represented by the following equation:

[0043]

[0044] where

[0045] k = maximum fiber length

[0046] x i = fiber length

[0047] n i = number of fibers of length xi

[0048] n = total number of fibers measured.

[0049] One characteristic of the average fiber length data measured by the Kajaani fiber analyzer is that it does not distinguish between different types of fibers. Thus, the average length represents the average of the lengths of all different types (if any) of fibers in the sample.

[0050] As used herein, the term "short fiber" refers to discontinuous fibers made of synthetic polymers or regenerated cellulose such as polypropylene, polyester, post-consumer recycled (PCR) fibers, polyester, nylon, viscose, rayon, etc., and those non-hydrophilic ones can be treated to be hydrophilic. Short fibers can be cut fibers, etc. Short fibers can have a cross-section that is round, bicomponent, multicomponent, shaped, hollow, etc.

[0051] The terms "twisted" or "bonded" or "joined" herein refer to the joining, adhesion, connection, attachment, etc. of two elements. Two elements will be considered to be twisted, bonded, or joined together when they are joined, adhered, connected, attached, etc. to each other directly or indirectly, such as when each is directly bonded to an intermediate element. The twisting, bonding, or joining of one element to another can be carried out by continuous or intermittent bonding.

[0052] As used herein, a "binder fiber" is a fiber that can be bonded to other fibers in a substrate by chemical, mechanical, or thermal means. Binder fibers can include heat-bondable fibers that, when heated, form a thermal bond with other fibers at their intersection points. In one aspect, the binder fiber comprises a surface polymer having a lower melting temperature. For example, the binder fiber can be made of a polymer (such as a polyolefin) having a melting temperature of less than 200 °C, such as less than 180 °C, such as less than 160 °C, such as less than 140 °C, such as less than 120 °C, such as less than 100 °C, and greater than 80 °C, such as greater than 90 °C. In one aspect, the binder fiber includes composite fibers, such as bicomponent fibers. The composite fiber can have a core structure and a sheath structure, including a core polymer surrounded by a sheath polymer. The core polymer can have a higher melting temperature than the sheath polymer. The core polymer can be selected according to strength and high melting point, and the sheath polymer can be made of a polymer selected according to a lower melting point. For example, the core polymer can have a melting temperature higher than that of the sheath polymer. Thus, when the sheath polymer is heated, it will melt and bond to other fibers at the intersection points within the web. However, the core polymer keeps the bicomponent binder fiber in its shape and provides strength.

[0053] As used herein, a "synthetic polymer fiber" refers to a fiber made of a polymer that is not a binder fiber. Synthetic polymer fibers can include polyester fibers, such as fibers made of polyethylene terephthalate polymers. Other polymer synthetic fibers include polyolefin fibers, such as polyethylene fibers, polypropylene fibers, and fibers made of copolymers of the above.

[0054] As used herein, "saturation capacity" refers to the result of a saturation capacity test and is area normalized. The saturation capacity test for an absorbent article is performed using a tabletop saturation capacity tester as described herein. First, the dry sample mass is measured. Subsequently, the sample is saturated in a saline solution (0.9 wt% NaCl) for 20 minutes and then drip-dried for 1 minute. Next, the sample is placed face-down on the screen of a tabletop saturation capacity tester (commercially available from Taconic Plastics Inc., Petersburg, N.Y.) having a 0.25 inch (6.4 mm) opening, the screen is then placed on a vacuum chamber, and covered with a flexible rubber barrier material such as a latex sheet. A vacuum of 3.5 kPa (0.5 pounds per square inch) is drawn in the vacuum chamber for 5 minutes. The sample is then removed from the vacuum chamber and weighed to determine the saturated weight or wet weight of the sample. If a material such as a superabsorbent material or fiber is drawn through a fiberglass screen while on the vacuum chamber, a screen with a smaller opening should be used. Alternatively, a piece of tea bag material (such as heat-sealable tea bag material (grade 542, commercially available from Kimberly-Clark Corporation)) can be placed between the material and the screen, and the final value adjusted for the fluid retained by the tea bag material. The saturation capacity is the total weight of the wet sample minus the dry weight of the sample. The area-normalized saturation capacity is calculated by dividing the saturation capacity (in grams) by the area of the absorbent material (in square centimeters). Detailed Description

[0055] Those of ordinary skill in the art will understand that this discussion is only a description of exemplary embodiments and is not intended to limit the broader aspects of the disclosure.

[0056] The present disclosure relates to methods and systems for producing nonwoven substrates. While the present disclosure provides examples of substrates made by foam forming, it is contemplated that the methods and apparatus described herein can be useful for benefiting wet-laid and / or air-laid manufacturing processes.

[0057] Each example is given by way of illustration and not limitation. For example, features illustrated or described as part of one embodiment or figure can be used in another embodiment or figure to yield yet another embodiment. It is intended that the present disclosure cover such modifications and variations.

[0058] When introducing elements of the present disclosure or its preferred embodiments, the articles "a", "an", "the", and "said" are intended to mean that there is one or more of the elements. The terms "comprising", "including", and "having" are intended to be inclusive, meaning that additional elements may exist beyond the listed elements. As used herein, the terms "first", "second", "third", etc. do not specify an indicated order, but rather are used as a means of distinguishing different events when referring to various features in the present disclosure. Many modifications and variations can be made to the present disclosure without departing from the spirit and scope thereof. Accordingly, the exemplary embodiments described herein should not be used to limit the scope of the invention.

[0059] Generally, the present disclosure relates to a multi-layer substrate, particularly a multi-layer substrate having excellent fluid handling characteristics, including the ability to absorb large amounts of fluid. In one aspect, the multi-layer substrate can be manufactured using a foam forming process, which has been found to have a number of advantages and benefits.

[0060] The multi-layer substrate manufactured according to the present disclosure not only has good fluid absorbency characteristics, but also has excellent strength characteristics. Thus, the substrate is easy to handle and manipulate. For example, a multi-layer substrate manufactured according to the present disclosure can be formed and then wound into a roll for later feeding into a process for producing an absorbent article. According to the present disclosure, the multi-layer substrate of the present disclosure has at least two layers. One layer is an absorbent layer containing a large amount of superabsorbent material that can rapidly absorb and retain fluid. The absorbent layer is combined with at least one outer layer. The at least one outer layer contains a binder, particularly binder fibers, which provide structure to the substrate without significantly affecting the thickness of the substrate. The at least one outer layer generally does not contain a large amount of superabsorbent material. In addition, the absorbent layer containing the superabsorbent material is configured to contain the least amount of binder fibers or no binder fibers. Thus, the binder fibers do not interfere with the ability of the absorbent layer to absorb fluid and swell unrestrictedly. The multi-layer substrate of the present disclosure is particularly suitable for absorbent articles intended to absorb large amounts of fluid, such as diapers, other baby care products, and adult incontinence products.

[0061] By selecting the materials contained in each layer of the multi-layer substrate and by controlling the amounts of the components contained in each layer, the multi-layer substrate manufactured according to the present disclosure can have an excellent balance of absorbency and strength. For example, with respect to fluid handling characteristics, the multi-layer substrate of the present disclosure can exhibit 30-second AUL test results greater than about 10 g / g, such as greater than about 11 g / g, such as greater than about 12 g / g, such as greater than about 13 g / g, such as greater than about 14 g / g, such as greater than about 15 g / g, such as greater than about 16 g / g, such as greater than about 17 g / g, such as greater than about 18 g / g, such as greater than about 19 g / g. The substrate can exhibit 30-second AUL test results less than about 30 g / g. In addition, the substrate can exhibit greater than about 0.25 g / cm2 , such as greater than about 0.5 g / cm 2 , such as greater than about 0.8 g / cm 2 , such as greater than about 1.0 g, such as greater than about 1.2 g, such as greater than about 1.5 g / cm 2 , and less than about 2.5 g / cm 2 of the area-normalized saturation capacity. The initial saturation capacity before normalization can be greater than about 200 g, such as greater than about 225 g, such as greater than about 250 g, such as greater than about 275 g, such as greater than about 300 g, such as greater than about 325 g, such as greater than about 350 g, such as greater than about 375 g, such as greater than about 400 g, such as greater than about 425 g, such as greater than about 450 g, such as greater than about 475 g, such as greater than about 500 g. The absorption capacity can be less than about 1,000 g.

[0062] In addition to the above-described fluid handling characteristics, the multi-layer substrate can also exhibit a tensile strength greater than about 2,000 grams-force per 3 inches in at least one direction. For example, the tensile strength of the substrate in one direction can be greater than about 2,500 grams-force per 3 inches, such as greater than about 3,000 grams-force per 3 inches, such as greater than about 3,500 grams-force per 3 inches, such as greater than about 4,000 grams-force per 3 inches, such as greater than about 4,500 grams-force per 3 inches, such as greater than about 5,000 grams-force per 3 inches, such as greater than about 5,500 grams-force per 3 inches, such as greater than about 6,000 grams-force per 3 inches, such as greater than about 6,500 grams-force per 3 inches, such as greater than about 7,000 grams-force per 3 inches, such as greater than about 7,500 grams-force per 3 inches, such as greater than about 8,000 grams-force per 3 inches, such as greater than about 8,500 grams-force per 3 inches, such as greater than about 9,000 grams-force per 3 inches, such as greater than about 9,500 grams-force per 3 inches, such as greater than about 10,000 grams-force per 3 inches, and less than about 20,000 grams-force per 3 inches. The normalized tensile strength can be greater than about 333 grams-force per inch, such as greater than about 500 grams-force per inch, such as greater than about 700 grams-force per inch, such as greater than about 1,000 grams-force per inch, such as greater than about 1,200 grams-force per inch, such as greater than about 1,300 grams-force per inch, such as greater than about 1,500 grams-force per inch, such as greater than about 2,000 grams-force per inch, such as greater than about 2,500 grams-force per inch, such as greater than about 3,000 grams-force per inch, and generally less than about 10,000 grams-force per inch.

[0063] See Figure 1A and Figure 1B , shown for exemplary purposes only, are examples of multi-layer absorbent substrates made in accordance with the present disclosure. Figure 1A A three-layer embodiment is shown, while Figure 1BShows a two-layer embodiment. However, in other embodiments, it should be understood that the absorbent substrate can contain more than three layers.

[0064] See Figure 1B , the two-layer substrate 110 includes a first layer 12 and a second layer 13. The second layer 13 is an absorbent layer that can contain a large amount of superabsorbent material. In another aspect, the first layer 12 can be configured to have a relatively thin thickness while providing strength and have high permeability to allow fluid to quickly pass through the first layer 12 and be absorbed by the second layer 13.

[0065] As Figure 1B shown, the multi-layer substrate 110 can also include an interface 15 located between the first layer 12 and the second layer 13. In one aspect, at least some of the materials contained in the first layer 12 can be mixed with at least some of the materials in the second layer 13. For example, the fibers of the first layer 12 can be mixed with the fibers and / or superabsorbent materials contained in the second layer 13. The interface 15 can provide the beneficial effect of having some fiber distribution or other material distribution between each of the layers 12 and 13, which can provide inhalation beneficial effects and some stable characteristics between the two layers.

[0066] According to the present disclosure, the first layer 12 can be the top layer facing the wearer when the multi-layer substrate 110 is incorporated into the absorbent article. In one aspect, the first layer 12 can also be an inhalation layer designed to allow the fluid to be quickly absorbed by the second layer 13. For example, in one embodiment, the first layer 12 can be a low-density layer with high permeability characteristics. According to the present disclosure, the first layer 12 can also contain a binder, such as binder fibers, that provides strength and integrity to the entire substrate 110.

[0067] The binder contained within the first layer 12 can be any suitable binder material capable of binding adjacent fibers together. For example, the binder can be in powder form, such as polyethylene powder. In one aspect, the binder becomes water-insoluble once dried on the multi-layer substrate. In other embodiments, the binder can be an adhesive material, such as latex. The latex can be cationic or anionic to facilitate adhesion to the fibers contained within the substrate. Binders that can be used include anionic styrene-butadiene copolymers, polyvinyl acetate homopolymers, vinyl acetate-ethylene copolymers, vinyl acetate-acrylic copolymers, ethylene-vinyl chloride copolymers, ethylene-vinyl chloride-vinyl acetate terpolymers, acrylic polyvinyl chloride polymers, acrylic polymers, nitrile polymers, and other suitable anionic latex polymers known in the art. However, in one aspect, the multi-layer substrate of the present disclosure can be formed in the first layer 12 without using an adhesive but using binder fibers.

[0068] Binder fibers that can be incorporated into the first layer 12 include single-component fibers and multi-component fibers. For example, the multi-component fibers can include a core polymer surrounded by a sheath polymer. The sheath polymer can be composed of a low melting point thermoplastic polymer such as polyethylene. In one aspect, the binder fibers include bicomponent fibers that contain a core polymer made of a polyester polymer or a polypropylene polymer. For example, the core polymer can be a polyethylene terephthalate polymer. In another aspect, the sheath polymer can have a lower melting temperature than the core polymer and can include a polyolefin such as polyethylene.

[0069] The binder fibers can have any suitable size and length. For example, the binder fibers can have a length between about 0.5 mm and about 50 mm, such as between about 0.75 mm and about 30 mm. In one aspect, the binder fibers have a length of about 1 mm to about 25 mm. The binder fibers can have a size of about 0.1 denier to about 10 denier. For example, the size can be less than about 15 denier, such as less than about 10 denier, such as less than about 7 denier, such as less than about 3 denier, such as less than about 2 denier, and greater than about 0.7 denier, such as greater than about 1 denier.

[0070] In one aspect, the first layer 12 can contain from about 10 wt% to 100 wt% of binder fibers, including all 1% increments therebetween. For example, the first layer 12 can contain an amount greater than about 20 wt%, such as greater than about 30 wt%, such as greater than about 40 wt%, such as greater than about 50 wt%, such as greater than about 60 wt%, such as greater than about 70 wt%, such as greater than about 80 wt% of binder fibers. The binder fibers can generally be present in an amount less than about 90 wt%, such as in an amount less than about 80 wt%, such as in an amount less than about 70 wt%.

[0071] In one aspect, the first layer 12 can contain more than one binder fiber. For example, the average fiber length and / or fiber size of each binder fiber can be different. In one aspect, for example, the first layer 12 can comprise a combination of a first binder fiber and a second binder fiber. For example, the first binder fiber can have a fiber size greater than that of the second binder fiber and can be present in the top layer in an amount greater than that of the second binder fiber. The first binder fiber, for example, can have a fiber size greater than about 3 denier, such as greater than about 4 denier, such as greater than about 5 denier, and less than about 15 denier, such as less than about 10 denier, such as less than about 8 denier. The first binder fiber can be present in the top layer in an amount from about 10 wt% to about 55 wt%. For example, the first binder fiber can be present in an amount greater than about 20 wt%, such as in an amount greater than about 25 wt%, such as in an amount greater than about 30 wt%, such as in an amount greater than about 35 wt%, and in an amount less than about 65 wt%, such as in an amount less than about 60 wt%, such as in an amount less than about 55 wt%, such as in an amount less than about 50 wt%, such as in an amount less than about 45 wt%, such as in an amount less than about 40 wt% in the top layer. The first binder fiber can provide void volume and resilience for rapid fluid absorption.

[0072] The second binder fiber contained in the top layer can have a fiber size less than about 3 denier, such as less than about 2.5 denier, and greater than about 0.3 denier, such as greater than about 0.8 denier, such as greater than about 1 denier. The second binder fiber can be present in an amount greater than about 5 wt%, such as in an amount greater than about 8 wt% and in an amount less than about 40 wt%, such as in an amount less than about 35 wt%, such as in an amount less than about 30 wt%, such as in an amount less than about 25 wt%, such as in an amount less than about 20 wt% in the top layer. The second binder fiber can increase the strength of the substrate.

[0073] Although the first layer 12 provides strength to the multi-layer substrate 110, it can be relatively light, thin, and have good liquid permeability. Generally, the basis weight of the first layer 12 can be from about 10 gsm to about 100 gsm, including all 1 gsm increments therebetween. For example, the basis weight can be less than about 90 gsm, such as less than about 80 gsm, such as less than about 70 gsm, such as less than about 60 gsm, such as less than about 50 gsm, such as less than about 40 gsm, such as less than about 30 gsm, such as less than about 20 gsm. The basis weight is typically greater than about 15 gsm, such as greater than about 20 gsm, such as greater than about 25 gsm, such as greater than about 30 gsm, such as greater than about 35 gsm, such as greater than about 40 gsm, such as greater than about 45 gsm, such as greater than about 50 gsm.

[0074] In addition to the binder fibers, the first layer 12 can also contain various other materials, including other fibers. In one aspect, for example, the first layer 12 can contain polymer synthetic fibers. Polymer synthetic fibers, for example, can be made of polymer materials and can be non-absorbent. As described above, in one aspect, the multi-layer substrate 110 can be produced using a foam forming process, in which the fibers and other materials are suspended in the foam and then deposited on a forming surface to form a multi-layer structure. Advantageously, the foam forming process can accommodate all different types of materials and fibers (including polymer synthetic fibers). For example, polymer synthetic fibers can have a flexural stiffness that is substantially unaffected by the presence of the forming fluid.

[0075] Examples of synthetic polymer fibers include polyolefins, polyesters (PET), polyamides, polylactic acid, or other fiber-forming polymers. Polyolefin fibers, such as polyethylene (PE) and polypropylene (PP), and polyethylene terephthalate fibers are particularly suitable for the present disclosure. In some embodiments, the non-absorbent fibers can be recycled fibers, compostable fibers, and / or marine degradable fibers. In this regard, due to their very low level of water absorption, water-resistant fibers do not experience a significant change in flexural stiffness when in contact with an aqueous fluid and are thus able to maintain an open composite structure when wetted. The fiber diameter of the fibers can contribute to increasing the flexural stiffness. For example, PET fibers have a higher flexural stiffness than polyolefin fibers both in the dry state and in the wet state. The higher the fiber denier, the higher the flexural stiffness exhibited by the fibers. Water-resistant fibers desirably have a water retention value (WRV) of less than about 1 and more desirably between about 0 and about 0.5. In certain aspects, it is desirable that the fiber or at least a portion thereof comprises non-absorbent fibers.

[0076] The synthetic fibers and / or water-resistant fibers can have a fiber length greater than about 0.2 mm, including, for example, having an average fiber length between about 0.5 mm and about 50 mm, or between about 0.75 mm and about 30 mm, or even between about 1 mm and about 25 mm. In one aspect, the synthetic polymer fibers can have an average fiber length of about 4 mm to about 10 mm, such as about 4 mm to about 8 mm.

[0077] Synthetic polymer fibers can have a fiber size of from about 0.3 denier to about 25 denier, including all 0.1 denier increments therebetween. For example, in one aspect, relatively fine fibers having a denier of less than about 2, such as less than about 1.5, such as less than about 1, such as less than about 0.8, and greater than about 0.3, such as greater than about 0.5 can be used. Alternatively, the size of the polymer synthetic fiber can be from about 2 denier to about 20 denier. In one aspect, the size of the fiber can be from about 4 denier to about 8 denier. In another aspect, the size of the fiber can be from about 8 denier to about 15 denier, such as from about 9 denier to about 13 denier.

[0078] In some embodiments, the synthetic and / or water-resistant fibers can have a crimped structure to enhance the volume generating ability of the fibrous substrate for foam formation. For example, compared to PET staple fibers having the same fiber diameter and fiber length, PET crimped staple fibers may be able to generate a higher thickness (or result in a lower sheet density).

[0079] For illustrative purposes, the first layer 12 can contain an amount of synthetic polymer fibers typically from about 1 wt% to about 80 wt%, including all 1 wt% increments therebetween. For example, the polymer synthetic fibers can be present in the first layer 12 in an amount greater than about 5 wt%, such as in an amount greater than about 10 wt%, such as in an amount greater than about 15 wt%, such as in an amount greater than about 20 wt%, such as in an amount greater than about 25 wt%, such as in an amount greater than about 30 wt%, such as in an amount greater than about 40 wt%, such as in an amount greater than about 50 wt%, such as in an amount greater than about 60 wt%. The polymer synthetic fibers can be present in the first layer 12 in an amount less than about 90 wt%, such as in an amount less than about 80 wt%, such as in an amount less than about 70 wt%, such as in an amount less than about 60 wt%, such as in an amount less than about 50 wt%, such as in an amount less than about 40 wt%, such as in an amount less than about 35 wt%, such as in an amount less than about 30 wt%, such as in an amount less than about 25 wt%, such as in an amount less than about 20 wt%, such as in an amount less than about 15 wt%.

[0080] In addition to or as an alternative to polymer synthetic fibers, the first layer 12 may also contain cellulose fibers. A variety of different types of cellulose fibers can be incorporated into the first layer 12. In some embodiments, the fibers used can be conventional papermaking fibers, such as wood pulp fibers formed by a variety of pulping processes, such as kraft pulp, sulfite pulp, bleached chemi-thermomechanical pulp (BCTMP), chemi-thermomechanical pulp (CTMP), pressure / pressure thermomechanical pulp (PTMP), thermomechanical pulp (TMP), thermomechanical chemical pulp (TMCP), etc. By way of example only, the fibers and methods for preparing wood pulp fibers are disclosed in US 4,793,898 to Laamanen et al., US 4,594,130 to Chang et al., US 3,585,104 to Kleinhart, US 5,595,628 to Gordon et al., US 5,522,967 to Shet, etc. In addition, the fibers can be any wood pulp with a high average fiber length, a low average fiber length, or a mixture thereof. Examples of suitable high average length pulp fibers include softwood fibers, such as but not limited to northern softwood, southern softwood, redwood, red cedar, hemlock, pine (e.g., southern pine), spruce (e.g., black spruce), and the like. Examples of suitable low average length pulp fibers include hardwood fibers, such as but not limited to eucalyptus, maple, birch, poplar, etc.

[0081] In addition, if desired, secondary fibers obtained from recycled materials, such as fiber pulp from, for example, newsprint, recycled cardboard, and office waste paper sources, can be used. In some embodiments, the refined fibers can reduce the total amount of original and / or high average fiber length wood fibers (such as softwood fibers).

[0082] Regardless of the source of the wood pulp fibers, the wood pulp fibers preferably have an average fiber length greater than about 0.2 mm and less than about 3 mm, such as between about 0.35 mm and about 2.5 mm, or between about 0.5 mm and about 2.5 mm or even between about 0.7 mm and about 2.0 mm.

[0083] In addition, other cellulose fibers that can be used in the present disclosure include non-wood fibers. As used herein, the term "non-wood fiber" generally refers to cellulose fibers derived from the stems of non-woody monocotyledonous or dicotyledonous plants. Non-limiting examples of dicotyledonous plants that can be used to produce non-wood fibers include kenaf, jute, flax, ramie, and hemp. Non-limiting examples of monocotyledonous plants that can be used to produce non-wood fibers include cereal straws (wheat, rye, barley, oats, etc.), stalks (corn, cotton, sorghum, heitzperro, etc.), rattans (bamboo, sisal, bagasse, etc.), and grasses (miscanthus, spanish grass, lemon, sabai, switchgrass, etc.). In some other cases, non-wood fibers can be derived from aquatic plants such as water hyacinth, microalgae such as spirulina, and macroalgae such as red algae or brown algae.

[0084] In addition, other cellulose fibers used to manufacture the substrates herein can include synthetic cellulose fiber types formed by spinning, including rayon in all its types, and other fibers derived from viscose fibers or chemically modified cellulose, such as, for example, those available under the trade names LYOCELL and TENCEL.

[0085] Crosslinked cellulose fibers (such as CMC 535) can also be used to form the materials 10, 110 described herein. Crosslinked cellulose fibers can provide increased volume and elasticity, as well as improved softness.

[0086] In some embodiments, the non-wood and synthetic cellulose fibers can have a fiber length greater than about 0.2 mm, including, for example, having an average fiber size between about 0.5 mm and about 50 mm, or between about 0.75 mm and about 30 mm, or even between about 1 mm and about 25 mm. Generally, when using fibers with a relatively large average length, it is usually advantageous to vary the amount and type of foaming surfactant. For example, in some embodiments, if fibers with a relatively large average length are used, it may be beneficial to utilize a relatively higher amount of foaming surfactant to help achieve a foam with a desired foam half-life.

[0087] For illustrative purposes only, the first layer 12 may contain cellulose fibers in an amount generally from about 1 wt% to about 80 wt%, including all 1 wt% increments therebetween. For example, the cellulose fibers may be present in the first layer 12 in an amount greater than about 5 wt%, such as in an amount greater than about 10 wt%, such as in an amount greater than about 15 wt%, such as in an amount greater than about 20 wt%, such as in an amount greater than about 25 wt%, such as in an amount greater than about 30 wt%, such as in an amount greater than about 40 wt%, such as in an amount greater than about 50 wt%, such as in an amount greater than about 50 wt%. The cellulose fibers may be present in the first layer 12 in an amount less than about 90 wt%, such as in an amount less than about 80 wt%, such as in an amount less than about 70 wt%, such as in an amount less than about 60 wt%, such as in an amount less than about 50 wt%, such as in an amount less than about 40 wt%, such as in an amount less than about 35 wt%, such as in an amount less than about 30 wt%, such as in an amount less than about 25 wt%, such as in an amount less than about 20 wt%, such as in an amount less than about 15 wt%. The cellulose fibers may be a single type of fiber or may be a mixture of different cellulose fibers. For example, the cellulose fibers incorporated in the first layer 12 may be regenerated cellulose fibers, pulp fibers (including crosslinked pulp fibers), or mixtures thereof. In yet another embodiment, the cellulose fibers may include cotton fibers alone or in combination with pulp fibers.

[0088] In one aspect, the first layer 12 may have a basis weight greater than about 35 gsm, such as greater than about 40 gsm, such as greater than about 45 gsm, such as greater than about 50 gsm, and less than about 100 gsm, such as less than about 90 gsm, such as less than about 80 gsm. In this embodiment, the first layer 12 may contain from about 20% to about 80% binder fibers, such as from about 20% to about 60% binder fibers. The binder fibers may be combined with polymer synthetic fibers. The polymer synthetic fibers may generally be present in an amount greater than about 40 wt%, such as in an amount greater than about 50 wt%, such as in an amount greater than about 60 wt%, and in an amount less than about 90 wt%, such as in an amount less than about 80 wt%, such as in an amount less than about 70 wt%, such as in an amount less than about 60 wt%. In one aspect, the first layer 12 is free of cellulose fibers.

[0089] In another aspect, the first layer 12 can have a basis weight of less than about 35 gsm, such as less than about 30 gsm, such as less than about 25 gsm, such as less than about 20 gsm, and greater than about 10 gsm, such as greater than about 15 gsm, such as greater than about 20 gsm. The first layer 12 can contain an amount of binder fibers from about 10 wt% to about 80 wt%, and can be combined with cellulose fibers (especially pulp fibers and / or crosslinked cellulose fibers). The pulp fibers can be present in an amount greater than about 20 wt%, such as in an amount greater than about 30 wt%, such as in an amount greater than about 40 wt%, such as in an amount greater than about 50 wt% and less than about 90 wt%, such as in an amount less than about 80 wt%, such as in an amount less than about 70 wt%, such as in an amount less than about 60 wt%. The first layer 12 can contain only binder fibers combined with cellulose fibers or can also contain polymer synthetic fibers. In this embodiment, the polymer synthetic fibers can be present in an amount greater than about 5 wt%, such as in an amount greater than about 10 wt%, such as in an amount greater than about 15 wt%, such as in an amount greater than about 20 wt%, and generally in an amount less than about 60 wt%, such as in an amount less than about 40 wt%, such as in an amount less than about 20 wt% in the first layer 12.

[0090] The absorbent layer 13 contained in the multi-layer substrate 110 is generally configured to absorb fluids, especially liquids, and contains absorbent materials. The absorbent materials can include absorbent particles that contain fibers and / or other absorbent components. In one aspect, the second layer 13 has a size and mass capable of absorbing a relatively large amount of liquid, so the substrate 110 is very suitable for incorporation into absorbent articles (such as diapers, children's pants, adult incontinence products, etc.). For example, the second layer 13 or the absorbent layer can have sufficient mass such that the multi-layer substrate 110 exhibits an area-normalized saturation capacity greater than about 0.25 g / cm 2 , such as greater than about 0.5 g / cm 2 , such as greater than about 0.8 g / cm 2 , such as greater than about 1.0 g / cm 2 of the area-normalized saturation capacity.

[0091] In one aspect, the second layer 13 is mainly made of superabsorbent material (SAM). SAM is typically provided in particulate form and in some aspects may include polymers of unsaturated carboxylic acids or their derivatives. However, in some forms, SAM can be constructed in fibrous form. These polymers are generally made water-insoluble but water-swellable by crosslinking the polymers with a difunctional or polyfunctional internal crosslinking agent. These internally crosslinked polymers are at least partially neutralized and typically contain pendant anionic carboxyl groups on the polymer backbone, which enable the polymers to absorb aqueous fluids such as body fluids. Typically, the SAM particles are post-treated to crosslink the pendant anionic carboxyl groups on the particle surface. SAM is manufactured by known polymerization techniques, desirably by polymerization in an aqueous solution by gel polymerization. The product of this polymerization process is an aqueous polymer gel, i.e., a SAM hydrogel that is reduced in size to small particles by mechanical force and then dried using drying procedures and equipment known in the art. After the drying process, the resulting SAM particles are ground to the desired particle size. Examples of superabsorbent materials include, but are not limited to, those described in US7396584 to Azad et al., US7935860 to Dodge et al., US2005 / 5245393 to Azad et al., US2014 / 09606 to Bergam et al., WO2008 / 027488 to Chang et al., etc.

[0092] In some embodiments involving SAM, the SAM can be treated with a water-soluble protective coating having a selected dissolution rate such that the component is substantially not exposed to the aqueous liquid carrier until a highly expanded foam has been formed and the drying operation to remove the coating has begun. Alternatively, to prevent or limit premature swelling during processing, the SAM can be introduced into the process at a low temperature.

[0093] The superabsorbent material can be included in the second layer 13 in an amount of about 20% to 100% by weight, including all 1% by weight increments therebetween. The second layer 13, for example, can contain an amount greater than about 30% by weight, such as greater than about 40% by weight, such as greater than about 50% by weight, such as greater than about 60% by weight, such as greater than about 70% by weight, such as greater than about 80% by weight, such as greater than about 90% by weight, such as greater than about 95% by weight of the superabsorbent material. In various embodiments, the superabsorbent material can be included in the second layer 13 in an amount less than about 95% by weight, such as less than about 90% by weight, such as less than about 80% by weight, such as less than about 70% by weight, such as less than about 60% by weight. The second layer 13 can have a basis weight greater than that of the first layer 12. In one aspect, the basis weight of the second layer 13 is greater than about 200 gsm, such as greater than about 250 gsm, such as greater than about 300 gsm, such as greater than about 350 gsm, such as greater than about 400 gsm, such as greater than about 450 gsm, such as greater than about 500 gsm. The basis weight of the second layer 13 can be less than about 1,000 gsm, such as less than about 800 gsm, such as less than about 600 gsm.

[0094] In one aspect, the second layer 13 contains little to no binder fibers so that the second layer 13 can absorb liquid and swell. For example, the second layer 13 can contain an amount less than about 20% by weight, such as less than about 5% by weight, such as less than about 4% by weight, such as less than about 3% by weight, such as less than about 2% by weight, such as less than about 1% by weight, such as less than about 0.5% by weight of binder fibers. In one embodiment, the second layer 13 contains no binder fibers or can contain only binder fibers that have migrated from the first layer 12 to the second layer 13 through the interface 15.

[0095] In addition to the superabsorbent material, the second layer 13 can also contain synthetic polymer fibers and / or cellulose fibers. When other fibers are present in the second layer 13, the binder fibers can be present in an amount less than about 5% by weight, such as less than about 3% by weight, such as less than about 1% by weight based on the total weight of the fibers contained in the layer.

[0096] In one aspect, the second layer 13 contains cellulose fibers. The cellulose fibers can be any of the cellulose fibers described above, including regenerated cellulose fibers, cotton fibers, other natural cellulose fibers, pulp fibers, or mixtures thereof. The pulp fibers can be, for example, softwood fibers, hardwood fibers, bast fibers, or mixtures thereof. The pulp fibers can include delignified cellulose fibers. In one aspect, pulp fibers are present in the second layer 13, and the pulp fibers include crosslinked cellulose fibers or crosslinked pulp fibers. When polymer synthetic fibers are present, the cellulose fibers can be present in an amount greater than about 5 wt%, such as greater than about 10 wt%, such as greater than about 15 wt%, such as greater than about 20 wt%, such as greater than about 25 wt%, such as greater than about 30 wt%, such as greater than about 35 wt%, such as greater than about 45 wt%, such as greater than about 50 wt%, such as greater than about 55 wt%, such as greater than about 60 wt% in the second layer 13. One or more different types of cellulose fibers can generally be present in an amount greater than 100 wt%, and in one aspect, in an amount less than about 80 wt%, such as less than about 70 wt%, such as less than about 60 wt%, such as less than about 50 wt%, such as less than about 40 wt% in the second layer 13.

[0097] The second layer 13 can also contain polymer synthetic fibers. The polymer synthetic fibers can be used alone or in combination with cellulose fibers. The polymer synthetic fibers incorporated into the second layer 13 can be any of the polymer synthetic fibers (including polyester fibers, polyolefin fibers, etc.) described above. Although the polymer synthetic fibers are optional, when the polymer synthetic fibers are present in the second layer 13, the polymer synthetic fibers can generally be present in an amount greater than about 3 wt%, such as greater than about 5 wt%, such as greater than about 10 wt%, such as greater than about 15 wt%, such as greater than about 20 wt%, such as greater than about 25 wt%, such as greater than about 30 wt%. The polymer synthetic fibers can generally be present in an amount less than about 60 wt%, such as less than about 50 wt%, such as less than about 40 wt%, such as less than about 30 wt%, such as less than about 20 wt%, such as less than about 15 wt%, such as less than about 10 wt%, such as less than about 5 wt% in the second layer 13.

[0098] In one aspect, the second layer 13 can contain about 25 wt% to about 35 wt% of PET fibers having a size of about 5 denier to about 7 denier, about 50 wt% to about 70 wt% of crosslinked cellulose pulp fibers, and about 5 wt% to about 15 wt% of binder fibers having a size of about 0.8 denier to about 3 denier.

[0099] Now refer to Figure 1A , which shows another embodiment of the multi-layer substrate 10 fabricated in accordance with the present disclosure. Similar reference numerals are used to indicate similar elements. Specifically, the multi-layer substrate 10 includes a first layer 12 and a second layer 13 adjacent to the first layer and may have a structure similar to the corresponding layers described in Figure 1B . An interface 15 is between the first layer 12 and the second layer 13. In this embodiment, the multi-layer substrate 10 further includes a third layer 17. As shown, the second layer 13 is positioned between the first layer 12 and the third layer 17. As Figure 1A shown, the substrate 10 further includes an interface 19 between the second layer 13 and the third layer 17. In one aspect, some of the materials contained in the second layer may be mixed with some of the materials contained in the third layer. The interface 19 can provide the beneficial effect of having a certain fiber distribution between the second layer 13 and the third layer 17, which can provide enhanced stability characteristics between the two layers.

[0100] The third layer 17 and the first layer 12 can serve as leak-proof layers for the second layer 13. Specifically, the first layer 12 and the third layer 17 can be configured to be relatively thin and have a low basis weight while providing sufficient strength for handling and converting, with a minimal increase in stiffness. In addition, the first layer 12 and the third layer 17 can prevent the superabsorbent material contained in the second layer 13 from migrating to the surface of the substrate. In this way, the first layer 12 and the third layer 17 can improve the feel and comfort of the multi-layer substrate 10 by reducing any gritty feeling that may occur when in contact with the superabsorbent material. The first layer 12 and the third layer 17 can also prevent the escape of superabsorbent particles, making the material easier to handle and process. In addition, the first layer 12 and the third layer 17 can be configured to allow the second layer 13 to absorb fluid and swell without significant restriction.

[0101] As Figure 1A shown, the third layer 17 generally may have a relatively low basis weight. For example, the third layer 17 can have a basis weight of less than about 40 gsm, such as less than about 30 gsm, such as less than about 25 gsm, such as less than about 20 gsm, such as less than about 15 gsm, such as even less than about 10 gsm. The basis weight of the third layer 17 can be greater than about 5 gsm, such as greater than about 10 gsm, such as greater than about 15 gsm.

[0102] The third layer 17 may contain binder fibers alone or in combination with cellulose fibers and / or polymer synthetic fibers. The binder fibers may be present, for example, in an amount of from about 20 wt% to about 100 wt%, including all 1 wt% increments therebetween, in the third layer 17. For example, binder fibers, such as bicomponent fibers, may be present in an amount greater than about 20 wt%, such as in an amount greater than about 30 wt%, such as in an amount greater than about 40 wt%, and in an amount less than about 80 wt%, such as in an amount less than about 70 wt%, such as in an amount less than about 60 wt%, such as in an amount less than about 50 wt%, such as in an amount less than about 40 wt% in the third layer 17. The binder fibers may have a size of less than about 6 denier, such as less than about 4 denier, such as less than about 3 denier, such as less than about 2 denier, such as less than about 1.5 denier, such as less than about 1 denier, and greater than about 0.3 denier.

[0103] In one aspect, the third layer 17 contains binder fibers in combination with cellulose fibers (especially pulp fibers). The pulp fibers may be softwood fibers, hardwood fibers, or a combination thereof. In one aspect, the pulp fibers are crosslinked pulp fibers. The cellulose fibers may be present in an amount greater than about 10 wt%, such as in an amount greater than about 20 wt%, such as in an amount greater than about 30 wt%, such as in an amount greater than about 40 wt%, such as in an amount greater than about 50 wt%, such as in an amount greater than about 60 wt%, such as in an amount greater than about 70 wt%, such as in an amount greater than about 80 wt% in the third layer 17. The cellulose fibers may be present in an amount less than about 90 wt%, such as in an amount less than about 80 wt%, such as in an amount less than about 70 wt%, such as in an amount less than about 60 wt%, such as in an amount less than about 50 wt% in the third layer 17. The cellulose fibers may improve the wicking properties of the layer and may result in a layer of very low basis weight while being able to accommodate the superabsorbent material within the second layer 13.

[0104] As an alternative to or in addition to cellulosic fibers, the third layer 17 may also contain synthetic polymer fibers. The synthetic polymer fibers may be any of the fibers described above, such as polyester fibers or polyolefin fibers. When synthetic polymer fibers are included within the third layer 17, the synthetic polymer fibers may be present in an amount greater than about 3 wt%, such as greater than about 5 wt%, such as greater than about 10 wt%, such as greater than about 20 wt%, such as greater than about 30 wt%, such as greater than about 40 wt%, such as greater than about 50 wt%, such as greater than about 60 wt%, and generally in an amount less than about 80 wt%, such as less than about 70 wt%, such as less than about 60 wt%, such as less than about 50 wt%, such as less than about 40 wt%, such as less than about 30 wt%, such as less than about 25 wt%.

[0105] In one aspect, the third layer 17 may be configured to be relatively liquid-impermeable, as opposed to the configuration of the first layer 12. The third layer 17, for example, may be configured not only to avoid the loss of superabsorbent material from the absorbent substrate 10, but also to prevent the migration of liquid through the third layer 17 of the multi-layered substrate 10 in the event that the second layer 13 has absorbed liquid.

[0106] In other embodiments, the third layer 17 may be configured to be liquid-permeable. For example, the third layer 17 may include three-dimensional synthetic fibers, such as crimped synthetic fibers, which may provide larger pore sizes to increase bulk and improve wicking.

[0107] In addition to the materials described above that form the different layers in the multi-layered substrate, the multi-layered substrate may also contain various other additives and components. For example, wet strength additives may be added during substrate formation to help improve the relative strength of the multi-layered substrate.

[0108] Such strength additives suitable for use in papermaking fibers and tissue manufacturing are known in the art. The temporary wet strength additives may be cationic, non-ionic or anionic. Examples of such temporary wet strength additives include PAREZ TMThe 631NC and PAREZ(R) 725 temporary wet strength resins are cationic acetalated polyacrylamides available from Cytec Industries of West Paterson, N.J. These and similar resins are described in U.S. Pat. Nos. 3,556,932 to Coscia et al. and 3,556,933 to Williams et al. Additional examples of temporary wet strength additives include dialdehyde starches and other aldehyde-containing polymers such as those described in U.S. Pat. Nos. 6,224,714 to Schroeder et al., 6,274,667 to Shannon et al., 6,287,418 to Schroeder et al., and 6,365,667 to Shannon et al., etc.

[0109] Permanent wet strength agents comprising cationic oligomeric or polymeric resins can also be used in the present disclosure. Polyamide-polyamine-epichlorohydrin type resins such as KYMENE 557H sold by Solenis are the most widely used permanent wet strength agents and are suitable for the present disclosure. Such materials have been described in the following U.S. Pat. Nos. 3,700,623 to Keim, 3,772,076 to Keim, 3,855,158 to Petrovich et al., 3,899,388 to Petrovich et al., 4,129,528 to Petrovich et al., 4,147,586 to Petrovich et al., 4,222,921 to Van Eenam, etc. Other cationic resins include polyvinylimine resins and aminoplast resins obtained by the reaction of formaldehyde with melamine or urea. In the manufacture of the composite cellulose products of the present disclosure, permanent and temporary wet strength resins can be used together. Additionally, dry strength resins can also optionally be applied to the composite cellulose web of the present disclosure. Such materials can include, but are not limited to, modified starches and other polysaccharides such as cationic, amphoteric, and anionic starches, and guar gum and locust bean gum, modified polyacrylamides, carboxymethyl cellulose, sugars, polyvinyl alcohol, chitosan, etc.

[0110] When using wet strength or dry strength additives, it is preferred to select additives that are compatible with the blowing agents used in the foaming process. For example, when the strength additive is a cationic resin, due to the incompatibility between cationic and anionic substances, cationic surfactants are preferably used as blowing agents, or vice versa. Nonionic surfactants are generally compatible with any cationic and anionic strength additives.

[0111] If such wet strength and dry strength additives are used, they can be present in an amount of from about 0.01% to about 5% by dry weight of the cellulosic fibers contained in the multi-layer substrate. In certain embodiments, the strength additive can be present in an amount between about 0.05% and about 2% by dry weight of the cellulosic fibers, or even between about 0.1% and about 1% by dry weight of the cellulosic fibers.

[0112] Additional other components can be added to the multi-layer substrate material. For materials formed using a foam forming process, other additional components should be examined to ensure that they do not significantly interfere with the formation of the foam, hydrogen bonding between the cellulosic fibers, or other desired properties of the material. As an example, additional additives can include, as needed, one or more pigments, opacifying agents, antimicrobial agents, pH regulators, skin beneficial agents, odor absorbers, fragrances, thermally expandable microspheres, foam particles (such as shredded foam particles), etc., to impart or improve one or more physical or aesthetic properties. In certain embodiments, the multi-layer substrate can contain skin beneficial agents such as antioxidants, astringents, conditioners, emollients, deodorants, topical analgesics, film formers, humectants, hydrotropes, pH regulators, surface modifiers, skin care agents, etc.

[0113] The multi-layer substrate as described herein can preferably be formed by a foam forming process. Figure 2 A schematic view of an exemplary apparatus 11 that can be used as part of a foam forming process to manufacture a multi-layer substrate 10 as a foam formed product is provided. Figure 2 The apparatus 11 can include a first tank 14 configured to hold a first fluid supply 16. In some embodiments, the first fluid supply 16 can be a foam. The first fluid supply 16 can include a fluid provided by a fluid supply 18. In some embodiments, the first fluid supply 16 can include a plurality of fibers provided by a fiber supply 20 and preferably includes at least some absorbent fibers. However, in other embodiments, the first fluid supply 16 can be completely free of a plurality of fibers. The first fluid supply 16 can also include a surfactant provided by a surfactant supply 22. In some embodiments, the first tank 14 can include a mixer 24, which will be discussed in more detail below. The mixer 24 can mix (e.g., agitate) the first fluid supply 16 to mix the fluid, fibers (if present), and surfactant with air or some other gas to produce a foam. The mixer 24 can also mix the foam with the fibers (if present) to produce a foam suspension of the fibers, where the foam holds and separates the fibers to facilitate the distribution of the fibers within the foam (e.g., as an artifact of the mixing process in the first tank 14). A uniform fiber distribution can facilitate the desired absorbent material 10, including, for example, the visual appearance of strength and quality.

[0114] Device 11 may also include a second tank 26 configured to hold a second fluid supply 28. In some embodiments, the second fluid supply 28 may be foam. The second fluid supply 28 may include a fluid provided by a fluid supply 30 and a surfactant provided by a surfactant supply 32. In some preferred embodiments, as Figure 2 depicted, the second fluid supply 28 is fiber-free. In other embodiments, in addition to or as an alternative to the fibers present in the first fluid supply 16, the second fluid supply 28 may include multiple fibers. In some embodiments, the second tank 26 may include a mixer 34. The mixer 34 may mix the second fluid supply 28 to mix the fluid and surfactant with air or some other gas to form foam.

[0115] In some embodiments, device 11 may also include a third tank 31 configured to hold a third fluid supply 33. In some embodiments, the third fluid supply 33 may be foam. The third fluid supply 33 may include a fluid provided by a fluid supply 35 and multiple fibers provided by a fiber supply 37, and preferably includes at least some synthetic fibers. The third fluid supply 33 may also include a surfactant provided by a surfactant supply 39. In some embodiments, the third tank 31 may include a mixer 41. The mixer 41 may mix the third fluid supply 33 to mix the fluid and surfactant with air or some other gas to form foam.

[0116] In some embodiments, device 11 may also include a fourth tank 66 configured to hold a fourth fluid supply 68. In some embodiments, the fourth fluid supply 68 may be foam. The fourth fluid supply 68 may include a fluid provided by a fluid supply 69 and multiple fibers provided by a fiber supply 70. The fourth fluid supply 68 may also include a surfactant provided by a surfactant supply 71. In some embodiments, the fourth tank 66 may include a mixer 72. The mixer 72 may mix the fourth fluid supply 68 to mix the fluid and surfactant with air or some other gas to form foam.

[0117] In tanks 14, 26, 31, 66, the first fluid supply 16, the second fluid supply 28, the third fluid supply 33, and the fourth fluid supply 68 can be actuated, respectively, to form foam. In some embodiments, the foaming fluid and other components are actuated to form a porous foam having an air content greater than about 50 volume % and desirably an air content greater than about 60 volume %. In certain aspects, a highly expanded foam is formed having an air content between about 60% and about 95%, and in additional aspects, between about 65% and about 85%. In certain embodiments, the foam can be actuated to introduce the foam such that the expansion ratio (the volume of air to other components in the expanded stable foam) is greater than 1:1, and in certain embodiments, the air:other components ratio can be between about 1.1:1 and about 20:1 or between about 1.2:1 and about 15:1 or between about 1.5:1 and about 10:1 or even between about 2:1 and about 5:1.

[0118] The foam can be generated by one or more means known in the art. Examples of suitable methods include, but are not limited to, vigorous mechanical agitation such as by mixers 24, 34, 41, 72, injection of compressed air, and the like. Mixing the components by using a high-shear high-speed mixer is particularly suitable for forming the desired highly porous foam. Various high-shear mixers are known in the art and are considered suitable for the present disclosure. High-shear mixers typically use a tank that holds the foam precursor and / or one or more pipes through which the foam precursor is directed. High-shear mixers can use a series of screens and / or rotors to process the precursor and result in vigorous mixing of the components and air. In a particular embodiment, the first tank 14, the second tank 26, the third tank 31, and / or the fourth tank 66 is provided with one or more rotors or impellers and an associated stator therein. The rotor or impeller rotates at a high speed so as to cause flow and shear. For example, air can be introduced into the tank at various locations or simply drawn in by the action of mixers 24, 34, 41, 72. Although the specific mixer design may affect the speed required to achieve the desired mixing and shear, in certain embodiments, a suitable rotor speed can be greater than about 500 rpm and, for example, between about 1000 rpm and about 6000 rpm or between about 2000 rpm and about 4000 rpm. In other embodiments, a suitable rotor speed can be less than 500 rpm.

[0119] In addition, it should be noted that for the first can 14, the second can 26, the third can 31, and / or the fourth can 66, the foaming process can be completed in a single foam generation step or in successive foam generation steps. For example, in one embodiment, all of the components of the first fluid supply 16 in the first can 14 (e.g., the supplies of fluid 18, fibers 20, and surfactant 22) can be mixed together to form a slurry, and the foam is formed from the slurry. Alternatively, one or more individual components can be added to the foaming fluid to form an initial mixture (e.g., a dispersion or foam), and then the remaining components can be added to the initially foamed slurry, and then all of the components act to form the final foam. In this regard, the fluid 18 and the surfactant 22 can begin to mix and act to form an initial foam before any solids are added. If desired, the fibers can subsequently be added to the water / surfactant foam, and then the fibers further act to form the final foam. As another alternative, the fluid 18 and the fibers 20 (such as high density cellulose pulp sheets) can be vigorously mixed at a higher consistency to form an initial dispersion, and then the foaming surfactant 22, additional water, and other components (such as synthetic fibers) are added to form a second mixture, and then the second mixture is mixed and acts to form the foam.

[0120] The foam density of the foam formed from the first fluid supply 16 in the first can 14, the second fluid supply 28 in the second can 26, the third fluid supply 33 in the third can 31, and / or the fourth fluid supply 68 in the fourth can 66 can vary depending on the particular application and various factors, such as the fiber stock used. In some embodiments, for example, the foam density of the foam can be greater than about 100 g / L, such as greater than about 250 g / L, such as greater than about 300 g / L. The foam density is generally less than about 800 g / L, such as less than about 500 g / L, such as less than about 400 g / L, such as less than about 350 g / L. In some embodiments, for example, a lower density foam having a foam density generally less than about 350 g / L, such as less than about 340 g / L, such as less than about 330 g / L is used.

[0121] The apparatus 11 may also include a first pump 36, a second pump 38, a third pump 43, and a fourth pump 73. The first pump 36 may be in fluid communication with a first fluid supply 16 and may be configured to pump the first fluid supply 16 to transfer the first fluid supply 16. The second pump 38 may be in fluid communication with a second fluid supply 28 and may be configured to pump the second fluid supply 28 to transfer the second fluid supply 28. The third pump 43 may be in fluid communication with a third fluid supply 33 and may be configured to pump the third fluid supply 33 to transfer the third fluid supply 33. The fourth pump 73 may be in fluid communication with a fourth fluid supply 68 and may be configured to pump the fourth fluid supply 68 to transfer the fourth fluid supply 68. In some embodiments, the first pump 36, the second pump 38, the third pump 43, and / or the fourth pump 73 may be a screw pump or a centrifugal pump; however, other suitable types of pumps may be contemplated for use.

[0122] As Figure 2 depicted therein, the apparatus 11 may also include a component feed system 40. The component feed system 40 may be used to convey a supply of a component 44 in cases where the multi-layer substrate 10 requires the component 44 by delivering the component 44 to one or more of the fluid supplies 16, 28, 33, 68 or directly to the headbox 80. An exemplary component feed system 40 that may be used may include a component supply area 42 for receiving a supply of the component. The component feed system 40 may also include an outlet conduit 46. The component feed system 40 may also include a hopper 48. The hopper 48 may be coupled to the component supply area 42 and may be used to refill the supply of the component 44 into the component supply area 42.

[0123] In some embodiments, the component feed system 40 may include a positive displacement pump. Some examples of positive displacement pumps that may be used herein may include systems that utilize screws / augers, belts, vibrating trays, turntables, or other known systems for handling and discharging a supply of the component 44. Other types of feeders may be used for the component feed system 40, such as batching feeders, such as those manufactured by Christy Machine & Conveyor, Fremont, Ohio. In some embodiments, the component feed system 40 may also be configured as a conveyor system.

[0124] In some embodiments, the component feed system 40 may also include a pressure control system 50. In some embodiments, the pressure control system 50 may include a housing 52. The housing 52 may form a pressurized sealed volume around the component feed system 40. In other embodiments, the pressure control system 50 may be formed as an integral part of the structural component feed system 40 itself, such that a separate housing 52 around the component feed system 40 may not be required. In some embodiments, the pressure control system 50 may also include a bleed orifice 54.

[0125] The supply of component 44 can be in the form of granules and / or fibers and / or powders. In one embodiment described herein, the supply of component 44 can be a superabsorbent material (SAM) in the form of granules. In some embodiments, the SAM can be in the form of fibers. Of course, as previously discussed, other types of components can also be contemplated for use in apparatus 11 and methods for forming absorbent material 10 as described herein. The component feed system 40 as described herein can be particularly beneficial for maintaining the supply of component 44 in a dry environment, with minimal exposure to the fluids or foams used in apparatus 11 and methods described herein.

[0126] Apparatus 11 can also include a first mixing junction 56 and a second mixing junction 58. In a preferred embodiment, the first mixing junction 56 can be an ejector (commonly also referred to as an ejector pump). The first mixing junction 56 can be in fluid communication with the outlet conduit 46 of the component feed system 40 and in fluid communication with the second fluid supply 28. The first mixing junction 56 can include a first inlet 60 and a second inlet 62. The first inlet 60 can be in fluid communication with the supply of component 44 via the outlet conduit 46. The second inlet 62 can be in fluid communication with the second fluid supply 28. The first mixing junction 56 can also include a discharge port 64. In a preferred embodiment, the first mixing junction 56 can be configured as a coaxial ejector, where the axis of the first inlet 60 is coaxial with the axis of the outlet conduit 46 that provides the supply of component 44. The first mixing junction 56 can also be configured such that the discharge axis of the discharge port 64 is coaxial with the outlet axis of the outlet conduit 46. Thus, the first mixing junction 56 can be configured such that the axis of the first inlet 60 can be coaxial with the axis of the discharge port 64 of the first mixing junction 56. The second inlet 62 that provides the second fluid supply 28 to the first mixing junction 56 can be arranged to enter the first mixing junction 56 on one side of the first mixing junction 56.

[0127] When configured as an ejector, the first mixing junction 56 can mix the supply of component 44 from the component feed system 40 with the second fluid supply 28. By transferring the second fluid supply 28 into the first mixing junction 56 at the second inlet 62 and through the first mixing junction 56, the second fluid supply 28 provides motive pressure to the supply of component 44. The motive pressure can create a vacuum on the supply of component 44 and on the component feed system 40 to assist in drawing the supply of component 44, such that it is mixed and entrained in the second fluid supply 28. In some embodiments, the motive pressure can create a vacuum of less than 1.5 inHg on the supply of component 44. However, in other embodiments, the motive pressure can create a vacuum of 5 inHg or greater, or 10 inHg or greater on the supply of component 44.

[0128] The pressure control system 50 can assist in managing the proper distribution and entrainment of the supply of component 44 into the second fluid supply 28. For example, when the second fluid supply 28 creates a dynamic pressure on the component feed system 40, a vacuum pull on the supply of component 44 may cause additional air to be entrained in the second fluid supply 28. In some cases, it may be desirable to entrain additional air in the second fluid supply 28. However, in other cases, it may be desirable to control the gas content of the second fluid supply 28 while introducing the supply of component 44 into the second fluid supply 28 at the first mixing joint 56. For example, in some cases where the second fluid supply 28 is a foam, the gas content in the foam may be desired to remain relatively constant as the foam passes through the first mixing joint 56. Thus, the pressure control system 50 can control the pressure on the component feed system 40 to help counteract the dynamic pressure on the supply of component 44 and the component feed system 40 created by the second fluid supply 28.

[0129] In some embodiments, the pressure control system 50 can include sealing the component feed system 40. For example, as discussed above, the pressure control system 50 can include a housing 52 to provide a seal on the component feed system 40. Sealing the component feed system 40 can help prevent additional air from being entrained in the second fluid supply 28 when the supply of component 44 is introduced into the second fluid supply 28 in the first mixing joint 56.

[0130] However, in some embodiments, it may be beneficial for the pressure control system 50 to also include additional capabilities. For example, in some embodiments, the pressure control system 50 can include a bleed hole 54. The bleed hole 54 can be configured to bleed pressure, such as atmospheric pressure, to provide additional pressure control of the component feed system 40. It has been found that by providing the bleed hole 54 to introduce some atmospheric pressure to the component feed system 40, back-splashing of the second fluid supply 28 in the first mixing joint 56 can be reduced or eliminated. Reducing back-splashing of the second fluid supply 28 in the first mixing joint 56 can help prevent the component feed system 40 from becoming clogged or requiring cleaning, especially in cases where the component feed system 40 may be transporting a dry component such as particulate SAM.

[0131] Additionally or alternatively, the pressure control system 50 can be configured to provide additional positive pressure to prevent backfill of the component feed system 40 in some situations, such as in the case of a downstream blockage in the device 11 outside the first mixing joint 56. In such a situation where the blockage creates an increased pressure, the second fluid supply 28 may desire to backfill the component feed system 40. Backfilling the fluid into the component feed system 40 can be detrimental to processing, especially in the case where the supply of component 44 is a component (such as SAM) that is preferably kept under dry conditions. The pressure control system 50 configured to be able to provide positive pressure to the component feed system 40 can help prevent such backfill of the component feed system 40.

[0132] It is also contemplated that other additional aspects of the pressure control system 50 can be used to maintain the pressure at a suitable level for the component feed system 40, including but not limited to, in addition to or as an alternative to venting air and / or the aforementioned positive pressure at the vent hole 54, supplying a vacuum to the component feed system 40.

[0133] The first mixing joint 56 can also provide pressure control for the transfer of the second fluid supply 28 including component 44 when it exits the discharge port 64 of the first mixing joint 56, compared to when the second fluid supply 28 enters the first mixing joint 56. The second fluid supply 28 can be transferred at a second fluid pressure before the first mixing joint 56. The second fluid supply 28 including components from the supply of component 44 can leave the discharge port 64 of the first mixing joint 56 at a discharge pressure. The pressure difference between the second fluid pressure before the first mixing joint 56 and the discharge pressure can be controlled. In some embodiments, this pressure difference can be controlled by changing the flow rate of the second fluid supply 28 or by the positioning of the outlet conduit 46 in the first mixing joint 56. In some embodiments, it is preferred to control the pressure difference between the second fluid pressure before the first mixing joint 56 and the discharge pressure to be less than or equal to 5 pounds per square inch.

[0134] It should be noted that although a single outlet conduit 46 and a single first mixing joint 56 of the component feed system 40 are shown in Figure 2 , it is contemplated that the outlet conduit 46 can be divided into two or more conduits to feed two or more first mixing joints 56 for mixing the supply of component 44 with the second fluid supply 28. In such a configuration, the second fluid supply 28 can include as many conduits as there are first mixing joints 56. By having more than one outlet conduit 46 and more than one first mixing joint 56 to mix the supply of component 44 with the second fluid supply 28, a greater flow rate of the second fluid supply 28 including components from the supply of component 44 can be achieved.

[0135] Reference Figure 2, in some embodiments, the apparatus 11 may include a second mixing joint 58. The second mixing joint 58 may provide the function of mixing a second fluid supply 28 of components including a supply from component 44 with the first fluid supply 16. When the second fluid supply 28 of components including a supply from component 44 exits the discharge port 64 of the first mixing joint 56, it may be transferred to the second mixing joint 58. The first fluid supply 16 may be delivered to the second mixing joint 58 by the first pump 36. The second mixing joint 58 may mix any component of the first fluid supply 16 and its components (e.g., fluid 18, fiber 20, surfactant 22) with any component of the second fluid supply 28 and its components (e.g., fluid 30, surfactant 32) and the components from the supply of component 44 to deliver a mixture of the first fluid supply 16, the second fluid supply 28, and component 44 to the headbox 80.

[0136] Alternatively, in some embodiments, the second mixing joint 58 may be omitted from the apparatus 11, and the second fluid supply 28 of components including a supply from component 44 may be delivered to the headbox 80.

[0137] As Figure 2 and Figure 3 shown, the headbox 80 may include one or more z-direction dividers 78a, 78b for separating different inputs of the headbox 80 when forming different layers of the absorbent material 10. The third fluid supply 33 and any component of its components (e.g., fluid 35, fiber 37, surfactant 39) may be delivered to the inlet 81 of the headbox 80 via the third pump 43 and may be delivered above the first z-direction divider 78a in the first z-direction layer 85a of the headbox 80. The output of the second mixing joint 58, which is a mixture of the first fluid supply 16 and any component of its components (e.g., fluid 18, fiber 20, surfactant 22), the second fluid supply 28 and any component of its components (e.g., fluid 30, surfactant 32), and component 44, may be delivered to the inlet 81 of the headbox 80 below the first z-direction divider 78a and above the second z-direction divider 78b in the second z-direction layer 85b of the headbox 80. The fourth fluid supply 68 and any component of its components (e.g., fluid 69, fiber 70, surfactant 71) may be delivered to the inlet 81 of the headbox 80 via the fourth pump 73 and may be delivered below the second z-direction divider 78b in the third z-direction layer 85c of the headbox 80. This configuration of the two z-direction dividers 78a, 78b is beneficial for forming a three-layer substrate 10, such as described above and Figure 1AAs shown. Of course, the two-layer substrate 110 described herein can be formed by a headbox 80 including a single z-direction separator 78a that provides a first z-direction layer 85a and a second z-direction layer 85b of the headbox 80. Additionally, in some embodiments, the headbox 80 need not include any z-direction separators 78a, 78b, which may be particularly beneficial if further mixing of fibers and / or components within the headbox 80 is desired.

[0138] The headbox 80 can provide the resulting slurry 76 to the forming surface 94. The forming surface 94 can be a porous sheet, such as a woven belt or a screen, or any other suitable surface for receiving the resulting slurry 76.

[0139] The apparatus 11 can also include a dewatering system 96 that can be configured to remove liquid from the resulting slurry 76 (e.g., the forming fluid) on the forming surface 94. In some embodiments, the dewatering system 96 can be configured to provide a vacuum to the resulting slurry 76 to draw out the liquid, and in doing so, can transform the resulting slurry 76 including multiple fibers 20 and components 44 (if present) into a multi-layer substrate 10. In some embodiments, the dewatering system 96 can begin dewatering the fibers and / or components while they are still within the headbox 80.

[0140] The dewatering system 96 that draws liquid from the resulting slurry 76 may also inadvertently draw components 44 (such as particulate SAM) through the forming surface 94 and / or cause components 44 to become trapped within the forming surface 94. This can not only result in the formed substrate 10 not including the expected amount of components 44, but also the trapping of components 44 within the forming surface 94 and / or their being drawn through the forming surface 94 can cause processing problems, including but not limited to reduced dewatering and / or increased drying requirements for the resulting slurry 76, machine downtime for cleaning, and increased complexity of the dewatering liquid due to the inclusion of such components 44. Compared to dry forming techniques (such as airlaid forming techniques or binder-based techniques), forming a multi-layer substrate 10 (such as foam forming) containing components 44 in a fluid may exacerbate the problem of movement of components 44 within the resulting slurry 76.

[0141] Forming the third layer 17 as part of the substrate 10 that directly abuts the forming surface 94 can help protect the components 44 of the substrate 12, such as the SAM in the absorbent layer 13. The third layer 17 can protect the components 44 of the substrate 10 from the effects of the forming surface to help ensure that the components 44 remain within the substrate 10, or at least reduce the likelihood that the components 44 become trapped in the forming surface 94 or are drawn through the forming surface 94. Additionally, the third layer 17 can help retain the components 44 within the absorbent material 10 because the components have the potential to be transported for further processing and / or for use in other products in which the multi-layer substrate 10 may be incorporated, such other products as personal care absorbent articles. Forming the third layer 17 in-line with the absorbent layer 13 as a laminated composite eliminates the need for additional processing (such as using an adhesive to attach a separate third layer 17 to the absorbent layer 13) to form the composite absorbent substrate 10, where at least some of the fibers of the third layer 17 are mixed with at least some of the fibers of the absorbent layer 13 at the interface 19. Eliminating the binder can result in reduced processing equipment and raw material costs and can also improve the fluid handling characteristics of the absorbent substrate 10. Additionally, forming the third layer 17 as part of the substrate 10 can also provide improved integrity and tensile strength to the absorbent material 10, thereby providing enhanced processing capabilities for the substrate 10.

[0142] Figure 2 The apparatus 11 and method described in Figure 4 depict an alternative embodiment of an apparatus 111 and method for forming a multi-layer substrate 10. Figure 4 The apparatus 111 of Figure 2 can be used as part of a foam forming process similar to that described above for Figure 3 ; however, the headbox 180 is a vertical twin former known in the art. The headbox 180 can include a first porous element 119 and a second porous element 121. The first porous element 119 and the second porous element 121 can help define the internal volume of the headbox 180. Similar to the discussion of the headbox 80 in Figure 4 above, the headbox 180 can include a first divider 178a and a second divider 178b that can provide a first z-direction layer 185a, a second z-direction layer 185b, and a third z-direction layer 185c within the headbox 180, but Figure 4 the layers 185a, 185b, 185c in

[0143] In some embodiments, the first fiber supply 20 can be supplied to the headbox 180, and in some embodiments, the first fiber supply 20 can be in the form of a foam. The supply of the fibers 20 can include at least some absorbent fibers. The supply of the component 44 can also be directly supplied to the headbox 180, and in some embodiments, the supply of the component 44 can be in the form of a foam. The supplies of the fibers 20 and the component 44 can be conveyed to the second z-direction layer 185b of the headbox 180. It should be noted that in some embodiments, the second z-direction layer 185b of the headbox 180 can be provided only with the supply of the component 44 and not the fiber supply 20. In some embodiments, a second fiber supply 123 can be provided to the headbox 180 and can be in the form of a foam in some embodiments. The second fiber supply 123 can be provided to the first z-direction layer 185a of the headbox 180. In some embodiments, a third fiber supply 125 can be provided to the headbox 180 and can be in the form of a foam in some embodiments. The third fiber supply 125 can be provided to the third z-direction layer 185c of the headbox 180. The fibers 20, the fiber 123, the fiber 125, and the component 44 can be processed in the headbox 180 along the longitudinal direction 185 toward the outlet 182 of the headbox 180 to provide the absorbent material 10, similar to Figure 2 the apparatus 11 described in

[0144] The apparatuses 11, 111 described herein can also include a drying system 98 to further dry and / or cure the absorbent materials 10, 110. The drying system 98 can apply heat to the absorbent material 10, such as by providing heated air in a through-air drying system.

[0145] In some embodiments, the apparatuses 11, 111 can include a winding system 99 (as shown in Figure 2 ), which can be configured to wind the absorbent materials 10, 110 in the form of a roll. In other embodiments, the apparatuses 11, 111 can suspend the absorbent materials 10, 110, or collect the absorbent materials 10, 110 in any other suitable configuration (such as winding).

[0146] As described above, the foam forming process as described herein may include a foaming fluid. In some embodiments, the foaming fluid may comprise from about 85% to about 99.99% (by weight) of the foam. In some embodiments, the foaming fluid used to make the foam may comprise at least about 85% of the foam (by weight). In certain embodiments, the foaming fluid may comprise from about 90% to about 99.9% (by weight) of the foam. In certain other embodiments, the foaming fluid may comprise from about 93% to 99.5%, or even from about 95% to about 99.0% (by weight) of the foam. In a preferred embodiment, the foaming fluid may be water; however, other processes may conceivably utilize other foaming fluids.

[0147] The foam forming process as described herein may utilize one or more surfactants. Fibers and surfactants, together with the foaming liquid and any additional components, may form a stable dispersion that is capable of substantially maintaining a high porosity for a longer period of time than a drying process. In this regard, surfactants are selected to provide a foam having a foam half-life of at least 2 minutes, more preferably at least 5 minutes, and most preferably at least 10 minutes. The foam half-life can be a function of the surfactant type, surfactant concentration, foam component / solid level, and mixing ability / air content in the foam. The foaming surfactants used in the foam can be selected from one or more foaming surfactants known in the art that are capable of providing the desired degree of foam stability. In this regard, the foaming surfactants can be selected from anionic, cationic, nonionic, and amphoteric surfactants, provided that they provide the necessary foam stability or foam half-life either alone or in combination with other components. It should be understood that more than one surfactant can be used, including different types of surfactants (as long as they are compatible) and more than one surfactant of the same type. For example, a combination of a cationic surfactant and a nonionic surfactant or a combination of an anionic surfactant and a nonionic surfactant can be used in some embodiments due to their compatibility. However, in some embodiments, a combination of a cationic surfactant and an anionic surfactant may not combine satisfactorily due to incompatibility between the surfactants.

[0148] Anionic surfactants that are considered suitable for the present disclosure include, but are not limited to, anionic sulfate surfactants, alkyl ether sulfonates, alkyl aryl sulfonates, or mixtures or combinations thereof. Examples of alkyl aryl sulfonates include, but are not limited to, alkyl benzene sulfonic acid and its salts, dialkyl benzene disulfonic acid and its salts, dialkyl benzene sulfonic acid and its salts, alkyl phenol sulfonic acid / condensed alkyl phenol sulfonic acid and its salts, or mixtures or combinations thereof. Examples of additional anionic surfactants that are considered suitable for the present disclosure include alkali metal sulforicinates; sulfonated glycerol esters of fatty acids such as sulfonated monoglyceride of coconut fatty acid; salts of sulfonated monohydric alcohol esters such as sodium oleylisethianate; metal soaps of fatty acids; amides of sulfamic acid such as sodium salt of oleylmethyl taurine; sulfonated products of fatty acid nitriles such as palm nitrile sulfonate; alkali metal alkyl sulfates such as sodium lauryl sulfate, ammonium lauryl sulfate, or triethanolamine lauryl sulfate; ether sulfates having an alkyl group of 8 or more carbon atoms such as sodium lauryl ether sulfate, ammonium lauryl ether sulfate, sodium alkyl aryl ether sulfate, and ammonium alkyl aryl ether sulfate; sulfuric acid esters of polyoxyethylene alkyl ethers; sodium, potassium, and amine salts of alkyl naphthalene sulfonic acid. Certain phosphate surfactants, including phosphate esters such as sodium lauryl phosphate ester or those available commercially under the trade name TRITON from Dow Chemical Company, are also considered suitable herein. A particularly desirable anionic surfactant is sodium dodecyl sulfate (SDS).

[0149] Cationic surfactants are also considered suitable for some embodiments used in conjunction with the present disclosure for manufacturing substrates. In some embodiments, such as those including superabsorbent materials, cationic surfactants may be less preferred due to potential interactions between the cationic surfactant and the superabsorbent material (which can be anionic). Foaming cationic surfactants include, but are not limited to, mono-carbon ammonium salts, di-carbon ammonium salts, tri-carbon ammonium salts, mono-carbon phosphonium salts, di-carbon phosphonium salts, tri-carbon phosphonium salts, carbonyl carboxyl salts, quaternary ammonium salts, imidazolines, ethoxylated amines, quaternary phospholipids, etc. Additional examples of cationic surfactants include various fatty acid amines and amides and their derivatives, as well as salts of fatty acid amines and amides. Examples of aliphatic fatty acid amines include dodecylamine acetate, octadecylamine acetate, and acetate of amines of tallow fatty acids; homologs of aromatic amines with fatty acids, such as dodecylanalin; fatty acid amides derived from aliphatic diamines, such as undecylimidazoline; fatty acid amides derived from aliphatic diamines, such as undecylimidazoline; fatty acid amides derived from disubstituted amines, such as oleylaminodiethylamine; derivatives of ethylenediamine; quaternary ammonium compounds and their salts, such as tallow trimethylammonium chloride, distearyldimethylammonium chloride, didodecyldimethylammonium chloride, dicetylammonium chloride, alkyltrimethylammonium hydroxide, distearyldimethylammonium hydroxide, tallow trimethylammonium hydroxide, trimethylammonium hydroxide, methylpolyoxyethylene coconut ammonium chloride, and dipalmitoyl hydroxyethyl methyl sulfate; amide derivatives of amino alcohols, such as β-hydroxyethyl stearamide; and amine salts of long-chain fatty acids. Additional examples of cationic surfactants considered suitable for the present disclosure include benzalkonium chloride, benzethonium chloride, cetrimonium bromide, distearyldimethylammonium chloride, tetramethylammonium hydroxide, etc.

[0150] Nonionic surfactants that are considered suitable for the present disclosure include, but are not limited to, condensates of ethylene oxide with long-chain fatty alcohols or fatty acids, condensates of ethylene oxide with amines or amides, condensation products of ethylene oxide and propylene oxide, fatty acid alkanolamides, and fatty amine oxides. Various additional examples of nonionic surfactants include stearyl alcohol, sorbitan monostearate, octyl glucoside, octaethylene glycol monododecyl ether, lauryl glucoside, cetyl alcohol, cocoamide MEA, glycerol monolaurate, polyoxyalkylene alkyl ethers such as polyethylene glycol long-chain (12-14C) alkyl ethers, polyoxyalkylene sorbitan ethers, polyoxyalkylene alkoxylated esters, polyoxyalkylene alkylphenol ethers, ethylene glycol propylene glycol copolymers, polyvinyl alcohol, alkyl polysaccharides, polyethylene glycol sorbitan monooleate, octylphenol ethylene oxide, etc. When using the SAM foam-forming absorbent materials 10, 110, nonionic surfactants may be preferred. If there are residual ionic surfactants, then for using the absorbent materials 10, 110 in personal care absorbent articles, an increase in the ionic strength of the dirt can reduce SAM swelling.

[0151] The foaming surfactant can be used in different amounts as needed to achieve the desired foam stability and air content in the foam. In certain embodiments, the foaming surfactant can be between about 0.005% and about 5% (by weight) of the foam. In certain embodiments, the foaming surfactant can be between about 0.05% and 3%, or even between about 0.05% and about 2% (by weight) of the foam.

[0152] As pointed out above, the apparatuses 11, 111 and methods described herein can include providing fibers from the fiber supplies 20, 37, 70, 123, 125. In some embodiments, the fibers can be suspended in a fluid supply 16, 28, 33, 68 that can be in the form of a foam. The foam suspension of the fibers can provide one or more fiber supplies. As described above, the fibers used herein can include natural fibers and / or synthetic fibers. In some embodiments, the fiber supplies 20, 37, 70, 123, 125 can include only natural fibers or only synthetic fibers. In other embodiments, the fiber supplies 20, 37, 70, 123, 125 can include a mixture of natural fibers and synthetic fibers. Some of the fibers used herein can be absorbent, while other fibers used herein can be non-absorbent. The non-absorbent fibers can provide characteristics to the substrate formed by the methods and apparatuses described herein, such as improving the inhalation or distribution of fluids.

[0153] In some embodiments, the fluid supplies 16, 28, 33, 68 can contain a binder material (as described above), which can be provided together with or independently of the supply of the fibers 20, 37, 70, 123, 125 or the supply of the component 44.

[0154] The binder can alternatively or additionally be provided in liquid form, such as a latex emulsion, and can be present in the foam in an amount of from about 0% to about 10% by weight. In certain embodiments, the non-fibrous binder can be present in the foam in an amount of from about 0.1% to 10% by weight, or even from about 0.2% to about 5% by weight, or even in an amount of from about 0.5% to about 2% by weight of the foam.

[0155] The binder fibers can be proportionally added to the other components during use to achieve the desired fiber ratio and structure while maintaining the total solids content of the foam below the above amount. For example, in some embodiments, the binder fibers can be present in an amount of from about 0% to about 50% of the total fiber weight, and more preferably in some embodiments in an amount of from about 5% to about 40% of the total fiber weight.

[0156] In some embodiments, if the fluid supplies 16, 28, 33, 68 are configured as foams, the foam can optionally further comprise one or more foam stabilizers known in the art, and the one or more foam stabilizers are compatible with the components of the foam and, moreover, do not interfere with the hydrogen bonding between the cellulose fibers. Foam stabilizers considered suitable for the present disclosure include, but are not limited to, one or more zwitterionic compounds, amine oxides, alkylated polyalkylene oxides, or mixtures or combinations thereof. Specific examples of foam stabilizers include, but are not limited to, coconut amine oxide, isononyl dimethyl amine oxide, n-dodecyl dimethyl amine oxide, and the like.

[0157] In some embodiments, if utilized, the foam stabilizer can be present in the foam in an amount of from about 0.01% to about 2% by weight. In certain embodiments, the foam stabilizer can be present in the foam in an amount of from about 0.05% to 1% by weight, or even in an amount of from about 0.1% to about 0.5% by weight of the foam.

[0158] As mentioned above, the foam forming process can include adding one or more components 44 as additional additives (such as SAM) to be incorporated into the absorbent materials 10, 110. In some embodiments incorporating SAM, SAM can be present in the foam in an amount of from about 0% to about 40% by weight. In certain embodiments, SAM can be present in the foam in an amount of from about 1% to about 30% by weight, or even in an amount of from about 10% to about 30% by weight of the foam.

[0159] If used, the wet strength and dry strength additives can be present in an amount of from about 0.01% to about 5% of the dry weight of the cellulose fibers. In certain embodiments, the strength additives can be present in an amount of from about 0.05% to about 2% of the dry weight of the cellulose fibers, or even in an amount of from about 0.1% to about 1% of the dry weight of the cellulose fibers.

[0160] When in use, the miscellaneous components (such as those described above, such as pigments, antimicrobial agents, etc.) that can also be used in the absorbent material can desirably account for less than about 2% (by weight) of the foam, and more desirably less than about 1% (by weight) of the foam, and even less than about 0.5% (by weight) of the foam.

[0161] In some embodiments, the solids content, including the fibers or particles contained herein, desirably does not exceed about 40% of the foam. In certain embodiments, the cellulose fibers can account for between about 0.1% and about 5% of the foam, or between about 0.2% and about 4% of the foam, or even between about 0.5% and about 2% of the foam.

[0162] The methods and apparatuses 11, 111 described herein facilitate the formation of one or more absorbent materials 10, 110. The absorbent materials 10, 110 described herein can be used as components of personal care products. For example, in one embodiment, the absorbent materials 10, 110 described herein can be absorbent composite materials for personal care absorbent articles. The multilayer absorbent materials 10, 110 described herein can also be beneficial for use in other products such as, but not limited to, facial tissues, toilet papers, wipes, and swabs.

[0163] The multilayer substrates manufactured in accordance with the present disclosure can be incorporated into all different types of absorbent articles. The absorbent articles can be, for example, diapers, child training pants, or other child absorbent pants. The absorbent articles can also be adult incontinence products. The absorbent articles can include a fluid-permeable liner and an outer cover layer. The multilayer substrate of the present disclosure can form an absorbent core positioned between the fluid-permeable liner and the outer cover layer. In one embodiment, a surge layer can be placed between the absorbent core and the fluid-permeable liner for guiding and channeling fluids to the absorbent core in a fast and efficient manner.

[0164] The present disclosure can be better understood by reference to the following examples.

[0165] Test Procedures

[0166] Tensile properties:

[0167] The strip tensile strength value is basically determined according to ASTM standard D-5034. Specifically, cut samples or otherwise provide samples with dimensions of 3 inches (76.2 mm) (width) × 6 inches (152.4 mm) (length). A constant rate of extension type tensile tester is used. The tensile test system is the Sintech tensile tester available from MTS Corp., Eden Prairie, Minn. The tensile tester is equipped with TESTWORKS 4.08B software from MTS Corporation to support the test. Select an appropriate load cell so that the test value falls within the range of 10% to 90% of the full scale load. Fix the sample between clamps with a front and a back and with dimensions of 1 inch (25.4 mm) × 3 inches (76 mm). Treat the clamp faces with rubber, and the longer dimension of the clamp is perpendicular to the pulling direction. The tensile test runs at a rate of 300 mm per minute, with a gauge length of 3 inches and a fracture sensitivity of 40%. Test three samples along the longitudinal direction (“MD”) and three samples along the transverse direction (“CD”). The ultimate tensile strength (“peak load”) is recorded in grams force. The results can be normalized by dividing by the three-inch width. Test samples can be tested with widths from 1 inch to 5 inches and normalized.

[0168] Absorbency Under Load (AUL) Test:

[0169] Sample Preparation: Use a 15 / 16” circular die to cut absorbent composite samples and classify the samples by weight to obtain N = 5 samples closest to the target basis weight of interest. If the absorbent material distribution in the absorbent composite sample is uneven, mark the surface with the highest percentage of superabsorbent material closest to the surface.

[0170] Figure 5 and Figure 6 Shows the equipment used during the test, including an AUL cylinder (acrylic) with a 15 / 16” ID and a plastic platen weight.

[0171] AUL Test Procedure: Place a 15 / 16” diameter absorbent composite sample in the AUL cylinder. Gently tap / push down the side edges of the absorbent composite sample using a laboratory spatula to make it fit tightly against the bottom of the AUL cylinder. If the SAM distribution in the absorbent composite sample is uneven, place the sample surface with the highest SAM percentage facing the bottom of the AUL cylinder.

[0172] Gently place the plastic platen (0.01 PSI) weight (acrylic) into the AUL cylinder (see Figure 6 ).

[0173] Weigh the AUL cylinder + sample + platen unit and record this weight, accurate to the milligram, as the dry weight of the AUL cylinder + sample + platen unit.

[0174] Pour a small amount of test fluid (0.9% NaCl saline) into a fluid bath with a screen at the bottom, as Figure 5 shown. The screen can be a stainless steel or plastic mesh screen with an open area. Pour in enough fluid so that the liquid level is just above the screen.

[0175] Start the timer while placing the AUL cylinder + sample + platen unit on the screen in the fluid bath. Add more test fluid if necessary. The fluid level in the bath should be at a height to provide at least a 1 cm positive head above the base of the cylinder;

[0176] Note: Five samples must be tested at each predetermined time interval. The required time intervals are 30 seconds and 60 minutes.

[0177] Remove the cylinder from the fluid bath at the specified time and wipe the outside of the cylinder with a paper towel or tissue paper.

[0178] Weigh the AUL cylinder + sample + platen unit and record this weight, accurate to the milligram, as the wet weight of the AUL cylinder + sample + platen unit.

[0179] Repeat this for all test samples of interest.

[0180] Subtract the average dry weight of the AUL cylinder + sample + platen unit from the average wet weight of the AUL cylinder + sample + platen unit to obtain Average Total AUL .

[0181] Carrier test method:

[0182] The carrier test replicates the true positioning of the garment on the wearer and can be used to determine the inhalation rate, backflow, and fluid distribution of the garment. This method uses a slotted carrier, as Figure 4 shown in b and U.S. Patent 6,727,404. The slotted carriers are all made of a waterproof material (such as acrylic plastic) and simulate the body curvature of the wearer. Two different sizes of carriers are used - one for adult care garments and the other for baby diapers.

[0183] The adult carrier has a total length of 425 mm, a left - right width of 425 mm, and a height of 290 mm (including approximately 50 mm of height below the slot). The thickness of the material used in the construction varies from 6 mm to 12 mm. The lowest point of the carrier has a 6 - mm - wide slot that extends along the length of the carrier. The curvature of the carrier is formed by a 75 - degree angle.

[0184] The baby carrier has a total length of 305 mm, a left - right width along the slot direction of 350 mm, and a height of 255 mm (including 57 mm height below the slot). The thickness of the material used for construction varies from 6 mm to 12 mm. The lowest point of the carrier has a slot 6 mm wide, which extends along the length of the carrier. The curvature of the carrier is formed by a 60 - degree angle.

[0185] 1. Product Preparation

[0186] A. For adult care garments, cut the three - dimensional pant - type product at the side or side seam to make the product two - dimensional.

[0187] B. Do not cut the elastic bands of the legs and leak guards.

[0188] C. Weigh the product to the nearest 0.01 gram value and record the value. D. Measure the pad length (using a light board) to the nearest 1 mm value and record the value.

[0189] E. Measure the product length and mark the center.

[0190] F. Mark the soiled area 95 mm forward from the center of the product to the nearest 1 mm value. Place the ruler at the horizontal center.

[0191] 2. Product Testing (Test Fluid = 0.9 w / v% saline solution)

[0192] A. Confirm that the pump delivers the required amount of test fluid for the soiling + / -

[0193] 0.5 ml. The flow rate should be set at 8 ml / sec. The test fluid amount for adult care products is 50 ml, and for baby diaper products is 85 ml. The hose end or nozzle should have an outlet diameter of 0.125 inches.

[0194] B. For the slot carrier, place a collection container of known weight under the carrier slot to collect the spilled fluid. Weigh the collection container to the nearest 0.01 gram. Note: Low - volume products without flaps (i.e., cloth underwear, cloth training pants, vinyl / cloth training pants) are prone to spillage.

[0195] D. Position the sample, liner / inside up, so that the "pre - marked" center of the product aligns with and touches the lowest point in the carrier. The entire length of the outer cover / exterior of the product should be in contact with the carrier. Clip or attach the product to the carrier at the front and back waist edges to hold the product in place. Gently pull the front / back waist of the sample to smooth out any wrinkles or creases in the product. For carrier testing, all product codes will be soiled 95 mm forward from the center of the product.

[0196] E. Hold the nozzle above the target area and perpendicular to the sample. The bottom of the nozzle should be within 5 mm to 10 mm from the sample.

[0197] F. When the test fluid leaves the nozzle, start the soiling and start the stopwatch. Once the soiling is complete, move the nozzle to the side to observe the test fluid.

[0198] G. Immediately stop the stopwatch when the test fluid is no longer visible on the sample surface. Record the inhalation time to the nearest 0.01 second. If the fluid spills into the collection container, record the inhalation time when the fluid is no longer visible on the surface.

[0199] H. Once the soiling is absorbed, immediately set the timer for 15 minutes. Keep the specimen in the holder for the entire waiting period.

[0200] I. Repeat steps F, G, and H twice for a total of 3 soiling operations, with a 15-minute interval between each.

[0201] Fluid Inhalation Under Pressure (FIUP) Test Method:

[0202] The first, second, third, and fourth inhalation times of the experimental code are measured according to the following protocol and using the exemplary equipment for Fluid Inhalation Under Pressure (FIUP) testing shown in Figure 7 The specimen 200 is prepared to the following dimensions: 295 mm long and 70 mm wide, and placed between a topsheet with winglets and a backsheet from a commercially available ultra-thin 5-drop pad. The topsheet can be a 20 gsm polypropylene spunbond nonwoven liner material treated with a hydrophilic treatment, such as the XHBY21520 / YSQS215 material provided by LanxiXinghan Plastic Material Co. (Hengyao). The backsheet can be a 24 gsm polyethylene film. For specimens without an inhalation layer, a fresh piece of 185 mm by 49 mm inhalation layer material of 42 gsm polyethylene / polypropylene bicomponent TABCW (Jing Lan) is placed on the core as the inhalation layer, and 6 gsm of adhesive is applied (from the adhesive swirl on the release paper) to the top and bottom of the inhalation layer. The sides of the sample 200 are sealed using double-sided tape. The specimen 200 is conditioned under TAPPI conditions for at least 4 hours.

[0203] The FIUP test uses as shown in Figure 7 and Figure 8The "airbag box" 210 shown in Figure 7 and Figure 8 The three latches 205 depicted in. When the lid 201 is open, the test specimen 200 can be placed on top of the thin plastic film 206, which is placed on top of the airbag 203. The test specimen should be placed on the film 206 and the airbag 203 such that the specimen 200 is centered below the suction port 207. The airbag 203 can be an inflatable airbag, such as an Aero Tec Labs airbag, which can fit inside the housing 202 and can be filled with compressed air.

[0204] The suction port 207 can include a threaded funnel 208 that screws into a threaded plug 209 having a 1" diameter opening at the bottom of the threaded plug 209 and provides communication with the test specimen 200. The suction port 207 can also include an O-ring 211 that seals the threaded plug 209 to the lid 201. The suction port 207 can also include a circular flat gasket (not shown) to seal between the threaded funnel 208 and the threaded plug 209. The bottom of the suction port 207 should be flush with the underside of the lid 201.

[0205] The control unit 204 can be a process controller, such as a 1 / 16 DIN Fuzzy Logic; example: Omega, part number CN48001-F1-AL2:G1 or equivalent, and can be configured to communicate with a pressure transmitter that measures the pressure of the airbag 203. An exemplary pressure transmitter can be Omega Engineering, part number PX181-015GSV. The control unit 204 can also communicate with a fluid dispensing pump (e.g., a Cole-Parmer peristaltic pump, P / N 07551-20) and a pump head (P / N 77201-60) that is set to deliver fluid to the test sample at a specified flow rate of 8 mL / s via a transparent pump tube 214 (e.g., Masterflex transparent tubing L / S14, L / S25, or L / S17). The end fittings on the tube can have an outlet diameter of 0.125", such as a Cole-Parmer reducer connector, nylon, 1 / 4" x 3 / 16", model 30622-30.

[0206] After the test specimen 200 is placed in the airbag box housing 202 by centering it below the suction port 207. AsFigure 7 As shown, the bottom of the lid 201 may include two hook-and-loop straps 213 (e.g., model 1055 of the Dariss brand) for helping to secure the test specimen 200. After the sample is centered, the lid 201 is closed and the latch 205 is locked. The hook-and-loop straps 213 should be applied to the lid 201 such that the hook-and-loop straps 213 only touch the non-absorbent material of the test specimen 200. The power for the control unit 204 is turned on to set the pressure of the airbag 203 to 0.25 psi. Once the control unit 204 recognizes that the airbag 203 has reached a stable pressure of 0.25 psi, the pressure gauge 212 can be checked to verify that the pressure in the airbag 203 is within 0.25 + / - 0.01 psi. If the pressure is not within 0.01 psi to 0.25 psi, the test should be stopped and the set pressure should be adjusted to compensate until the pressure gauge 212 reads within 0.01 psi to 25 psi.

[0207] The soiled liquid for the FIUP test is 0.9 ± 0.005% (w / w) aqueous isotonic saline 215, which is placed in a heating water bath 216 at a temperature of 98.6 ± 1.8°F / 37 ± 1°C before the test. Before contaminating the test specimen 200, the temperature of the saline solution 215 should be confirmed using a thermometer. The first soiling is 25 mL of soiling, and it is supplied by tilting the bottom inclined side of the fluid aiming funnel 208 through the suction port 207. Once the pump is turned on to deliver the fluid to the suction port 207, the first suction time of the first soiling begins and continues until all the fluid drops have been absorbed within the top layer of the test specimen 200. The second 25 mL of soiling is applied 15 minutes after the first soiling has been completely absorbed, and the second suction time is measured in the same manner as the first soiling time. The third 25 mL of soiling is applied 15 minutes after the second soiling has been completely absorbed, and the third suction time is measured in the same manner as described above. The fourth 25 mL of soiling is applied 15 minutes after the third soiling has been completely absorbed, and the fourth suction time is measured in the same manner as described above.

[0208] After recording the fourth suction time, a timer should be started to allow two minutes to pass. The control unit 204 is then calibrated to stop the test by releasing the pressure of the airbag 203 in the airbag box 210. If any fluid spills out of the test specimen 200 at any point during the contamination test and reaches the plastic sheet 206 covering the airbag 203, the test should be marked as "FAIL" and not be recorded.

[0209] The test is conducted using a sample set with N = 5.

[0210] Rewetting test method:

[0211] The rewettability of the experimental code was measured by using the same sample from the FIUP test discussed above. The rewettability test is a continuation test after the FIUP test. Specifically, 2 minutes after the completion of the fourth contamination in the FIUP test, the sample was removed from the airbag box 210 and placed on a flat surface with the contaminated side facing up. The test was completed using two stacked blotting papers (e.g., 300 g / m2 (100 lb / ream)) - Verigood Grade 88 by 300 ± 13 mm (3.5 by 12 ± 0.5 inches) to absorb free brine from the contaminated points of the specimen 200 under an external load after the FIUP test. The two blotting papers were pre-weighed and each blotting paper was sized 3.5” × 12”. The center of the contaminated point of the specimen was covered by the following operation: the FIUP test plate was removed and a 249 g cylindrical weight with a diameter of 1 inch was added at the contaminated point on top of the blotting paper to form a pressure of 0.7 psi for a period of two minutes. Subsequently, the mass of the blotting paper that measured the wetting amount was measured, and the rewettability amount was calculated as follows: Rewettability amount = Total wet mass – Dry mass. The higher the wet weight measured from the test, the higher the rewettability amount value of the specimen.

[0212] Thickness measurement method:

[0213] Both the dry thickness measurement and the wet thickness measurement of the experimental code were measured as part of the FIUP test discussed above. The thickness measurement utilized a standard volume tester with a transparent acrylic resin base that could provide 0.05 psi. When the sample was dry, the dry thickness measured the dry volume at the center point and measured the thickness of the sample in the form of a complete product when placed in an ultra-thin chassis that included winglets, an outer cover, and a liner (only the outer cover and the liner formed part of the thickness measurement because the winglets were outside the platen area). After the rewettability amount test was completed, the wet thickness was measured by measuring the volume at the center point.

[0214] Example 1

[0215] In the following examples, various different multi-layer substrates were produced and the strength and fluid control characteristics of these multi-layer substrates were tested. All the following samples were produced using a foam forming process. The following multi-layer substrates were produced:

[0216]

[0217]

[0218] The superabsorbent material (SAM) is commercially obtained SXM 5660 manufactured by Evonik, but sample numbers 4, 13, and 14 contain the product code LK601N obtained from LG, and sample number 1 contains the product code 9807X obtained from BASF. The PET fibers used have a length of 6 mm, are crimped, and have a size of 6.7 dTex. The binder fibers used are a polyethylene / PET sheath / core structure manufactured by Trevira, which has a fiber diameter of 2.2 dTex and a fiber length of 6 mm. The crosslinked pulp fibers used are commercially available from International Paper.

[0219] In this example, tensile strength tests were performed on sample numbers 1 - 14 and tested according to the AUL absorbency test. The following results were obtained:

[0220]

[0221] As shown above, the multilayer substrate manufactured according to the present disclosure does not contain a large amount of binder fibers in the second layer, and this multilayer substrate shows higher 30 - second AUL test results and excellent strength characteristics.

[0222] Example 2

[0223] Then, dry volume and wet volume tests were performed on the various substrates determined above in Example 1 and tested according to the cradle test. In some experiments, the surge layer was placed on the top layer of the multilayer substrate. In the first set of experiments, the material was tested in an adult care clothing product with a soiled volume of 50 mL and an absorption size of 75 mm × 320 mm. In the second set of experiments, the material was tested in a baby diaper product with a soiled volume of 85 mL and an absorption size of 100 mm × 354 mm.

[0224] The following results were obtained:

[0225]

[0226]

[0227] As shown above, sample numbers 5 and 10 show excellent absorbency characteristics.

[0228] Example 3

[0229] Various different multilayer substrates were produced using a foam forming process, and the strength and fluid control characteristics of these multilayer substrates were tested. The following multilayer substrates were produced:

[0230]

[0231]

[0232]

[0233] SBSK - Southern Bleached Softwood Kraft Fibre

[0234] Then, the above - mentioned multi - layer substrates were tested for average tensile peak load (average of five samples) and absorbency under load (average of three samples). The following results were obtained:

[0235]

[0236] As shown above, all multi - layer absorbent substrates exhibited excellent tensile strength characteristics and fluid handling characteristics.

[0237] Except for sample number 15, all of the above substrates were also tested for fluid intake under pressure (FIUP) (38 ml / soiling, 4 soiling events in total, 152 ml of saline in total) and re - wetting. The following results were obtained.

[0238]

[0239]

[0240] All substrates exhibited excellent fluid control characteristics. As shown, substrates manufactured according to the present disclosure can exhibit FIUP intake of less than about 20 seconds, such as less than about 18 seconds, for the first intake, can exhibit FIUP intake of less than about 60 seconds, such as less than about 50 seconds, such as less than about 40 seconds, such as less than about 30 seconds, for the second intake, can exhibit FIUP intake of less than about 95 seconds, such as less than about 85 seconds, such as less than about 70 seconds, such as less than about 55 seconds, for the third intake, can exhibit FIUP intake of less than about 140 seconds, such as less than about 120 seconds, such as less than about 100 seconds, such as less than about 85 seconds, for the fourth intake, and can exhibit re - wetting of less than about 0.8 grams, such as less than about 0.7 grams, such as less than about 0.6 grams, such as less than about 0.5 grams, such as less than about 0.4 grams. Sample number 14, for example, exhibited FIUP intake of 15 seconds for the first intake, 28 seconds for the second intake, 46 seconds for the third intake, 61 seconds for the fourth intake, and re - wetting of about 0.4 grams. Additionally, it was observed that the samples exhibited improved flexibility.

[0241] These and other modifications and variations of the present invention may be practiced by those of ordinary skill in the art without departing from the spirit and scope of the invention more particularly described in the appended claims. In addition, it should be understood that aspects of various embodiments may be interchanged, in whole or in part. Further, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only and is not intended to limit the invention as further described in such appended claims.

Claims

1. A multi-layer substrate, the multi-layer substrate comprising: A first layer, the first layer containing a binder; A second layer, the second layer comprising a superabsorbent material; And Wherein the multi-layer substrate has a tensile strength greater than about 333 grams-force per inch in at least one direction and exhibits a 30-second AUL test result greater than about 10 g / g.

2. The multi-layer substrate according to claim 1, wherein the binder comprises binder fibers.

3. The multi-layer substrate according to claim 1 or claim 2, wherein the multi-layer substrate has an area-normalized saturation capacity greater than about 0.25 g / cm 2 , such as greater than about 0.5 g / cm 2 , such as greater than about 0.8 g / cm 2 , such as greater than about 1.0 g / cm 2 , such as greater than about 1.2 g / cm 2 , such as greater than about 1.5 g / cm 2 , and less than about 5 g / cm 2 .

4. The multi-layer substrate according to claim 2, wherein the second layer comprises less than about 20 wt% binder fibers, such as less than about 10 wt% binder fibers, such as less than about 4 wt% binder fibers, such as less than about 3 wt% binder fibers, such as less than about 2 wt% binder fibers, such as less than about 1 wt% binder fibers.

5. The multi-layer substrate according to claim 2, wherein the second layer comprises less than 5 wt% binder fibers based on the total weight of all fibers contained in the second layer.

6. The multi-layer substrate according to any one of the preceding claims, wherein the multi-layer substrate has a tensile strength greater than about 700 grams-force per inch in at least one direction, such as greater than about 1,000 grams-force per inch, such as greater than about 1,200 grams-force per inch, such as greater than about 1,400 grams-force per inch, such as greater than about 1,500 grams-force per inch, such as greater than about 2,000 grams-force per inch, such as greater than about 2,500 grams-force per inch, such as greater than about 3,000 grams-force per inch, and less than about 10,000 grams-force per inch.

7. The multi-layer substrate according to any one of the preceding claims, wherein the multi-layer substrate exhibits a 30-second AUL test result greater than about 12 g / g, such as greater than about 13 g / g, such as greater than about 14 g / g, such as greater than about 15 g / g, such as greater than about 16 g / g, such as greater than about 17 g / g, such as greater than about 18 g / g.

8. The multi-layer substrate according to any one of the preceding claims, the multi-layer substrate further comprising a third layer, the second layer being positioned between the first layer and the third layer.

9. The multi-layer substrate according to claim 8, wherein the first layer comprises a top outer layer and the third layer comprises a bottom outer layer, the first layer being configured to face a user when incorporated into an absorbent article.

10. The multi-layer substrate according to any one of the preceding claims, wherein the second layer has a basis weight greater than about 200 gsm, such as greater than about 250 gsm, such as greater than about 300 gsm, such as greater than about 350 gsm, and less than about 800 gsm, such as less than about 600 gsm.

11. The multi-layer substrate according to any one of the preceding claims, wherein the second layer contains an amount greater than about 10% by weight, such as greater than about 30% by weight, such as greater than about 50% by weight, such as greater than about 60% by weight, such as greater than about 70% by weight, such as greater than about 80% by weight, such as greater than about 90% by weight, such as greater than about 95% by weight of the superabsorbent material.

12. The multi-layer substrate according to claim 10, wherein the second layer further contains pulp fibers, synthetic polymer fibers, or a mixture thereof.

13. The multi-layer substrate according to claim 2, wherein the first layer contains an amount greater than about 20% by weight, such as greater than about 30% by weight, such as greater than about 40% by weight, such as greater than about 50% by weight, and up to 100% by weight, such as less than about 80% by weight, such as less than about 70% by weight of binder fibers.

14. The multi-layer substrate according to claim 13, wherein the first layer contains a first binder fiber and a second binder fiber, the first binder fiber having a size of about 3 denier or greater, and the second binder fiber having a size less than 3 denier.

15. The multi-layer substrate according to claim 13, wherein the first layer further contains synthetic polymer fibers, pulp fibers, or a mixture thereof.

16. The multi-layer substrate according to claim 2, wherein the first layer has a basis weight greater than about 35 gsm, such as greater than about 40 gsm, such as greater than about 45 gsm, such as greater than about 50 gsm, and less than about 100 gsm, such as less than about 90 gsm, such as less than about 80 gsm, and wherein the first layer contains from about 20% to about 80% by weight of binder fibers, the binder fibers being combined with synthetic polymer fibers.

17. The multi-layer substrate according to claim 2, wherein the first layer has a basis weight less than about 35 gsm, such as less than about 30 gsm, such as less than about 25 gsm, such as less than about 20 gsm, and greater than about 10 gsm, such as greater than about 15 gsm, such as greater than about 20 gsm, and wherein the first layer contains from about 10% to about 80% by weight of binder fibers, the binder fibers being combined with pulp fibers and optionally with synthetic polymer fibers.

18. The multi-layer substrate according to claim 8 or claim 9, wherein the third layer has a basis weight greater than about 5 gsm, such as greater than about 10 gsm, such as greater than about 15 gsm, and less than about 50 gsm, such as less than about 30 gsm, such as less than about 25 gsm, such as less than about 20 gsm, and wherein the third layer contains binder fibers.

19. The multi-layer substrate according to claim 18, wherein the third layer further contains pulp fibers, such as crosslinked pulp fibers, and the binder fibers contained in the third layer have a size less than about 6 denier.

20. The multi-layer substrate according to any one of the preceding claims, wherein the first layer contains less than 2% by weight, such as less than 1% by weight, of a superabsorbent material or does not contain a superabsorbent material.

21. The multi-layer substrate according to claim 2, wherein the binder fibers comprise bicomponent fibers, the bicomponent fibers containing a core polymer component surrounded by a sheath polymer component or two polymer components placed side by side.

22. The multi-layer substrate according to claim 21, wherein the bicomponent fibers comprise a first polymer component and a second polymer component, the first polymer component comprising a polyester polymer or a polypropylene polymer, and the second polymer component comprising a polyethylene polymer.

23. An absorbent article, the absorbent article comprising: a fluid-permeable liner; a backsheet; and an absorbent core positioned between the liner and the backsheet, the absorbent core comprising the multi-layer substrate according to any one of the preceding claims.

24. The absorbent article according to claim 23, wherein the absorbent article comprises a diaper or children's pants.

25. The absorbent article according to claim 23, wherein the absorbent article comprises an adult incontinence product.

Images