Absorbent composite web containing a highly porous layer and particles mixed with continuous microfilaments.

Abstract

The present invention relates to an absorbent composite web in which particles mixed with continuous microfilaments are arranged within the pores of a high-loft web, and to a method for forming the web, the web being applicable to filtration applications or (particularly when the particles are liquid absorbent particles) to absorbent hygiene products.

Description

[Technical Field]

[0001] The present invention relates to an absorbent composite web in which particles mixed with continuous microfilaments are arranged within the pores of a high-loft web, and to a method for forming the web, the web being applicable to filtration applications or (particularly when the particles are liquid absorbent particles) to absorbent hygiene products. [Background technology]

[0002] Webs containing particulate materials are widely used, for example, in air purification applications that remove pollutants by adsorption mechanisms. There are also extensive applications for absorbent structures in absorbent products, such as personal hygiene absorbent products like disposable infant diapers, toddler training pants, or adult incontinence underwear, which are designed to absorb and retain bodily exudates, particularly urine. These absorbent products consist of multiple layers, each with a different function, and typically include a top sheet, a back sheet, and an absorbent core placed between them. The absorbent core is desirable to be able to absorb and retain liquid exudates for extended periods, such as overnight use in the case of diapers, and must minimize re-wetting to keep the wearer dry and prevent contamination of clothing and sheets. Modern absorbent cores typically have an absorbent structure that includes a composite of superabsorbent polymer (SAP) particles (also called absorbent gelling material (AGM)) and fibrous materials such as natural fibers (e.g., cellulose fibers), modified natural fibers (e.g., regenerated cellulose-based materials), or synthetic fibers.

[0003] It is known that suitable absorbent structures can be formed "in-line" or "in-situ" on a converting line for forming an entire absorbent product. For example, WO2022 / 120693A1 (P&G) relating to an absorbent core used in an absorbent product discloses an absorbent core comprising a liquid-permeable top cover layer, a bottom cover layer, a high-loft central layer positioned between them, and first and second superabsorbent polymers that at least partially permeate the high-loft central layer, further comprising a cover layer fixed by adhesive. Also, WO2014 / 001487 (C4S) discloses particles embedded in a porous web, which are described as being immobilized (for example) between cover webs by ultrasound.

[0004] However, such methods require each product manufacturing line (also called a converter) to be equipped with a suitable handling system for particle addition, as well as a system for feeding and connecting pre-formed webs. Furthermore, the formation of absorbent cores can sometimes limit overall production volume.

[0005] Alternatively, instead of in-line core formation, composite absorbent webs containing particles such as superabsorbent particles can be mass-produced offline. These are then supplied as so-called roll stock to converter lines that form absorbent products, which can then be combined with other elements to create the absorbent products. This allows for advantageous simplification of converting equipment and processes, as well as cost advantages from mass production.

[0006] WO2021 / 188330A1 (P&G) discloses an absorbent core for use in absorbent products, the absorbent core comprising a liquid-permeable top layer, a bottom layer, a high-loft middle layer, and superabsorbent polymer particles dispersed at least partially within the middle layer.

[0007] WO2020 / 025401 (BASF) discloses a liquid-absorbing core comprising at least an upper and lower layer, each layer comprising 0-10% by weight of fibrous material (natural or synthetic) and 90-100% by weight of superabsorbent polymer particles. The absorbent core is formed by dispersing a first superabsorbent polymer or a blend thereof onto one surface of a nonwoven fabric material. The upper tissue paper is then laminated with adhesive, and after inverting the composite, a second superabsorbent polymer is dispersed onto the other surface of the nonwoven fabric, and the lower tissue paper is then laminated with adhesive. The absorbent composite is then slit to a desired width and rolled up.

[0008] However, there is still room for improvement in terms of structure. For example, there is a need for adhesive-free structures to facilitate the recycling of factory waste and post-use waste, and to reduce the environmental impact of such products. Furthermore, the use of adhesives involves significant energy consumption. In addition, the use of adhesives within absorbent structures may adversely affect the liquid handling performance.

[0009] Furthermore, WO2013 / 152809 (TWE / Libeltex) discloses an adhesive-free method in which particles are embedded within the pores of a pre-formed web. To adequately retain the particles, the web containing such particles undergoes a separate process of being wrapped in packaging material such as tissue or nonwoven web.

[0010] WO2020 / 103964A1 (Reifenhauser and PFN) discloses an open porous spunbond web made of continuous crimped fibers, in which at least some of the pores of the web can be filled with particles such as superabsorbent particles. However, even when using crimped fibers, there are problems such as a reduced manufacturing speed, insufficient particle capture due to their thickness, the need for a covering web, and relatively low flexibility.

[0011] WO2021 / 198894(GDM) discloses a web containing elastic meltblown fibers, and possibly inelastic meltblown filaments, in which particulate material is trapped within the pores of the web and, due to its adhesive properties during meltblown molding, at least a portion of it adheres to the fibers. Such composites can also be combined with auxiliary webs, such as nonwoven fabrics for particle retention or high-loft materials to improve liquid dispersibility during use. This method utilizes discontinuous meltblown fibers formed by "air knife" technology, which cuts the polymer filaments into short fragments by applying decelerating air at an oblique angle to the filaments at the exit of the molding nozzle. As a result, the particle retention function is reduced. Furthermore, the need to use elastic polymers increases costs and reduces production flexibility and speed, and is therefore not always desirable.

[0012] Overall, while methods for forming absorbent structures offline have advantages over in-line formation, such as enabling extremely high-volume production in a single production unit, there is still a need to improve economic efficiency and / or the properties of the resulting absorbent structures. Furthermore, the use of adhesives within absorbent structures complicates recycling, particularly of factory waste, and may negatively impact consumer perception as unwanted chemicals.

[0013] Therefore, the present invention aims to provide economic advantages by combining mass production using a single production unit with low-cost raw materials, particularly a configuration that does not use adhesives. This can be achieved without impairing particle retention performance not only before and during manufacturing but also during use.

[0014] summary The present invention is a continuous absorbent composite web comprising a filament-particle mixture containing polymer filaments and particles mixed with each other, a high loft polymer fiber matrix having a large number of pores, and a scrim layer composed of substantially continuous polymer filaments. At least one layer (preferably two layers) of the filament-particle mixture is arranged in contact with the high loft filament matrix, and at least a part of the particles mixed with the filaments penetrates into the pores of the high loft fiber matrix. At least one layer (preferably two layers) of scrim layer containing substantially continuous filaments forms the surface layer of the continuous absorbent composite web.

[0015] The continuous absorbent composite web preferably satisfies one or more conditions selected from the following. a) The filaments are coaxial melt blown filaments; b) The composite web substantially does not contain an adhesive; c) The composite web substantially does not contain cellulose; d) The scrim layer adheres to the layers arranged adjacent to the inside thereof without using an adhesive. e) The particles are present in an amount exceeding about 80%, preferably exceeding about 90%, more preferably exceeding about 95% based on the total weight of the composite web; f) The particles are present in an amount exceeding about 50 g / m 2 preferably exceeding about 100 g / m 2 more preferably exceeding about 200 g / m 2 and most preferably exceeding about 300 g / m 2 ; g) A single scrim layer (130) has a basis weight of less than about 10 g / m 2 preferably less than about 5 g / m 2 more preferably less than about 3 g / m 2 ; h) The high loft polymer filament matrix exceeds about 20 g / m 2 preferably exceeds about 40 g / m 2 more preferably exceeds about 50 g / m2 having a basis weight exceeding; i) the polymeric filaments commingled with said particles comprise greater than about 95% polypropylene, said polypropylene exhibiting a MFR greater than about 25 g / 10 min, preferably greater than about 45 g / 10 min, at 230° C. and 2.16 kg; j) said composite web has particle-free longitudinal regions; k) said high loft polymer matrix comprises sub-matrices, preferably sub-layers, which exhibit at least a 10% difference with respect to a high value of at least one property selected from the following. k1) density; k2) fiber or filament thickness; k3) fiber or filament composition. l) the particle retention in the dry state exceeds about 90%, preferably exceeds about 95%, more preferably exceeds about 98%, and most preferably exceeds about 99%.

[0016] In another aspect, a method of forming a continuous absorbent composite web includes the steps of providing. At least one, preferably two, coaxial meltblowing (CAM) units forming a scrim; A first filament-particle mixing unit comprising a first polymer supply and a first CAM filament forming unit, and a first particle supply unit, preferably further comprising a further polymer supply and a further CAM filament forming unit, the first filament-particle mixing unit; Optionally, a second filament particle mixing unit (1200’’) comprising a second polymer supply and a second CAM filament forming unit, a second particle supply unit, preferably further comprising a further polymer supply and a further CAM filament forming unit, the second filament particle mixing unit; Pre-formed web feed unit as a high-loft web supply unit; At least one mobile recovery unit, Preferably a movable perforated belt system; A web inversion unit optionally comprising a web inversion unit, which allows the upper and lower surfaces of a web or web complex to be swapped in the direction of gravity. Furthermore, the following process steps are performed. A-Scrim forming CAM unit forms a scrim using a continuous filament, and the first scrim is supplied to the recovery unit; A B-filament-particle mixture is formed, and the mixture is supplied to the recovery unit; C-High loft web, By feeding out a pre-formed web on a high-loft web feeder, or Preferably, a high-loft web is provided by forming it from a polymer, preferably polyester, using a spunbond method. Then, send the high-loft web towards the collection unit. X - Selectively perform a web inversion process to orient the web or composite web in the direction of gravity. In the order selected from the following groups: A', C, B, A'' A', B', C, B'', A''; C, B', A', X, B'', A'' Reverse it; Here, A' and B' represent the first execution of each process, and A'' and B'' represent the second execution of each process.

[0017] This process produces approximately 500 m³ of output, which is expressed as the product of the production width [m] and the production speed [m / min]. 2 Exceeding / min, preferably 1000m 2 Exceeding / min, and more preferably 2000m 2 Exceeding / min, more preferably 4000m 2 Exceeding / min, most preferably 5000m 2 It may be operated under conditions exceeding one minute. A method for forming a continuous absorbent composite web may further include a step of processing the particles of the filament-particle mixture into the high-loft material, preferably selected from the group consisting of the following: - Air intake; - mechanical vibration; - Application of ultrasound. [Brief explanation of the drawing]

[0018] Figures 1A and 1B show the absorbent composite web according to the present invention in a partially disassembled state and an undisassembled state. Figures 2A and 2B show another absorbent composite web according to the present invention in a partially disassembled and undisassembled state. Figure 3 shows an example of the configuration of an apparatus suitable for the method according to the present invention. Figures 4A to 4C show processing options according to the present invention. These diagrams are schematic and not to scale. The same symbol indicates the same or equivalent element or component, and a single (') or multiple ('', ''', etc.) apostrophes indicate corresponding overlapping elements such as left / right or front / back. Unless otherwise specified, all percentages (%) refer to weight percentages. [Modes for carrying out the invention]

[0019] In this specification, the term “fiber” refers to elongated fibers with a length-to-diameter ratio of at least about 3:1, often exceeding 10:1, and even exceeding 100:1. Synthetic fibers or artificial natural material fibers are typically formed by solidifying continuous filaments of molten polymers. These polymers may be homogeneous, single-component polymers, or polymer blends, and may form different cross-sectional regions within the filament, in which case crimped or crimpable fibers are obtained. The term “filament” may also be used to refer to substantially continuous solidified fibers, while “fiber” is used to describe discontinuous structures. A typical method for forming webs from substantially continuous filaments is known as the “spunbond method” (see, for example, U.S. Patent No. 5935512 (KC)), which forms substantially continuous filaments with diameters ranging from about 1 to 50 μm, often 15 to 35 μm.

[0020] The term "microfiber" refers to fibers produced by melt-blown web formation methods, such as those described in U.S. Patent No. 8017534 (KC). In this method, a low-viscosity polymer is extruded from a nozzle and stretched by a high-speed airflow blown obliquely onto the formed filaments. This process causes the molten polymer to diffuse and solidify, forming a fibrous web.

[0021] In recent years, coaxial melt-blown (CAM) technology has attracted particular attention, as it allows for the production of substantially continuous microfilaments. Such CAM filament molding is described in more detail, for example, in U.S. Patent No. 9,303,334 (Biax), and constitutes one of the important elements of the present invention, as will be discussed later.

[0022] A wide range of polymers can be selected for use in such filaments, but polyolefins are preferred, and polypropylene is more preferred. Elastic polyolefins can also be used, but they are not necessarily required from a performance standpoint and are not preferred from a commercial standpoint due to their high cost. When these are used, it is desirable that their amount used be less than 5% by weight of the total weight of the filament polymer. The most preferred polymers have a melt flow rate (MFR) of more than about 25 g / 10 min, preferably more than about 45 g / 10 min, and usually less than about 2000 g / 10 min, which can be measured according to ASTM D1238 and ISO 1133. In the case of polypropylene, it is appropriate to express the polymer in grams per 10 minutes (g / 10 min) under conditions of 210°C and a 2.16 kg load, as these polymers can be adequately processed with current equipment and processes.

[0023] In this specification, “web” means a matrix consisting of a single type of fiber or filament, or a mixture thereof, which may be oriented or randomly oriented, and which is bound together by friction and / or adhesion and / or aggregation. These bonds may be imparted, for example, in the deposition process during fiber or filament formation, immediately after filament formation. Typically, webs are self-supporting and can be handled on manufacturing or converting equipment, although in the case of subwebs of composite webs, they may not have sufficient strength on their own. Webs may contain particles as filament-particle mixtures. A “composite web” refers to a combination of (sub)webs in a laminated configuration, and a “continuous web” is substantially infinite in the longitudinal direction, i.e., the X direction, corresponding to the machine direction (MD) during manufacturing, and is wound onto rolls or spools, or folded in a box (stored in a festoon-like manner), and connected to form a substantially infinite length web. Therefore, a continuous web has a width direction (cross direction during manufacturing) perpendicular to the length direction, and its width may be several meters during web manufacturing, or less than one meter when used for converting or molding products. In addition, a continuous web has a thickness direction perpendicular to the length and width directions, and its thickness is significantly smaller than either of the two aforementioned directions.

[0024] A more important element in this invention is the high-loft web. The term "high loft" refers to a low-density, bulky fabric compared to a flat, paper-like fabric. High-loft webs are characterized by relatively high porosity. This means that there are a relatively large number of voids between the fibers, allowing for the dispersion of particles such as superabsorbent polymer particles within these voids. A high-loft web applicable to this invention (without superabsorbent particles) has a density of 0.15 g / cm³ at a pressure of 0.83 kPa (0.12 psi). 3 It has a density of less than 0.01 g / cm³, especially 0.01 g / cm³. 3 ~0.15g / cm 3 , or 0.05 g / cm³ 3~0.12 g / cm³ 3 , or 0.08 g / cm³ 3 ~0.10 g / cm³ 3 This is within the range. Preferably, the high-loft web maintains its openness even under high pressure of 4.14 kPa (0.6 psi), and its density is approximately 0.20 g / cm³. 3 It is less than 0.01 g / cm³, especially 0.01 g / cm³. 3 ~0.20 g / cm³ 3 , or 0.05 g / cm³ 3 ~0.15g / cm 3 This is the range. Here, density can be calculated by dividing the basis weight of the high-loft layer by the thickness measured under each pressure.

[0025] The appropriate basis weight and thickness of the high-loft web can be adjusted according to the requirements of the specific application. The high-loft (sub)web has a thickness of at least 0.30 mm, particularly in the range of 0.30 mm to 2.00 mm, or 0.50 mm to 1.5 mm, when measured under a pressure of 4.14 kPa (0.6 psi). The basis weight of the high-loft (sub)web is, for example, 15 g / m². 2 ~500g / m 2 This range is particularly 30g / m 2 ~200g / m 2 For example, 50g / m 2 ~120g / m 2 That is the case.

[0026] The fibers constituting the high-loft web may be formed partially or entirely from relatively elastic synthetic fibers, particularly polypropylene (PP), polyamide (PA, nylon, etc.), or polyethylene terephthalate (PET) fibers. The fiber diameter may be, for example, in the range of 0.01 mm to 0.50 mm.

[0027] An example of a high-loft web is through-air bonded nonwoven fabric, which is produced by passing staple fibers through a combing unit or carding unit. In this process, the staple fibers are separated and generally oriented in the direction of the machine, forming a fibrous nonwoven web that is generally aligned in the direction of the machine. This web is then passed through a heated drum, forming bonds throughout the fabric without applying any specific pressure (through-air bonding method).

[0028] Optionally, the high-loft web may include subweb layers having different properties and functions. These properties include density, fiber thickness, or fiber composition, and the difference in each property is preferably greater than approximately 3%, 5%, or even 10%, based on the higher value of each property.

[0029] A third important element in this invention is the particles that are placed within the pores of the high-loft web. Such particles can offer a wide range of functions, including coloring, polishing, or adsorption of gases or gaseous contaminants for filtration purposes. Specific applications include liquid absorption, in which case the particles are adapted to absorb water or aqueous solutions, such as bodily exudates, in amounts several times their own weight. In this specification, “superabsorbent polymer (SAP)” refers to an absorbent material capable of absorbing at least 10 times its own weight of 0.9% saline solution, as measured by the centrifugal retention capacity (CRC) test (EDANA method NWSP 241.0.R2(19)). SAP preferably has a CRC value of at least 15 g / g. SAP is typically a cross-linked polymer that is insoluble in water but swells in water, allowing it to absorb large amounts of liquid. SAP has a particulate form to allow it to flow when dry. Typical particulate SAPs are polyacrylate-based polymers, but the use of other polymer materials is not excluded. For example, in addition to starch-based particulate absorbent polymer materials, starch-based copolymers obtained by graft polymerization of polyacrylamide copolymers, ethylene-maleic anhydride copolymers, crosslinked carboxymethylcellulose, polyvinyl alcohol copolymers, crosslinked polyethylene oxide, and polyacrylonitrile can also be used.

[0030] SAP may be a polyacrylate-based or polyacrylic acid-based polymer that is crosslinked internally and / or on the surface. The superabsorbent polymer of the present invention can be selected from polyacrylate and polyacrylic acid-based polymers that are crosslinked internally and on the surface. The superabsorbent polymer may be internally crosslinked, i.e., polymerization is carried out in the presence of a compound having two or more polymerizable groups that can be radically copolymerized in the polymer network. Preferably, the SAP particles include a crosslinked polymer of polyacrylic acid or a salt thereof, or polyacrylate or a derivative thereof.

[0031] The particles may be relatively small, with a maximum dimension of less than 1 mm in a dry state, and may be generally circular in shape, but granules, fibers, flakes, spherical, powder, plate-like, and other shapes and forms are also well known to those skilled in the art. Nearly spherical particles can facilitate penetration into the pores of high-loft webs.

[0032] In the composite web according to the present invention, particles are mixed with polymer microfilaments, thereby forming a filament-particle mixture. This is easily understood by considering that the mixture can be generated by supplying a particle stream to the fine-graining zone of a filament forming apparatus, as will be described in more detail below. Thus, the filaments entangle particles as they move together toward the collection belt. Since the open porous high-loft web is already positioned on the collection belt, the mixture accumulates on the high-loft web, and at least a portion of the filament-particle mixture penetrates into the pores of the high-loft web. This may be assisted by penetration-assisting steps such as vibration or suction, if necessary.

[0033] Having described the main elements of a continuous absorbent composite web, we now refer to Figures 1A and 1B. These figures show such a web 100 as a cross-sectional and exploded view, respectively, for further explanation without limitation.

[0034] The high-loft web 110 is positioned next to the first (in this case, lower) scrim layer 130'. Furthermore, a filament-particle mixture 120 containing particles 125 and filaments is shown. Importantly, the filaments here are continuous CAM filaments 128; discontinuous meltblown fibers, let alone spunbond filaments, would not provide sufficient particle entanglement. In Figure 1A, the filament-particle mixture 120 is shown overlapping the high-loft layer 110, indicating that at least some of the particles 125 penetrate into the pores of the high-loft web 110. The second (in this case, upper) scrim layer 130'' is positioned on top of the mixture / high-loft web. Note that the composite web described does not require the addition of adhesives or glues. This is because the filaments formed in situ have sufficient tackiness to hold the structure together, especially to hold the particles.

[0035] Figures 2A and 2B illustrate an exemplary embodiment of the composite web 100 according to the present invention, which is similar to that shown in Figure 1, but differs in that it includes a second filament-particle mixture 120'' in addition to the first filament-particle mixture 120', so that the particles penetrate the high loft layer 110 from both sides.

[0036] In any embodiment, the particles may or may not completely penetrate the high-loft web 110, and some parts of the high-loft web 110 may not contain particles. This may be particularly preferable when it is desired to improve fluid distribution in the x and y directions.

[0037] The particle retention can be evaluated by the shake test described below. Preferably, at least about 90%, or more than about 95%, more than 98%, or more than 99% of the weight of the added particles is retained within the composite web after the test is performed.

[0038] It should be noted that this excellent retention performance is achieved through a combination of filament-particle embedding within the pores of the high-loft web and coating by the scrim layer, without the need for additional retaining webs such as tissue or pre-formed nonwoven fabrics.

[0039] Referring to Figures 3 and 4, processing options for forming the continuous absorbent composite web 100 are described.

[0040] In the first exemplary embodiment shown in Figure 3, the process is carried out on a continuous absorbable composite web forming unit 1000, which includes a first (1100') scrim forming CAM unit and optionally a second (1100'') scrim forming CAM unit, which are well known and described in more detail in the above referenced literature [...]. Each scrim forming unit 1100 comprises a polymer supply unit for scrim 1110 and a filament forming die head 1120 for forming filaments 1115.

[0041] As shown in this embodiment, the high-loft web 110 is supplied from the unwinder 1510 of the high-loft web supply device 1500.

[0042] The first, and in this embodiment, filament-particle mixing unit 1200' comprises a first particle supply unit 1230', a first polymer supply unit 1211' for filaments formed by the first CAM filament forming unit 1213', and the first particle supply unit 1230'. Optionally, and preferably in many embodiments, the filament-particle mixing unit comprises a further polymer supply unit 1221' and a further CAM filament forming unit 1223', positioned opposite the first CAM filament forming unit 1213' with respect to the inlet of the particle input unit 1233. The collection unit 1900 is preferably a porous belt system with various suction devices 1950, positioned below the subweb forming unit in the direction of gravity.

[0043] As further shown in Figures 4A to 4C, the process 2000 according to these embodiments of the present invention is a combination of process steps performed on the above apparatus, using the following abbreviations. In steps A, A', and A'', the scrim web is formed by the scrim forming units 1100, 1100', or 1100'' described above. In steps B, B', and B'', the filament-particle mixture is formed on the filament-particle mixing units 1200, 1200', and 1200'', respectively. In step C, the high-loft web 110 is supplied from the high-loft web supply unit 1500 by unwinding the formed web 110 with the high-loft web unwinder 1510 and guiding it to the collection unit via the guide roll 1515. Alternatively, the high-loft web 110 may be formed in situ on the collection unit 1900 by a spunbond method from a polymer (preferably polyester). It should be noted that each of the second processes A'' and B'' may be performed under different process conditions than the respective first processes A' and B'.

[0044] Therefore, in this embodiment, the steps for providing the continuous absorbent composite web 100 shown in Figure 1 are performed in the order A'-CBA” with respect to the mechanical direction defined by the movement of the collection unit 1900 (see Figure 4A).

[0045] When providing the continuous absorbent composite web 100 shown in Figure 2, the process may be carried out in the order A'-B'-CB”-A” with respect to the mechanical direction defined by the movement of the collection unit 1900 (see Figure 4B).

[0046] As a further modification, as shown in Figure 5C, a structure substantially identical to that in Figure 2 can be formed, with the option of including an additional step X that reverses the direction of gravity of the subweb on the turning unit 1700.

[0047] While we do not wish to be bound by theory, this modification is thought to further facilitate the penetration of particles into the high-loft web. Therefore, the process begins with step C, which provides a high-loft web 110 on a high-loft supply unit 1500, feeds the web onto a first collection unit 1900', and supplies the filament-particle mixture to a first particle-filament mixing unit B'(1220') to place it on the high-loft web. With the assistance of gravity and appropriate suction units 1950 of the collection unit 1900', the particles penetrate deeply into the pores of the high-loft web 110. Then, as step A', a first scrim is applied to the surface of the composite of the high-loft web and the filament-particle mixture by a scrim-forming unit 1100'.

[0048] The next step X, "inversion" of the web, can be performed by conventional means on the web turning unit 1700, such as twisting a pair of web supports, such as parallel belts, by 180°. When the subweb is further sent to another web support unit 1900”, the top surface of the high-loft material is facing upward, and as step B”, in the filament-particle mixing unit 1220”, a second filament-particle mixture can be deposited on it. Furthermore, as step A”, in the scrim forming unit 1100”, it is covered with a second scrim.

[0049] Therefore, this process can be described by steps C-B'-A'-XB"-A" (see Figure 4C).

[0050] A notable advantage of the process of the present invention is that, without the use of additional adhesive, structural integrity and particle retention can be ensured by utilizing the tackiness of the filaments formed in situ.

[0051] Furthermore, this process enables extremely high production volumes of the resulting continuous absorbent composite webs, allowing operation at very high production speeds of over 500 m / min, over 700 m / min, and even over 1000 m / min.

[0052] Furthermore, the web width can be set to over 1m, or over 3m, over 5m, or over 7m, which can result in an overall production speed of over 500m² / min, or over 1000m² / min, over 2000m² / min, over 4000m² / min, and even over 5000m² / min.

[0053] Test method Shakeout test The susceptibility of particle-containing fibrous webs or matrices to particle migration and shedding can be evaluated using a shakeout test, in which the sample is shaken in a controlled manner and the total mass loss from the sample is measured. A sample of the matrix or composite is prepared in the form of a rectangular plate measuring 9 inches (22.86 cm) in length and 4 inches (10.16 cm) in width. The sample has the same structure as when it is incorporated into the final product.

[0054] The shakeout test can be performed using the "Model #RX-24 PORTABLE SIEVE SHAKER" (hereinafter referred to as "RX-24") manufactured by WSTyler Inc., USA. For use in the shakeout test, the RX-24 is modified to allow the sample to be shaken, and the resistance of the web to particle migration can be evaluated based on the amount of material lost during shaking. The sample holder consists of a frame made of polyacrylate plate and two mesh screens. The frame is 17 inches (43.18 cm) long, 11.5 inches (29.21 cm) wide, and 0.20 inches (0.51 cm) thick. The frame has a rectangular opening that is 15.25 inches (38.74 cm) long and 6.25 inches (15.88 cm) wide, located approximately in the center of the frame. One mesh screen, slightly larger than the opening, is operatively attached to both sides of the frame (e.g., with duct tape) to hold the test sample. The mesh screen has a 0.4cm x 0.4cm rectangular opening, and the total weight of the sample holder is approximately 500g. A substantially equivalent shaker system may be used as optional.

[0055] To perform the shakeout test, the absorbent composite sample is placed in the center of the sample holder, and the sample holder is placed horizontally (i.e., parallel to the floor) on the wire screen used to support the sample in the modified RX-24. The RX-24 then shakes the sample at a frequency of approximately 520 cycles / minute for 5 minutes. After the shaking phase of the test is complete, the mass loss and superabsorbent polymer loss are determined by comparing the original mass of the sample when it was first placed on the support screen with the remaining total mass of the absorbent composite sample, according to the following formula. Mass loss (%)=100%×((M0-M end )÷M0) Here, M0 = Sample mass before the shakeout test (e.g., grams) M end = The mass of the sample remaining after the test (e.g., grams). The mass lost from the sample generally falls through the openings of the support screen. The shakeout value (%) is the total mass loss (%) that occurred under the shaking conditions described above.

[0056] While the above description details preferred methods for conducting shakeout tests using specific types of apparatus, those skilled in the art will understand that other apparatuses can be constructed that allow for equivalent tests where the agitation applied to the web yields the same mass loss results as the disclosed shakeout test.

[0057] Centrifugal volume test This test generally follows Edana NWSP241.0.R2(15) "Polyacrylate-based superabsorbent powders - Measurement of retention capacity in saline solution by gravimetric measurement after centrifugation," but differs in that it applies to the absorbent material in accordance with the test method pA07 / 05 of Hygiene-TechnologiegmbH (Hy-Tec) of Hahn, Germany. A test sample treated according to the free swelling absorption test is placed in a commercially available centrifuge and subjected to a centrifugal force of approximately 250 G (for example, achieved by rotating at 1400 rpm with an inner diameter of 225 mm) for 3 minutes. The test piece is removed and weighed, and the centrifugal absorption capacity is recorded in grams.

Claims

1. A continuous absorbent composite web (100), A filament-particle mixture (120) containing polymer filaments (128) and particles (125) mixed together; A high-loft polymer filament matrix containing pores (110) and; A scrim layer containing substantially continuous polymer coaxial meltblown microfilaments (130); It is equipped with, The polymer filaments (128, 130) are substantially continuous coaxial meltblown microfilaments, and at least one, preferably two, layers of the filament-particle mixture (120) are arranged in contact with the high-loft polymer filament matrix (110), with at least a portion of the particles (125) mixed with the filaments penetrating into the pores of the high-loft polymer filament matrix (110); A scrim layer comprising at least one, preferably two, substantially continuous coaxial meltblown microfilaments (130) forms the surface layer of the continuous absorbent composite web (100). A continuous absorbent composite web characterized by the following features.

2. The continuous absorbent composite web according to claim 1, further satisfying one or more conditions selected from the group consisting of the following. b) The composite web is substantially free of adhesives; c) The composite web is substantially free of cellulose; d) The scrim layers are bonded to adjacent inner layers without the use of adhesive.

3. A continuous absorbent composite web according to claim 1 or 2, further satisfying one or more conditions selected from the group consisting of the following. e) The particles are present in an amount exceeding about 80%, preferably exceeding about 90%, and more preferably exceeding about 95% of the total weight of the composite web; f) The particles are approximately 50 g / m² ２ An amount exceeding this, preferably about 100 g / m² ２ An amount exceeding this, more preferably about 200 g / m² ２ An amount exceeding this, most preferably about 300 g / m² ２ Existing in quantities exceeding; g) A single scrim layer (130) is approximately 10 g / m ２ Less than, preferably about 5 g / m ２ Less than, more preferably about 3 g / m ２ Having a basis weight of less than; h) The high loft polymer filament matrix has a basis weight greater than about 20 g / m ２ and preferably greater than about 40 g / m ２ and more preferably greater than about 50 g / m ２ ; i) The polymer filaments mixed with the particles contain more than 95% polypropylene, and the polypropylene exhibits an MFR of more than 25 g / 10 min, preferably more than 45 g / 10 min, under conditions of 230°C and 2.16 kg; j) The composite web has a vertical region that does not contain particles; k) The high-loft polymer matrix includes submatrices, preferably sublayers, which exhibit a difference of at least 10% to a high value of at least one of the following properties: k1) Density; k2) Thickness of the fiber or filament; k3) Composition of the fiber or filament.

4. A continuous absorbent composite web according to any one of claims 1 to 3, further satisfying one or more conditions selected from the group consisting of the following. l) The particle retention rate in the dry state exceeds about 90%, preferably about 95%, more preferably about 98%, and most preferably about 99%.

5. A method for forming a continuous absorbent composite web, comprising the steps of providing the following: At least one, preferably two, coaxial melt-blown (CAM) units (1100, 1100', 1100") for forming the scrim; A first filament-particle mixing unit (1200'), First polymer supply unit (1211') and first CAM filament molding unit (1213'), and a first particle supply unit (1230') is provided. Preferably, the system includes a further polymer supply unit (1221') and a further CAM filament molding unit (1223'). First filament-particle mixing unit (1200'), Optionally, a second filament particle mixing unit (1200''), A second polymer supply unit (1211") and a second CAM filament molding unit (1213"), Second particle supply unit (1230'', Preferably, the system includes a further polymer supply unit (1221") and a further CAM filament molding unit (1223"), Second filament particle mixing unit (1200''), A pre-formed web feed unit (1510) as a high-loft web supply unit (1500); At least one mobile recovery unit (1900), Preferably a movable perforated belt system; A web inversion unit (1700) optionally comprising a web inversion unit (1700) that swaps the upper and lower surfaces of the web or web complex in the direction of gravity; Furthermore, the following process steps are performed: A-Scrim forming CAM unit (1100') forms a scrim using a continuous filament (130), and the first scrim is supplied to the recovery unit (1900); A B-filament-particle mixture (120) is formed, and the mixture is supplied to the recovery unit (1900); C-High loft web (110), By feeding out the pre-formed web (110) on a high-loft web feeder (1510), or Preferably, the high loft web (110) is formed by a spunbond method from a polymer, preferably polyester, to provide the product. The high-loft web (110) is supplied to the recovery unit (1900); X - Selectively perform a web inversion process (1700) to orient the web or composite web in the direction of gravity. In the order selected from the following groups: A', C, B, A” A', B', C, B", A"; C, B', A', X, B", A" Reverse; Here, A' and B' represent the first execution of each process, and A'' and B'' represent the second execution of each process.

6. A method for forming a continuous absorbent composite web as described in claim 5, The production volume, expressed as the product of the production width [m] and the production speed [m / min], is approximately 500 m ２ Exceeding one minute, preferably 1000 m ２ Exceeding / min, and more preferably 2000m ２ / min or more, more preferably 4000m ２ Exceeding 1 minute, most preferably 5000 m ２ A method of operation that exceeds the condition of per minute.

7. A method for forming a continuous absorbent composite web according to claim 5 or 6, further comprising the step of processing the particles of the filament-particle mixture into the high-loft material, preferably selected from the group consisting of: - Air intake; - Mechanical vibration; - Application of ultrasound.

8. A method for forming a continuous absorbent composite web according to any one of claims 5 to 7, wherein each second step A'', B'' is performed with a different process setting than each first step A', B'.

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