Patent Application
20170000663
The business of manufacturing and marketing disposable absorbent articles for personal care or hygiene (such as disposable diapers, training pants, adult incontinence undergarments, feminine hygiene products, breast pads, care mats, bibs, wound dressing products, and the like) is relatively capital intensive and highly competitive. To maintain or grow their market share and thereby maintain a successful business, manufacturers of such articles must continually strive to enhance their products in ways that serve to differentiate them from those of their competitors, while at the same time controlling costs so as to enable competitive pricing and the offering to the market of an attractive value-to-price proposition.
One way in which some manufacturers may seek to enhance such products is through enhancements to softness. Parents and caregivers naturally seek to provide as much comfort as they can for their babies, and utilizing products such as disposable diapers that they perceive as relatively soft provides reassurance that they are doing what they can to provide comfort in that context. With respect to other types of disposable absorbent articles that are designed to be applied and/or worn close to the skin, an appearance of softness can reassure the wearer or caregiver that the article will be comfortable.
Thus, manufacturers may devote efforts toward enhancing the softness of the various materials used to make such products, such as various web materials, including nonwoven web materials formed from polymer fibers, and laminates thereof, forming the products. Such laminates may include, for example, laminates of polymer films and nonwoven web materials forming the backsheet components of the products.
It is believed that humans' perceptions of softness of a nonwoven web material can be affected by tactile signals, auditory signals and visual signals.
Tactile softness signals may be affected by a variety of the material's features and properties that have effect on its tactile feel, among them volume density, basis weight, pliability and flexibility of the nonwoven web, and loft or caliper.
It is believed that perceptions of softness of a material also may be affected by visual signals, i.e., its visual appearance. It is believed that, if a nonwoven material looks relatively soft to a person, it is much more likely that the person will perceive it as having relative tactile softness as well. Visual impressions of softness may be affected by a variety of features and properties, including but not limited to color, opacity, light reflectivity, refractivity or absorption, macroscopic physical surface features, and again, loft or caliper.
Loft or caliper in nonwovens may have importance for reasons in addition to or other than creating an impression of softness. In some applications, nonwovens may be used as components of cleaning articles, such as wipes or dusters. Improving loft of such a nonwoven can also improve its efficacy as a cleaning element. In another particular application, a nonwoven may be used to form the loops component of a hook-and-loop fastening system. Improving loft of such a nonwoven can improve its suitability for this purpose.
Various efforts have been made to provide or alter features of nonwoven web materials with the objective of enhancing loft and/or consumer perceptions of softness. These efforts have included selection and/or manipulation of fiber chemistry, basis weight, fiber density, configuration and size, tinting and/or opacifying, embossing or bonding in various patterns, etc.
For example, in U.S. application Ser. No. 13/428,404 (incorporated by reference herein to the extent not inconsistent herewith), features of a bonding pattern, reflecting corresponding features of a calender bonding roller (bonding protrusions and the configurations thereof on the roller), are disclosed. It is believed that the disclosed features, in various combinations, advantageously promote and affect airflow through the nip between the bonding roller and mating anvil roller in a way that causes air to tease or fluff fibers of the nonwoven as it exits the nip, enhancing the loft of the nonwoven product.
The approach described above, however, has not fully addressed all needs. In one particular, it would be advantageous if the loft-enhancing features of the bonding roller described in the cited reference could be enjoyed, while providing further enhancements to mechanical strength (machine direction and cross direction tensile strength) and dimensional stability (resistance to neckdown) of the nonwoven web product.
The challenge to improve loft while preserving or even improving mechanical strength and dimensional stability becomes more difficult as nonwoven web basis weight is reduced, because, as basis weight is reduced, fewer fibers per unit surface area are available to contribute to loft and strength of the web.
“Absorbent article” refers to devices that absorb and contain body exudates, and, more specifically, refers to devices that are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. Absorbent articles may include diapers, training pants, adult incontinence undergarments and pads, feminine hygiene pads, breast pads, care mats, bibs, wound dressing products, and the like. As used herein, the term “exudates” includes, but is not limited to, urine, blood, vaginal discharges, breast milk, sweat and fecal matter.
“Absorbent core” means a structure typically disposed between a topsheet and backsheet of an absorbent article for absorbing and containing liquid received by the absorbent article. The absorbent core may also include a cover layer or envelope. The cover layer or envelope may comprise a nonwoven. In some examples, the absorbent core may include one or more substrates, an absorbent polymer material, and a thermoplastic adhesive material/composition adhering and immobilizing the absorbent polymer material to a substrate, and optionally a cover layer or envelope.
“Absorbent polymer material,” “absorbent gelling material,” “AGM,” “superabsorbent,” and “superabsorbent material” are used herein interchangeably and refer to cross linked polymeric materials that can absorb at least 5 times their weight of an aqueous 0.9% saline solution as measured using the Centrifuge Retention Capacity test (Edana 441.2-01).
“Absorbent particulate polymer material” is used herein to refer to an absorbent polymer material which is in particulate form so as to be flowable in the dry state.
“Absorbent particulate polymer material area” as used herein refers to the area of the core wherein the first substrate and second substrate are separated by a multiplicity of superabsorbent particles. There may be some extraneous superabsorbent particles outside of this area between the first substrate 64 and second substrate.
“Airfelt” is used herein to refer to comminuted wood pulp, which is a form of cellulosic fiber.
A “batt” is used herein to refer to fiber materials prior to being consolidated in a final calendering process as described herein. A “batt” comprises individual fibers, which are usually unbonded to each other, although a certain amount of pre-bonding between fibers may be performed and is also included in the meaning, such as may occur during or shortly after the lay-down of fibers in a spunlaying process, or as may be achieved be a pre-calendering. This pre-bonding, however, still permits a substantial number of the fibers to be freely moveable such that they can be repositioned. A “batt” may comprise several strata, such as may result from depositing fibers from several beams in a spunlaying process.
“Bicomponent” refers to fiber having a cross-section comprising two discrete polymer components, two discrete blends of polymer components, or one discrete polymer component and one discrete blend of polymer components. “Bicomponent fiber” is encompassed within the term “multicomponent fiber.” A Bicomponent fiber may have an overall cross section divided into two or more subsections of the differing components of any shape or arrangement, including, for example, coaxial subsections, core-and-sheath subsections, side-by-side subsections, radial subsections, etc.
“Bond area percentage” on a nonwoven web is a ratio of area occupied by bond impressions, to the total surface area of the web, expressed as a percentage, and measured according to the Bond Area Percentage Method set forth herein.
“Bonding roller,” “calender roller” and “roller” are used interchangeably.
A “bond impression” in a nonwoven web is the surface structure created by the impression of a bonding protrusion on a calender roller into a nonwoven web. A bond impression is a location of deformed, intermeshed or entangled, and melted or thermally fused, materials from fibers superimposed and compressed in a z-direction beneath the bonding protrusion, which form a bond. The individual bonds may be connected in the nonwoven structure by loose fibres between them. The shape and size of the bond impression approximately corresponds to the shape and size of the bonding surface of a bonding protrusion on the calender roller.
A “column” of bonds on a nonwoven web is a group of bonds of like shape and rotational orientation that are arranged in regularly repeating configuration along a line that extends most predominately in the machine direction.
“Cross direction” (CD)—with respect to the making of a nonwoven web material and the nonwoven web material, refers to the direction along the web material substantially perpendicular to the direction of forward travel of the web material through the manufacturing line in which the web material is manufactured. With respect to a batt moving through the nip of a pair of calender rollers to form a bonded nonwoven web, the cross direction is perpendicular to the direction of movement through the nip, and parallel to the nip.
“Disposable” is used in its ordinary sense to mean an article that is disposed or discarded after a limited number of usage events over varying lengths of time, for example, fewer than about 20 events, fewer than about 10 events, fewer than about 5 events, or fewer than about 2 events.
“Diaper” refers to an absorbent article generally worn by infants and incontinent persons about the lower torso so as to encircle the waist and legs of the wearer and that is specifically adapted to receive and contain urinary and fecal waste. As used herein, term “diaper” also includes “pant” which is defined below.
“Fiber” and “filament” are used interchangeably.
“Fiber diameter” reflects the diameter or width of a fiber and is typically expressed in microns (μm). The terms “denier” (“den”) and “decitex” (“dTex”) are units that are alternatively used to characterize the fineness or coarseness of a fiber. 1 denier (or den) equals 1 gram of fiber per 9000 m. 1 decitex (or dTex) equals 1 gram per 10000 m. Denier and decitex relate to the fiber diameter and the mass/volume density of the material(s) of which the fiber is formed.
“Film”—means a skin-like or membrane-like layer of material formed of one or more polymers, which does not have a form consisting predominately of a web-like structure of consolidated polymer fibers and/or other fibers.
“Length” or a form thereof, with respect to a diaper or training pant, refers to a dimension measured along a direction perpendicular to the waist edges and/or parallel to the longitudinal axis.
“Machine direction” (MD)—with respect to the making of a nonwoven web material and the nonwoven web material, refers to the direction along the web material substantially parallel to the direction of forward travel of the web material through the manufacturing line in which the web material is manufactured. With respect to a nonwoven batt moving through the nip of a pair of calender rollers to form a bonded nonwoven web, the machine direction is parallel to the direction of movement through the nip, and perpendicular to the nip.
“Machine direction bias,” with respect to fibers forming a nonwoven, means that the fibers' lengths have machine direction vector components that are greater than their cross direction vector components.
“Machine direction row overlap,” with respect to two adjacent bonding shapes in successive rows, means that a line along the cross direction is tangent to or crosses the perimeters of both shapes. The machine direction row overlap is measured as the distance OD between a first cross direction line 107a tangent to the forward-most edge of the shape in the trailing row, and a second cross direction line 107b tangent to the rearward-most edge of the shape in the leading row; see, e.g.,
“Multicomponent” refers to fiber having a cross-section comprising more than one discrete polymer component, more than one discrete blend of polymer components, or at least one discrete polymer component and at least one discrete blend of polymer components. “Multicomponent fiber” includes, but is not limited to, “bicomponent fiber.” A multicomponent fiber may have an overall cross section divided into subsections of the differing components of any shape or arrangement, including, for example, coaxial subsections, core-and-sheath subsections, side-by-side subsections, radial subsections, islands-in-the-sea, etc.
“Neckdown” refers to the tendency of a web material to exhibit a reduction in cross-direction width when strained in the machine direction, a Poisson effect-like behavior.
A “nonwoven” is a manufactured sheet or web of directionally or randomly oriented fibers which are first formed into a batt and then consolidated and bonded together by friction, cohesion, adhesion or one or more patterns of bonds and bond impressions created through localized compression and/or application of pressure, heat, ultrasonic or heating energy, or a combination thereof. The term does not include fabrics which are woven, knitted, or stitch-bonded with yarns or filaments. The fibers may be of natural or man-made origin and may be staple or continuous filaments or be formed in situ. Commercially available fibers have diameters ranging from less than about 0.001 mm (1 μm) to more than about 0.2 mm (200 μm) and they come in several different forms: short fibers (known as staple, or chopped), continuous single fibers (filaments or monofilaments), untwisted bundles of continuous filaments (tow), and twisted bundles of continuous filaments (yarn). Nonwoven fabrics can be formed by many processes including but not limited to meltblowing, spunbonding, spunmelting, solvent spinning, electrospinning, carding, film fibrillation, melt-film fibrillation, airlaying, dry-laying, wetlaying with staple fibers, and combinations of these processes as known in the art. The basis weight of nonwoven fabrics is usually expressed in grams per square meter (gsm).
“Opacity” is a numeric value relating to the ability of a web material to transmit light therethrough, measured according the Opacity Measurement Method set forth herein.
“Pant” or “training pant”, as used herein, refer to disposable garments having a waist opening and leg openings designed for infant or adult wearers. A pant may be placed in position on the wearer by inserting the wearer's legs into the leg openings and sliding the pant into position about a wearer's lower torso. A pant may be preformed by any suitable technique including, but not limited to, joining together portions of the article using refastenable and/or non-refastenable bonds (e.g., seam, weld, adhesive, cohesive bond, fastener, etc.). A pant may be preformed anywhere along the circumference of the article (e.g., side fastened, front waist fastened). While the terms “pant” or “pants” are used herein, pants are also commonly referred to as “closed diapers,” “prefastened diapers,” “pull-on diapers,” “training pants,” and “diaper-pants”. Suitable pants are disclosed in U.S. Pat. No. 5,246,433, issued to Hasse et al. on Sep. 21, 1993; U.S. Pat. No. 5,569,234, issued to Buell et al. on Oct. 29, 1996; U.S. Pat. No. 6,120,487, issued to Ashton on Sep. 19, 2000; U.S. Pat. No. 6,120,489, issued to Johnson et al. on Sep. 19, 2000; U.S. Pat. No. 4,940,464, issued to Van Gompel et al. on Jul. 10, 1990; U.S. Pat. No. 5,092,861, issued to Nomura et al. on Mar. 3, 1992; U.S. Patent Publication No. 2003/0233082 A1, entitled “Highly Flexible And Low Deformation Fastening Device”, filed on Jun. 13, 2002; U.S. Pat. No. 5,897,545, issued to Kline et al. on Apr. 27, 1999; U.S. Pat. No. 5,957,908, issued to Kline et al. on Sep. 28, 1999.
When used as an adjective in connection with a component of a material, the term “predominately” means that the component makes up greater than 50% by weight of the material. When used as an adjective in connection with a directional orientation of a physical feature or geometric attribute thereof, “predominately” means the feature or attribute has a projection onto a line extending along the direction indicated, greater in length than the projection onto a line perpendicular thereto. Within other contexts, the term “predominantly” refers to a condition which imparts a substantial effect on a property or feature. Thus, when a material comprises “predominantly” a component said to impart a property, this component imparts a property that the material otherwise would not exhibit. For example, if a material comprises “predominantly” heat-fusible fibers, the quantity and components of these fibers must be sufficient to allow heat fusion of the fibers.
A “bonding protrusion” or “protrusion” is a feature of a bonding roller at its radially outermost portion, surrounded by recessed areas. Relative the rotational axis of the bonding roller, a bonding protrusion has a radially outermost bonding surface with a bonding surface shape and a bonding surface shape area, which generally lies along an outer cylindrical surface with a substantially constant radius from the bonding roller rotational axis; however, protrusions having bonding surfaces of discrete and separate shapes are often small enough relative the radius of the bonding roller that the bonding surface may appear flat/planar; and the bonding surface shape area is closely approximated by a planar area of the same shape. A bonding protrusion may have sides that are perpendicular to the bonding surface, although usually the sides have an angled slope, such that the cross section of the base of a bonding protrusion is larger than its bonding surface. A plurality of bonding protrusions may be arranged on a calender roller in a pattern. The plurality of bonding protrusions has a bonding area per unit surface area of the outer cylindrical surface which can be expressed as a percentage, and is the ratio of the combined total of the bonding shape areas of the protrusions within the unit, to the total surface area of the unit.
A “row” of bonds on a nonwoven web is a group of bonds of like shape and rotational orientation that are arranged in regularly repeating configuration along a line that extends most predominately in the cross direction.
“Tensile Strength” refers to the maximum tensile force (Peak Force) a material will sustain before tensile failure, as measured by the Tensile Strength Measurement Method set forth herein.
“Thickness” and “caliper” are used herein interchangeably.
“Total Stiffness” refers to the measured and calculated value relating to a material, according to the Stiffness measurement method set forth herein.
“Volume mass” is the ratio of basis weight and caliper and indicates the bulkiness and fluffiness of the product, which are important properties of the nonwoven web according to the invention. The lower the value, the bulkier is the web.
Volume mass (kg/m3)=basis weight (g/m2)/caliper (mm).
“Width” or a form thereof, with respect to a diaper or training pant, refers to a dimension measured along a direction parallel to the waist edges and/or perpendicular to the longitudinal axis.
“Z-direction,” with respect to a web, means generally orthogonal or perpendicular to the plane approximated by the web along the machine and cross direction dimensions.
Examples of the present invention include disposable absorbent articles having improved softness attributes.
The diaper 10 generally may comprise a chassis 12 and an absorbent core 14 disposed in the chassis. The chassis 12 may comprise the main body of the diaper 10.
The chassis 12 may include a topsheet 18, which may be liquid pervious, and a backsheet 20, which may be liquid impervious. The absorbent core 14 may be encased between the topsheet 18 and the backsheet 20. The chassis 12 may also include side panels 22, elasticized leg cuffs 24, and an elastic waist feature 26. The chassis 12 may also comprise a fastening system, which may include at least one fastening member 46 and at least one landing zone 48. One or more layers of the topsheet and/or backsheet may be formed of a nonwoven web as described below.
The leg cuffs 24 and the elastic waist feature 26 may each typically comprise elastic members 28. One end portion of the diaper 10 may be configured as a first waist region 30 of the diaper 10. An opposite end portion of the diaper 10 may be configured as a second waist region 32 of the diaper 10. An intermediate portion of the diaper 10 may be configured as a crotch region 34, which extends longitudinally between the first and second waist regions 30 and 32. The crotch region 34 may include from 33.3% to 50% of the overall length of the diaper 10, and each of waist regions 30, 32 may correspondingly include from 25% to 33.3% of the overall length of the diaper 10.
The waist regions 30 and 32 may include elastic elements such that they gather about the waist of the wearer to provide improved fit and containment (elastic waist feature 26). The crotch region 34 is that portion of the diaper 10 which, when the diaper 10 is worn, is generally positioned between the wearer's legs.
The diaper 10 may also include such other features including front and rear ear panels, waist cap features, elastics and the like to provide better fit, containment and aesthetic characteristics. Such additional features are described in, e.g., U.S. Pat. Nos. 3,860,003 and 5,151,092.
In order to apply and keep diaper 10 in place about a wearer, the second waist region 32 may be attached by the fastening member 46 to the first waist region 30 to form leg opening(s) and an article waist. When fastened, the fastening system carries a tensile load around the article waist.
According to some examples, the diaper 10 may be provided with a re-closable fastening system or may alternatively be provided in the form of a pant-type diaper. When the absorbent article is a diaper, it may comprise a re-closable fastening system joined to the chassis for securing the diaper to a wearer. When the absorbent article is a pant-type diaper, the article may comprise at least two side panels joined to the chassis and to each other to form a pant. The fastening system and any component thereof may include any material suitable for such a use, including but not limited to plastics, films, foams, nonwoven, woven, paper, laminates, stretch laminates, activated stretch laminates, fiber reinforced plastics and the like, or combinations thereof. In some examples, the materials making up the fastening device may be flexible. In some examples, the fastening device may comprise cotton or cotton-like materials for additional softness or consumer perception of softness. The flexibility may allow the fastening system to conform to the shape of the body and thus, reduce the likelihood that the fastening system will irritate or injure the wearer's skin.
For unitary absorbent articles, the chassis 12 and absorbent core 14 may form the main structure of the diaper 10 with other features added to form the composite diaper structure. While the topsheet 18, the backsheet 20, and the absorbent core 14 may be assembled in a variety of well-known configurations, preferred diaper configurations are described generally in U.S. Pat. No. 5,554,145 entitled “Absorbent Article With Multiple Zone Structural Elastic-Like Film Web Extensible Waist Feature” issued to Roe et al. on Sep. 10, 1996; U.S. Pat. No. 5,569,234 entitled “Disposable Pull-On Pant” issued to Buell et al. on Oct. 29, 1996; and U.S. Pat. No. 6,004,306 entitled “Absorbent Article With Multi-Directional Extensible Side Panels” issued to Robles et al. on Dec. 21, 1999.
The topsheet 18 may be fully or partially elasticized and/or may be foreshortened to create a void space between the topsheet 18 and the absorbent core 14. Exemplary structures including elasticized or foreshortened topsheets are described in more detail in U.S. Pat. No. 5,037,416 entitled “Disposable Absorbent Article Having Elastically Extensible Topsheet” issued to Allen et al. on Aug. 6, 1991; and U.S. Pat. No. 5,269,775 entitled “Trisection Topsheets for Disposable Absorbent Articles and Disposable Absorbent Articles Having Such Trisection Topsheets” issued to Freeland et al. on Dec. 14, 1993.
The backsheet 20 may be joined with the topsheet 18. The backsheet 20 may serve to prevent the exudates absorbed by the absorbent core 14 and contained within the diaper 10 from soiling other external articles that may contact the diaper 10, such as bed sheets and clothing. Referring to
In some examples, the backsheet of the present invention may have a water vapor transmission rate (WVTR) of greater than about 2,000 g/24 h/m2, greater than about 3,000 g/24 h/m2, greater than about 5,000 g/24 h/m2, greater than about 6,000 g/24 h/m2, greater than about 7,000 g/24 h/m2, greater than about 8,000 g/24 h/m2, greater than about 9,000 g/24 h/m2, greater than about 10,000 g/24 h/m2, greater than about 11,000 g/24 h/m2, greater than about 12,000 g/24 h/m2, greater than about 15,000 g/24 h/m2, measured according to WSP 70.5 (08) at 37.8° C. and 60% Relative Humidity.
Suitable nonwoven web materials useful in the present invention include, but are not limited to spunbond, meltblown, spunmelt, solvent-spun, electrospun, carded, film fibrillated, melt-film fibrillated, air-laid, dry-laid, wet-laid staple fibers, and other and other nonwoven web materials formed in part or in whole of polymer fibers, as known in the art. A suitable nonwoven web material may also be an SMS material, comprising a spunbonded, a melt-blown and a further spunbonded stratum or layer or any other combination of spunbonded and melt-blown layers, such as a SMMS or SSMMS etc. Examples include one or more layers of fibers with diameters below 1 micron (nanofibers and nanofiber layers); examples of these rise in combinations of SMS, SMNS, SSMNS or SMNMS nonwoven webs (where “N” designates a nanofiber layer). In some examples, permanently hydrophilic non-wovens, and in particular, nonwovens with durably hydrophilic coatings may be desirable. Typically, the suitable non-woven is air permeable. Typically the suitable nonwoven is water or liquid permeable, but may also be water impermeable by reason of fiber size and density, and hydrophobicity of the fibers. Water or liquid permeability may be enhanced by treatments to render the fibers hydrophilic, as discussed below.
The nonwoven web may be formed predominately of polymeric fibers. In some examples, suitable non-woven fiber materials may include, but are not limited to polymeric materials such as polyolefins, polyesters, polyamide, or specifically polypropylene (PP), polyethylene (PE), poly-lactic acid (PLA), polyethylene terephthalate (PET) and/or blends thereof. Nonwoven fibers may be formed of, or may include as additives or modifiers, components such as aliphatic polyesters, thermoplastic polysaccharides, or other biopolymers (bio-based or renewable polymers).
The individual fibers may be monocomponent or multicomponent. The multicomponent fibers may be bicomponent, such as in a core-and-sheath or side-by-side arrangement. Often, the individual components comprise aliphatic polyolefins such as polypropylene or polyethylene, or their copolymers, aliphatic polyesters, thermoplastic polysaccharides or other biopolymers.
Further useful nonwovens, fiber compositions, formations of fibers and nonwovens and related methods are described in U.S. Pat. No. 6,645,569 to Cramer et al., U.S. Pat. No. 6,863,933 to Cramer et al., U.S. Pat. No. 7,112,621 to Rohrbaugh et al.; co-pending U.S. patent application Ser. Nos. 10/338,603 and 10/338,610 by Cramer et al., and Ser. No. 13/005,237 by Lu et al., the disclosures of which are incorporated by reference herein.
Some polymers used for nonwoven fiber production may be inherently hydrophobic, and for certain applications they may be surface treated or coated with various agents to render them hydrophilic. A surface coating may include a surfactant coating. One such surfactant coating is available from Schill & Silacher GmbH, Boblingen, Germany, under the Tradename Silastol PHP 90.
Another way to produce nonwovens with durably hydrophilic coatings, is via applying a hydrophilic monomer and a radical polymerization initiator onto the nonwoven, and conducting a polymerization activated via UV light resulting in monomer chemically bound to the surface of the nonwoven as described in co-pending U.S. Patent Publication No. 2005/0159720.
Another way to produce hydrophilic nonwovens made predominantly from hydrophobic polymers such as polyolefins is to add hydrophilic additives into the melt prior to extrusion.
Another way to produce nonwovens with durably hydrophilic coatings is to coat the nonwoven with hydrophilic nanoparticles as described in co-pending applications U.S. Pat. No. 7,112,621 to Rohrbaugh et al. and in PCT Application Publication WO 02/064877.
Typically, nanoparticles have a largest dimension of below 750 nm. Nanoparticles with sizes ranging from 2 to 750 nm may be economically produced. An advantage of nanoparticles is that many of them can be easily dispersed in water solution to enable coating application onto the nonwoven, they typically form transparent coatings, and the coatings applied from water solutions are typically sufficiently durable to exposure to water. Nanoparticles can be organic or inorganic, synthetic or natural. Inorganic nanoparticles generally exist as oxides, silicates, and/or carbonates. Typical examples of suitable nanoparticles are layered clay minerals (e.g., LAPONITE from Southern Clay Products, Inc. (USA), and Boehmite alumina (e.g., Disperal P2™ from North American Sasol. Inc.). According to one example, a suitable nanoparticle coated non-woven is that disclosed in the co-pending patent application Ser. No. 10/758,066 entitled “Disposable absorbent article comprising a durable hydrophilic core wrap” by Ponomarenko and Schmidt.
In some cases, the nonwoven web surface can be pre-treated with high energy treatment (corona, plasma) prior to application of nanoparticle coatings. High energy pre-treatment typically temporarily increases the surface energy of a low surface energy surface (such as PP) and thus enables better wetting of a nonwoven by the nanoparticle dispersion in water.
Notably, hydrophilic non-wovens are also useful in other parts of an absorbent article. For example, topsheets and absorbent core layers comprising permanently hydrophilic non-wovens as described above have been found to work well.
A nonwoven also may include other types of surface coating. In one example, the surface coating may include a fiber surface modifying agent that reduces surface friction and enhances tactile lubricity. Preferred fiber surface modifying agents are described in U.S. Pat. Nos. 6,632,385 and 6,803,103; and U.S. Pat. App. Pub. No. 2006/0057921.
According to one example, the nonwoven may comprise a material that provides good recovery when external pressure is applied and removed. Further, according to one example, the nonwoven may comprise a blend of different fibers selected, for example from the types of polymeric fibers described above. In some embodiments, at least a portion of the fibers may exhibit a spiral curl which has a helical shape. According to one example, the fibers may include bicomponent fibers, which are individual fibers each comprising different materials, usually a first and a second polymeric material. It is believed that the use of side-by-side bi-component fibers is beneficial for imparting a spiral curl to the fibers.
In order to enhance softness perceptions of the absorbent article, nonwovens forming the backsheet may be hydroenhanced or hydroengorged. Hydroenhanced/hydroengorged nonwovens are described in U.S. Pat. Nos. 6,632,385 and 6,803,103, and U.S. Pat. App. Pub. No. 2006/0057921, the disclosures of which are incorporated herein by reference.
A nonwoven may also be treated by a “selfing” mechanism. By “selfing” nonwovens, high densities of loops (>150 in 2) may be formed which protrude from the surface of the nonwoven substrate. Since these loops act as small flexible brushes, they create an additional layer of springy loft, which may enhance softness. Nonwovens treated by a selfing mechanism are described in U.S. Pat. App. Pub. No. US 2004/0131820.
Any of the nonwoven types described herein may be used for the topsheet, backsheet outer layer, loops component in a hook-and-loop fastening system of an absorbent article, or any other portion of a manufactured article such as cleansing wipes and other personal hygiene products, dusters and dusting cloths, household cleaning cloths and wipes, laundry bags, dryer bags and sheets comprising a layer formed of nonwoven web.
The absorbent core generally may be disposed between the topsheet 18 and the backsheet 20. It may include one or more layers, such as a first absorbent layer 60 and a second absorbent layer 62.
The absorbent layers 60, 62 may include respective substrates 64, 72, an absorbent particulate polymer material 66, 74 disposed on substrates 64, 72, and a thermoplastic adhesive material 68, 76 disposed on and/or within the absorbent particulate polymer material 66, 74 and at least portions of the substrates 64, 72 as an adhesive for immobilizing the absorbent particulate polymer material 66, 74 on the substrates 64, 65.
The substrate 64 of the first absorbent layer 60 may be referred to as a dusting layer and has a first surface which faces the backsheet 20 and a second surface which faces the absorbent particulate polymer material 66. Likewise, the substrate 72 of the second absorbent layer 62 may be referred to as a core cover and has a first surface facing the topsheet 18 and a second surface facing the absorbent particulate polymer material 74.
The first and second substrates 64 and 72 may be adhered to one another with adhesive about the periphery to form an envelope about the absorbent particulate polymer materials 66 and 74 to hold the absorbent particulate polymer material 66 and 74 within the absorbent core 14.
The substrates 64, 72 may be of one or more nonwoven materials, and may be liquid permeable.
As illustrated in
The foregoing description describes features of an absorbent article, any combination of which can be employed to enhance consumer perceptions of softness of the article. In addition, however, it is believed that manufacturing a nonwoven web, and using it as a component of an absorbent article including, e.g., a topsheet 18 and/or backsheet 20 (see
As previously noted, referring to
The nonwoven 21 may be formed from one or more resins of polyolefins, polyesters, polyamide including but not limited to polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET), poly-lactic acid (PLA), and blends thereof. Resins including polypropylene may be particularly useful because of polypropylene's relatively low cost and surface friction properties of fibers formed from it (i.e., they have a relatively smooth, slippery tactile feel). Resins including polyethylene may also be desirable because of polyethylene's relative softness/pliability and even more smooth/slippery surface friction properties. Relative each other, PP currently has a lower cost and fibers formed from it have a greater tensile strength, while PE currently has a greater cost and fibers formed from it have a lower tensile strength but greater pliability and a more smooth/slippery feel. Accordingly, it may be desirable to form nonwoven web fibers from a blend of PP and PE resins, finding a balance of the best proportions of the polymers to balance their advantages and disadvantages. In some examples, the fibers may be formed of PP/PE blends such as described in U.S. Pat. No. 5,266,392. Nonwoven fibers may be formed of, or may include as additives or modifiers, components such as aliphatic polyesters, thermoplastic polysaccharides, or other biopolymers.
The individual fibers may be monocomponent or multicomponent. The multicomponent fibers may be bicomponent, such as in a core-and-sheath or side-by-side arrangement. Often, the individual components comprise aliphatic polyolefins such as polypropylene or polyethylene, or their copolymers, aliphatic polyesters, thermoplastic polysaccharides or other biopolymers.
A batt may be formed from any of these resins by conventional methods, such as carding, meltblowing, spunlaying, airlaying, wet-laying etc. A preferred execution relates to spunbonding processes, in which the resin(s) are heated and forced under pressure through spinnerets. The spinnerets eject fibers of the polymer(s), which are then directed onto a moving belt; as they strike the moving belt they may be laid down in somewhat random orientations, but often with a machine-direction bias, to form a spunlaid batt. The batt then may be calender-bonded to form the nonwoven web.
Nonwovens formed of any basis weight may be used. However, as noted in the background, relatively higher basis weight, while having relatively greater apparent caliper and loft, also has relatively greater cost. On the other hand, relatively lower basis weight, while having relatively lower cost, adds to the difficulty of providing a backsheet that has and sustains a dramatic visual 3-dimensional appearance following compression in a package, and has suitable mechanical properties. It is believed that the combination of features described herein strikes a good balance between controlling material costs while providing a dramatic visual 3-dimensional appearance and suitable mechanical properties. It is believed that the features of consolidating bond shapes and patterns described herein may be particularly useful in applications of nonwovens of relatively low basis weights in some applications, in that it is believed that such features provide a way to enhance loft while reducing, or at least without adding, basis weight. Accordingly, for such applications, a nonwoven having a basis weight from 6.0 to 50 gsm, more preferably from 8.0 to 35 gsm, even more preferably from 9.0 to 25 gsm, and still more preferably from 10 to 20 gsm may be used. When used as a component of an absorbent article such as a topsheet, a lower basis weight nonwoven may provide strikethrough superior to that of a higher basis weight nonwoven. A lower basis weight nonwoven may be preferable to a higher basis weight one when used, for example, as a component of a zero-strain stretch laminate, because it will be more accommodating of an activation/incremental stretching process. In other applications, such as, for example, use of nonwovens to form products such as disposable clothing articles, wipes or dusters, higher basis weights up to 100 gsm, or even 150 gsm, may be desired. It is believed that the features of bonding protrusions, bonding shapes and bonding patterns described herein may have beneficial effects on loft and/or softness perception, even with nonwovens of such higher basis weights. Optimal basis weight is dictated by the differing needs in each application, and cost concerns.
It is believed that the desired overall visual softness signals of a backsheet laminate may be better achieved when the backsheet laminate is substantially white in color, and has an Opacity of at least 45%, more preferably at least 70%, even more preferably at least 73%, and still more preferably at least 75%, as measured by the Opacity Measurement Method set forth below. Accordingly, it may be desirable to add a white-tinting/opacifying agent also to the polymer(s) forming the polymeric film, and to the polymer(s) supplying the spinnerets used to form the fibers of the nonwoven web.
It may be desirable that a white-tinting/opacifying agent be added to the polymer resin that is spun to make the nonwoven. Adjusting the opacity of the nonwoven web, through addition of an opacifying agent, may be desirable, such that the nonwoven web has an Opacity of at least 10%, more preferably at least 18%, and still more preferably at least 40%.
While a variety of whitening/opacifying agents may suffice, it is believed that titanium dioxide (TiO2) may be particularly effective because of its brightness and relatively high refractive index. It is believed that addition of TiO2 to the polymer(s) from which the fibers are to be formed, in an amount up to 5.0% by weight of the nonwoven, may be effective to achieve the desired results. However, because TiO2 is a relatively hard, abrasive material, inclusion of TiO2 in amounts greater than 5.0% by weight may have deleterious effects, including wear and/or clogging of spinnerets; interruption and weakening of the structure of the fibers and/or calender bonds therebetween; undesirably increasing the surface friction properties of the fibers (resulting in a less smooth tactile feel); and unacceptably rapid wear of downstream processing equipment components. It is believed that the increased opacity provided by whitener helps to produce a visually distinctive, soft appearance of the nonwoven. It also may be desired in some applications that a coloring or tinting agent be added to one or more the polymer resin(s) from which the nonwoven fibers will be spun.
Opacity can also be enhanced by using fiber having cross-sectional shapes other than round and solid (non-hollow) geometries, namely trilobal or multilobal cross-sections, or hollow configurations or combinations thereof. Those non-circular cross-sectional shapes can also provide advantages in terms of loft and compression resilience.
Spunbonding includes the step of calender-bonding the batt of spunlaid fibers, to consolidate them and bond them together to some extent to create the web as a fabric-like structure and enhance mechanical properties e.g., tensile strength, which may be desirable so the material can sufficiently maintain structural integrity and dimensional stability in subsequent manufacturing processes, and in the final product in use. Referring to
One or both of the rollers may have their circumferential surfaces machined, etched, engraved or otherwise formed to have thereon a bonding pattern of bonding protrusions and recessed areas, so that bonding pressure exerted on the batt at the nip is concentrated at the bonding surfaces of the bonding protrusions, and is reduced or substantially eliminated at the recessed areas. The bonding surfaces have bonding surface shapes. As a result, an impressed pattern of bonds between fibers forming the web, having bond impressions and bond shapes corresponding to the pattern and bonding surface shapes of the bonding protrusions on the roller, is formed on the nonwoven web. One roller such as roller 51 may have a smooth, unpatterned cylindrical surface so as to constitute an anvil roller, and the other roller 50 may be formed with a pattern as described, to constitute a bonding pattern roller; this combination of rollers will impart a pattern on the web reflecting the pattern on the bonding pattern roller. In some examples both rollers may be formed with patterns, and in particular examples, differing patterns that work in combination to impress a combination pattern on the web such as described in, for example, U.S. Pat. No. 5,370,764.
A repeating pattern of bonding protrusions and recessed areas such as, for example, depicted in
Referring to
Nonwoven webs of the type contemplated herein may be calender-bonded at line speed greater than 300 m/min., or 600 m/min., or even 800 m/min., or more, depending upon nonwoven web composition, basis weight, bonding pattern, and equipment and process variables selected. Referring again to
It is believed that features of a bonding roller including the bonding protrusions affect these air flows. In the nip, the profiles of bonding protrusions present obstructions to airflow, while the recessed areas between the bonding protrusions present passageways. Thus, it is believed that for certain configurations, shapes, and positions of bonding protrusions, as will be reflected in the bond impressions created in the web, rotational orientation(s) and repeating patterns of the bonding shapes can be selected and formed to have a beneficial effect on these air flows. It is believed, further, that patterns of bonding protrusions having bonding surface shapes with certain features, reflected in the bonding surfaces and the cross sections of the protrusions along planes substantially parallel with the bonding surfaces, rotational orientations relative the plane approximated by the web surface, and spacing, may be employed to channel these air flows in a way that causes them to reposition the fibers during the calender bonding process, such as by teasing or fluffing the fibers, thus providing an enhanced calender-bonded nonwoven web having greater loft/caliper than a similar nonwoven web having other consolidated bond shapes and patterns, all other variables being the same.
Referring to
Still referring to
In one example (not shown), the shape perimeter may have a convex portion, with or without a varying radius, on both sides of shape length line 104, such that it resembles the contour of an airfoil with symmetrical camber, in cross section. In another example (not shown), the shape perimeter may have a convex portion on one side of shape length line 104 and a straight portion on or on the other side of shape length line 104, such that it resembles the contour of an airfoil/aircraft wing with asymmetrical camber, in cross section. In another example, the shape perimeter may have a convex portion 102a and/or 102b on one side of shape length line 104 and a concave portion 103a and/or 103b disposed substantially opposite the concave portion, as reflected in
The extent of the concavity of concave portion 103a and/or 103b may be quantified by measuring the depth thereof, relative the greatest measurable length. The concavity depth Da and/or Db may be measured by identifying a shape concavity line 106a and/or 106b that is parallel with the shape length line 104 and tangent to the deepest point along the concave portion 103a and/or 103b. The concavity depth Da and/or Db is the distance between the shape length line and the shape concavity line 106a and/or 106b. The extent of the concavity of concave portion 103a and/or 103b may be expressed as a ratio of concavity depth Da and/or Db to shape length L (hereinafter, “concavity depth ratio”). Although shapes that do not have a concave portion 103a, 103b are contemplated, it may be desirable that a bonding shape has a concave portion having a concavity depth ratio between 0.00 and 0.30, more preferably between 0.00 and 0.25, and even more preferably between 0.00 and 0.20. Again, the bond shapes and sizes impressed on the nonwoven web will reflect and correspond with the bonding shapes and sizes on the roller.
While the explanation above refers to bonding protrusions and resulting consolidated bond shapes in the web, which have bonding shape/bond shape perimeters following “convex” and/or “concave,” curvature, suggesting smooth curves, it may be appreciated that the effect may be substantially realized by approximating smooth curves with chains of straight line segments. Accordingly, each of the terms “convex” and “concave” herein includes a portion of a shape perimeter formed of a chain of 3 or more straight line segments lying on one side of a shape length line and connected end-to-end, that is each a chord of a smooth convex or concave curve lying on one side of the shape length line, or portion of a curve lying on one side of the shape length line that does not include an inflection point.
Without intending to be bound by theory, it is believed that calender roller bonding protrusions having bonding shapes with one or more features as described above have aerodynamic effects on air flow in and about the nip, that cause acceleration and deceleration of air in and about the interstices of the nonwoven fibers in a way that repositions the fibers, and may effect teasing or fluffing, adding loft and caliper.
Additionally, the rotational orientations of the protrusions affect the orientations of the bonding protrusions at the nip, and it is believed that this has an impact. Bonding shapes 100 and the bonding protrusions supporting them may be arranged along an individual shape tilt angle relative the machine and cross directions. Without intending to be bound by theory, it is believed that the shape tilt angle should not exceed a certain amount for the bonding protrusion to have maximum beneficial effect on air flow. Referring again to
It is believed that air flows having cross-direction vector components flowing across or through the batt/web as it passes through and exits the nip may urge fibers in the cross-direction, helping add loft, caliper and/or cross direction tensile strength. It will be appreciated that the fibers of many nonwoven batts are laid down in the nonwoven web manufacturing process with a general machine direction bias, which tends to result in the finished web having relatively greater machine direction tensile strength, and relatively less cross direction tensile strength. Thus, any process that tends to impart some added cross-direction orientation to the fibers prior to or during bonding may be useful for increasing cross direction tensile strength, bringing about better balance between machine direction tensile strength and cross-direction tensile strength, and adding loft such as by repositioning of the fibers in the z-direction. It is believed that, for best results, it may be even more desirable that shape tilt angle αT is between 5 degrees and 15 degrees, more preferably between 8 degrees and 12 degrees, and even more preferably between 9 degrees and 11 degrees, for the most beneficial effects on airflow at the line speeds contemplated herein. The rotational orientation of the bonding pattern impressed on the nonwoven web will reflect and correspond with the rotational orientation of the bonding pattern on the roller.
As suggested above, in order to gain the benefit of energy from a substantial mass of air under pressure flowing through the nip, it is also believed desirable that a pattern of bonding protrusions not be excessively obstructive of air flow through the nip, nor that it remove too much energy from the air flow by overly slowing, or halting, and absorbing the energy from, forward (machine-direction) momentum of air flows. Referring to
It is also believed that arranging the bonding protrusions in a pattern such that a straight, unobstructed passageway between them exists along recessed areas 101 at the nip, at least partially along the machine direction, may have beneficial effects. Referring again to
The minimum passageway clearance line MC crosses and identifies a “venturi passageway” if the perimeter of each of the adjacent shapes 100a, 100b diverges away from the passageway line PL moving along the perimeter away from the minimum clearance line MC in both directions. It can be seen in
Without intending to be bound by theory, it is believed that such venturi passageways have the effect of causing localized zones of acceleration and deceleration, and increases and decreases in pressure, as well as turbulence, of air as it passes through the nip. It is believed that these effects serve to tease and/or fluff the fibers of the batt and web about the nip.
For purposes of downstream handling and manufacturing processes using the nonwoven web product, it may be desirable to ensure that no line along the machine direction exists along the nonwoven web surface that is indefinitely long without intersecting a bond impression. This condition (indefinitely long machine direction strip of web without bonds) may result in relatively long lengths of unbonded fibers that may be prone to moving away from a cutting knife in downstream machine direction web slitting operations, resulting in a poorly defined or sloppy slit edge. Additionally, such long, unbonded fibers may also separate from a manufactured edge or slit edge of the web (fraying), which may cause other difficulties in downstream operations. To avoid this condition, it may be desirable to impart a pattern tilt angle γP to the bonding pattern. Referring to
It has been discovered, also, that imparting a pattern tilt angle γP to the pattern as described above has the effect at smoothing out variations of bonding pressure between the bonding surfaces and the anvil roller, along the nip (cross direction) as the calender roller and the anvil roller rotate. This effect is analogous to the force- and torque-smoothing effect of parallel axis helical meshing gears as compared with parallel axis spur meshing gears. The benefit for purposes of calender bonding a nonwoven is more evenly distributed bonding pressure, yielding consistency of bonding and consistency of formation of bond shapes impressed into the nonwoven, and even wear and longevity of the calender bonding roller.
Another functional feature of the pattern examples depicted in
The features described above apply to the shapes of bonding surfaces of bonding protrusions in a pattern on a bonding roller, and it will be understood that these features are impressed by the roller into the nonwoven batt to form bond impressions having bond shapes and bonds thereat, to form the calender-bonded nonwoven web. As impressed into a nonwoven web, the bonding shapes are reflected as bond shapes, and are identifiable, and measurable in the web, in laminates that include such nonwoven web as a composite layer, and in composite products made from such nonwoven web and/or such laminates.
An additional aspect that it believed important is bonding area of a roller, reflected in bond area on the web. Imagining a pattern of bonding surfaces having shapes reflected in, for example,
The bonding area reflects the combination of bonding protrusion density (number of bonding protrusions per unit surface area) and average surface area of the bonding shapes 100 in the unit surface area. Thus, increasing the number of bonding protrusions and/or increasing the surface area of the individual bond shapes 100 increases the bonding area, and vice versa. It is believed that bonding area has an impact on the entrainment of air as well as the proportion of entrained air carried toward the nip, which will pass through the nip. If bonding area is relatively greater, this means that more and/or larger bonding protrusions are present at the nip point at any time to obstruct air flow through the nip; conversely, if bonding area is relatively less, this means that fewer and/or smaller bonding protrusions are present at the nip point at any time to obstruct air flow through the nip. Bond area has another effect as well. Increasing bond area increases the number and proportion of the fibers in the nonwoven web that are bonded together, and vice versa. Within a certain range of bond area, tensile strength of the nonwoven web in the machine and/or cross directions may be increased by increasing the bond area. However, bending stiffness of the nonwoven web may be correspondingly increased, and loft decreased—compromising the soft feel and/or appearance of the nonwoven. In order to best realize the benefits of air flow, air compression and channeling believed to be occurring through use of the bond shapes described herein, enhancing loft, while still imparting satisfactory tensile properties to the web, it is believed that bonding area should be in the range of 8.0% and 20%, more preferably between 10% and 18%, and even more preferably between about 12% and 16%. At the line speeds contemplated herein, and relative to the bonding area, the average surface area per bonding shape affects bonding area and bonding protrusion density. It is believed desirable that the average bonding shape 100 surface area be in the range of from 2.5 mm2 to 8.0 mm2, more preferably from 3.0 mm2 to 6.0 mm2, and even more preferably from 3.5 mm2 to 5.5 mm2. Correspondingly, it is believed desirable that the density of the bonding protrusions, and correspondingly, the impressed bond shapes (bond number density), be from 1.5 bonding protrusions/cm2 to 6.0 bonding protrusions/cm2, more preferably from 2.0 bonding protrusions/cm2 to 5.0 bonding protrusions/cm2, and even more preferably from 2.5 bonding protrusions/cm2 to 4.0 bonding protrusions/cm2.
In one particular non-limiting example, the bonding pattern on a calender roller may have the appearance of
bonding area approximately 13.9%
bonding protrusion height BPH approximately 1 mm
shape aspect ratio approximately 2.5
shape tilt angle αT approximately 10 degrees
nip airflow restriction ratio approximately 0.19
cross-nip airflow angle βA approximately 85.7 degrees
pattern tilt angle γP approximately 4.3 degrees
machine direction overlap approximately 19 percent
Experiments with a calender bonding roller having an engraved pattern with the features described immediately above showed that it imparted improved (reduced) neckdown and improved tensile strength with substantially the same loft/caliper, to two spunlaid nonwoven webs with basis weights of 13 gsm and 25 gsm, as compared with a calendar bonding roller engraved with a pattern as depicted
It is also believed that the speed of travel of the batt toward the bonding nip (batt line speed) is important. It will be appreciated that, if the batt line speed is too slow, air mass entrained by the batt as it approaches the nip will not have sufficient momentum to maintain a large enough zone of sufficiently elevated air pressure at the entry side effective to ensure that substantial air mass is urged through the nip, rather than being merely urged around the nip and the rollers along alternate pathways. Accordingly, it is believed that line speed at which the batt is conveyed toward the nip should be equal to or greater than 300 meters/minute, more preferably, equal to or greater than 600 meters/minute, and even more preferably, equal to or greater than 800 meters/minute.
It is believed that use of a calender roller having bonding patterns and bonding shapes as described herein take advantage of air flows resulting from entrainment of air along a moving nonwoven batt and calender rollers, and air compression, that occur during calender-bonding, in a way that causes the resulting nonwoven web to have enhanced loft and a soft feel. It is believed also that the bonding shapes need not be all of like kind or rotational orientation, but rather, that suitable combinations of differing shapes including bonding shapes having features as described herein, and optionally, in combination with other shapes, may be used and included. Employment of the described features may reduce or eliminate a need for other loft enhancement processes, such as hydroengorgement or hydroentanglement—which may save costs of additional equipment and operation.
Basis Weight
The “basis weight” of a nonwoven web is measured according to the European standard test EN ISO 9073-1:1989 (conforms to WSP 130.1). There are 10 nonwoven web layers used for measurement, sample size 10×10 cm2.
Thickness
The “thickness” of a nonwoven web is measured according to the European standard test EN ISO 9073-2:1996 (conforms to WSP 120.6) with following modification: the overall weight of upper arm of the machine including added weight is 130 g.
MD/CD Ratio
The “MD/CD ratio” is the ratio of material's tensile strength at peak in the MD and CD direction. Both were measured according to the EDANA standard method WSP 110.4-2005, where sample width is 50 mm, jaw distance is 100 mm, speed 100 mm/min and preload 0.1N. MD/CD ratio=tensile strength at peak in MD[N/5 cm]/tensile strength at peak in CD[N/5 cm]
Softness
The “softness” of a nonwoven web may be measured using to the “Handle-O-Meter” test. The test used herein is the INDA IST 90.3-01. The lower the value, the softer is the web.
Volume Mass
The “volume mass” is the ratio of basis weight and thickness and indicates the bulkiness and fluffiness of the product, which are important qualities of the nonwoven web according to the invention. The lower the value, the bulkier is the web.
Volume mass [kg/m3]=basis weight [g/m2]/thickness [mm].
Hydrophilic Properties
The “hydrophilic properties” of a nonwoven web may be measured using the “Strike Through Time” test. The test used herein is the EDANA standard test WSP 70.3-2005 The lower the value, the more hydrophilic is the web.
Opacity
The opacity of a material is the degree to which light is blocked by that material. A higher opacity value indicates a higher degree of light block by the material. Opacity may be measured using a 0° illumination/45° detection, circumferential optical geometry, spectrophotometer with a computer interface such as the HunterLab LabScan XE running Universal Software (available from Hunter Associates Laboratory Inc., Reston, Va.). Instrument calibration and measurements are made using the standard white and black calibration plates provided by the vendor. All testing is performed in a room maintained at about 23±2° C. and about 50±2% relative humidity.
Configure the spectrophotometer for the XYZ color scale, D65 illuminant, 10° standard observer, with UV filter set to nominal. Standardize the instrument according to the manufacturer's procedures using the 1.20 inch port size and 1.00 inch area view. After calibration, set the software to the Y opacity procedure.
To obtain the specimen, lay the sample flat on a bench, body facing surface downward, and measure the total longitudinal length of the article. Note a site 33% of the total length from the front waist of the article along the longitudinal axis and a second site, 33% of the total length from the back waist of the article. Carefully remove the backsheet laminate, consisting of both the film and nonwoven web, from the garment-facing side of the article. A cryogenic spray, such as Cyto-Freeze (obtained from Control Company, Houston, Tex.), may be used to separate the backsheet laminate from the article. Cut a piece 50.8 mm by 50.8 mm centered at each site identified above. Precondition samples at about 23° C.±2 C.° and about 50%±2% relative humidity for 2 hours prior to testing.
Place the specimen over the measurement port. The specimen should completely cover the port with the surface corresponding to the garment-facing surface of the article directed toward the port. Cover the specimen with the white standard plate. Take a reading, then remove the white tile and replace it with black standard tile without moving the specimen. Obtain a second reading, and calculate the opacity as follows:
Opacity=Y value(black backing)/Y value(white backing)×100
A total of five identical articles are analyzed and their opacity results recorded. Calculate and report the average opacity and standard deviation for the 10 backsheet laminate measurements to the nearest 0.01%.
Using the same specimens as above, remove the nonwoven web from the film layer for analysis. The cryogenic spray can once again be employed. Precondition samples at about 23° C.±2 C.° and about 50%±2% relative humidity for 2 hours prior to testing. In like fashion, analyze the nonwoven web layer following the above procedure. Calculate and report the average opacity and standard deviation for the 10 nonwoven web measurements to the nearest 0.01%.
Bond Shape Measurement Methods
Area, distance and angle measurements are performed on images generated using a flat bed scanner capable of scanning at a resolution of at least 4800 dpi in reflectance mode (a suitable scanner is the Epson Perfection V750 Pro, Epson, USA). Measurements are performed using ImageJ software (Version 1.43u, National Institutes of Health, USA) and calibrated against a ruler certified by NIST.
Samples of the subject nonwoven web that are 80 mm by 80 mm are used. Precondition the samples at about 23° C.±2 C.° and about 50%±2% relative humidity for 2 hours prior to testing. Identify the machine direction of the nonwoven web and draw a fine line on each sample along the machine direction to enable scanned images to be aligned.
Place the sample to be measured on the flat bed scanner, with the surface bearing the bond impressions or bond shapes facing downward, with the ruler directly adjacent. Placement is such that the dimension corresponding to the machine direction of the nonwoven is parallel to the ruler. A black backing is placed over the specimen and the lid to the scanner is closed. Acquire an image composed of the nonwoven and ruler at 4800 dpi in reflectance mode in 8 bit grayscale and save the file. Open the image file in ImageJ and perform a linear calibration using the imaged ruler.
Unless otherwise stated, dimensional and area measurements are made in triplicate, of three similar bond shapes on each sample for 6 similar samples. The 18 values are averaged and reported.
Not intending to be bound by the specific examples,
Greatest Measurable Length (L)
The bond shape has a perimeter and a greatest measurable length. Identify a shape length line (e.g. line 104) which intersects the two farthest-most points along the perimeter. Draw a shape length line through these points. With the measuring tool, measure the length along the line segment between these points to the nearest 0.001 mm. For example, the greatest measurable lengths in
Greatest Measurable Width (W)
Relative the greatest measurable length, the bond shape has a greatest measurable width measured along a direction perpendicular to the shape length line. Draw two lines, parallel to the shape length line, and tangent to the bond shape perimeter at one or more outermost points that are most distant from the shape length line. These are the shape width lines. With the measuring tool, measure the greatest measurable width between the shape width lines along a line segment perpendicular to the shape length line to the nearest 0.001 mm. For example, the greatest measurable widths in
Minimum Passageway Clearance
Any two adjacent bond shapes have minimum passageway clearance, defined as the smallest measurable distance therebetween. Identify the two parallel lines, one tangent to the perimeter of the first shape where it appears closest to the second shape, and one tangent to the perimeter of the second shape where it appears closest to the first shape, that lie closer together than any other such parallel lines that can be identified. The minimum passageway clearance is the distance between the identified parallel lines, measured along a line perpendicular to them.
Camber Height (CH)
If the bond shape has a perimeter with a convex portion, the convex portion has a maximum distance from the shape length line, referred to herein as the camber height. Draw a line that is tangent to the convex portion, and parallel to the shape length line. With the measuring tool, measure the distance between width between this tangent line and the shape length line along a direction perpendicular to the shape length line, to the nearest 0.001 mm. For example, the camber heights of the convex portions in
Concavity Depth (D)
If the bond shape has a perimeter with a concave portion, the concave portion has a maximum distance from the facing shape width line. Draw a line that is tangent to the deepest point along the concave portion of the profile, and parallel to the shape length line. This is the shape concavity line. With the measuring tool, measure the distance between shape concavity line and the shape length line along a direction perpendicular to the shape length line to the nearest 0.001 mm. For example, the concavity depths of the concave portions in
Shape Tilt Angle (UT
The bond shape is rotationally oriented relative the machine direction by shape tilt angle αT. Draw a line in the cross direction, intersecting the shape length line. Draw a line in the machine direction perpendicular to the cross direction line, intersecting both the cross direction line and the shape length line. Using the angle measuring tool, measure the smaller angle between the machine direction line and the shape length line to the nearest 0.1 degree. For example, the angle between lines 108 and 104 in
Pattern Tilt Angle (γP)
The bond shapes may form a pattern that is tilted from the machine direction by the angle γP. Identify a repeating series of bond shapes in a column. Draw a column line that is tangent on one side at the same position on two similar shapes having similar rotational orientations in the column. Draw a line in the machine direction that intersects this column line at an angle, if such a line exists. With the angle measuring tool, measure the smaller angle between the column line and the machine direction line to the nearest 0.1 degree.
Airflow Restriction Ratio
The bond shapes form a pattern that identifies a maximum airflow restriction by the corresponding bonding roller at the nip. Identify a repeating series of bond shapes lying in a row. Draw a line in the cross direction which intersects these bond shapes at the position relative the machine direction where the shapes occupy the greatest proportion of the distance along the cross direction line. It will be appreciated that it may be necessary to take measurements along several cross direction lines to empirically and/or iteratively identify the one along which the bond shapes occupy the greatest proportion of the distance. With the measuring tool, measure the length from the start of the repeating series to the corresponding location at the end of the repeating series (including distances between bonding shapes) to the nearest 0.001 mm. This is the repeat length in the cross direction. With the measuring tool, measure each of the lengths of the line segments on the cross direction line that lie over the bond shapes, to the nearest 0.001 mm. Add the lengths of all of these line segments within the repeat length, and divide the total by the repeat length. Report to the nearest 0.001. This is the airflow restriction ratio. For example, in
Cross-Nip Airflow Angle (βA)
The bond pattern may provide an airflow path that has a machine direction vector component. Draw a line in the cross direction. Identify a line that can be drawn that extends past at least eight rows of bond shapes without intersecting a bond shape, if such a line exists. This is the cross-nip airflow line. Extend this line to intersect the cross direction line. Using the angle measurement tool, measure the smaller angle between the cross direction line and the airflow line and report to the nearest 0.1 degree. For example, lines 109 in
Bond Area Percentage Identify a single repeat pattern of bond shapes and areas between them and enlarge the image such that the repeat pattern fills the field of view. In ImageJ, draw a rectangle that circumscribes the repeat pattern. Calculate area of the rectangle and record to the nearest 0.001 mm2. Next, with the area tool, trace the individual bond shapes or portions thereof that are entirely within the repeat pattern/rectangle and calculate and add the areas of all bond shapes or portions thereof that are within the repeat pattern/rectangle. Record to the nearest 0.001 mm2. Calculate as follows:
Bond Area %=(Sum of areas of bond shapes within repeat pattern)/(total area of repeat pattern)×100%
Repeat for a total of three non-adjacent regions randomly selected across the sample. Record as Percent Bond Area to the nearest 0.01%. Calculate the average and standard deviation of all 18 of the bond area percentage measurements and report to the nearest 0.01%.
Average Individual Bond Area
Enlarge the image of a region of the sample such that edges of a bond shape can be identified. With the area tool, manually trace the perimeter of a bond. Calculate and record the area to the nearest 0.001 mm2. Repeat for a total of five non-adjacent bonds randomly selected across the total sample. Measurements are made on each sample. A total of six samples are measured. Calculate the average and standard deviation of all 30 bond area measurements and report to the nearest 0.001 mm2.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
