US20060003656A1

US20060003656A1 - Efficient necked bonded laminates and methods of making same

Info

Publication number: US20060003656A1
Application number: US10/881,064
Authority: US
Inventors: Michael Morman
Original assignee: Kimberly Clark Worldwide Inc
Current assignee: Kimberly Clark Worldwide Inc
Priority date: 2004-06-30
Filing date: 2004-06-30
Publication date: 2006-01-05
Also published as: BRPI0507908A; WO2006007200A3; MXPA06014870A; WO2006007200A2; KR20070028460A

Abstract

The present invention provides an elastic necked-bonded laminate material or elastic neck stretched bonded laminate material including at least one necked material joined to at least one elastic sheet that has been stretched in the cross-machine direction and allowed to relax prior to joining with the necked material. The elastic sheet can be stretched prior to being joined with the necked material or following the joining to the necked material. Also disclosed is a method of producing a elastic necked-bonded laminate material including the step of stretching the elastic sheet in a macroscopic stretching apparatus, such as between the nip of a series of spaced apart discs on two axles.

Description

FIELD OF INVENTION

The present invention relates to methods of making elastic clothlike laminates, including laminates made from necked materials and elastic layers. In particular, the present invention relates to methods of making necked bonded laminates which can then be used at least as personal care product construction materials, such as bodyside facing liner material (or topsheets), outercovers, waist elastic materials, side panel materials and ear materials. The present invention also relates to apparatus that can be used in such methods, as well as other methods of manufacture.

BACKGROUND OF THE INVENTION

Polymeric films and nonwoven webs may be manufactured into personal care products and components of products so inexpensively that the products could be viewed as disposable after only one or a few uses. Such nonwoven webs may include bonded carded webs and webs formed by nonwoven extrusion processes such as meltblowing processes and spunbonding processes. Representatives of such products include articles such as diapers, adult incontinence devices, swimwear, feminine care products, and training pants. Other such personal care disposable products include tissues, wipes, mattress pads, veterinary products, mortuary products, article covers and medical related protective products such as garments worn in a medical setting, face masks, sterilization wraps and hospital packaging materials.
Some of the challenges associated with products in these groupings include the provision of an elastic material which is resilient and flexible while still having a pleasing feel. One specific problem is the provision of an elastic material which does not feel plastic or rubbery, a characteristic common to most elastic polymer materials.
It is generally known that the tactile properties of the elastic materials can be improved by forming a laminate of the elastic material with one or more nonelastic materials on the outer surface(s) of the elastic material. For instance, in one such laminate material, a nonelastic material is joined to an elastic material while the elastic material is in a stretched condition so that when the elastic material is relaxed, the nonelastic material gathers between the locations where it is bonded to the elastic material. The resulting elastic laminate material is stretchable to the extent that the nonelastic material gathered between the bond locations allows the elastic material to elongate. In the stretch bonded laminate process, a just -formed (or pre-formed) elastic material is stretched and then attached to the gatherable material. The elastic is then allowed to retract gathering the gatherable material and forming the stretch bonded laminate. Elastic materials just formed from the melt inherently have elastic performance on a “first time stretch” that is not as good (having higher immediate set) as opposed to subsequent stretches. The “first time stretch” is accomplished while forming the stretch bonded laminate material so the elastic performance of the finished stretch bonded laminate is high. For the purposes of this application, the term “first time stretch” refers to the first stretch of an elastic layer following formation. It could occur either during a manufacturing process, or alternatively by a consumer in using a product. For example, in the case of personal care products, a “first time stretch” may occur when a consumer opens a personal care garment to insert a user's legs or waist (such as in a diaper) and/or stretches a garment to secure it about their person. An example of this type of stretch bonded laminate material is disclosed, for example, by U.S. Pat. No. 4,720,415 to Vander Wielen et al., and U.S. Pat. No. 5,385,775 to Wright and Publication No. WO 01/88245, each of which are hereby incorporated by reference in its entirety. While stretch bonded laminate materials are effective in providing high levels of stretch and recovery, it is often not necessary to utilize such high performance elastic materials throughout an entire personal care product. It has been found that stretch bonded laminate materials tend to be fairly costly to manufacture and their inclusion in a product necessarily increases the cost of the end product to the consumer. It would therefore be desirable to provide efficient elastic materials, at a lower cost.
It is also known to laminate (or bond) a necked (neckable) material to an elastic sheet to produce a neck bonded laminate. This process involves an elastic member being bonded to a non-elastic member while only the non-elastic member is extended in one direction (usually the MD) and necked in the transverse direction so as to reduce its dimension in the direction orthogonal to the extension. Such is described in detail in U.S. Pat. Nos. 4,965,122, 4,981,747, 5,226,992, and 5,336,545 to Morman, each of which is incorporated by reference herein in its entirety. While such neck bonded laminates may be less costly to produce than stretch bonded laminates, the production of such laminates is often not efficient. In particular, it has been found that the use of the non-elastic nonwoven materials on such elastic sheets drags on the elastic sheets. Further, the bonding of the non-elastic members (sheet(s)) to the elastic member (sheet(s)) is accomplished using a process which does not take total advantage of the elastic sheet properties. In forming a necked bonded laminate, the “first time stretch” of the elastomeric layer doesn't occur, so essentially the “first time stretch”, which is done by the consumer, may not have the desired elastic properties unless very expensive elastomers are used.
It would be desirable to utilize a less costly material such as a necked and bonded laminate that took greater advantage of the elastic sheet material properties in the laminate. It would therefore also be desirable to alter the neck bonded laminate manufacturing process in order to more efficiently produce a higher performance neck bonded laminate when used in an end product. The term higher performance necked bonded laminate shall mean a performance of the neck bonded laminate in a product that offers lower permanent set upon stretching and lower force to extend upon usage of a product by a consumer, as compared to current similarly formulated neck bonded laminate materials in personal care products.
It is also known to utilize intermeshing grooved rolls or discs on axle apparatus for stretching nonwoven webs. For instance, it is known to use grooved rolls generally to stretch a formed elastic and non-elastic neck bonded laminate. See for example U.S. Publication 20040121687. However, such grooved roll stretching apparatus have posed problems from a manufacturing perspective, as they often lead to equipment failure if the rolls are not properly aligned, or alternatively to material failure if the roll speed and alignment are not controlled. Such grooved rolls, if not properly aligned (groove/peak and speed alignment) can be unduly harsh on nonwoven materials. Also, to date, such apparatus have not been used to benefit the elastic performance of elastic sheets themselves, (making only such elastic sheets more efficient without impacting the nonelastic sheet material) early in a manufacturing processes. There is therefore a need for more efficient elastic low cost laminates for use in personal care products and methods for making such laminates. It is to such needs that the current invention is directed.

Definitions

The term “elastic” is used herein to mean any material which, upon application of a biasing force, is stretchable, that is, elongatable, to a stretched, biased length which is at least about 150 percent of its relaxed unbiased length, and which will recover at least 50 percent of its elongation upon release of the stretching, elongating force. A hypothetical example would be a one (1) inch sample of a material which is elongatable to at least 1.50 inches and which, upon being elongated to 1.50 inches and released, will recover to a length of not more than 1.25 inches. Many elastic materials may be stretched by much more than 50 percent of their relaxed length, for example, 80 percent or more, and many of these will recover to substantially their original relaxed length, for example, to within 105 percent of their original relaxed length, upon release of the stretching force.
As used herein, the term “nonelastic” refers to any material which does not fall within the definition of “elastic,” above.
As used herein, the term “recover” refers to a contraction (or retraction) of a stretched material upon termination of a biasing force following stretching of the material by application of the biasing force. For example, if a material having a relaxed, unbiased length of one (1) inch is elongated 50 percent by stretching to a length of one and one half (1.5) inches the material would be elongated 50 percent (0.5 inch) and would have a stretched length that is 150 percent of its relaxed length. If this exemplary stretched material contracted, that is recovered to a length of one and one tenth (1.1) inches after release of the biasing and stretching force, the material would have recovered 80 percent (0.4 inch) of its one-half (0.5) inch elongation. Recovery may be expressed as [(maximum stretch length-final sample length)/(maximum stretch length-initial sample length)] times 100.
As used herein, the term “nonwoven web” means a web that has a structure of individual fibers or threads which are interlaid, but not in an identifiable, repeating manner. Nonwoven webs have been, in the past, formed by a variety of processes such as, for example, meltblowing processes, spunbonding processes and bonded carded web processes. Laminates containing such web materials may be formed and are considered a nonwoven material laminate.
As used herein, the term “microfibers” means small diameter fibers having an average diameter not greater than about 100 microns, for example, having a diameter of from about 0.5 microns to about 50 microns, more particularly, microfibers may have an average diameter of from about 4 microns to about 40 microns.
As used herein, the term “meltblown fibers” means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into a high velocity gas (e.g. air) stream which attenuates the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin, the disclosure of which is hereby incorporated by reference.
As used herein, the terms “spunbonded fibers” and “spunbond fibers” shall be used interchangeably and shall refer to small diameter fibers which are formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries of a spinnerette with the diameter of the extruded filaments then being rapidly reduced as by, for example, eductive drawing or other well-known spunbonding mechanisms. The production of spunbonded nonwoven webs is illustrated in patents such as, for example, in U.S. Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,542,615 to Dobo et al. The disclosures of these patents are hereby incorporated by reference.
As used herein, the term “bonded carded webs” refers to webs that are made from staple fibers which are usually purchased in bales. The bales are placed in a fiberizing unit/picker which separates the fibers. Next, the fibers are sent through a combining or carding unit which further breaks apart and aligns the staple fibers in the machine direction so as to form a machine direction-oriented fibrous nonwoven web. Once the web has been formed, it is then bonded by one or more of several bonding methods. One bonding method is powder bonding wherein a powdered adhesive is distributed throughout the web and then activated, usually by heating the web and adhesive with hot air. Another bonding method is pattern bonding wherein heated calender rolls or ultrasonic bonding equipment is used to bond the fibers together, usually in a localized bond pattern through the web and/or alternatively the web may be bonded across its entire surface if so desired. When using bicomponent staple fibers, through-air bonding equipment is, for many applications, especially advantageous.
As used herein, the term “conjugate fibers” refers to fibers which have been formed from at least two polymers extruded from separate extruders but spun together to form one fiber. Conjugate fibers are also sometimes referred to as multicomponent or bicomponent fibers. The polymers are usually different from each other though conjugate fibers may be monocomponent fibers. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the conjugate fibers and extend continuously along the length of the conjugate fibers. The configuration of such conjugate fiber may be, for example, a sheath/core arrangement wherein one polymer is surrounded by another or may be a side by side arrangement, a pie arrangement or an “islands-in-the-sea” arrangement. Conjugate fibers are taught in U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 4,795,668 to Krueger et al., and U.S. Pat. No. 5,336,552 to Strack et al. Conjugate fibers are also taught in U.S. Pat. No. 5,382,400 to Pike et al., and may be used to produce crimp in the fibers by using the differential rates of expansion and contraction of the two or more polymers. For two component fibers, the polymers may be present in varying desired ratios. The fibers may also have shapes such as those described in U.S. Pat. No. 5,277,976 to Hogle et al., U.S. Pat. No. 5,466,410 to Hills and U.S. Pat. Nos. 5,069,970 and 5,057,368 to Largman et al., which describe fibers with unconventional shapes.
As used herein, the term “sheet” means a layer which may either be a film or a nonwoven web.
As used herein, the term “necked material” refers to any material which has been narrowed in at least one dimension by application of a tensioning force in another direction (dimension).
As used herein, the term “neckable material” means any material which can be necked.
As used herein, the term “percent neckdown” refers to the ratio determined by measuring the difference between the un-necked dimension and the necked dimension of the neckable material and then dividing that difference by the un-necked dimension of the neckable material multiplied by a 100.
As used herein, the terms “elastic necked-bonded material” or “neck-bonded laminate” shall be used interchangeably and refer to a material having an elastic sheet joined to a necked material at least at two places. The elastic sheet may be joined to the necked material at intermittent points or may be completely bonded thereto. The joining is accomplished while the elastic sheet and the necked material are in juxtaposed configuration. The elastic necked-bonded material is elastic in a direction generally parallel to the direction of neckdown of the necked material and may be stretched in that direction to the breaking point of the necked material. An elastic necked-bonded material may include more than two layers. For example, the elastic sheet may have necked material joined to both of its sides so that a three-layer composite or laminate elastic necked-bonded material is formed having a structure of necked material/elastic sheet/necked material. Additional elastic sheets and/or necked material layers may be added. Yet other combinations of elastic sheets and necked materials may be used.
As used herein, the term “polymer” generally includes, but is not limited to, homopolymers, copolymers, such as, for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic and random symmetries.
“Neck bonding” refers to the process wherein an elastic member is bonded to a non-elastic member (facing) while only the non-elastic member (facing) is extended or necked so as to reduce its dimension in the direction orthogonal to the extension. Such materials generally have cross-machine direction stretch.
“Stretch bonding” refers to a process wherein an elastic member is bonded to another member while only the elastic member is extended, such as by at least about 25 percent of its relaxed length. “Stretch bonded laminate” refers to a composite elastic material made according to a stretch bonding process, i.e., the layers are joined together when only the elastic layer is in an extended condition so that upon relaxing the layers, the nonelastic layer is gathered. Such laminates usually have machine directional stretch properties and may be subsequently stretched to the extent that the nonelastic material gathered between the bond locations allows the elastic material to elongate.
“Neck-stretch bonding” generally refers to a process wherein an elastic member is bonded to another member while the elastic member is extended, such as by at least about 25 percent of its relaxed length and the other layer is a necked, non-elastic layer. “Neck-stretch bonded laminate” refers to a composite elastic material made according to the neck-stretch bonding process, i.e., the layers are joined together when both layers are in an extended condition and then allowed to relax. Such laminates usually have multi or omni-directional stretch properties. Neck stretch bonded laminates are described in U.S. Pat. Nos. 5,116,662 and 5,114,781 each incorporated by reference hereto in its entirety.
As used herein, the terms “machine direction” or MD means the direction along the length of a fabric or film in the direction in which it is produced. The terms “cross machine direction,” “cross directional,” or CD mean the direction across the width of fabric or film, i.e. a direction generally perpendicular to the MD.
The basis weight of nonwoven fabrics or films is usually expressed in ounces of material per square yard (osy) or grams per square meter (g/m²or gsm) and the fiber diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91). Film thicknesses may also be expressed in microns or mil.
As used herein the term “set” refers to retained elongation in a material sample following the elongation and recovery, i.e. after the material has been stretched and allowed to relax.
As used herein the term “percent set” (Tension Set) is the measure of the amount of the material stretched from its original length after being cycled. The remaining strain after the removal of the applied stress is measured as the percent set. The percent set can be described as where the retraction curve of a cycle crosses the elongation axis, and as further discussed below and is represented by the following formula: $\frac{Final length - Initial length}{Stretched length - Initial length} \times 100$
The “hysteresis” is determined by first elongating a sample to a given elongation (such as 50 or 100 percent) and determining the energy required to elongate the sample to the given elongation, and then allowing the sample to retract back to its original length and determining the energy recovered during retraction. The hysteresis value determining numbers would then be read for instance at the 50 percent and 100 percent elongation, in either the machine or the cross-machine directions. $Hysteresis = \frac{Energy Extension - Energy Retraction}{Energy Extension} \times 100$
A “pre-stretch” shall refer to a stretch of the elastic layer which occurs prior to the first stretch of the material by a consumer.
As used herein and in the claims, the term “comprising” is inclusive or open-ended and does not exclude additional unrecited elements, compositional components, or method steps. Accordingly, such terms are intended to be synonymous with the words “has”, “have”, “having”, “includes”, “including”, and any derivatives of these words.

SUMMARY OF THE INVENTION

A method for producing an elastic necked-bonded laminate material includes the steps of providing at least one neckable nonelastic material; applying a tensioning force to the neckable nonelastic material to neck the material; providing an elastic sheet; superposing the necked nonelastic material onto the elastic sheet; joining the necked nonelastic material and the elastic sheet at least at two places to form a laminate material; and stretching the elastic sheet in the cross-machine direction through the use of a macroscopic stretching apparatus.
In an alternative embodiment of the method, the stretching of the elastic sheet is performed prior to joining with the nonelastic material. In another alternative embodiment of the method, the stretching of the elastic sheet is performed following joining of the elastic sheet with the nonelastic material. In still another alternative embodiment of the method, the macroscopic stretching apparatus is a macroscopic grooved roll arrangement. In still another alternative embodiment of the method, the macroscopic stretching apparatus is a disc on axle arrangement.
In yet another alternative embodiment, a method of producing an elastic necked-bonded laminate material includes the steps of providing at least one neckable nonelastic material; applying a tensioning force to the neckable nonelastic material to neck the material; providing an elastic sheet; superposing the necked nonelastic material onto the elastic sheet; and joining the necked nonelastic material and the elastic sheet at least at two places to form a laminate material; and stretching the elastic sheet in the cross-machine direction with the use of macroscopic discs along axles. In an alternative embodiment of this method, the stretching of the elastic sheet is performed prior to joining to the nonelastic material. In a further alternative embodiment of this method, the stretching of the elastic sheet is performed following joining to the nonelastic material. In still a further alternative embodiment of this method, the elastic sheet is selected from the group consisting of an elastic film, an elastic nonwoven web, an elastic woven web, an elastic scrim or netting, and an elastic foam. In still a further alternative embodiment of this method, the neckable material is a material selected from the group consisting of knitted fabrics, loosely woven fabrics, and nonwoven webs.
In still a further alternative embodiment of this method, the neckable material is selected from the group consisting of a bonded carded web of fibers, a web of spunbonded fibers, a web of meltblown fibers, and a multilayer material including at least one of the webs.
In still a further alternative embodiment of this method, the stretching step is accomplished by passing the elastic sheet through a nip of intermeshing discs along axles positioned in the cross-machine direction. In yet a further alternative embodiment of this method, the discs along each axle of the nip are of the same diameter. In yet still a further alternative embodiment of this method, the discs on each axle are of the same diameter and the diameters of discs between axles is varied. In yet still a further alternative embodiment of this method, the diameter of discs along the same axle are varied. In yet still a further alternative embodiment of this method, the discs include ball bearings for free independent rotation about the axles. In yet still a further alternative embodiment of this method, the discs are non-circular in shape. In yet still a further alternative embodiment of this method, the discs are offset upon the axle in that the core of the discs are not in the center of the disc. In yet still a further alternative embodiment of this method, the spacial distance between discs along each axle is the same. In yet still a further alternative embodiment of this method, the spacial distance between discs along each axle is varied. In yet still a further alternative embodiment of this method, during the step of stretching the elastic sheet material the elastic material is held at its cross-machine direction edges so as to not move inward. In yet still a further alternative embodiment of this method, the elastic material is held at its cross-machine direction edges via the use of a belt arrangement. In yet still a further alternative embodiment of this method, the elastic layer is stretched in the machine direction while bonding with the nonelastic necked material.
A macroscopic disc stretching apparatus for stretching an elastic layer of a necked bonded laminate material includes a first axle, macroscopic discs positioned about the first axle, a second axle parallel and adjacent to the first axle, macroscopic discs positioned about the second axle, and at least one of the axles being adjustably moveable with respect to the other axle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an exemplary process for forming an efficient elastic necked-bonded material in accordance with the invention.
FIG. 2A is a schematic view of a portion of the schematic process of FIG. 1, showing one embodiment of the portion of the process, showing a macroscopic grooved roll arrangement.
FIG. 2B is a cross-sectional view of a portion of macroscopic grooved rolls from FIG. 2A.
FIG. 3 is a perspective view of an alternative portion of the schematic process of FIG. 1, showing a macroscopic disc on axle arrangement for stretching the elastic layer.
FIG. 3A is a top view of a noncircular macroscopic disc as may be used in the process of FIG. 1.
FIG. 3B is a perspective view of a macroscopic disc as may be used in the process of FIG. 1 (including ball bearings for free movement about a non-rotating axle).
FIG. 3C is a top view of a circular macroscopic disc with a non centered core.
FIG. 4 is a front view (in the MD direction) of a macroscopic disc on axle arrangement.
FIG. 5 is a front view (in the MD direction) of an alternative embodiment of a macroscopic disc on axle arrangement.
FIG. 6 is a side schematic view of a macroscopic disc on axle arrangement showing an alternative embodiment with a material edge hold-down mechanism.
FIG. 7 is an illustration of an exemplary personal care product utilizing material made in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

Increased elastic performance of an elastic necked-bonded laminate material can be achieved by stretching the elastic sheet component of the laminate either prior to lamination with a non-elastic necked material, or alternatively, following lamination to a non-elastic necked material. Such elastic sheet component is given a one-time stretch by a macroscopic stretching apparatus in the cross-machine direction (for instance, a pre-stretch prior to usage in a product) to improve the efficiency of the elastic component when in actual use by the consumer. Such one-time pre-stretch may be to between about 10 and 1000 percent of the initial width of the elastic sheet component. Such one-time pre-stretch may be a partial material stretch or a total material stretch (in the CD). Such material should then be allowed to either partially or totally recover prior to lamination to a necked non-elastic component. In an alternative embodiment, such one-time pre-stretch may be to between about 20 and 700 percent of its initial width and then allowed to either partially or totally recover prior to lamination to a necked non-elastic component. In still a further alternative embodiment, such one-time pre-stretch may be to between about 50 and 500 percent of its initial width and then allowed to either partially or totally recover prior to lamination to a necked non-elastic component.
By giving an elastic material a one time pre-stretch, the process removes the poor or less efficient “first” stretch out of the process. Such pre-stretch is separate and apart from any stretching that may occur in the initial formation of the film or elastic layer, such as stretching that may occur as a result of a machine direction orienter.
Also, by giving an elastic material a one time pre-stretch in the direction of consumer use (CD), before it has been laminated to a necked nonelastic material, such pre-stretch affects only the properties of the elastic material and not the nonelastic material. If one were to stretch both the elastic material and the nonelastic material, it would be possible to affect the performance and properties of the nonelastic material. For example, such prestretching would soften the nonelastic material, but could also cause fuzziness or fraying of the nonelastic material, which would be unacceptable for certain medical applications (where linting is discouraged). If it is desired to stretch both the nonwoven and the elastic layer, in one alternative embodiment the elastic layer is pre-stretched and the nonwoven is separately necked and pre-stretched.
If it is desired that materials ultimately stretch a certain percentage in use, the material could be essentially prestretched, such that it delivers the necessary elongation during use. Upon subsequent stretching, products employing the elastic necked material would then satisfy this objective. Such prestretching step acts to remove the first level of immediate set that is produced in the elastic material under normal usage. Instead of the ultimate consumer having to encounter the immediate set, and consequent loss of comfort (such as looseness of product), this immediate set is eliminated or reduced in processing, such that the consumer never encounters it, or encounters it to a lesser degree in actual use.
In a further alternative embodiment of the invention, such prestretching occurs as part of a neck stretch bonded laminate process. In such a fashion, an efficient neck bonded laminate is produced that also includes machine direction stretch capabilities.
In still another alternative embodiment, such prestretching is imparted to the elastic sheet material either prior to lamination or following lamination (if following lamination, then to the entire laminate material) by a macroscopic stretching apparatus.
For the purposes of this application, the term “macroscopic stretching apparatus”, shall refer to either a set of intermeshing grooved rolls or intermeshing discs on adjacent parallel axles. The distances between adjacent grooves or discs are clearly visible without the use of image enhancement/magnification lenses, because the macroscopic discs or grooves are of appreciable size/scale. In macroscopic grooved rolls the spaces between intermeshing peaks or raised areas on the grooved rolls is in one embodiment greater than about 0.5 inches. In one embodiment, the distance is greater than about 1 inch. In still another alternative embodiment, the distance is greater than about 2 inches. In still another alternative embodiment, the distance is between about 0.5 inch to 2 inches. These distances are shown in FIG. 2B as 57, from the center of adjacent peaks on the grooved roll. In another alternative embodiment, the depth of a groove, from top of peak to bottom of adjacent valley (59 on FIG. 2B) is greater than about 0.5 inches. In an alternative embodiment the depth is greater than about one inch. In still a further alternative embodiment, the depth is greater than about 4 inches. In still another alternative embodiment, the depth is greater than about 12 inches. In still a further alternative embodiment, the depth is between about 0.5 and 12 inches. In still another alternative embodiment, the depth of engagement (distance of penetration of peak into valley, and reflected as “Z” on FIG. 2B) is greater than about 0.5 inch. In still another alternative embodiment, the depth of engagement is greater than about one inch. In still another alternative embodiment, the depth of engagement is greater than about four inches. In still another alternative embodiment, the depth of engagement is greater than about eight inches. In yet another alternative embodiment, the depth of engagement is between about 0.5 and 8 inches.
For a macroscopic disc on axle arrangement, the diameter of such macroscopic discs is desirably greater than about 1 inch. In an alternative embodiment the diameter of the macroscopic disc is greater than about 2 inches. In still another alternative embodiment the diameter of the macroscopic disc is greater than about 4 inches. In still another alternative embodiment, the diameter of the macroscopic disc is greater than about 12 inches. In still a further alternative embodiment, the diameter of such discs is between about 1 inch and 12 inches. The diameter dimension of such disc is shown in FIG. 4 as C.
In one embodiment, the macroscopic disc has parallel side edges. In one desirable embodiment, such macroscopic disc has a thickness of greater than 0.25 inch. In another alternative embodiment, such macroscopic disc has a thickness of greater than about 0.5 inch. In still another alternative embodiment, such macroscopic disc has a thickness of greater than about 1 inch. In still a further alternative embodiment, the disc has a thickness of between about 0.25 inch and 1 inch. The thickness dimension of such disc is shown in FIG. 4 as D.
In still another alternative embodiment, the distance from the centerline of one disc to the centerline of an adjacent engaged (intermeshed) disc (on two different axle as shown as F in FIG. 4) is desirably greater than about 0.5 inch. In an alternative embodiment, the distance is greater than about an inch. In still another alternative embodiment, the distance is greater than about 2 inches. In still another alternative embodiment, the distance is between about 0.5 inch and 2 inch.
In still another alternative embodiment, the level of engagement of discs from two axles (intermeshing, shown as E on FIG. 4) is greater than about an inch. In an alternative embodiment, the level of engagement is greater than about 2 inches. In still another alternative embodiment, the level of engagement is greater than about 4 inches. In still a further alternative embodiment, the level of engagement is greater than about 12 inches. In yet another alternative embodiment, the level of engagement is between about 1 and 12 inches.
In still another alternative embodiment, the distance from the centerline of adjacent discs along the same axle (shown as G on FIG. 4) is greater than about one inch. In an alternative embodiment, the distance is greater than about 2 inches. In an alternative embodiment, the distance is greater than about 4 inches. In an alternative embodiment, the distance is between about 1 and 4 inches.
For the purposes of this application, the term “microscopic” shall refer to grooved rolls or discs that do not fall within the definitions of macroscopic above.
In one embodiment, such neckable material is necked between about 10 and 80 percent. In an alternative embodiment, such neckable material is necked between about 20 and 70 percent (percent neckdown).
Referring to FIG. 1 of the drawings there is schematically illustrated at 10 a process for forming an efficient elastic necked-bonded material (laminate). According to the present invention, a neckable material 12 is unwound from a supply roll 14 and travels in the direction indicated by the arrow associated therewith as the supply roll 14 rotates in the direction of the arrows associated therewith. The neckable material 12 passes through a nip 16 of the drive roller arrangement 18 formed by the drive rollers 20 and 22. The neckable material 12 may be formed by known nonwoven extrusion processes, such as, for example, known meltblowing processes, spunbonding or bonded carded web processes, and passed directly through the nip 16 without first being stored on a supply roll.
An elastic sheet 32 is unwound from a supply roll 34 and travels in the direction indicated by the arrow associated therewith as the supply roll 34 rotates. It should be recognized that the elastic sheet material (which forms the elastic component of the laminate) may be made online or provided from a supply roll as illustrated. The elastic sheet is either stretched in the CD at a nip of a macroscopic stretching apparatus 25 prior to being brought into contact with the non-elastic necked material, and/or following bonding at a post bonding macroscopic stretching apparatus 29. If the stretching occurs prior to lamination, the stretched material is allowed to partially or totally retract (relax or recover) prior to being brought in contact with the non-elastic necked sheet. If the elastic only partially retracts, subsequent retraction will gather the necked material in the CD, producing a combined neck bonded laminate/stretch bonded laminate with very high CD stretch. The elastic sheet material is stretched in the cross-machine direction by the macroscopic stretching apparatus, no matter which alternative stretching arrangement is utilized.
In either case, the elastic sheet passes through the nip 24 of the bonder roller arrangement 26 formed by the bonder rollers 28 and 30. The elastic sheet 32 may be formed by extrusion processes such as, for example, meltblowing processes, scrim forming processes or film extrusion processes, or alternatively foam forming processes, and passed directly through the nip 24 without first being stored on a supply roll.
In one embodiment, the neckable material 12 passes through the nip 16 of the S-roll arrangement 18 in a reverse-S path as indicated by the rotation direction arrows associated with the stack rollers 20 and 22. From the S-roll arrangement 18, the neckable material 12 passes through the pressure nip 24 formed by a bonder roller arrangement 26. Because the peripheral linear speed of the rollers of the S-roll arrangement 18 is controlled to be less than the peripheral linear speed of the rollers of the bonder roller arrangement 26, the neckable material 12 is tensioned between the S-roll arrangement 18 and the pressure nip of the bonder roll arrangement 26. By adjusting the difference in the speeds of the rollers, the neckable material 12 is tensioned so that it necks a desired amount and is maintained in such tensioned, necked condition while the elastic sheet 32 is joined to the necked material 12 during their passage through the bonder roller arrangement 26 to form a composite elastic necked-bonded laminate 40. Although not shown, the necking could occur in stages at various other positions in the process. For instance, the supply roll 14 could be slowed to create necking on the material prior to entering the reverse S-roll arrangement.
Other methods of tensioning the neckable material 12 may be used such as, for example, tenter frames or other cross-machine direction stretcher arrangements that expand the neckable material 12 in other directions such as, for example, the cross-machine direction so that the material shortens in the MD. After bonding to the elastic sheet 32, the resulting elastic necked-bonded material 40 will be elastic in a direction generally parallel to the direction of necking, i.e., in the machine direction.
The neckable material 12 may be a nonwoven material such as, for example, a spunbonded web, meltblown web or bonded carded web, or alternatively a woven or knit material. If the neckable material is a web of meltblown fibers, it may include meltblown microfibers. The neckable material 12 may be made of fiber forming polymers such as, for example, polyolefins, polyesters, as well as nylons. Exemplary polyolefins include one or more of polypropylene, polyethylene, ethylene copolymers, propylene copolymers, butene copolymers and blends of such polymers.
In one embodiment of the present invention, the neckable material 12 is a multilayer material having, for example, at least one layer of spunbonded web joined to at least one layer of meltblown web, bonded carded web or other suitable material. For example, neckable material 12 may be a multilayer spunbond/meltblown/spunbond material having a first layer of spunbonded polypropylene having a basis weight from about 0.2 to about 8 ounces per square yard (osy), a layer of meltblown polypropylene having a basis weight from about 0.2 to about 4 osy, and a second layer of spunbonded polypropylene having a basis weight of about 0.2 to about 8 osy. Alternatively, the neckable material 12 may be a single layer of material such as, for example, a spunbonded web having a basis weight of from about 0.2 to about 10 osy or a meltblown web having a basis weight of from about 0.2 to about 8 osy.
The neckable material 12 may also be a composite material made of a mixture of two or more different fibers of different composition or a mixture of fibers and particulates. Such mixtures may be formed by adding fibers and/or particulates to the gas stream in which meltblown fibers are carried so that an intimate entangled commingling of meltblown fibers and other materials, e.g., wood pulp, staple fibers and particulates such as, for example, hydrocolloid (hydrogel) particulates commonly referred to as superabsorbant materials, occurs prior to collection of the meltblown fibers upon a collecting device to form a coherent web of randomly dispersed meltblown fibers and other materials such as disclosed in U.S. Pat. No. 4,100,324, the disclosure of which is hereby incorporated by reference (coform). The neckable material may also include bicomponent fibers or conjugate fibers as well.
If the neckable material 12 is a nonwoven web of fibers, the fibers should be joined by interfiber bonding to form a coherent web structure which is able to withstand necking. Interfiber bonding may be produced by entanglement between individual meltblown fibers. The fiber entangling is inherent in the meltblown process but may be generated or increased by processes such as, for example, hydraulic entangling or needlepunching. Alternatively and/or additionally a bonding agent may be used to increase the desired bonding.
The elastic sheet 32 may be made from any material which may be manufactured in sheet form. Generally, any suitable elastomeric fiber forming resins or blends containing the same may be utilized for the nonwoven webs of elastomeric fibers of the invention and any suitable elastomeric film forming resins or blends containing the same may be utilized for the elastomeric films of the invention. The elastic sheet may also be a scrim-like or netting material, or an elastic foam.
For example, the elastic sheet 12 may be made from styrenic block copolymers available from the Kraton Polymers of Houston, Tex. under the designation KRATON G. Other such styrenic block copolymers are available from Septon Company of America, Dexco Polymers, and Dynasol of Spain. Still other exemplary elastomeric materials which may be used to form the elastic sheet 32 include polyurethane elastomeric materials such as, for example, those available under the trademark ESTANE from Noveon of Cleveland, Ohio, polyamide elastomeric materials such as, for example, those available under the designation PEBAX from AtoFina Chemicals Inc. of Philadelphia, Pa., and polyester elastomeric materials such as, for example, those available under the trade designation Hytrel from E. I. DuPont De Nemours & Company. Formation of elastic sheets from polyester elastic materials is disclosed in, for example, U.S. Pat. No. 4,741,949 to Morman et al., hereby incorporated by reference. Additionally, less elastic materials may be used as the elastic component, such as single site catalyzed polyolefins. Such single site catalyzed polyolefins include metallocene-catalyzed polyolefins and constrained geometry polyolefins, available from either ExxonMobil or Dow Chemical. The one time pre-stretch of these less elastic materials can improve their performance in use relative to more costly higher performance elastomer materials without the one time pre-stretching step.
A polyolefin may also be blended with the elastomeric polymer to improve the processability of the composition. The polyolefin must be one which, when so blended and subjected to an appropriate combination of elevated pressure and elevated temperature conditions, is extrudable, in blended form, with the elastomeric polymer. Useful blending polyolefin materials include, for example, polyethylene, polypropylene and polybutene, including ethylene copolymers, propylene copolymers and butene copolymers. Two or more of the polyolefins may be utilized. Extrudable blends of elastomeric polymers and polyolefins are disclosed in, for example., U.S. Pat. No. 4,663,220 to Wisneski et al., hereby incorporated by reference.
The elastic sheet 32 may also be a pressure sensitive elastomer adhesive sheet. For example, the elastic material itself may be tacky or, alternatively, a compatible tackifying resin may be added to the extrudable elastomeric compositions described above to provide an elastomeric sheet that can act as a pressure sensitive adhesive, e.g., to bond the elastomeric sheet to the tensioned, necked nonelastic web. In regard to the tackifying resins and tackified extrudable elastomeric compositions, note the resins and compositions as described in U.S. Pat. No. 4,789,699 of J. S. Keiffer and T. J. Wisneski, the disclosure of which is hereby incorporated by reference.
Any tackifier resin can be used which is compatible with the elastomeric polymer and can withstand the high processing (e.g., extrusion) temperatures. If blending materials such as, for example, polyolefins or extending oils are used, the tackifier resin should also be compatible with those blending materials. Generally, hydrogenated hydrocarbon resins are preferred tackifying resins, because of their better temperature stability. Other tackifying resins which are compatible with the other components of the composition and can withstand the high processing temperatures, can also be used.
A pressure sensitive elastomer adhesive may include, for example, from about 40 to about 80 percent by weight elastomeric polymer, from about 5 to about 40 percent polyolefin and from about 5 to about 40 percent resin tackifier.
The elastic sheet 32 may also be a multilayer material in that it may include two or more individual coherent webs or films or combinations of such. Additionally, the elastic sheet 12 may be a multilayer material in which one or more of the layers contain a mixture of elastic and nonelastic fibers or particulates. For an example of the latter type of elastic web, reference is made to U.S. Pat. No. 4,209,563, incorporated herein by reference, in which elastomeric and non-elastomeric fibers are commingled to form a single coherent web of randomly dispersed fibers. Another example of such a composite web would be one made by a technique such as disclosed in U.S. Pat. No. 4,100,324 also incorporated herein by reference. That patent discloses a nonwoven material which includes a mixture of meltblown thermoplastic fibers and other materials. The fibers and other materials are combined in the gas stream in which the meltblown fibers are borne so that an intimate entangled commingling of meltblown fibers and other materials, e.g., wood pulp, staple fibers or particulates such as, for example, hydrocolloid (hydrogel) particulates commonly referred to as super- absorbents occurs prior to collection of the fibers upon a collecting device to form a coherent web of randomly dispersed fibers. The elastic sheet 32 may also be further processed such as by slitting or aperturing stations.
The bonder roller arrangement 26 may be a smooth calender roller 28 and a smooth anvil roller 30 or may include one or both patterned calender roller(s), such as, for example, a pin embossing roller arranged with a smooth anvil roller. One or both of the calender roller and the smooth anvil roller may be heated and the pressure between these two rollers may be adjusted by well-known means to provide the desired temperature, if any, and bonding pressure to join the necked material 12 to the elastic sheet 32 forming a composite elastic necked-bonded material 40. Such material may then be rolled for storage upon a winding roll or passed directly to another processing station for further modifications.
The necked material and the elastic sheet may be completely bonded together and still provide a composite elastic necked-bonded material with good stretch properties. That is, a composite elastic material may be formed by joining a necked material to an elastic sheet utilizing bonding surfaces such as, for example, smooth rollers or platens to provide a high bond surface area. A composite elastic necked-bonded material 40 may also be formed utilizing a bonding pattern.
Necked materials may be joined to the elastic sheet 32 at least at two places by any suitable means such as, for example, thermal bonding or ultrasonic welding which softens at least portions of at least one of the materials, usually the elastic sheet because the elastomeric materials used for forming the elastic sheet 32 have a lower softening point than the components of the necked material 12. Joining may be produced by applying heat and/or pressure to the overlaid elastic sheet 32 and the necked material 12 by heating these portions (or the overlaid layer) to at least the softening temperature of the material with the lowest softening temperature to form a reasonably strong and permanent bond between the re-solidified softened portions of the elastic sheet 32 and the necked material 12. Additionally, such bonding arrangement may utilize an adhesive bonding arrangement as long as the adhesive does not significantly impact the elastic performance of the laminate. Additionally, such bonding arrangement may utilize an entangling process. Elastic sheets can be used having basis weights less than 0.5 osy (ounces per square yard), for example, from about 0.1 to about 0.4 osy, or alternatively between about 0.25 to about 0.4 osy. Such extremely low basis weight sheets are useful for economic reasons, particularly for use in disposable products. Additionally, elastic sheets having higher basis weights such as, for example, from about 0.5 to about 10 osy may also be used.
With regard to thermal bonding, one skilled in the art will appreciate that the temperature to which the materials, or at least the bond sites thereof, are heated for heat-bonding will depend not only on the temperature of the heated roll(s) or other heat sources but on the residence time of the materials on the heated surfaces, the basis weights of the materials and their specific heats and thermal conductivities. However, for a given combination of materials, and in view of the herein contained disclosure, the processing conditions necessary to achieve satisfactory bonding can be readily determined by one of skill in the art. Conventional drive means and other conventional devices which may be utilized in conjunction with the apparatus of FIG. 1 are well known and, for purposes of clarity, have not been illustrated in the schematic view of FIG. 1.
With specific reference to the macroscopic stretching apparatus shown schematically at either 25 or 29, a variety of apparatus may be used to impart a one time pre-stretch to the elastic sheet of the laminate. For example, FIG. 2A is a schematic view of a portion (either at 25 or 29) of the schematic process of FIG. 1, showing one embodiment of the prestretching portion of the process. Specifically, a macroscopic grooved roll arrangement is illustrated. In such embodiment a large diameter roll system 50 may be utilized, which employs one large diameter roll 51 (such as for example of approximately 6 feet in diameter) with machine direction oriented valleys going deeply into the roll. The peaks 55 and valleys (grooves) 53 run in the machine direction across the cross direction of the roll (from side to side). These can be seen in the cross-sectional view of FIG. 2B showing a machine direction view of the rolls. Either a single intermeshing grooved roll, or a series of satellite rolls 52, 54, and 56 could also be employed with peaks that fit within the valleys of the larger diameter roll. The satellite rolls could be adjustable such that their depth within the grooves/valleys of the larger roll could be changed. For example the rolls may be independently controlled with respect to each other, such that their speed of rotation and distance from each other may be independently adjustable. In this fashion, the first satellite roll could push the elastic material in (either by itself if positioned at 25, or with the necked nonelastic material, if positioned at 29), for example 4 inches, while the second satellite roll could push the material in, for example 8 inches and so on, until the material received the desired amount of stretch. The satellite rolls could be adjusted such that if less stretch is desired, the first could be pushed into the valleys of the bigger roll for example by 2 inches. The satellite roll system offers the elastic material multiple gentle stretches with relaxation between each stretch, instead of one large stretch extension with standard grooved rolls.
It is in one embodiment desirable that the macroscopic prestretching apparatus stretch the elastic sheet material (either prior to lamination to the nonelastic sheet or following lamination) an amount in the CD direction of greater than about 20 percent of the initial width, alternatively greater than about 50 percent, still alternatively, greater than about 100 percent, still alternatively, greater than about 200 percent, and still further alternatively, greater than about 300 percent. In a further alternative embodiment such elastic sheet is stretched in the CD in an amount of between about 20 and 300 percent.
In an alternative embodiment, following this roll apparatus, an identical roll apparatus shifted one half cycle to the left or right (not shown) could stretch the material that was not stretched in the first apparatus. This would produce a uniformly stretched material across the width of the material. That is, there are no unstretched bands of material where the material contacted the prestretching macroscopic grooves or discs. The material could be pinched on the edges of the bigger roll by a belt 61 in a groove such that the material could not slide in the CD, but would have stretch.
In still another alternative embodiment, only part of the elastic sheet material could be prestretched, so as to incur easy stretch in the pre-stretched part, while the remainder of the material would only be stretched with a higher force. Furthermore, some area on the elastic sheet material could have machine direction stretch, while other areas could have cross-directional stretch.
As can be seen in FIG. 3, a perspective view of an alternative portion of the schematic process of FIG. 1 shows a macroscopic “disc on axle” apparatus arrangement for use in stretching the elastic sheet either prior to or following lamination with the nonelastic necked material. While prestretching the elastic material of neck bonded laminates using grooved rolls offers benefits, it also raises apparatus difficulties. When using grooved rolls, each CD stretch profile and stretch amount requires a new set of rolls. Damage done to any portion of a roll requires a new roll to be made.
As an alternative, a macroscopic disc arrangement can be used such that the material is stretched between intermeshing/engaged macroscopic discs that are positioned along parallel and adjacent axle shafts. As previously stated, in one embodiment, the discs are at least 1 inch in diameter and may range in size to about 12 inches in diameter or greater. Desirably such discs are manufactured from rigid material (as with the grooved rolls) such as metal, or molded resins or rubbers. The disc design and set up minimizes material contact with metal surfaces and especially sharp metal edges that are encountered with microscopic grooved rolls. It is therefore contemplated that the discs will include rounded edges to further minimize contacting the material with harsh sharp edging. It is also contemplated that the individual discs adjustably slide on the axle shafts into position such that spaces between the discs may be readily changeable. However, it is also contemplated that “spacers” may be used to maintain separation between the discs, if the discs do not themselves include other known axle locking mechanisms. Such discs may either be freely rotatable about the axles or held fast to the axles (in which case the axles would be rotatable). Such spacers may include ball bearings to provide for free movement of adjacent discs. Similarly, such discs may likewise include ball bearings around their core (hole for receiving the axle shaft) to provide for free independent movement about the axles. In such a fashion, the discs can move at different revolutions per minute to accommodate their differing diameters. In a further alternative embodiment, such discs are held in place and the axle is operated to move, rather than the discs freely moving about the axle. Still in a further alternative embodiment, one or more shafts are motor driven while others are not.
Using discs of varying diameters (which is one embodiment contemplated) necessitates using individual free rotating discs as there is the same circumferential surface speed between discs necessitating different revolutions per minute (RPMs). Such a feature cannot be accomplished with grooved rolls.
At least two axle shafts with individual discs can engage (intermesh) such that the edges of such discs overlap (that is pass alongside or between discs on the other axle), during running of material through a nip formed by the discs. Desirably, in one embodiment, such discs are capable of being independently driven and adjusted toward or away from each other, (as shown as A and B in FIG. 3) as with the previously described grooved roll arrangement.
As can be seen in FIG. 3, the disc and axle arrangement 66 includes central shafts 67, 68, about which are positioned discs 69, 70. In one embodiment the discs are of equal diameters along each axle, and between all intermeshing axles (not shown). In a second embodiment, the discs are of the same diameter 74, 75 about one axle, and of different diameters between intermeshing discs (as shown, where one diameter 74 is larger than the other 75). As with the previously described satellite grooved roll arrangement, the disc on axle arrangement may include any number of satellite axles and discs that can engage to different disc depths with progressively more material stretching as material passes around the central largest axle. Alternatively, each of the satellite shafts may include discs at nonoverlapping portions about the central shaft, such that different portions of the material to be stretched would be stretched by different satellite disc and axle components around the central disc and axle shaft. Alternatively, such axle disc arrangement may include only two shafts (as shown).
The disc and axle arrangement are positioned in the process such that the disc outer edges 71 and 72 are aligned with the machine direction. As previously stated with respect to the grooved roll apparatus, one or more of the axles may be capable of movement A, B with respect to each other to provide for varying degrees of intermeshing. Spacers 73 may be used to separate the discs, or the discs may be held in place by other known mechanisms.
It should be noted that necked material normally has a CD basis weight and elastic property profile. Using discs to stretch one area of a material greater than another can be used to either amplify the profile to obtain a material with a very high CD stretch on the edges (as would be desired in a diaper outer cover or liner, or other personal care product) or flatten the profile (as would be desired when making wide material which will be eventually slit and consistent slits are desired).
By using CD movable discs along an axle (that is discs with their thin outer edge 71, 72 facing in the machine direction but stored along an axle from one CD end to the other, such that stretching occurs in the CD direction), multiple widths of material and multiple stretch profiles can be placed in a neck bonded laminate by simply changing the individual discs used (diameter and thickness of the discs), the location of the discs, whether the discs are centered (equidistant) from counterpart adjacent discs when in an intermeshed (or engaged) position, and the amount of intermeshing (engagement).
Unlike grooved roll apparatus, discs are relatively easy to maintain, and should they be damaged, can be easily removed and replaced. Additionally, the outer edge shape of discs can be of non-circular configuration, such as oval or elliptical in shape. Such an elliptical disc is shown in FIG. 3A having a circular core for receiving an axle. The CD elastic properties of the sheet could be altered in this fashion along the MD of the material. Essentially a pattern of greater stretch followed by less stretch could be achieved along the MD of the material, depending on the outer circumference shape of the disc. The material would demonstrate different CD stretch properties along the MD. Obviously the core would have to be circular, unless the disc was held unmoveably to the support shaft. The elliptical shaped disc is shown in FIG. 3A, having an outer circumference edge 71A. The core of the disc 73A is circular in shape, while the outer circumference edge is shaped as an ellipse. The edge to edge diameter distances 75A varies depending on which location on the edge one starts with. Further the disc contains distinct wide and narrow areas 74A. This will produce machine direction bands in the material that demonstrate varying periodic degrees of prestretching. As can be seen in FIG. 3B, the discs 69, may include ball bearings 170, for easy rotation about the axle shafts, if free rotation is desired. In a further alternative embodiment, as seen in FIG. 3C, the disc may be circular or some other noncircular shape, and include a core opening that is off center. Such a disc would also provide for high and low stretch effects on materials. In still a further alternative embodiment, the thickness of discs can be varied along an axle or between axles to provide for varying stretch effects on materials.
FIG. 4 illustrates a front view of an intermeshing disc on axle arrangement 76 showing the discs 78, 81 in an engaged position, and the elastic sheet material 96 passing through the nip of the discs towards the viewer in the MD. The intermeshing disc on axle arrangement includes two parallel axles 77, 90. The discs shown include discs of equal diameter 82, 86, having equal spacing between discs 83, 84, 79, 80. The Figure also shows equal spacing between discs but discs of different diameters, 80,85. Further, the figure also shows, discs having unequal spacing, but of equal diameter 87, 88, and 89. Spacers are shown between the discs on one axle 77.
FIG. 5 is a front view of an alternative embodiment of a disc on axle arrangement of FIG. 4. The discs are shown in a disengaged orientation. The axles 90 and 91 are moved apart, such that the discs 92, 93 do not intermesh as in FIG. 4. The Figure illustrates equal spacing between discs 94 and would-be intermeshing discs 95.
In an alternative embodiment (as seen in FIG. 6) of the disc on axle arrangement 100, a “V” belt 107 is included on the sides of the material so as to maintain the sides of the material 106 from sliding off the edge of disc 101 toward disc 102. Belt rolls 103 guide a belt to the sides of the material 106 as the material passes in the MD 109. Carrier rolls 105 help support the elastic material as it moves in the machine direction to the next processing station. In such an embodiment, the edges of the material are held so that they do not get pulled inward. Two belts are utilized, one on each side of the disc arrangement.
Prestretching an elastic material decreases the immediate percent set in the CD and the force required to stretch the material to the pre-stretch width (following retraction) on subsequent stretches up to the pre-stretched length. In other words, after being prestretched, the material retains its shape after subsequent stretching. In manufacturing of a product incorporating the material, the material should be first prestretched and then cut to its desired shape before insertion into the product. Prestretching also decreases the hysteresis in the CD on subsequent stretches. The step of prestretching a material prior to incorporating such material into a product allows for greater retraction in the product, as opposed to incorporation of the unstretched material into a final product. Essentially, by prestretching an elastic component of a necked bonded laminate, and in particular with a macroscopic stretching apparatus, a more efficient better performing elastic product is received by a consumer of such product. The consumer does not experience the first high resistance to stretch and immediate set upon initial stretch use of the material. Immediate set can translate directly into extension with less recovery, giving the impression of a loosening of the elastic components in a product and a reduction in product comfort and fit. Such prestretching is particularly effective for lower cost, lower performance elastomers.
In addition to the elastic material attributes (whether such has been made more efficient utilizing one of the previously described prestretching apparatus), the relation between the original dimensions of the neckable material 12 to its dimensions after tensioning also determines the approximate limits of stretch of the elastic necked-bonded material. Because the neckable material 12 is able to stretch and return to its prenecked dimensions in directions such as, for example the machine direction or the cross-machine direction, the composite elastic necked-bonded material will be stretchable in generally the same direction as the neckable material 12.
For example, if it is desired to prepare an elastic necked-bonded material stretchable to a 150% elongation, a first width of neckable material such as, for example, 250 cm, is tensioned so that it necks down to a second width of about 100 cm. The necked material is then joined to an elastic sheet having a width of approximately 100 cm and which is at least stretchable to a width of 250 cm. The resulting elastic necked-bonded material has a width of about 100 cm and is stretchable to at least the original 250 cm width of the neckable material for an elongation of about 150%. As can be seen from the example, the elastic limit of the elastic sheet needs only to be as great as the minimum desired elastic limit of the composite elastic necked-bonded material. If an elastic material is prestretched either prior to lamination with a nonelastic necked material, or following lamination as described, the consumer's stretch to the elastic limit (in the first instance) in use, encounters less resistance and suffers less set. For example, if the above material was prestretched 150% to its original 250 cm, it may retract back to about 150 cm for a percent set of 33%. Following stretches to between about 150 and 250 cm would be followed by a retraction back to approximately 150 cm. That is, there is little if any additional permenant set if the material encounters similar or less degrees of stretching. Thus, giving the material a one time first pre-stretch before the consumer uses the material, improves the performance of the material within a product.
The apparatus and method described above can be used to produce a material with bands of improved prestretched elastic performance material and bands of non-treated (non stretched) elastic performance material. The improved elastic performance material is produced between the disc or groove contact points where the material is stretched in the CD. The nontreated material is produced by having the surfaces that the material contacts on the discs or rolls, ie, the outer circumferential surfaces, being a high frictional surface so the material can not slide in the CD and remains unstretched. As the material is run in the MD, it is stretched in the CD from the MD oriented grooves or discs.
The resulting material can be characterized by stretching about 0.25 inch lengths of the material in the CD, ie, an 0.25 inch length in a known tensile tester. The prestretched and non prestretched bands will be readily apparent. In one embodiment, the nontreated (nonstretched) bands should be less than 2 inches, or alternatively less than 1 inch wide to ensure pieces of the material cut for product use contain at least some prestretched material. By varying the width and number of bands of nonstretched material, material can be produced which is essentually non stretched all the way to essentually totally prestretched.
With reference to FIG. 7, a personal care disposable absorbent product is illustrated which incorporates material made in accordance with the inventive method and the apparatus. In particular, a disposable diaper 130 generally defines a front waist section 132, a rear waist section 134, and an intermediate section 136 which interconnects the front and rear waist sections. The front and rear waist sections 132 and 134 include the general portions of the diaper which are constructed to extend substantially over the wearer's front and rear abdominal regions, respectively, during use. The intermediate section 136 of the diaper includes the general portion of the diaper that is constructed to extend through the wearer's crotch region between the legs. Thus, the intermediate section 136 is an area where repeated liquid surges typically occur in the diaper.
The diaper 130 includes, without limitation, an outer cover, or backsheet 138, a liquid permeable bodyside liner, or topsheet, 140 positioned in facing relation with the backsheet 138, and an absorbent core body, or liquid retention structure, 154, such as an absorbent pad, which is located between the backsheet 138 and the topsheet 140. The backsheet 138 defines a length, or longitudinal direction 150, and a width, or lateral direction 152 which, in the illustrated embodiment, coincide with the length and width of the diaper 130. The liquid retention structure 154 generally has a length and width that are less than the length and width of the backsheet 138, respectively. Thus, marginal portions of the diaper 130, such as marginal sections of the backsheet 138, may extend past the terminal edges of the liquid retention structure 154. In the illustrated embodiments, for example, the backsheet 138 extends outwardly beyond the terminal marginal edges of the liquid retention structure 154 to form side margins and end margins of the diaper 130. The topsheet 140 is generally coextensive with the backsheet 138 but may optionally cover an area which is larger or smaller than the area of the backsheet 138, as desired. The outercover can be manufactured from material produced in accordance with the described methods.
To provide improved fit and to help reduce leakage of body exudates from the diaper 130, the diaper side margins and end margins may be elasticized with suitable elastic members, as further explained below. For example, as representatively illustrated in FIG. 7, the diaper 130 may include leg elastics 156 which are constructed to operably tension the side margins of the diaper 130 to provide elasticized leg bands which can closely fit around the legs of the wearer to reduce leakage and provide improved comfort and appearance. Waist elastics 158 are employed to elasticize the end margins of the diaper 130 to provide elasticized waistbands. The waist elastics 158 are configured to provide a resilient, comfortably close fit around the waist of the wearer. The laminates of the inventive methods are suitable for use as the liner if porous or apertured, the backsheet, the leg elastics 156 and the waist elastics 158.
As is known, fastening means, such as hook and loop fasteners, may be employed to secure the diaper 130 on a wearer. Alternatively, other fastening means, such as buttons, pins, snaps, adhesive tape fasteners, cohesives, fabric-and-loop fasteners, or the like, may be employed. In the illustrated embodiment, the diaper 130 includes a pair of side panels 160 (or ears) to which the fasteners 162, indicated as the hook portion of a hook and loop fastener, are attached. Generally, the side panels 160 are attached to the side edges of the diaper 130 in one of the waist sections 132, 134 and extend laterally outward therefrom. The side panels 160 may be elasticized or otherwise rendered elastomeric by use of laminate made by the inventive methods. For example, the side panels 160, or indeed, any precursor webs of the garment, may be an elastomeric material such as a neck-bonded laminate made in accordance with the inventive method or neck stretch bonded laminate. Examples of absorbent articles that include elasticized side panels and selectively configured fastener tabs are described in PCT Patent Application No. WO 95/16425 to Roessler; U.S. Pat. No. 5,399,219 to Roessler et al.; U.S. Pat. No. 5,540,796 to Fries; and U.S. Pat. No. 5,595,618 to Fries each of which is hereby incorporated by reference in its entirety.
The diaper 130 may also include a surge management layer 142, located between the topsheet 140 and the liquid retention structure, to rapidly accept fluid exudates and distribute the fluid exudates to the liquid retention structure 154 within the diaper 130. The diaper 130 may further include a ventilation layer (not illustrated), also called a spacer, or spacer layer, located between the liquid retention structure 154 and the backsheet 138, to insulate the backsheet 138 from the liquid retention structure 154 to reduce the dampness of the garment at the exterior surface of a breathable outer cover, or backsheet, 138. Examples of suitable surge management layers 142 are described in U.S. Pat. No. 5,486,166 to Bishop and U.S. Pat. No. 5,490,846 to Ellis.
As representatively illustrated in FIG. 7, the disposable diaper 130 may also include a pair of containment flaps 164 which are configured to provide a barrier to the lateral flow of body exudates. The containment flaps 164 may be located along the laterally opposed side edges of the diaper 130 adjacent the side edges of the liquid retention structure 154. Each containment flap 164 typically defines an unattached edge which is configured to maintain an upright, perpendicular configuration in at least the intermediate section 136 of the diaper 130, to form a seal against the wearer's body. The containment flaps 164 may extend longitudinally along the entire length of the liquid retention structure 154 or may only extend partially along the length of the liquid retention structure. When the containment flaps 164 are shorter in length than the liquid retention structure 154, the containment flaps 164 can be selectively positioned anywhere along the side edges of the diaper 130 in the intermediate section 136. Such containment flaps 164 are generally well known to those skilled in the art. For example, suitable constructions and arrangements for containment flaps 164 are described in U.S. Pat. No. 4,704,116 to K. Enloe, incorporated by reference herein in its entirety. Such containment flaps may likewise be made from material produced according to the inventive methods.
The diaper 130 may be of various suitable shapes. For example, the diaper may have an overall rectangular shape, T-shape or an approximately hour-glass shape. In the shown embodiment, the diaper 130 has a generally I-shape. Other suitable components which may be incorporated on absorbent articles of the present invention may include waist flaps and the like which are generally known to those skilled in the art. Examples of diaper configurations suitable for use in connection with the instant invention which may include other components suitable for use on diapers are described in U.S. Pat. No. 4,798,603 to Meyer et al.; U.S. Pat. No. 5,176,668 to Bernardin; U.S. Pat. No. 5,176,672 to Bruemmer et al.; U.S. Pat. No. 5,192,606 to Proxmire et al. and U.S. Pat. No. 5,509,915 to Hanson et al. each of which is hereby incorporated by reference herein in its entirety.
The various components of the diaper 130 are assembled together employing various types of suitable attachment means, such as adhesive, ultrasonic bonds, thermal bonds or combinations thereof. In the shown embodiment, for example, the topsheet 140 and backsheet 138 may be assembled to each other and to the liquid retention structure 154 with lines of adhesive, such as a hot melt, pressure-sensitive adhesive. Similarly, other diaper components, such as the elastic members 156 and 158, fastening members 162, and surge layer 142 may be assembled into the article by employing the above-identified attachment mechanisms.
In a further alternative embodiment, such inventive materials may be particularly useful as an ear attachment (as previously described) for a diaper or other personal care product.
Although various embodiments of the invention have been described using specific terms, devices, and methods, such description is for illustrative purposes only. The words are words of description rather than of limitation. It is to be understood that changes and variations may be made by those of ordinary skill in the art without departing from the spirit or scope of the present invention, which is set forth in the following claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained therein.

Claims

1. A method of producing an elastic necked-bonded laminate material comprising:

providing at least one neckable nonelastic material;

applying a tensioning force to the neckable nonelastic material to neck said material;

providing an elastic sheet;

superposing the necked nonelastic material onto said elastic sheet;

joining said necked nonelastic material and said elastic sheet at least at two places to form a laminate material; and

stretching said elastic sheet in the cross-machine direction through the use of a macroscopic stretching apparatus.

2. The method of claim 1 wherein said stretching of said elastic sheet is performed prior to joining with said nonelastic material.

3. The method of claim 1 wherein said stretching of said elastic sheet is performed following joining of said elastic sheet with said nonelastic material.

4. The method of claim 1 wherein said macroscopic stretching apparatus is a macroscopic grooved roll arrangement.

5. The method of claim 1 wherein said macroscopic stretching apparatus is a macroscopic disc on axle arrangement.

6. A method of producing an elastic necked-bonded laminate material comprising:

providing at least one neckable nonelastic material;

providing an elastic sheet;

superposing the necked nonelastic material onto said elastic sheet;

stretching said elastic sheet in the cross-machine direction with the use of macroscopic discs along axles.

7. The method of claim 6 wherein said stretching of said elastic sheet is performed prior to joining to said nonelastic material.

8. The method of claim 6, wherein said stretching of said elastic sheet is performed following joining to said nonelastic material.

9. The method of claim 6 wherein said elastic sheet is selected from the group consisting of an elastic film, an elastic nonwoven web, an elastic woven web, an elastic scrim or netting, and an elastic foam.

10. The method of claim 6 wherein said neckable material is a material selected from the group consisting of knitted fabrics, loosely woven fabrics, and nonwoven webs.

11. The method of claim 6 wherein said neckable material is selected from the group consisting of a bonded carded web of fibers, a web of spunbonded fibers, a web of meltblown fibers, and a multilayer material including at least one of said webs.

12. The method of claim 6 wherein said stretching step is accomplished by passing said elastic sheet through a nip of intermeshing discs along axles positioned in the cross-machine direction.

13. The method of claim 12 wherein the discs along each axle of the nip are of the same diameter.

14. The method of claim 12 wherein the discs on each axle are of the same diameter and the diameters of discs between axles is varied.

15. The method of claim 12 wherein the diameter of discs along the same axle are varied.

16. The method of claim 12, wherein the discs include ball bearings.

17. The method of claim 12, wherein the discs are non-circular in shape.

18. The method of claim 12, wherein the discs are offset upon the axle in that the core of the discs are not in the center of the disc.

19. The method of claim 12 wherein the spacial distance between discs along each axle is the same.

20. The method of claim 12 wherein the spacial distance between discs along each axle is varied.

21. The method of claim 12 wherein during the step of stretching said elastic material said elastic material is held at its cross-machine direction edges so as to not move inward.

22. The method of claim 21, wherein said elastic material is held at its cross-machine direction edges via the use of a belt arrangement.

23. A necked nonwoven elastic laminate material produced by the method of claim 1.

24. A personal care product made with the material produced by the method of claim 1.

25. A necked nonwoven elastic laminate material produced by the method of claim 6.

26. A personal care product comprising the necked nonwoven elastic laminate of claim 23.

27. The personal care product of claim 26 comprising an ear material comprising the necked nonwoven elastic laminate.

28. The personal care product of claim 26 comprising an outercover material comprising the necked nonwoven elastic laminate.

29. The personal care product of claim 26 comprising a side panel material comprising the necked nonwoven elastic laminate.

30. The method of claim 1 wherein said elastic layer is stretched in the machine direction while bonding with said nonelastic necked material.

31. The method of claim 6 wherein said elastic layer is stretched in the machine direction while bonding with said nonelastic necked material.

32. A macroscopic stretching apparatus for stretching an elastic layer of a necked bonded laminate material comprising:

a first axle,

macroscopic discs positioned about said first axle,

a second axle parallel and adjacent to said first axle,

macroscopic discs positioned about said second axle, and

at least one of said axles being adjustably moveable with respect to the other axle.

33. A necked bonded laminate material including machine direction bands of prestretched and non prestretched zones wherein the nonprestretched zones are at least 0.25 inch wide.

34. The necked bonded laminate material of claim 33 wherein said bands are at least 0.5 inch wide.

35. The necked bonded laminate material of claim 33 wherein said bands are at least 1 inch wide.

36. The necked bonded laminate material of claim 33 wherein said machine direction bands demonstrate varying periodic degrees of prestretching.