Articles requiring a degree of elasticity have been formed by combining elastic materials with inelastic, or less elastic, materials through various lamination processes. Often, such composite laminate articles will be stretchable because of the presence of the elastic material and the particular manner in which the elastic and inelastic materials have been bonded together during the laminating process.
Typically, such stretchable laminates are formed by joining the inelastic material to the elastic material while the elastic material or sheet is in a stretched condition. After such joining of the materials, the laminated article is then allowed to relax, which results in the inelastic component gathering in the spaces between bonding sites on the elastic sheet. The resulting laminate article is then stretchable to the extent that the inelastic material gathered between the bond locations allows the elastic material to elongate. Examples of these types of composite laminate articles and materials are set forth in U.S. Pat. Nos. 4,720,415 and 5,385,775, each of which is incorporated herein by reference thereto.
In some stretchable laminate articles, elastic strands of continuous filaments are bonded to relatively inelastic sheet materials while the elastic strands are in a stretched condition. Such elastic continuous filaments may, in certain articles, be sandwiched between two or more relatively inelastic sheets. The relatively inelastic sheets may include nonwoven webs formed by meltblowing or spunbonding various polymers. Examples of such laminates are shown in U.S. Pat. No. 5,385,775 to Wright, which is incorporated herein in its entirety by reference thereto.
As shown in Wright, elastic continuous filaments may be extruded onto a horizontally moving sheet of material. The continuous filaments are extruded from above the horizontal plane of sheet material and directly onto the material for bonding thereto.
In other exemplary laminates, after bonding the elastic continuous filaments to the sheet material, which will often be relatively inelastic, the bonded elastic continuous filament/inelastic nonwoven sheet material will then be stretched and another relatively inelastic nonwoven sheet may be bonded to the elastic filaments. The forces that are holding the elastic continuous filaments in a stretched condition are then released to gather the inelastic nonwoven sheet(s) between the sheet bonding points. The product may then be stretched to expand and ungather the inelastic sheet(s), but will, upon release, return to the shortened, gathered state.
Such horizontally oriented processes may require expensive post-extrusion equipment in order to maintain the proper spacing between continuous filament strands. This is particularly true when the continuous filaments are not extruded as part of the laminating process and are, instead, unwound from various supply rolls. For example, when a thread such as Lycra™ is utilized, various combs and other alignment devices must be utilized in order to maintain the proper alignment between filaments as the filaments are being unwound from a typical supply spool.
Other lamination processes have also been developed for combining elastic and inelastic materials into a stretchable laminate product. For example, U.S. Pat. No. 4,910,064 to Sabee shows an apparatus for manufacturing an integral filamentary web comprising continuous filaments and meltblown fibers. A multiple number of continuous filaments are spun in curtain-like form, one side of which will have molten meltblown fibers deposited thereon and self-bonded to fix the continuous filaments in a controlled alignment. The process involves drawing continuous filaments either before, during, or after the deposition of the meltblown fibers in order to molecularly orient the continuous filaments. After stabilizing elastic continuous filaments by bonding to the meltblown fibers and relaxing the filaments, the elastic filaments and the web contract to form buckles, curls, or kinks in the non-elastic molecularly oriented permanently lengthened continuous filaments. The patent further describes the bonding of a second opposing meltblown web to the opposite side of the continuous filaments after the meltblown fiber/continuous filament composite is at least partially drawn to provide some degree of molecular orientation.
In addition, U.S. Pat. Nos. 5,200,246 and 5,219,633, also to Sabee, show a vertically-oriented process and apparatus for producing a fabric that combines elongatable continuous filaments with fibrous meltblown webs for interlocking the continuous filaments in an integrated, fibrous, continuous filament matrix. An extruder provides molten elastomeric continuous filaments which are cooled, solidified, and stretched as they are drawn from the meltblowing nozzle by counter-rotating temperature-controlled pull rolls. The solidified continuous filaments are then subsequently pulled into the nip of a pair of temperature-controlled deposition rolls whereat two opposing meltblown gas-fiber streams or sprays are simultaneously and turbulently intermingled with each other and between the tensioned continuous elastomeric filaments. Passing the fabric between higher velocity draw rolls may then further stretch the composite fabric.
While such laminating processes are known in the art, improvements to the processes that allow for more efficient laminate formation are needed. The present invention addresses some of the drawbacks and deficiencies of present elastic/less elastic laminating systems.