Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric – Including an additional nonwoven fabric
Reexamination Certificate
2001-04-12
2004-03-30
Morris, Terrel (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
Including an additional nonwoven fabric
C442S327000, C442S328000, C442S329000, C442S366000, C442S384000, C428S152000, C428S181000, C156S163000
Reexamination Certificate
active
06713415
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to unitary composite stretchable fabrics and, more specifically, to such fabrics having an inner layer of substantially parallel elastomeric fibers providing a flat-surface appearance.
DISCUSSION OF BACKGROUND ART
U.S. Pat. No. 3,575,782 to Hansen discloses puckered fabric-like web materials constructed using 820-1120 denier spandex yarn having 2-8 threadlines per inch of fabric width. The fabric is uniformly impregnated throughout with a polymeric binder. When the bonded composite is relaxed, shirrs or puckers with a high degree of curvature are formed; the thickness in the relaxed condition of the material is 20 mils whereas the thickness in the fully stretched condition is 7 mils.
U.S. Pat. No. 4,552,795 to Hansen discloses flat, flexible non-elastic sheet material containing, between two webs, a plurality of parallel elastomeric strands stretched to at least three times their relaxed length. At least one of the webs can be a nonwoven fabric if it contains a heat-sealable component. The sheet material can be converted to a shirred elastic condition at elevated temperatures.
U.S. Pat. No. 4,977,011 to Smith discloses elastic layered structures having controlled irregularity of pleats (shirrs). The central layer is a multiplicity of nonintersecting (within the width of the structure) elastic strands, 4 to 12 strands per transverse inch. The amplitude of the pleats are different along the elastic strands. They are bonded under tension to two nonwoven webs. When tension is released, pleats (puckers or shirrs) of controlled irregularity are formed. Alternatively, the adhesive is applied in a patterned structure. Upon relaxing, a mixture of short period low amplitude pleats and irregular high amplitude pleats are formed.
U.S. Pat. No. 4,984,584 to Hansen discloses a cohesive bandage comprising elastic yarns at 15-25 yarns per inch of width in a stretched condition, 3-5 times of their fully relaxed length, between two nonwoven webs. A polymer binder is applied (at least 50% by weight of the total) by the process of U.S. Pat. No. 3,575,782, depositing the binder throughout the structure. The structure is permitted to relax only partially (while being heat set) during the puckering step. The length of the partially relaxed web is said to be ⅓ to ⅔ of the fully extended length.
SUMMARY OF THE INVENTION
The laundry-durable unitary composite stretchable puckered fabric of this invention has substantially uniform flat surface appearance and comprises:
(a) two outer layers of nonwoven fabric of substantially equal width_wherein each layer has an inside surface and an outside surface with respect to the composite fabric;
(b) a uniform inner layer of elastomeric fibers comprising at least 8 threadlines/inch (3.15 threadlines/cm) wherein the elastomeric fiber is at least 400 decitex and wherein the number of threadlines and fiber decitex are in a relationship such that the retractive force of the stretchable fabric is at least 0.22 lb/inch (38.9 g/cm); and
(c) 10-35% by weight of the composite fabric of an adhesive composition bonding the outer and inner layers, wherein the adhesive only partially covers the inside surface of at least one outer layer and penetrates to the outside of each outer layer to an extent less than about 10% based on the surface area of each outer layer;
wherein the composite fabric has a calculated flatness factor of not more than 4.4.
DETAILED DESCRIPTION OF THE INVENTION
A unitary composite stretchable fabric has now been made that has a surprising combination of good laundry durability, flat surface appearance, and low-tack surfaces.
The unitary composite stretchable puckered fabric of this invention is composed of two outer layers of nonwoven fabric of substantially equal width and a uniform inner layer of substantially parallel, equally spaced elastomeric fibers of equal decitex which are capable of complete recovery from extensions as great as 300%. The elastomeric fibers can be substantially completely relaxed in the absence of externally applied forces.
“Uniform inner” layer means that the fibers are of substantially equal decitex and spacing, are substantially parallel to each other, and are subjected to substantially the same tension during preparation of the composite fabric.
The nonwoven fabrics can have a basis weight ranging from about 10 to about 30 g/m
2
. Many types of nonwoven fabrics are suitable for use in this invention. Representative examples are nonwovens composed of thermally bonded, spunbonded and hydroentangled fibers, and the two outer layers can be the same or different. Preferably, they are composed of synthetic polymeric fibers such as polyolefin, polyester and polyamide fibers.
The layer of elastomeric fibers is composed of at least eight threadlines per inch (3.15 threadlines/cm) of width, each threadline being at least 400 decitex. Preferably the number of threadlines per inch is not greater than 16 (6.30 threadlines/cm) and, most preferably, it is 12. The combination of these two parameters is chosen to provide a minimum retractive force of about 0.22 pounds per inch (38.9 g/cm), as measured in the finished product when it is stretched at 150% of its original length. The elastomeric fibers are substantially parallel to the edges of the nonwoven fabrics. The preferred elastomeric fiber is spandex fiber.
The three layers are bonded together by an adhesive composition which constitutes from about 10% to about 35%. of the weight of the composite fabric. Adhesive content in the composite above these levels can make the fabric bond to itself. The adhesive compositions can be hot melt adhesives, preferably styrene-based block copolymers such as styrene/isoprene and styrene/butadiene block copolymers. The styrene-based portions are preferably at least about 30 wt % of the total adhesive. Each element (layer) in the composite is bonded to at least one other element of the composite. The adhesive only partially covers the inside surface of the outer fabric layer. The adhesive penetrates to the outside of each outer layer to an extent less than about 10% based on the surface area of each outer layer. “Inside surface” refers to a nonwoven layer surface that is within the composite fabric of the invention.
The composite stretchable puckered fabric can be prepared by placing between two layers of nonwoven fabric uniformly tensioned elastomeric filaments which are spaced a substantially equal distance apart and are of substantially equal decitex no less than 400 decitex per filament. There must be at least 8 filaments (threadlines) per inch of width and the threadlines are substantially parallel to each other and to the edges of the nonwoven fabrics. The three layers are bonded with an adhesive followed by removing the tension after bonding. This process produces a puckered fabric having a substantially uniform flat surface appearance which results from small substantially uniform puckers.
In a preferred process for preparing the puckered fabric, a layer of substantially parallel and equally spaced elastomeric fibers is stretched not less than 100% and placed on top of one of the layers of nonwoven fabric. An adhesive, preferably a hot melt adhesive, is applied onto the elastomeric fibers and bottom nonwoven layer. The other layer of nonwoven is then placed on top of the adhesive-treated combination and the combined structure is bonded by heat and pressure while the elastomeric fibers remain in the stretched condition. Alternatively, the adhesive can be applied to the elastomeric fibers prior to their placement between layers of nonwoven fabric. When the bonding is completed, the tension is substantially completely released and the composite fabric relaxes to form the desired puckered structure.
The hot melt adhesive can be applied in several different ways. In one method, the melted adhesive can be deposited as a discontinuous web from a spray nozzle, a process known as melt blowing. In another method, the melted adhesive can be deposited as a solid stream from a nozzle which moves in
E. I. du Pont de Nemours and Company
Guarriello John J.
Morris Terrel
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