Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-12-17
2003-08-26
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S229000, C156S494000, C156S578000, C427S424000, C118S324000
Reexamination Certificate
active
06610161
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to adhesive dispersing systems and more particularly to processes and apparatus for bonding one or more relatively elongated strands to one or more substances, especially bonding stretched elastic strands to fabrics in the manufacture of absorbent garments.
2. Description of Related Art
Disposable absorbent garments such as infant diapers or training pants, adult incontinence products, and other such products are well-known in the art. Typically, the chassis of such garments comprises a liquid-permeable body-contacting liner sheet (or “topsheet”), a liquid-impermeable backing sheet (or “backsheet”) (collectively the “sheets”), and a moisture-absorbent core fiber (or “absorbent core”) that usually is made of a non-woven mat of randomly arranged fiber and is generally disposed between the topsheet and the backsheet.
These absorbent garments often times incorporate elastic elements in the waist, tummy and leg areas for improving the fit of the garment. The waist and tummy elastic elements increase the flexibility of the garment, allowing the same garment to accommodate a greater range of body sizes. In addition, they make the garment more form-fitting for the wearer. Leg gather elastic elements and standing leg gathers have also been employed to help reduce leakage of bodily exudates from the garment when the absorbent core cannot absorb body exudates fast enough. Leg gathers are known in the art, and U.S. Pat. No. 5,660,664 issued to Herman (the “'664 Patent”) discloses an exemplary method of manufacturing leg gathers, the disclosure of which is incorporated by reference herein in its entirety.
These garments typically are prepared by continuously supplying the various components of the garment, and forming these components into the final garment. The elastic elements are continuously supplied at several different points of the assembly process, they typically are extended and then adhered to the garment components.
Typically the adhesive is sprayed onto stretched elastic strands disposed on or very near an underlying fabric substrate moving relative to one or more adhesive dispensing nozzles. The adhesive usually is a hot melt adhesive that is applied generously to both the substrate and the elastic strands simultaneously. Application of generous amounts of adhesive to substrate is often the result of inefficiency of application methods and does not typically provide bonding benefits. The stretched elastic strand is usually bonded between overlapping fabric layers. As the stretched elastic strands contracts, the fabric adhered thereto is bunched together forming generally pleated waist bands and other stretchable portions of the undergarment. It is important that the elastic strand be bonded to the fabric substantially continuously along its axial length to be bonded to ensure uniform pleating, or bunching, of the fabric, which is necessary for optimum comfort and fluid absorption, and to provide an aesthetically pleasing product.
Methods of bonding elastics to garment materials have been previously discussed in the art. An example of disposing elastic elements between layers of sheet material is provided in U.S. Pat. No. 5,870,778 issued to Tharpe, the disclosure of which is incorporated by reference herein in its entirety. Tharpe discloses coating the garment materials with adhesive to affix the elastic elements therein. A common procedure for affixing elastic elements in the industry today is a spiral spray adhesive application as disclosed in U.S. Pat. No. 4,815,660, issued to Boger, the disclosure of which is incorporated by reference herein in its entirety. Spiral spray adhesive application consists of ejecting a bead of hot melt adhesive, directing jets of pressurized air to form an elongated adhesive fiber from the bead, and imparting a rotational motion to the adhesive fiber. The spirals of adhesive are then deposited on the target substrate, typically a non-woven material. In usage, the adhesive spray coats not only the elastic elements but also “oversprays” to other sites, causing a number of undesirable consequences.
Some of these disadvantages include: The garment materials that are “oversprayed,” e.g., portions of the topsheet, the bottom sheet, and the absorbent core, become rigid upon hardening of the “oversprayed” adhesive making the garment less comfortable for its wearer. This has been referred to as the “plywood effect.” The “overspray” also may coat parts of the assembly machinery that must then be periodically cleaned of the adhesive. The elastic elements and/or the substrates to which they are to adhere may not be uniformly coated with the adhesive due to the nature of the spraying operation, and therefore the elastic elements may not bond to the garment materials as well as if they had been more uniformly and completely coated with the adhesive. Finally, the “overspray” is wasted adhesive, increasing the cost of materials for the finished garment.
Attempts have been made to reduce the amount of excess adhesive that is applied to the garment. U.S. Pat. No. 5,993,433 issued to St. Louis et al., which is incorporated herein by reference in its entirety, discloses an adhesive pattern for applying adhesives to the gathers, but such adhesive patterns still contribute to excessive garment stiffness and cost. U.S. Pat. No. 6,235,137 B1 issued to Van Eperen et al., which is incorporated herein by reference in its entirety, discloses a method of coating an elastic strand with a filament of adhesive, but this coating process is still subject to overspraying, and does not provide a complete coating of adhesive on the elastic.
In addition to stiffness and cost concerns, applying excess adhesive onto the elastic strands and underlying substrate than is required for bonding may, in the case of the typically used hot melt adhesives, have a tendency to deform the relatively thin, temperature sensitive fabric, thereby providing an undesirable appearance. In extreme cases the hot adhesive may destroy the fabric by burning a hole through the fabric.
Further excess adhesive applied onto the fabric may reduce the fluid absorbing capacity of the fabric and possibly result in the leakage of bodily fluids from the absorbent garment. Additionally, the adhesive stiffened fabric may be slightly abrasive against the skin, and in some extreme cases may irritate sensitive skin.
U.S. Pat. No. 5,507,909 to Rollins et al., (the “Rollins '909 Patent”) discloses a process and apparatus for helically wrapping adhesive onto an elastic strand, which is bonded to a substrate in the manufacture of disposable absorbent products. The disclosure of the Rollins '909 patent is incorporated by reference herein in its entirety. To helically coat the elastic strand with adhesive, the strand is rotated about its axis as it is drawn past an adhesive flow from a dispensing orifice, for example by drawing the elastic strand between a nip roll assembly rotated at an angle relative thereto.
The process and apparatus disclosed in the Rollins '909 Patent allegedly reduces the amount of adhesive applied to the substrate and applies more conservative amounts of adhesive onto the elastic strand, but the uniform application of adhesive helically about the strand requires consistently and uniformly controlling the rotation of the strand during the drawing thereof. If the adhesive is not applied uniformly along the axial dimension of the strand, the stretched strand may not bond uniformly to the substrate, which adversely affects uniform bunching of the fabric. Non-uniform bunching is undesirable from an aesthetic viewpoint, and more substantively non-uniform bunching of the fabric compromises the ability of the fabric to form an effective fluid seal, and reduces the softness and comfort thereof when stretched against the wearer's body.
U.S. Pat. No. 6,077,375 to Kwok (the “Kwok '375 Patent”) discloses applying fluids including adhesives onto strands. More particularly the Kwok '375 Patent disclo
Aftergut Jeff H.
Hunton & Williams
Paragon Trade Brands, Inc.
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