Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Extrusion molding
Reexamination Certificate
2000-11-16
2003-03-11
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Extrusion molding
C053S403000, C053S432000, C053S477000, C264S211170, C264S234000, C264S345000, C264S476000
Reexamination Certificate
active
06531085
ABSTRACT:
BACKGROUND
People rely on disposable absorbent articles to help participate in, and enjoy, their daily activities.
Disposable absorbent articles, such as adult incontinence articles and diapers, are generally manufactured by combining several components. These components typically include a liquid-permeable topsheet; a liquid-impermeable backsheet attached to the topsheet; and an absorbent core located between the topsheet and the backsheet. When the disposable article is worn, the liquid-permeable topsheet is positioned next to the body of the wearer. The topsheet allows passage of bodily fluids into the absorbent core. The liquid-impermeable backsheet helps prevent leakage of fluids held in the absorbent core. The absorbent core is designed to have desirable physical properties, e.g. a high absorbent capacity and high absorption rate, so that bodily fluids can be transported from the skin of the wearer into the disposable absorbent article.
Some disposable absorbent articles are constructed with various types of elasticized waistbands and elasticized leg bands or leg cuffs. One method of constructing elasticized regions is to incorporate elastic strands into the disposable absorbent product. For example, elastic strands have been laminated between layers of polymer film and/or layers of woven or nonwoven fabrics to provide such regions. Folded-over layers have also been employed to enclose or envelop selected strands of material. These folded-over layers have been employed to enclose elastomeric strands within the waistband, leg cuff and inner barrier cuff components of disposable diapers and other disposable absorbent articles. The polymeric film or films, layers of woven or nonwoven fabrics, and/or folded-over layers may be an integral portion of the topsheet and/or backsheet discussed above, or may be separate components that are attached to the topsheet and/or backsheet.
In order to introduce an elastic strand to the product being made, a spool of the strand is generally placed on an unwind stand. The strand is then continuously unwound, in the machine direction, with the strand being attached to a substrate, such as a base layer of material, to provide a substrate composite. As stated above, examples of a base material include, but are not limited to, polymeric films and/or woven or nonwoven fabrics. If the elastic strand does not have the integrity to withstand forces placed on it during production of the article being made, then the strand may break. For example, the tension placed on a segment of the elastic strand between an unwind stand and the point of attachment on a base material may exceed the tensile strength of that segment, causing a break. Such breaks lead to costly downtime. Accordingly, producers of disposable absorbent articles, as well as other manufacturers using elastic strand as raw material in a production process, seek ways of ensuring that the strength characteristics of the elastic strand are sufficient to withstand forces placed on the strand during production, thereby decreasing or minimizing the number of breaks. Furthermore, producers of articles, such as disposable absorbent articles, seek ways of improving the function of the elastic strand in the article. Typically, one function is to help define elasticized regions so that the disposable absorbent article better fits the wearer of the article. One way of decreasing the number of strand breaks on a production machine, improving the function of elastic strand in an article, or both, is to increase certain strength characteristics of elastic strand.
Accordingly, what is needed is a method for treating an elastic strand to improve the strength of the strand; and substrate composites or disposable absorbent articles comprising such strand.
SUMMARY
We have determined that strength characteristics of elastic strand improve when the strand is heated. Thus, the present invention is directed to improving strength characteristics of an elastic strand by heating the strand. The strand may be heated by thermal conduction and/or convection, or by irradiative methods, incorporating, for example, infrared radiation or microwave radiation, or some combination of these. If the elastic strand is made at a location different from the location where the strand is used as a raw material, the strand may be heated at either location, or both locations. Furthermore, the strand may be heated in-line, i.e. as part of the process that makes the strand or the process that uses the strand as a raw material, or off-line, i.e. in a step separate from either of the aforementioned processes. And, as noted below, the strand may be heat treated and its exposure to water or water vapor may be regulated.
One method having features of the present invention includes the steps of: providing an elastic strand, the elastic strand having been made by steps comprising extruding, spinning, or otherwise making the strand; and heating the strand so that the peak-load value of the heated elastic strand is about 10% greater, specifically about 20% greater, particularly about 30% greater, and more particularly about 40% greater than the peak-load value of the elastic strand before heating.
In some representative embodiments, the elastic strand comprises polyester, polyurethane, polyether, polyamide, polyacrylate, polyester-b-polyurethane block co-polymer, polyether-b-polyurethane block co-polymer, or polyether-b-polyamide block co-polymer.
Methods by which the elastic strand may be heated include use of infrared radiation, microwave radiation, convective heat, conductive heat, or some combination thereof.
Some methods having features of the present invention include the steps of: providing an elastic strand, the elastic strand having been made by steps comprising extruding, spinning, or otherwise making the strand; and directing the strand to an environment having a temperature of about 120° F. or more, the strand remaining in the environment for about 4 or more hours, particularly about 8 or more hours, and more particularly about 24 or more hours.
Other methods having features of the present invention include the steps of: providing an elastic strand, the elastic strand having been made by steps comprising extruding, spinning, or otherwise making the strand; and directing the strand to an environment having a temperature of about 212° F. or more, the strand remaining in the environment for about 2 or more hours, particularly about 4 or more hours, and more particularly about 8 or more hours.
Still other methods having features of the present invention include the steps of: providing an elastic strand, the elastic strand having been made by steps comprising extruding, spinning, or otherwise making the strand; and directing the strand to an environment having a temperature of about 150° C. or more, the strand remaining in the environment for about 10 or more minutes, particularly about 20 or more minutes, and more particularly about 30 or more minutes.
In some representative embodiments, the strand is heated in-line on a production machine used to make a substrate composite comprising the strand or a disposable absorbent article comprising the strand.
In other embodiments of the present invention, the elastic strand is processed by steps comprising: providing an elastic strand, the elastic strand having been made by steps comprising extruding, spinning, or otherwise making the strand; heating the strand so that the peak-load value of the heated elastic strand is about 10% greater, specifically about 20% greater, particularly about 30% greater, and more particularly about 40% greater than the peak-load value of the elastic strand before heating; and regulating exposure of the strand to water or water vapor, as disclosed in co-pending U.S. Patent Application No. 60/166348, entitled “Method for Regulating Strength Degradation in an Elastic Strand,” which was filed on Nov. 19, 1999 and from which the present non-provisional application both claims priority and incorporates by reference in a manner consistent herewith. The co-pending applicat
Ng Wing-Chak
Zhou Peiguang
Kimberly--Clark Worldwide, Inc.
Pugliese III Sebastian C.
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