Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
1996-06-21
2001-11-06
Dawson, Glenn K. (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C604S366000, C604S372000, C604S373000, C604S370000, C604S385250, C604S385290, C604S385300, C156S183000, C156S345420, C428S198000, C428S221000
Reexamination Certificate
active
06313372
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an elastic composite which comprises a non-woven fabric and an elastic sheet, and which exhibits excellent elastic recovery and a soft surface touch. The elastic composite can be advantageously utilized in elasticizing an article which is brought into direct contact with the human skin during use, such as a sleeve of a medical gown, or a waist or crotch portion of a sanitary article.
BACKGROUND OF THE INVENTION
In recent years, disposable articles, including medical and sanitary articles, etc., have widely used elastic material to improve the fit to the human body. Particularly, infant articles utilize an elastic sheet and a non-woven fabric composite much more frequently than an elastic sheet alone. In the elastic sheet and the non-woven fabric composite, the elastic sheet exhibits elastic properties and the non-woven fabric provides improved surface structure and reinforcement of the elastic sheet.
A typical example of such an elastic composite is a three-layer composite called S.M.S. (spunbonded/meltblown/spunbonded) which is disclosed in U.S. Pat. Nos. 4,663,220; 4,652,487; and 4,720,415. This composite is manufactured by a method called S.B.L. (Stretch-Bonded Laminate) wherein the elastic sheet is first stretched and is in its stretched state bonded to the non-woven fabric to form the composite upon release. The composite manufactured in accordance with this method has a stable range of elasticity and neither expands beyond the range nor breaks during normal use since its expansion limit corresponds to its stretched range during manufacture. However, the composite disadvantageously uses more of the non-woven fabric than may be necessary and is bulky so that it is not well-suited for high-speed commercial production.
Japanese Patent No. 4-281059 also discloses a method for directly entangling fibers into an elastic net, which, however, is costly. In order to remedy these drawbacks, an attempt (EPC No. 556,749) has been made to bond an elongatable non-woven fabric to an elastic film on line to form a composite of channel-like construction.
Japanese Utility Model No. 3-39509 discloses an elastic composite which is constructed by hydro-entangling a web comprising staple fibers and a non-woven fabric directly formed of thermoplastic elastomers. In order for the composite to have stretchability of higher than 70%, the web includes fibers which slightly crimp upon application of heat or which split into fibers of finer than 1 denier.
The above conventional composites are capable of expanding over a wide range from a breaking point of the non-woven fabric to a breaking point of the elastic sheet. Their critical points however create difficulty in designing products and defining its specifications. It also leaves users with insufficient knowledge of the proper use since they do not know at what point the composite breaks.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a highly productive, economical and functional elastic composite which utilizes individual properties of a non-woven fabric and an elastic sheet in combination. Another object of the invention is to provide a method for manufacturing such an elastic composite.
In accordance with the embodiments of the present invention, there is provided a stretch-activated elastic composite which comprises a non-woven fabric having a potential elongatability of higher than 100% in a biased direction, an elastic sheet having an elastic recovery rate of higher than 60%, and an elastic limit of higher than 200%. The non-woven fabric in its unelongated state is partially bonded to one surface of the unstretched elastic sheet in securement regions. The elastic composite exhibits, per unit width of 5 cm, (1) a stress of lower than 1000 g at 30% stretch, (2) a stress of higher than 400 g at 100% stretch, (3) a breaking point of higher than 400 g, and (4) an elastic limit of higher than 200%. The elastic composite after being stretched less than 200% exhibits, per unit width of 5 cm, (1) a stress of lower than 500 g at 30% stretch and (2) a stress of higher than 100 g at 100% stretch. The elastic composite after three repeated cycles of 150% stretching and relaxing exhibits an elastic recovery rate of higher than 60%. “Strain” as used herein means the amount of elongation of the material when a stretching force is applied. “Stress” is the force applied to produce the strain.
In order to optimize the elastic composite structure in accordance with the preferred embodiments of the present invention, it becomes important to combine respective characteristics of the non-woven fabric and the elastic sheet thereby improving their functions synergistically. Since the elastic sheet may be expensive relative to the non-woven fabric, the addition of the non-woven fabric thereto further improves the cost/performance ratio of the elastic composite.
In accordance with the present invention, the designs of the expandable non-woven fabric and selections of the bonding method provide a wide range of selection of the elastic sheet and permit the elastic sheet to fully exhibit its desired functionality.
(1) The expandability of the non-woven fabric enables the elastic composite, which is not elastically stretchable in a normal condition, to have the property that it is activated by expansion to become elastically stretchable and contractable.
(2) With a suitable selection of its entanglement condition an expandable, hydro-entangled non-woven fabric enables the resulting non-woven fabric to have good expandability as well as two-phase expandability which creates a second increase in stress beyond a first stress point.
(3) Securement regions for securing the elastic sheet to the non-woven fabric are provided to extend transversely of the expandable direction of the elastic composite so that the securement regions provide less resistance to the expandability of the elastic composite.
(4) The securement regions provided between the non-woven fabric and a top surface of the elastic sheet are staggered from the securement regions provided between the non-woven fabric and a bottom surface of the elastic sheet to prevent the top and bottom securement regions from overlapping. This prevents brittleness. Where heat bonding is used, some brittleness may occur where the heat is applied. By staggering, as described, such brittleness (which may be undesirable) does not extend through the composite.
The above considerations in designing the elastic composite enable production of an elastically recoverable elastic composite which has excellent expandability under low strain.
The present invention further provides a method for manufacturing an elastic composite having the above-described characteristics. This method will now be explained in detail with reference to the accompanying drawings.
REFERENCES:
patent: 4205679 (1980-06-01), Repke et al.
patent: 4450026 (1984-05-01), Pieniak et al.
patent: 4938757 (1990-07-01), Van Gompel et al.
Dawson Glenn K.
Hunton and Williams
Paragon Trade Brands, Inc.
Reichie K. M.
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