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United States Patent im
Swenson et al.
 Patent Number:  Date of Patent:
 References Cited
U.S. PATENT DOCUMENTS
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4,880,706 11/1989 Mazuera et al 428/910
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FOREIGN PATENT DOCUMENTS
2244422 12/1991 United Kingdom A61F 13/15
WO91/07277 5/1991 WIPO B32B 5/04
Primary Examiner—James J. Bell
Attorney, Agent, or Firm—Gary L. Griswold; Walter N.
Kirn; William J. Bond
An elastic film is provided with non-elastic regions and elastic regions formed from a multi-layer film of an elastomeric layer and a relatively inelastic layer(s).
1 Claim, 2 Drawing Sheets
U.S. Patent June 6, 1995 Sheet 1 of 2 5,422,178
U.S. Patent June 6, 1995 Sheet 2 of 2 5,422,178
ELASTIC FILM LAMINATE
This is a division of application Ser. No. 07/901,420, Jun. 19, 1992, now U.S. Pat. No.. 5,376,430.
FIELD OF THE INVENTION
The invention concerns elastomeric films and more specifically concerns an improved elastomeric laminate.
Elastomeric films have for some time been used and discussed in the literature with regard to their applications in disposable products, such as baby diapers and adult incontinent devices. These elastomeric webs or films are used primarily in the body hugging portions of garments. Many of these elastics are temperaturetreated to provide for controlled elastic recovery. In diapers, for example, elastomeric bands are typically used in the waistband portions such as discussed in U.S. Pat. No. 4,681,580, issued to Reising et al., and Lash, U.S. Pat. No. 4,710,189. Both of these patents describe the use of elastomeric materials which have a heat stable and a heat unstable form. The heat unstable form is created by stretching the material when heated around its crystalline or second phase transition temperature followed by a rapid quenching to freeze in the heat unstable extended form. The heat unstable elastomeric film can then be applied to the, e.g., diaper and then heated to its heat stable elastomeric form.
Berger, U.S. Pat. No. 3,694,815, proposed a method for attaching a stretched relaxed elastic ribbon to a garment by stretching conventional elastic ribbons and immediately freezing the elastomeric material at relatively extreme low temperatures (e.g., well below ambient).
UK Pat. Application 2190406 A proposed maintaining a conventional elastomer in a stretched condition, while attaching it to the member to be shirred (e.g., a diaper), by a rigidifying member, which would then be removed or destroyed following the attachment procedure. As described, the elastomers are first stretched then applied to the rigidifying member in its stretched form.
Matray et al., UK Pat. 2,160,473, proposes an elastomer which will shrink at an elevated temperature (e.g., at or above 175° F. or 79.4° C). The allegedly novel feature of this material, compared to the heat shrink materials discussed above, is that it does not require preheating or cold treatment during the stretching operation but rather could be stretched at ambient temperatures by a differential speed roll process or by "cold rolling". The polymer proposed was a copolymer having alternating segments of polyamidepolyether block polymers, commercially available under the trade name Pebax, particularly Pebax Extrusion grades 2533 and 3533.
Problems with these elastomeric films include the difficulties inherent in applying a stretched elastic film to a flexible substrate such as a disposable diaper. For example, these film elastics, after being attached to a flexible substrate, such as by adhesives, will place shear stresses on the attachment areas. This can result in the elastic detaching from the flexible substrate, particularly after repeated elongations.
In copending application Set. No. 07/438,593, filed 11/17/89, having a common assignee, there is disclosed an elastomeric laminate having at least one elastomeric
layer and at least one skin layer which addresses some of the above-noted problems in the art.
Despite the numerous advantages in the materials of the copending application, there is room for improve
5 ment for some applications. In order to activate the nonelastomeric laminate into a state that will allow it to recover and become elastomeric, the laminate must be stretched a substantial amount, for many materials contemplated as useful for the skin and core layers. Further,
10 when the elastic is applied to a garment, equally high stretch ratios are generally required to provide sufficient elastic force to functionally elasticize the garment. This is problematic for applications where low elastic stretch ratios would be desirable, for example, when
15 high levels of gathering of a garment is undesirable or where required by manufacturing needs. There is also a need for elastics that will provide elasticity only in specified areas without requiring the application of separate discrete elastic elements at each area.
20 The desirability of obtaining elasticity in specified areas of a ribbon or tape-like substrate is illustrated by U.S. Patent Nos. 3,800,796, 4,834,820, 4,778,701 and 4,227,952, which disclose the use of composite materials designed to have specified areas of elasticity for use in
25 diaper systems. However, these composites require complicated construction mechanisms to bring the diverse elements of the composite together and/or special procedures for their manufacture and use, that limit their general applicability.
SUMMARY OF THE INVENTION
The present invention relates to improved non-tacky, microtextured, multi-layer elastomeric laminates. The laminates of the present invention are comprised of am
35 elastomeric polymeric core layer(s), which provides elastomeric properties to the laminate and one or more polymeric skin layers. Laminates can be prepared by coextrusion of the selected polymers for the skin and core layers or by application of one or more elastomer
40 layer(s) onto one or more already formed skin layer(s). The novel, non-tacky microtextured laminate is obtained by stretching the laminate past the elastic limit of the skin layers and, while the laminate is stretched, selectively deactivating the elasticity of the laminate at
45 predetermined regions. The laminate then recovers, in the non-deactivated regions, which can be instantaneous, over an extended time period, which is skin layer controllable, or by the application of heat, which is also skin layer controllable.
50 The selectively deactivated areas provide highstrength inelastic regions. The recovered regions can be microtextured or have detached skin layers.
BRIEF DESCRIPTION OF THE DRAWINGS
55 FIG. 1 is a schematic representation of a process and apparatus used to coextrude the laminates of the invention.
FIG. 2 is the cross-sectional segment of a laminate with microstructuring caused by uniaxially stretching a 60 film of the invention.
FIG. 3 is a perspective view of a microtextured skin embodiment of the invention.
FIG. 4 is a perspective view of a delaminated skin embodiment of the invention. 65 FIG. 5 is a diaper tape tab formed of the invention laminate.
FIG. 6 is an end view of the FIG. 4 embodiment as it would appear in a diaper.