Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1994-10-26
1998-06-23
Johnstone, Adrienne C.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156163, 156183, 156229, 156290, 156292, 1563084, 156494, 428152, 604373, 6043852, A61F 1315, B32B 3104, B32B 3108, B32B 3120
Patent
active
057699933
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
This invention concerns a process for producing an elastic multilayer web of material consisting of a flexible elastic backing film and a thermoplastic elastomer and a nonwoven web 5 attached in a wavy pattern to both the top and bottom sides of the backing film, whereby the latter are welded together and the weld joints are distributed over the web of material in the form of a grid-like arrangement of spot welding areas and also yield areas of increased air permeability, unstretched length, arrangement consisting of the backing film in the middle and nonwoven webs on the outside, cylinder having welding spikes as part of a welding station, to it after leaving the welding station.
(Note: "1100" denotes the unstretched length.)
Such a process is described in European Patent A 2,274,752 especially with reference to FIGS. 16 to 18 in that patent specification Elastic multilayer webs of material that are produced as laminates are used, for example, as elastic sealing cuffs in manufacturing baby diapers. The laminate should be impervious to liquids but should be gas permeable so it is pleasant to wear. It should be like a textile from both a visual and a haptic standpoint. Therefore, as indicated above, a flexible backing film which should be impermeable to liquids and should not be self-sticking is bonded to appropriate webs of a nonwoven material in a wavy pattern. In general, an autogenous welding process is used such as ultrasonic welding or heat welding.
In the known process the welding spots are also designed as perforations which serve to allow ventilation.
Welding is performed with the backing film stretched or partially stretched, in which case the stretching is performed just before the film enters the welding station. If the nonwoven webs are then applied to the backing film in an unstretched condition or if they are less stretched than the backing film they will pucker and develop a wavy pattern when the backing film is released again after passing through the welding station. Thus all three layers are welded together, forming holes with the material fused around the edges of these holes.
In the state of the art described above, suitable combinations of materials are mentioned. Such materials--thermoplastic elastomers-- are also suitable for the present case. In particular, the backing film is made of a blended PE/PE copolymer. However, other materials such as block copolymers of A--B--A' type are also suitable.
Disadvantage of the known web of material is that when it is stretched for use purposes, the webs of nonwoven attached in a wavy (crepe-like) manner to the top and bottom sides of the backing film also become stretched, thus destroying the textile-like impression given by the web of material. In addition, large perforations are also formed in an unwanted manner.
The problem was to develop a process for producing an elastic multilayer web of material that will yield a product that would retain its textile-like appearance in the desired fluffy form even when stretched to the limits of elasticity.
This problem is solved by a process of the type described initially which is characterized in that the two webs of nonwoven are guided together and then stretched to a specific extent (100+b) % or (100+c) % while maintaining the following condition: film and of nonwovens 1 and 2) are great enough to yield a wavy or crepe-like layer of the web of nonwoven material. Then, steps b and c mentioned initially are carried out (actual values for a, b and c are as follows: a: 20 to 100; c about 5 and b 0 to 2).
Thus with the new process the upper and lower layers of nonwoven are brought together with the backing film at different degrees of stretching. Preferably one web of nonwoven remains completely unstretched while the other undergoes a prestretching which corresponds approximately to half the stretch applied to the backing film, in other words, a.apprxeq.2c. In the relaxed state, the material has the known fluffy creped appearance of known woven laminate sheeting.
REFERENCES:
patent: 4606964 (1986-08-01), Wideman
patent: 4720415 (1988-01-01), Vander Wielen et al.
patent: 4770656 (1988-09-01), Proxmire et al.
patent: 4847134 (1989-07-01), Fahren-Krug et al.
Amoco Corporation
Hensley Steven L.
Johnstone Adrienne C.
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