Inelastic, heat-elasticizable sheet material for diapers

DETAILED DESCRIPTION In FIG.
1, heat-shrinkable composite 10 comprises a plurality of parallel elastomeric strands, each stretched to several times its relaxed length, sandwiched between first cover web 11 and second cover web 14.
Cover web 11 comprises support 12 and heat-sealable binder 13; correspondingly, cover web 14 comprises support 15 and heat-sealable binder 16.
(Heat-sealable binders 13 and 16 can be eliminated if supports 12 and 15 are themselves heat-sealable.
) Binders 13 and 16 are sealed to each other and to interposed elastomeric strands 17 along heat seal lines 18.
The entire heat-shrinkable composite 10 is laminated, (e.
g.
, by sonic bonding, interposition of an adhesive, etc.
) to flexible substrate 20, thereby forming laminate 30.
At room temperature, the stiffness of webs 11 and 14 is sufficient to prevent stretched elastomeric strands 17 from returning to their relaxed length.
As a result, composite 10 remains in substantially flat condition, even when not subjected to tension, and can be readily handled on conventional assembly lines.
After composite 10 is bonded to substrate 20, of course, the ability of elastomeric strand 17 to contract is still further inhibited.
When composite 10 or laminate 30 is subjected to a temperature sufficient to render the assembly significantly more flexible, however, the retracting force of strands 17 functions to effect shirring, as is shown in FIG.
2.
FIGS.
3 and 4 correspond, respectively, to FIGS.
1 and 2, substrate 20 in FIGS.
3 and 4 being the outer polyethylene cover of a disposable diaper, the inner aspect being lined with absorbent material (not shown) and protectively covered by moisture-transmitting liner 21.
As is shown in FIG.
4, the existence of shirred areas along the sides of the disposable diaper provides an elastic, stretchy area that conforms snugly to the legs of a baby wearing the diaper, greatly reducing the possibility of leakage.
FIG.
5 shows, in schematic form, a convenient method of manufacturing composite 10