NOVEL ABSORBENT LAMINATE FOR DISPOSABLE ABSORBENT ARTICLES
Novel absorbent laminate for use in absorbent articles comprising thermoplastic adhesive compositions with a glass transition temperature higher than 25° C. are described. The laminate exhibits improved absorption properties upon storage and improved delamination strength.
1 . An absorbent laminate, comprising:
a. an upper layer;
b. a lower layer; and
c. an intermediate layer positioned between the upper and lower layers and comprising particulate superabsorbent material and a thermoplastic adhesive composition, wherein the adhesive has a glass transition temperature (Tg) greater than about 25° C., wherein the thermoplastic adhesive composition exhibits an average rate of change in vertical delamination strength with respect to temperature in the interval from about Tg−2° C. to about Tg+4° C. that is greater than the rate of change in vertical delamination strength with respect to temperature in the interval from about Tg+4° C. to about Tg+20° C., with the delamination strength decreasing as the temperature increases.
2 . An absorbent laminate as claimed in claim 1 , wherein the thermoplastic adhesive composition comprises a hot-melt thermoplastic adhesive composition.
3 . An absorbent laminate as claimed in claim 2 , wherein the thermoplastic adhesive composition comprises a pressure-sensitive thermoplastic adhesive composition.
4 . An absorbent laminate as claimed in claim 3 , wherein the thermoplastic adhesive composition comprises a synthetic rubber-based thermoplastic adhesive composition.
5 . An absorbent laminate as claimed in claim 1 , wherein the thermoplastic adhesive composition comprises fibers.
6 . An absorbent laminate as claimed in claim 1 , wherein the thermoplastic adhesive composition is thermally stable at temperatures that yield a viscosity below about 2000 mPa·s.
7 . An absorbent laminate as claimed in claim 1 , wherein the thermoplastic adhesive composition is thermally stable at temperatures that yield a viscosity below about 1400 mPa·s.
8 . An absorbent laminate as claimed in claim 1 , wherein at least one of the upper layer and the lower layer comprises tissue.
9 . An absorbent laminate as claimed in claim 1 , wherein both the upper layer and the lower layer comprise tissue.
10 . An absorbent laminate as claimed in claim 1 , wherein the absorbent laminate exhibits a lower 2 ml free surface absorption time upon aging at storage temperatures below Tg than for storage temperatures above Tg.
11 . An absorbent laminate as claimed in claim 10 , wherein the absorbent laminate exhibits a 2 ml free surface absorption time of less than about 10 seconds after a month in storage at temperatures below the glass transition temperature.
12 . An absorbent laminate as claimed in claim 1 , wherein the weight of thermoplastic adhesive composition is less than about 5% of the weight of the superabsorbent material.
13 . An absorbent laminate as claimed in claim 1 , wherein the laminate exhibits a vertical delamination strength of at least about 5 N.
14 . An absorbent laminate as claimed in claim 4 , wherein the thermoplastic adhesive composition is selected from the group comprising styrene-butadiene-styrene (SBS) and styrene-isoprene-styrene (SIS) block copolymers.
15 . An absorbent laminate as claimed in claim 1 , wherein the particulate superabsorbent material and the thermoplastic adhesive composition comprise a mixture.
16 . An absorbent laminate for an absorbent article, comprising a thermoplastic adhesive composition and particulate superabsorbent material, wherein the thermoplastic adhesive composition has a glass transition temperature (“Tg”) greater than about 25° C., and exhibits an average rate of change in vertical delamination strength with respect to temperature in the interval from about Tg−2° C. to about Tg+4° C. that is greater than the rate of change in vertical delamination strength with respect to temperature in the interval from about Tg+4° C. to about Tg+20° C., with the delamination strength decreasing as the temperature increases.
17 . An absorbent laminate, comprising:
a. an upper layer comprising tissue;
b. a lower layer comprising tissue; and
c. an intermediate layer positioned between the upper and lower layers and comprising particulate superabsorbent material and a pressure-sensitive, synthetic rubber-based thermoplastic adhesive composition, wherein the thermoplastic adhesive composition has a glass transition temperature (Tg) greater than 25° C.; and
d. wherein the average rate of change in vertical delamination strength of the laminate with respect to temperature is greater across the temperature interval of the thermoplastic adhesive composition's glass transition temperature than across the interval of the glass transition temperature +4 degrees ° C. to about +20 degrees ° C.
18 . An absorbent laminate as claimed in claim 17 , wherein the rate of change in the 2 ml free absorption time with respect to storage time is less for materials stored at a temperature at least about 5° C. below the thermoplastic adhesive composition's glass transition temperature than for materials stored at a temperature at least about 5° C. above the thermoplastic adhesive composition's glass transition temperature.