Nonwoven web material containing crosslinked elastic component formed from a pentablock copolymer
View Patent ↗A nonwoven web material that includes an elastic component or material (e.g., nonwoven web, nonwoven web laminated to an elastic material, etc.) is provided. The elastic component contains a crosslinked network formed from a pentablock copolymer containing at least two monoalkenyl aromatic midblocks positioned between conjugated diene endblocks, such as butadiene-styrene-butadiene-styrene-butadiene (“BSBSB”) or isoprene-styrene-isoprene-styrene-isoprene (“ISISI”). Prior to crosslinking, the pentablock copolymers have a relatively low viscosity and thus may be readily formed into a precursor elastic material (e.g., film, strands, web, etc.) that is subsequently crosslinked to achieve the desired elastic and mechanical properties.
1. A nonwoven web material comprising an elastic component that includes a crosslinked elastomeric network, the crosslinked network containing a pentablock copolymer having at least two monoalkenyl aromatic midblocks positioned between conjugated diene endblocks.
2. The nonwoven web material of claim 1 , wherein the monoalkenyl aromatic midblocks include styrene or a derivative thereof and the conjugated diene endblocks include butadiene, isoprene, or a mixture thereof.
3. The nonwoven web material of claim 1 , wherein the pentablock copolymer is linear and has the general structure “ABABA”, wherein “A” refers to a conjugated diene block and “B” refers to a monoalkenyl aromatic block.
4. The nonwoven web material of claim 3 , wherein the linear pentablock copolymer is selected from the group consisting of butadiene-styrene-butadiene-styrene-butadiene (“BSBSB”), isoprene-styrene-isoprene-styrene-isoprene (“ISISI”), butadiene-styrene-isoprene-styrene-butadiene (“BSISB”), butadiene-styrene-butadiene-styrene-isoprene (“BSBSI”), butadiene-styrene-isoprene-styrene-isoprene (“BSISI”), isoprene-styrene-butadiene-styrene-butadiene (“ISBSB”), isoprene-styrene-isoprene-styrene-butadiene (“ISISB”), isoprene-styrene-butadiene-styrene-isoprene (“ISBSI”), and mixtures thereof.
5. The nonwoven web material of claim 1 , wherein the pentablock copolymer is branched and has the general structure “(A-B-A) n ”, wherein “A” refers to a conjugated diene block, “B” refers to a monoalkenyl aromatic block, “n” is equal to about 2 or more.
6. The nonwoven web material of claim 5 , wherein “n” is from about 3 to about 30.
7. The nonwoven web material of claim 1 , wherein the pentablock copolymer constitutes about 10 wt. % or more of the elastic material.
8. The nonwoven web material of claim 1 , wherein the pentablock copolymer constitutes about 50 wt. % or more of the elastic material.
9. The nonwoven web material of claim 1 , wherein the material is a composite that contains a nonwoven web facing laminated to the elastic component.
10. The nonwoven web material of claim 9 , wherein the elastic component is a film, strands, web, or a combination thereof.
11. An absorbent article comprising an absorbent core positioned between a substantially liquid-impermeable layer and a liquid-permeable layer, the absorbent article comprising the nonwoven web material of claim 1 .
12. A method for forming a nonwoven composite, the method comprising:
melt extruding the pentablock copolymer having at least two monoalkenyl aromatic midblocks positioned between conjugated diene endblocks;
forming a precursor elastic material from the melt extruded pentablock copolymer;
laminating the precursor elastic material to a nonwoven web facing; and
crosslinking the pentablock copolymer to form a crosslinked elastomeric network.
13. The method of claim 12 , wherein the precursor elastic material includes a film, strands, web, or a combination thereof.
14. The method of claim 12 , wherein the laminating occurs prior to crosslinking of the pentablock copolymer.
15. The method of claim 12 , wherein the laminating occurs after crosslinking of the pentablock copolymer.
16. The method of claim 12 , wherein crosslinking is induced by electromagnetic radiation.
17. The method of claim 16 , wherein the electromagnetic radiation has a wavelength of about 100 nanometers or less.
18. The method of claim 16 , wherein the dosage of the electromagnetic radiation is from about 1 to about 30 Megarads.
19. The method of claim 16 , wherein the dosage of the electromagnetic radiation is from about 5 to about 15 Megarads.
20. The method of claim 12 , wherein the monoalkenyl aromatic midblock includes styrene or a derivative thereof and the conjugated diene endblocks include butadiene, isoprene, or a mixture thereof.
21. The nonwoven web material of claim 1 , wherein the monoalkenyl aromatic midblocks constitute from about 1 wt. % to about 40 wt. % of the copolymer.
22. The nonwoven web material of claim 1 , wherein the monoalkenyl aromatic midblocks constitute from about 15 wt. % to about 35 wt. % of the copolymer.