Biodegradable continuous filament web
View Patent ↗A biodegradable nonwoven web comprising substantially continuous multicomponent filaments is provided. The filaments comprise a first component and a second component. The first component contains at least one high-melting point aliphatic polyester having a melting point of from about 160° C. to about 250° C. and the second component contains at least one low-melting point aliphatic polyester. The melting point of the low-melting point aliphatic polyester is at least about 30° C. less than the melting point of the high-melting point aliphatic polyester. The low-melting point aliphatic polyester has a number average molecular weight of from about 30,000 to about 120,000 Daltons, a glass transition temperature of less than about 25° C., and an apparent viscosity of from about 50 to about 215 Pascal-seconds, as determined at a temperature of 160° C. and a shear rate of 1000 sec −1 .
1. A biodegradable nonwoven web comprising substantially continuous multicomponent filaments, wherein the multicomponent filaments comprise a first component and a second component, the first component containing a first aliphatic polyester having a melting point of from about 160° C. to about 250° C. and the second component containing a second aliphatic polyester, wherein the melting point of the second aliphatic polyester is at least about 30° C. less than the melting point of the first aliphatic polyester, and wherein the second aliphatic polyester has a number average molecular weight of from about 30,000 to about 120,000 Daltons, a glass transition temperature of less than about 25° C., and an apparent viscosity of from about 50 to about 215 Pascal-seconds, as determined at a temperature of 160° C. and a shear rate of 1000 sec −1 , wherein the second component is free of a multi-carboxylic acid nucleating agent.
2. The biodegradable nonwoven web of claim 1 , wherein the first aliphatic polyester is polylactic acid.
3. The biodegradable nonwoven web of claim 1 , wherein the second aliphatic polyester has an apparent viscosity of from about 80 to about 150 Pascal-seconds, as determined at a temperature of 160° C. and a shear rate of 1000 sec −1 .
4. The biodegradable nonwoven web of claim 1 , wherein the second aliphatic polyester has a melting point at least about 40° C. less than the melting point of the first aliphatic polyester.
5. The biodegradable nonwoven web of claim 1 , wherein the second aliphatic polyester has a melting point of from about 100° C. to about 140° C.
6. The biodegradable nonwoven web of claim 1 , wherein the second aliphatic polyester has a number average molecular weight of from about 40,000 to about 100,000 Daltons.
7. The biodegradable nonwoven web of claim 1 , wherein the second aliphatic polyester has a polydispersity index of from about 1.0 to about 3.0.
8. The biodegradable nonwoven web of claim 1 , wherein the second aliphatic polyester has a melt flow index of from about 20 to about 120 grams per 10 minutes, measured at a force of 2160 grams and temperature of 190° C. in accordance with ASTM Test Method D1238-E.
9. The biodegradable nonwoven web of claim 1 , wherein the second aliphatic polyester has a glass transition temperature of about 0° C. or less.
10. The biodegradable nonwoven web of claim 1 , wherein the second aliphatic polyester has a glass transition temperature of about −10° C. or less.
11. The biodegradable nonwoven web of claim 1 , wherein the second aliphatic polyester is polybutylene succinate.
12. The biodegradable nonwoven web of claim 1 , wherein the filaments have a sheath/core or side-by-side configuration.
13. The biodegradable nonwoven web of claim 1 , wherein the web exhibits a peak elongation in the machine direction of at least about 10%.
14. The biodegradable nonwoven web of claim 1 , wherein the web exhibits a peak elongation in the machine direction of at least about 35%.
15. The biodegradable nonwoven web of claim 1 , wherein the web exhibits a peak elongation in the cross machine direction of at least about 35%.
16. The biodegradable nonwoven web of claim 1 , wherein the web exhibits a peak elongation in the cross machine direction of at least about 50%.
17. The biodegradable nonwoven web of claim 1 , wherein the web exhibits a peak load in the machine direction of at least about 3500 grams-force per inch.
18. The biodegradable nonwoven web of claim 1 , wherein the web exhibits a peak elongation in the cross machine direction of at least about 1500 grams-force per inch.
19. The biodegradable nonwoven web of claim 1 , wherein the filaments are autogenously bonded at intermittent compacted areas.
20. The biodegradable nonwoven web of claim 19 , wherein at least a portion of the high melting point aliphatic polyester within the compacted areas retains a substantially fibrous form.
21. The biodegradable nonwoven web of claim 20 , wherein the substantially fibrous high melting point polymer is oriented in two or more directions.
22. A method for forming the biodegradable nonwoven web of claim 1 , the method comprising:
co-extruding a first thermoplastic composition and a second thermoplastic composition to form the multicomponent filaments, the first thermoplastic composition comprising the first aliphatic polyester and the second thermoplastic composition comprising the second aliphatic polyester;
randomly depositing the filaments onto a forming surface; and
melt-fusing the filaments at intermittent bond regions.
23. The method of claim 22 , wherein the second thermoplastic composition is extruded at a temperature ranging from about 145° C. to about 195° C.
24. The method of claim 22 , wherein the filaments are melt-fused by passing the web through a nip formed between two rolls.
25. The method of claim 24 , wherein one or both of the rolls are heated to a temperature of from about 50° C. to about 160° C.
26. The method of claim 24 , wherein one or both of the rolls are heated to a temperature of from about 100° C. to about 140° C.
27. The method of claim 24 , wherein a pressure of from about 5 to about 150 pounds per square inch is applied at the nip.
28. The method of claim 24 , wherein a pressure of from about 30 to about 60 pounds per square inch is applied at the nip.
29. The method of claim 22 , wherein the bond regions cover less than 50% of a surface of the web.
30. An absorbent article comprising an absorbent core positioned between a substantially liquid-impermeable layer and a liquid-permeable layer, wherein the substantially liquid-impermeable layer contains the biodegradable nonwoven web of claim 1 .
31. The absorbent article of claim 30 , wherein the substantially liquid-impermeable layer forms an outer cover of the absorbent article.
32. The absorbent article of claim 30 , wherein the biodegradable nonwoven web is laminated to a breathable film.
33. The biodegradable nonwoven web of claim 1 , wherein the second aliphatic polyester has a number average molecular weight of from about 45,000 to about 85,000 Daltons.