Absorbent articles including ultrasonically bonded laminated structures
View Patent ↗The present invention is generally directed to adhesive compositions comprising selected ratios of crystalline and amorphous polymers. In some versions of the invention, polymers capable of existing in different configurations (e.g., a polymer such as polypropylene which can exist in an atactic, syndiotactic. or isotactic configuration) is used to prepare adhesives of the present invention. As an example, a selected amount of isotactic polypropylene is blended with a selected amount of atactic polypropylene to prepare an adhesive composition having one or more performance properties (e.g., bond strength) that are superior to the performance properties of a conventional hot-melt adhesive.
1. An article comprising an ultrasonically bonded laminated structure, the laminated structure comprising a first material, a second material, and an adhesive composition, the adhesive composition comprising an atactic polymer and an isotactic polymer, wherein the atactic polymer is atactic polystyrene, the atactic polymer having a degree of crystallinity of about 20% or less and a number-average molecular weight of from about 1,000 to about 300,000 and the isotactic polymer having a degree of crystallinity of about 40% or more and a number-average molecular weight of from about 3,000 to about 200,000, wherein at least one of the first material and the second material is a cellulosic material, and wherein the first material and the second material are ultrasonically bonded together.
2. The article as set forth in claim 1 wherein the degree of crystallinity of the atactic polymer is about 15% or less.
3. The article as set forth in claim 1 wherein the degree of crystallinity of the isotactic polymer is about 60% or more.
4. The article as set forth in claim 1 wherein the number-average molecular weight of the atactic polymer is between about 3,000 and about 100,000.
5. The article as set forth in claim 1 wherein the number-average molecular weight of the isotactic polymer is between about 10,000 and about 100,000.
6. The article as set forth in claim 1 wherein the adhesive composition is hot-melt processable at about 400 degrees Fahrenheit or less.
7. The article as set forth in claim 1 wherein the adhesive composition is hot-melt processable at about 375 degrees Fahrenheit or less.
8. The article as set forth in claim 1 wherein the adhesive composition has a melt index of from about 100 to about 2000 grams per 10 minutes.
9. The article as set forth in claim 1 wherein the adhesive composition comprises from about 50 to about 90 weight percent of the atactic polymer and from about 5 to about 50 weight percent of the isotactic polymer.
10. The article as set forth in claim 1 wherein the isotactic polymer comprises isotactic polypropylene.
11. The article as set forth in claim 1 wherein the isotactic polymer is selected from the group consisting of high density polyethylene, isotactic polystyrene, isotactic polybutene, and combinations thereof.
12. The article as set forth in claim 11 wherein the high density polyethylene has a density in the range of 0.935 to 0.980 grams per cubic centimeter.
13. The article as set forth in claim 1 wherein the first material comprises polypropylene and the second material comprises a cellulosic material.
14. The article as set forth in claim 1 wherein the first material comprises polyethylene and the second material comprises a cellulosic material.
15. The article as set forth in claim 1 wherein the first material comprises a cellulosic material and the second material comprises a cellulosic material.
16. The article as set forth in claim 1 wherein the first material comprises polylactic acid and the second material comprises a cellulosic material.
17. The article as set forth in claim 1 wherein the first material comprises nylon and the second material comprises a cellulosic material.
18. The article as set forth in claim 1 wherein the first material comprises polystyrene and the second material comprises a cellulosic material.
19. The article as set forth in claim 1 wherein the first material comprises polyester and the second material comprises a cellulosic material.
20. The article as set forth in claim 1 wherein the first material comprises rubber and the second material comprises a cellulosic material.
21. The article as set forth in claim 1 wherein the first material comprises polyurethane and the second material comprises a cellulosic material.
22. The article as set forth in claim 1 wherein the adhesive composition additionally comprises a further component selected from the group consisting of tackifiers, antioxidants, color pigments, viscosity modifiers, fillers, and polymeric compatibilizers.