Articles containing nanofibers produced from low melt flow rate polymers
The present invention is directed to hygiene articles comprising nanofibers. The nanofibers are made from a melt film fibrillation process with a polymer composition having a melt flow rate of less than about 400 decigram per minute. The nanofibers, having a diameter of less than 1 micron, must comprise a significant number of the fibers in one layer of the web contained by the hygiene article. The hygiene articles include diapers, training pants, adult incontinence pads, catamenials products such as feminine care pads and pantiliners, tampons, personal cleansing articles, personal care articles, and personal care wipes including baby wipes, facial wipes, and feminine wipes.
1. A process of making nanofibers, said process comprising the steps of:
a. providing a polymer composition having a melt flow rate of less than about 400 decigram per minute; and
b. employing a melt film fibrillation process utilizing a central fluid stream to form an elongated hollow polymeric film tube from said polymer composition, and using a fluid to form multiple nanofibers with diameters less than one micron from the hollow tube.
2. The process according to claim 1 further comprising a step c) of laying said nanofibers on a collector to form a nonwoven web comprising a layer having a significant number of nanofibers with diameters less than one micron.
3. The process of claim 2 wherein the layer comprises at least about 35% of nanofibers having a diameter of less than one micron.
4. The process of claim 1 wherein the polymer composition has a melt flow rate of less than 200 decigram per minute.
5. The process of claim 1 wherein the polymer composition has a melt flow rate of less than 100 decigram per minute.
6. The process of claim 1 wherein one polymer the polymer composition is selected from the group consisting of polyolefins, polyesters, polyamides, biodegradable polymers, polyurethanes, and combinations thereof.
7. The process according to claim 2 wherein the layer comprises two or more pluralities of fiber diameter distributions wherein at least one plurality has a fiber diameter of less than about one micron.
8. The process according to claim 1 wherein the polymer composition comprises polypropylene.
9. The process of claim 2 wherein the nonwoven web further comprises one or more layers of spunbond fibers.
10. The process of claim 9 wherein the nonwoven web has a basis weight of from about 10 to about 100 gsm.
11. The process of claim 2 wherein the nanofiber layer of the nonwoven web has a basis weight of from about 0.5 gsm to about 30 gsm.
12. The process of claim 1 wherein said melt film fibrillation process is a single step process.