Creped nonwoven materials

Details Creped nonwoven materials Creped nonwoven materials

1997-10-31

2001-03-06

Morris, Terrel (Department: 1771)

Stock material or miscellaneous articles

Structurally defined web or sheet

Continuous and nonuniform or irregular surface on layer or...

C428S198000, C428S099000, C442S328000, C442S398000

Reexamination Certificate

active

06197404

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to permanently creped nonwoven materials having low density, high permeability, improved loft and softness, looping, and out-of-plane fiber orientation.
BACKGROUND OF THE INVENTION
Creped thermoplastic nonwoven materials are known from U.S. Pat. No. 4,810,556, issued to Kobayashi et al. In the disclosed process, a raw nonwoven fabric is coated with a lubricant and then pressed between a drive roll and a plate having a rough sandpaper-like surface. The plate is positioned near the drum and is substantially parallel or tangential to the outer surface of the drum. The raw nonwoven fabric is crinkled in a wavelike fashion in the direction of movement of the fabric by the frictional force caused by the pressing. The resulting creped fabric has wavelike crepes which contribute to softness. However, the creping accomplished by this process is not believed to be permanent. It is believed that the creping accomplished by this process can be removed or reduced significantly by subjecting the nonwoven web to mechanical stretching sufficient to flatten out the wavelike crepes. Also, the creping is naturally reduced over time during use of the fabric.
The creping of paper is also known in the art. However, paper has traditionally been creped using processes different from those used to crepe thermoplastic nonwoven webs. U.S. Pat. No. 3,879,257, issued to Gentile et al., discloses a process used for producing creped paper. A bonding material, preferably elastomeric, is applied to first and second surfaces of the paper so that it covers from about 15-60% of both paper surfaces and penetrates into about 10-40% of the paper thickness from both surfaces. Then, one side of the paper is adhered to a creping surface, such as a creping drum, using the bonding material to cause the adhesion. Then, the paper is creped from the creping surface using a doctor blade positioned at an angle to the surface. This creping method greatly disrupts the fibers in the unbonded regions of the paper increasing the overall softness, absorbency and bulk of the paper, and finely crepes the bonded areas of the paper to soften them.
There is a need or desire for a creped thermoplastic nonwoven web in which some or portions of the fibers are greatly disrupted to cause permanent creping. There is also a need or desire for a permanently creped nonwoven web containing individual filament loops, suitable for use as the female component in a hook-and-loop fastener.
SUMMARY OF THE INVENTION
The present invention is a permanently creped thermoplastic nonwoven web having interfilament bonded areas which are bent or oriented permanently out of plane, unbonded areas between the bonded areas, and substantial filament looping in the unbonded areas. The permanently creped web has low density, high permeability and excellent softness, and is useful as a loop material for a hook and loop fastener. The web also has a crinkled, puckered texture, and is useful for liners, transfer and surge layers, outercovers, wipes, and other fluid handling products.
The starting material used to make the invention is an uncreped thermoplastic nonwoven web which can, for instance, be a thermoplastic spunbonded web or a thermoplastic meltblown web. The nonwoven web is at least partially coated on one side with an adhesive, so that about 5-100% (preferably 10-70%) of the total surface area on one side is coated, and about 0-95% (preferably 30-90%) of the area is uncoated. The nonwoven web also possesses interfilament bonding, in the form of a pattern called the “nonwoven web bond pattern,” which is imparted during manufacture of the nonwoven web. The adhesive penetrates the nonwoven web to some extent in the coated areas, causing increased interfilament bonding in those areas. The at least partially coated side of the thermoplastic nonwoven web is then placed against a creping surface, such as a creping drum, and is peelably bonded to the creping surface. The creping surface is preferably heated, and is moved (e.g. rotated) in a machine direction. As the creping surface moves, the leading edge of the nonwoven web bonded to the surface is creped off using a doctor blade.
The doctor blade penetrates the adhesive coating underneath the web and lifts the nonwoven web off the drum, resulting in permanent filament bending in the bonded areas corresponding to the nonwoven web bond pattern, and permanent looping of the filaments in the unbonded areas. Only one side of the web need be creped in this fashion to form a loop material suitable for use as the female component in a hook and loop fastener. Alternatively, both sides of the web may be creped by applying the adhesive on the second surface of the web as well as the first, adhering the second surface of the web to the same or a different creping surface, and creping the second side of the web from the creping surface using a doctor blade.
With the foregoing in mind, it is a feature and advantage of the invention to provide a permanently creped nonwoven web having low density, high permeability and excellent softness and texture.
It is also a feature and advantage of the invention to provide a permanently creped nonwoven web having a looped structure suitable for use as the female component of a hook and loop fastener.
It is also a feature and advantage of the invention to provide a permanently creped nonwoven web having a textured surface suitable for use in liners, transfer and surge layers, outercovers, wipers, and other fluid handling materials.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are intended to be merely illustrative rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.


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