Monofilament tape

Details Monofilament tape Monofilament tape

2002-11-04

2004-06-01

Wilson, John J. (Department: 3732)

Toilet

Toothpick

C132S323000

Reexamination Certificate

active

06742528

ABSTRACT:

The present invention relates to a monofilament tape, which may be used as a dental floss. The floss is easy to slide between the teeth, effective at cleaning, gentle to the gums, and capable of carrying more flavor than comparable flosses.
The use of dental floss is recommended by virtually all dental health practitioners. Dental flossing has been shown to be effective in removing interdental plaque according to the Council on Dental Therapeutics. Despite these facts, only about 12% of the United States population use floss regularly. Of those who do use floss, consumers prefer flosses which are shred and fray resistant, pass easily between tight teeth, are gentle to the gums, refreshen the mouth, clean effectively, and are easy to use. Mouth freshening is controlled through the use of coatings, which typically comprise flavors, mouth fresheners, cleaning agents, polishing agents and the like. The more coating the floss substrate can carry, the better the floss may be at mouth freshening and cleaning.
Monofilament flosses made from poly(tetrafluoroethylene)/(“PTFE”) provide most of the attributes discussed above, except for the ability to carry more flavor and other additives, and ease of handling. Many consumers feel that PTFE monofilament floss does not clean as well as conventional multi-filament flosses. In addition, the cost of PTFE floss is relatively high, mainly due to the high resin cost. Therefore, there is a need to replace PTFE with lower cost materials that will provide the above-mentioned consumer preferred attributes.
One technology that may be useful for dental floss applications is bicomponent fiber technology. Bicomponent fibers are fibers which are made from two different polymers. Bicomponent fibers are also known as “conjugate”, “composite” or “hetero” fibers. The main advantage of using this technology is to combine polymers with different properties in a single filament. Bicomponent fibers are commonly classified by their cross-sectional structures such as core-sheath; side-by-side; islands-in-the-sea; and pie-shaped.
U.S. Pat. No. 5,845,652 discloses the preparation of core-sheath bicomponent fibers using different materials and yarn constructions. The sheath polymers are thermoplastic elastomers, such as Pebax® and Hytrel® Brand polymers, and the core polymer is nylon. The specific examples set forth in the patent are based on 70/30 core-sheath fibers made from nylon/Pebax® 2533; nylon/Hytrel® 3078 and nylon
ylon having e.g., 144 filaments; a denier ranging from 580-730; no twist and tensile strengths of 3.4-5 g/d. These fibers were flattened on heated godets to bond the sheaths of the filaments during the fiber spinning process. The patent discloses the aspects of forming bulkable floss by utilizing different materials, mainly by using side-by-side bicomponent fibers. It also teaches methods of obtaining self-bulking and tension-induced bulkable floss.
U.S. Pat. No. 5,904,152 discloses a multifilament floss which has multiple cores made from nylon with either a Hytrel® or Pebax® Brand thermoplastic elastomeric polymer as the sheath.
U.S. Pat. No. 5,875,797 discloses a multicomponent, co-extruded, monofilament dental floss comprising a core comprising a first material such as nylon. The core is embedded in a sheath comprising a second material such as a thermoplastic elastomeric polymer. The floss has a continuous outer surface. The monofilament floss is prepared by using core-sheath technology and a die assembly during the co-extrusion process. Typical flosses disclosed in this patent have a denier of 600-700 and comprise 34 filaments with a 70/30 ratio of core polymer/sheath polymer. The disclosed flosses have a tenacity of 3-4.5 g/d and an elongation of at least 300%.
Despite the disclosure of the references, there is a continuing need for a floss which is shred and fray resistant, gentle to the gums, mouth freshening, effective at cleaning, easy to use, and passes readily between tight teeth.
The present invention provides an article comprising a bicomponent monofilament tape, said bicomponent monofilament tape comprising at least about 60 individual core fibers comprising a first polymer, said individual core fibers being embedded in and substantially completely surrounded by a fused sheath comprising a second polymer.
In another aspect, the present invention provides a process which includes the steps of providing at least about 60 bicomponent core-sheath fibers and fusing the sheaths to form a monofilament tape.
The bicomponent monofilament tape of the invention is made from the fusion of the sheaths of bicomponent core-sheath fibers. The bicomponent core-sheath fibers may be made by any process known in the art, including, but not limited to, using a co-extrusion melt spinning or solution spinning process. Co-extrusion of bicomponent fibers can be defined as extruding two polymers through the same spinneret with both polymers contained within the same filament with a distinct boundary between them.
FIG. 1
is a schematic illustration of a suitable process for making bicomponent fibers. The polymers utilized to form the core and the sheath are placed in single screw extruders (
1
A) and (
1
B). The polymers are heated and melted in the extruders, then passed through a spinneret (
2
) to form a plurality of co-extruded bicomponent fibers (
3
). The co-extruded bicomponent fibers are drawn by at least one roller (
4
). The co-extruded bicomponent fibers (
3
) are cooled in the region between the spinneret and the roller (
4
). The cooling may be provided by means known in the art, such as, but not limited, to chilled air (
5
). During the co-extrusion of the bicomponent fibers, the viscosities of the two polymers at the spinneret are preferably matched in order to prevent extrudate dogleg, which is the undesirable bending of the co-extruded bicomponent fiber (
3
) as it exits the spinneret (
2
). Matching of the viscosities may be achieved through the selection of polymeric components and the control of the temperature of the polymers in the single screw extruders (
1
A) and (
1
B) and the spinneret (
2
).
A spin finish may be applied by a roller (
6
) disposed in the cooling region (
5
) between the spinneret (
2
) and the first roller (
4
). Suitable spin finishes include, but are not limited to, Fasavin®2830 and Fasavin® 2758, which are commercially available through Zschimmer and Schwarz.
Roller (
4
) draws the plurality of bicomponent fibers exiting spinneret (
2
), i.e. the fibers are drawn, or stretched, as they pass through cooling zone (
5
) toward first roller (
4
). The effect of this drawing or stretching step is two-fold: first the fibers are reduced in diameter (i.e., their denier is reduced) and secondly, their tensile strength is increased. As is well known, the term “denier” refers to the weight in grams per 9000 meters of fiber.
For example, at a constant rate of extrusion of polymer melt from spinneret (
2
), the fiber denier is reduced by increasing the rate of rotation of roller (
4
). Roller (
4
) typically rotates at a rate of from about 100 meters per minute to about 2000 meters per minute, preferably from about 400 meters per minute to about 1000 meters per minute. Preferably, a second roller (
7
) is used in conjunction with the first roller (
4
). The second roller (
7
) rotates at substantially the same speed as first roller (
4
). As can be seen by reference to FIG.
1
and
FIG. 1A
, the plurality of bicomponent fibers (
3
) are collated as they leave the lower region of the cooling zone and then come into contact with the lower surface of roller (
4
). The collated bicomponent fibers (
3
A) leave roller (
4
) and then come into contact with the lowermost surface (as seen in
FIG. 1
) of roller (
7
). The fibers continue to pass around roller (
7
) in a counterclockwise direction until they reach the uppermost surface (as seen in
FIG. 1
) of roller (
7
). The fibers are then conducted across the gap between rollers (
4
) and (
7
) and are brought into contact with the uppermost surface (as seen in
FIG. 1
) of rol

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