Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
1998-10-30
2001-07-17
Ruhl, Dennis (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C428S343000, C428S3550RA
Reexamination Certificate
active
06261278
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a film that comprises a mixture of a polyethylene polymer and a block copolymer. The film exhibits improved self-adhesive properties and is suitable for use in a disposable absorbent product intended for the absorption of fluids such as body fluids.
2. Description of the Related Art
Disposable absorbent products currently find widespread use in many applications. For example, in the infant and child care areas, diapers and training pants have generally replaced reusable cloth absorbent articles. Other typical disposable absorbent products include feminine care products such as sanitary napkins or tampons, adult incontinence products, and health care products such as surgical drapes or wound dressings. A typical disposable absorbent product generally comprises a composite structure including a topsheet, a backsheet, and an absorbent structure between the topsheet and backsheet. These products usually include some type of fastening system, such as adhesive fastening tapes, for fitting the product onto a wearer.
Although current disposable baby diapers and other disposable absorbent products have been generally accepted by the public, these products still have need of improvement in specific areas. For example, the fastening system used on many disposable absorbent products could use improving.
As such, there is a need for new materials that may be used in disposable absorbent products that are useful as an adhesive fastening tape.
It is therefore an object of the present invention to provide a film which exhibits improved adhesive properties.
It is also an object of the present invention to provide a composition comprising polyethylene and a block copolymer which may be easily and efficiently formed into a film which may be useful as an adhesive fastening tape.
SUMMARY OF THE INVENTION
The present invention concerns a film that exhibits desirable adhesive properties and is useful as an adhesive fastening tape in a disposable absorbent product.
One aspect of the present invention concerns a film that comprises a mixture of a first component and a second component.
One embodiment of such a film comprises a mixture of a polyethylene and a block copolymer, wherein the film exhibits desired properties.
One particular embodiment of the present invention is a film comprising a mixture of a block copolymer selected from the group consisting of poly(styrene)-co-poly (ethylene-butylene)-co-poly(styrene) copolymer, poly(styrene)-co-poly(ethylene-butylene) copolymer, and a mixture of such copolymers, wherein the block copolymer is present in the film in a weight amount that is between about 30 weight percent to about 95 weight percent, and a polyethylene polymer, wherein the polyethylene polymer is present in the thermoplastic composition in a weight amount that is between about 5 weight percent to about 70 weight percent, wherein all weight percents are based on the total weight amount of the block copolymer and the polyethylene polymer present in the film, wherein the film exhibits a Peak Load of Auto-Adhesive Strength value that is greater than about 400 grams per inch width of the film.
In another aspect, the present invention concerns a disposable absorbent product comprising a film of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is directed to a film which includes a first component and a second component. As used herein, the term “film” is meant to describe a substantially nonwoven, continuous sheet of material with no identifiable, individual fibers or the like. Nonwoven films are known to be able to be prepared by a variety of processes such as, for example, extrusion processes.
As used herein, the term “comprising” is intended to be synonymous with “including”, “having”, “containing”, or “characterized by”, and is intended to be inclusive or open-ended and is not intended to exclude additional, unrecited elements or method steps.
The first component in the film is a block copolymer. A number of block copolymers can be used to prepare the film of this invention. Such block copolymers generally comprise an elastomeric midblock portion and a thermoplastic endblock portion. The block copolymers used in this invention generally have a three-dimensional physical crosslinked structure below the endblock portion glass transition temperature (Tg) and are elastomeric. The block copolymers are also thermoplastic in the sense that they can be melted above the endblock glass transition temperature, formed, and resolidified several times with little or no change in physical properties (assuming a minimum of oxidative degradation).
As used herein, the term “thermoplastic” is meant to describe a material that softens when exposed to heat and which substantially returns to its original condition when cooled to room temperature.
One way of synthesizing such block copolymers is to polymerize the thermoplastic endblock portions separately from the elastomeric midblock portions. Once the midblock and endblock portions have been separately formed, they can be linked. Typically, midblock portions can be obtained by polymerizing di- and tri-unsaturated C
4
-C
10
hydrocarbons such as, for example, dienes such as butadiene and isoprene, and trienes such as 1,3,5-heptatriene. When an endblock portion A is joined to a midblock portion B, an A-B block copolymer unit is formed, which unit can be coupled by various techniques or with various coupling agents C to provide a structure such as A-B-A, which is believed to comprise two A-B blocks joined together in a tail-to-tail A-B-C-B-A arrangement. By a similar technique, a radial block copolymer can be formed having the formula (A-B)
n
C, wherein C is the hub or central, polyfunctional coupling agent and n is a number greater than 2. Using the coupling agent technique, the functionality of C determines the number of A-B branches.
Endblock portion A generally comprises a poly(vinylarene), such as polystyrene, having a weight average molecular weight between about 1,000 and about 60,000. Midblock portion B generally comprises a substantially amorphous polyolefin such as polyisoprene, ethylene/propylene copolymers, ethylene/butylene copolymers, polybutadiene, or mixtures thereof, having a weight average molecular weight between about 5,000 and about 450,000. The total weight average molecular weight of the block copolymer is suitably between about 10,000 to about 500,000 and more suitably between about 200,000 to about 300,000. Any residual unsaturation in the midblock portion of the block copolymer can be hydrogenated selectively so that the content of olefinic double bonds in the block copolymers can be reduced to a residual proportion of beneficially less than about 5 percent and suitably less than about 2 percent. Such hydrogenation tends to reduce sensitivity to oxidative degradation and may have beneficial effects upon elastomeric properties.
Suitable block copolymers used in this invention comprise at least two substantially polystyrene endblock portions and at least one substantially ethylene/butylene midblock portion. Suitably, the block copolymer useful in the present invention is selected from the group consisting of poly(styrene)-co-poly (ethylene-butylene)-co-poly(styrene) copolymer, poly(styrene)-co-poly(ethylene- butylene) copolymer, and a mixture of such copolymers. Ethylene/butylene typically comprises the major amount of the repeating units in such block copolymers and can constitute, for example, 70 percent by weight or more of the block copolymer. The block copolymer, if radial, can have three or more arms, and good results can be obtained with, for example, four, five, or six arms. The midblock portion can be hydrogenated, if desired.
In one embodiment of the present invention, in addition to using a block copolymer selected from the group consisting of poly(styrene)-co-poly(ethylene-butylene)-co-poly(styrene) copolymer, poly(styrene)-co-poly(ethylene-butylene) copolymer, and a mixture of such copolymers, it
Chen Franklin M. C.
Huang Yung Hsiang
Roessler Thomas H.
Kimberly--Clark Worldwide, Inc.
Pugliese III Sebastian C.
Ruhl Dennis
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