Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-07-28
2002-03-19
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C526S348100, C526S348200
Reexamination Certificate
active
06359050
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to polyethylene compositions that are new and useful, and films produced therefrom that are characterized by preferably having increased moisture vapor transmission rates (MVTR).
BACKGROUND OF THE INVENTION
It is known that properly formulated films fabricated from polyethylene that have been filled with solid particles (e.g., a mineral such as calcium carbonate) can be stretched under appropriate conditions creating a porous structure that allows for the diffusion of water vapor while providing a liquid barrier. This is a desirable property in markets such as hygienics, industrial and medical. Indeed, a major consideration in the comfort of a garment is its ability to maintain a balance between heat production and heat loss. The loss of heat through clothing may occur through direct dry heat loss or by moisture evaporation. In respect to the latter, the moisture vapor transmission rate of the material utilized in forming the garment is generally related to the breathability of the material. Breathability is the ability to diffuse moisture/water vapor through a film or garment. In addition to this property, there are many applications requiring that the material used in preparing the garment be impermeable to a liquid. Such applications include diaper back sheets, sanitary napkins, medical protective garments, surgical incise drapes, transdermal patches, wound care bandages and dressings, intravenous site dressings, ostomy site dressings, breathable housewrap, among others.
Films which are permeable to water vapor and are porous but yet are intended to be impermeable to a liquid are described in U.S. Pat. Nos. 4,626,252 and 5,073,316. As disclosed, a porous film is obtained by mixing a polyolefin resin, an inorganic filler and a plasticizer; forming a film from the mixture; and uniaxially or biaxially stretching the film. Films of this type are also disclosed in U.S. Pat. No. 5,998,505 and PCT International Application Publication No. WO 98/05501.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide new and improved polyethylene compositions or blends.
It is a further object of this invention to provide novel polyethylene compositions or blends of specific polyethylenes and fillers.
It is a further object of this invention to provide novel films produced from the novel compositions, which films are characterized by having improved moisture vapor transmission rates (MVTR).
These and other objects and advantages of the present invention will be apparent to those skilled in the art from the following detailed description and claims.
In accordance with the present invention, it has been found that the above and still further objects are achieved by combining at least one or more specific polyethylenes and a filler to provide a new and novel composition that is suitable to provide films that are characterized by having improved moisture vapor transmission rates (MVTR). The compositions and films are useful in many applications.
More particularly, in accordance with the present invention, a polyethylene composition is provided comprising (a) an ethylene homopolymer or ethylene interpolymer having a density of from about 0.91 to about 0.93 g/cc (grams/cubic centimeter), a melt index (M.I.) of from about 1 to about 5 grams per 10 minutes (g/10 min), a weight percent high temperature fraction (% HT) as determined by TREF of about 25 to about 50 weight %, and a number average molecular weight (Mn) of the HT fraction collected during TREF procedure of from about 35,000 to about 52,000 g/mol, with the % HT preferably ranging from about 30 to about 45%; preferably the ethylene homopolymer or interpolymer component is present in the composition in an amount of from about 20 to about 80 weight percent (%); and (b) a filler present in an effective amount, such that a film formed from the novel polyethylene composition has increased MVTR; preferably the filler is present in the composition in an amount of from about 20 to about 80 weight percent.
In addition to the novel compositions, the present invention is also directed to films formed from the novel compositions that are characterized by having increased moisture vapor transmission rates.
Additionally, the present invention is directed to articles of manufacture incorporating the novel compositions and novel films, of the present invention. Such articles include garments, diapers, sanitary napkins, medical protective garments, surgical incise drapes, transdermal patches, wound care bandages and dressings, intravenous site dressings, and ostomy site dressings, and others, incorporating the novel thermoplastic compositions and films of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The compositions of the present invention comprise (a) at least one, or more, of an ethylene homopolymer or ethylene interpolymer having a density of from about 0.91 to about 0.93 g/cc (gram/cubic centimeter), a melt index (M.I.) of from about 1 to about 5 grams per 10 minutes (g/10 min), a weight percent high temperature fraction (% HT) as determined by TREF of about 25 to about 50 weight %, and a number average molecular weight (Mn) of the HT fraction collected during TREF procedure of from about 35,000 to about 52,000 g/mol, with the % HT preferably ranging from about 30 to about 45%; preferably the ethylene homopolymer or interpolymer component is present in the composition in an amount of from about 20 to about 80 weight percent (%); and (b) a filler present in an effective amount, such that a film formed from the novel polyethylene composition has increased MVTR; preferably the filler is present in the composition in an amount of from about 20 to about 80 weight percent.
The ethylene component of the present composition is a homopolymer of ethylene or an interpolymer of ethylene and at least one or more other olefin(s). Preferably, the olefins are alpha-olefins. The olefins may contain from about 2 to about 16 carbon atoms. The interpolymer of ethylene and at least one other olefin comprise an ethylene content of at least about 50% by weight of the total monomers involved. Exemplary olefins that may be utilized herein are propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene and the like. Also utilizable herein are polyenes such as 1,3-hexadiene, 1,4-hexadiene, cyclopentadiene, dicyclopentadiene, 4-vinylcyclohex-1-ene, 1,5-cyclooctadiene, 5-vinylidene-2-norbornene and 5-vinyl-2-norbornene.
The ethylene homopolymer or interpolymer of the present composition may be prepared by any manner known to those skilled in the art. In the present instance, the ethylene homopolymers and interpolymers were prepared using the following procedure.
The polymerization process utilized herein was carried out in a fluidized-bed reactor for gas-phase polymerization, consisting of a vertical cylinder of diameter 0.74 meters and height 7 meters and surmounted by a velocity reduction chamber. The reactor is provided in its lower part with a fluidization grid and with an external line for recycling gas, which connects the top of the velocity reduction chamber to the lower part of the reactor, at a point below the fluidization grid. The recycling line is equipped with a compressor for circulating gas and a heat transfer means such as a heat exchanger. In particular the lines for supplying ethylene, an olefin such as 1-butene, 1-pentene and 1-hexene, hydrogen and nitrogen, which represent the main constituents of the gaseous reaction mixture passing through the fluidized bed, feed into the recycling line. Above the fluidization grid, the reactor contains a fluidized bed consisting of a polyethylene powder made up of particles with a weight-average diameter of about 0.5 mm to about 1.4 mm. The gaseous reaction mixture, which contains ethylene, olefin comonomer, hydrogen, nitrogen and minor amounts of other components, passes through the fluidized bed under a pressure ranging from about 280 psig to about 300 psig with an ascendi
Barr Dennis Brannon
Crawford Emmett Dudley
Dohrer Kathryn Kobes
Edmund Mark Alan
Hale Wesley Raymond
Eastman Chemical Company
Graves, Jr. Bernard J.
Wood Jonathan D.
Yoon Tae H.
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