Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2001-10-04
2003-06-24
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S423900, C428S424200, C428S424800, C002S167000, C002S168000
Reexamination Certificate
active
06582788
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to powder-free natural rubber and synthetic elastomer gloves having an inner coating of a cross-linked polyurethane impregnated with silicone and their method of manufacture. More particularly, the invention relates to unique powder-free medical, surgical or industrial gloves having a silicone impregnated cross-linked polyurethane inner coating which are easy to don and which can be manufactured without manual glove-turning steps during post-processing off-line, such as chlorination, acid rinsing or other treatment processes. Additionally the gloves of the invention exhibit good grippability, good donnability, tensile strength, elongation to break and stress at 500% modulus.
BACKGROUND OF THE INVENTION
Commercially available powder-free natural rubber and synthetic elastomer gloves are typically manufactured by first preparing a powdered glove using conventional latex dipping technology and manufacturing techniques. The gloves are then post-processed off-line to remove powder by chlorination or acid treatment followed by rinsing. Both processes removes powders which have been deposited on the glove during the manufacturing process. The chlorination process also oxidizes the surface of the glove and provides the glove with improved donning characteristics.
These processes have several disadvantages. First of all, they are time and labor-intensive. Chlorination, for example, is a multi-step processs which first requires that the gloves be removed from the former and turned inside out. The gloves are then subjected to several cycles of chlorination, neutralization, rinsing, glove inverting and drying operation steps. In the normal operating cycle for producing powder-free gloves, two manual glove turning steps are required. Since the inner surface or donning side of the glove is the side that is to be chlorinated, the glove must first be turned inside out so that the inner surface of the glove is now on the exterior. After the glove is chlorinated, the glove must then be manually turned again so that the freshly chlorinated donning side is returned to the inner surface of the glove. As a result, post-processing chlorination is also costly.
Another issue associated with chlorination is that the chlorination process may also degrade the polymeric coating applied to the glove's surfaces to render the glove powder free. Generally, the chlorination-associated glove degradation results in poor glove donning, gloves sticking to each other on the coated side, poor coating adhesion and flaking of the coating. Consequently, any polymeric coating applied to the glove surfaces that will be subsequently chlorinated to render the glove powder-free must possess excellent resistance to degradation by chlorination.
SUMMARY OF THE INVENTION
The present invention provides a powder-free, inner-mated, natural rubber or synthetic elastomer glove for medical, surgical and/or industrial applications which has good donning characteristics and good grippability (as measured by the coefficient of friction of the donning and gripping surfaces). The glove of the invention also exhibits good tensile strength, stress at 500% modulus and elongation to break. The gloves can also be manufactured without costly glove-turning steps in the post-processing chlorination.
The inner coating on the gloves of the invention is a cross-linked polyurethane which has been impregnated with a silicone. The inventive gloves have improved donnability over gloves coated on their inner surface with a non-cross-linked polyurethane The inventive gloves also have improved donnability as compared to gloves with an inner coating of cross-linked polyurethane which does not contain silicone. The polymeric coating of the inventive gloves also exhibits excellent adhesion to the natural rubber or synthetic elastomer rubber and can be chlorinated without being significantly degraded by the chlorination process.
PREFERRED EMBODIMENTS OF THE INVENTION
The gloves of the invention are comprised of a natural rubber, nitrile, polychloroprene, polybutadiene, polyvinylchloride, polyurethane, polyisoprene, styrene diblock and triblock copolymers, or other synthetic elastomers, including blends thereof, which have on their inner surface a coating comprised of a cross-linked polyurethane impregrated with silicone.
The natural rubber may be compounded with stabilizers, a crosslinker, a vulcanization activator, a vulcanization accelerator, an antioxidant, an antiozonant and optionally, white pigment.
Suitable stabilizers include oleates, stearates, alginates, polyacrylates, xanthan gums, caseinates or other nonionic and ionic surfactants. Typical crosslinkers which may used in the compounding formulation include sulfur or other organic peroxides. Suitable vulcanization activators include metal oxides, such as magnesium oxide, lead oxide, and preferably, zinc oxide. The vulcanization accelerator may be chosen from mercaptobenzothiazoles and their derivatives, dithiocarbamates and their derivatives, sulfur donors, guanidines and aldehyde-amine reaction products. Suitable antioxidants include hindered arylamines or polymeric hindered phenols. Typical antiozonants which may be used in the compounding formulation include paraffinic waxes, microcrystalline waxes and intermediate types of waxes (which are blends of both paraffinic and microcrystalline waxes). Typical white pigments that may be used include titanium dioxide and zinc oxide.
Synthetic diene based elastomers such as polybutadiene, polyisoprene, nitrile, polychloroprene and its blends can be compounded with similar compounding ingredients as set forth above. Other synthetic thermoplastic elastomeric materials used for the base glove such as polyvinylchloride, polyurethanes, styrene diblock and triblock copolymers and its blends do not require crosslinking to prepare a glove with the desired physical properties. Accordingly, these synthetic elastomers may be compounded with stabilizers, antioxidants, antiozonants and color pigments as described above.
Those skilled in the art will readily be able to vary the compounding ingredients in the dipping formulation to suit the particular elastomers used to form the base glove as well as the final article desired. It will also be understood by those skilled in the art that the specific chemicals or compounds which have been listed above are representative of conventional materials that may be used in formulating diene-based and thermoplastic elastomers and are non-limiting examples of each such component of the formulation.
The polyurethane dispersion used to coat the interior surface of the formed glove is a crosslinkable anionic polyurethane dispersion with a particle size of less than about 0.5 micron, preferably less than about 0.1 micron with carboxylic acid functionality having an acid value of more than about 15 calculated based on the amount of carboxylic acid-containing material used in synthesizing the polyurethane (assuming total incorporation of the carboxylic acid functionality in the monomer into the finished polymer). Preferably, the polyurethane dispersion is a dispersion blend of [A], a crosslinkable anionic polyester-based polyurethane with a Sward hardness of about 74 or greater (wherein the Sward hardness is measured using ASTM D2134) and an acid value of about 24 or less and [B] a self-crosslinkable anionic polyester-based polyurethane with a Sward hardness of about 38 or less and an acid value of about 24 or greater. The self-crosslinkable polyurethane of the invention is a polyurethane with functionality that can be readily cross-linked using heat, radiation or chemical means with or without the use of external crosslinkers. Most preferably, the polyurethane dispersion is a dispersion blend of [A] about 50 parts of a crosslinkable anionic polyester-based polyurethane with a Sward hardness of about 74 or greater and an acid value of about 24 or less and [B] about 50 parts of a self-crosslinkable anionic polyester-based polyurethane with a Sward ha
Allegiance Corporation
Nolan Sandra M.
Rozycki Andrew G.
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