Surgery – Male reproductory tract shields or birth control devices – Condoms
Reexamination Certificate
2000-05-26
2004-05-11
Brown, Michael A. (Department: 3764)
Surgery
Male reproductory tract shields or birth control devices
Condoms
C128S918000
Reexamination Certificate
active
06732735
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to reticulated coatings and, in particular, to reticulated coatings that exhibit enhanced lubricity or “slip” with respect to both dry and damp surfaces and are suitable for use in medical device products.
2. Description of the Related Art
Thin polymer films are used in the manufacture of a variety of medical device products, such as medical gloves, condoms, wound dressings, catheters, angioplasty balloons and the like. In the case of medical gloves, such as surgeon's gloves or examination gloves, the ease of donning the glove is an important consideration, as too is the breathability of the base polymer, to reduce the build-up of moisture within the glove. Consequently, such gloves usually require the application of powders or coatings which confer anti-frictional properties. Ultimately, however, the barrier properties of gloves and condoms are of primary concern and it is essential that the application of any coating should not reduce these properties. An additional requirement of such a coating is that it must adhere strongly to the underlying substrate and must be able to be applied to a variety of substrate materials without degrading the intrinsic properties of the substrate material. Soft elastomeric films are of particular value as coatings (and also as “film articles”, such as condoms) but are characterised by the tacky or “blocky” nature of the film surfaces when dry, which can lead to problems of unwanted adhesion when products are stored or dried in bulk. In order to overcome this, products are frequently treated with a dusting powder, such as corn starch, to render the surface tack-free. However, post-operative adhesions and granulomas have become increasingly associated with the presence of such powders on invasive medical devices, whilst undesirable allergic hypersensitivity reactions to latex used in medical gloves may be exacerbated by the presence of such powders. Consequently, the alternative of using a powder free, anti-block coating to prevent adhesion and confer slip properties has particular value.
U.S. Pat. No. 4,642,267, for example, discloses a hydrophilic blend comprising an organic solvent-soluble, thermoplastic polyurethane and a hydrophilic poly(N-vinyl lactam) which is slippery in aqueous environments and may be used as a low-friction coating for catheters. The blend is prepared using conventional melt-blending techniques or by dissolving the components in a solvent, which is subsequently evaporated to yield the blend. In the latter case, however, this document discloses that the solvent must be capable of dissolving both polymer components in a single-phase solution and that the relative volatilities must be such that, at no point during evaporation and drying, must the solution tend to precipitate either polyurethane or poly(N-vinyl lactam) or an association complex of these polymers which may have different solubility characteristics than either material by itself.
Anti-block coatings prepared by conventional methods often require elaborate and expensive manufacturing procedures and the properties of the coatings so obtained are often inferior to those of dusting powders. It is an object of the present invention to overcome some of the aforementioned disadvantages by providing a novel method of forming a reticulated coating that has good “slip” properties when damp or dry.
SUMMARY OF THE INVENTION
Accordingly, in a first aspect of the invention, there is provided a method of forming a reticulated coating on a substrate, comprising providing an agglomerate dispersion of a pre-formed first polymer in a polar liquid carrier on a surface of the substrate, and evaporating the liquid carrier to form the coating.
In one embodiment, the reticulated coating is adapted to render the surface of the substrate substantially tack-free or anti-blocking when dry, so as to ensure that articles that are provided with the coating, such as medical gloves, do not adhere to each other. Preferably, the reticulated coating is substantially free of substances capable of causing undesirable allergic hypersensitivity reactions, which is particularly important if the coatings are to be used for medical applications. In another embodiment, the coating has an Ra value of at least 0.5 &mgr;M.
In the context of the present invention, the term “R
a
value” is understood to refer to the arithmetic mean of the absolute departures of the roughness profile of the surface from the mean line, in accordance with its usual meaning in relation to engineering surfaces (see, for example, ISO 4287/1:1997, and also ISO 11 562). Similarly, R
q
or RMS is the root mean square parameter corresponding to R
a
, whilst R
max
is the maximum peak to valley height of the profile in the assessment length. The first polymer may be any material capable of forming a film coating when wet but is generally a thermoplastic, a thermosetting resin or an elastomer and will already have been polymerized before it is used to prepare the agglomerate dispersion, i.e., the agglomerate dispersion will not usually be obtained as the product of an in situ polymerization reaction. Preferably, the thermoplastic, thermosetting resin or elastomer is selected from the group consisting of polythene, polypropene, polymethylpentane, polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylonitrile, polyacrylamide, aromatic polyesters, polycarbonates, polyamines, polytetrafluoroethene, alkyd resins, unsaturated polyesters, urea-methanal polymers, polyureas, melamines, polyurethanes, polyamides, epoxy resins, polyethene oxide, polyphenylene oxide, polyacetals, polyaldehydes, phenolic resins, polysulphones, natural rubbers, polyisoprene, polybutadiene, polychloroprenes, butyl rubbers, styrene-butadiene rubbers, acrylonitrile-butadiene rubbers, polysulphides, silicones and mixtures thereof. In the context of the invention, the phrase “mixtures thereof” should be understood to include co-polymers of any of the preferred monomers, as well as simple mixtures of the fully polymerised compounds. It is especially preferred that the thermoplastic, thermosetting resin or elastomer is selected from the group consisting of polyurethanes, neoprene, latex, styrene acrylic emulsions and nitriles. Most preferably, the first polymer is a polyurethane or a natural rubber, such as latex. Polyurethanes are especially preferred, particularly those prepared from polyesterpolyols, polyetherpolyols, polycarbonatepolyols and mixtures of these. The polar liquid carrier may be any liquid carrier capable of developing an electrical charge and forming an agglomerated dispersion with the first polymer. Such liquid carriers may include but are not limited to water, dilute mineral acids, methanol, ethanol, diethylether, dimethylsulphoxide and dimethylsulphone. Preferably, the liquid carrier is aqueous. In one embodiment, the agglomerated dispersion of the first polymer is applied to the surface of the substrate after it has been formed, preferably by spraying the agglomerated dispersion onto the substrate or by dipping the substrate in the agglomerated dispersion. In an alternative embodiment, the agglomerate dispersion is formed in situ on the surface of the substrate, preferably by applying a colloidal dispersion of the first polymer to the surface of the substrate and by inducing agglomeration, for example, by electrolysis. In a preferred embodiment, the agglomerate dispersion of the first polymer is formed from a colloidal dispersion of the first polymer in the polar liquid carrier. In this embodiment, the colloidal dispersion preferably contains micelles of the first polymer having an average particle size in the range of 0.1-100 nm, preferably 1-75 nm, and especially about 50 nm.
Preferably, the reticulated coating is lubricious and confers enhanced slip with respect to both dry and damp surfaces. In any of these embodiments, the average size of the particles in the agglomerated phase may be in the range of 0.1-10
Brown Michael A.
Ranier Limited, Fountain House
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