Method of Forming a Membrane, Especially a Latex Membrane, Having a Biocide Barrier

Latex materials have long been used as gloves and condoms for the purpose of inhibiting the transmission of disease producing microbes and other harmful agents. Both the chemical inertness and the physical density of latex make it difficult for molecules and microbes to pass through the structure of the latex material. Nevertheless, latex materials are known to possess imperfections in the form of pits, pores, and holes, which can facilitate the transmission of such microbes and harmful agents through the latex material.

The present invention relates to the desireable goal of forming a chemical barrier against the transmission of such microbes and other harmful agents through a membrane such as latex.

The present invention relates to methods of forming a chemical barrier against the transmission of disease-causing microbes and other harmful agents through a membrane such as latex. In the principal method, a mold or former is coated with a coagulant, which is dried, then the former is dipped into liquid latex, which is allowed to gel, then the former is dipped into a solution containing the biocide, and then the former is dipped again into the liquid latex, after which the entire coating on the former is cured. Alternatively, the biocide may be sprayed or otherwise applied onto the gelled latex.

The present invention relates to methods of forming a chemical barrier against disease-causing microbes and other harmful agents through a membrane fashioned of latex or another material such as natural skin, natural rubber, solvent cast membranes, elastomers, and polymers that are formed by curing the material from a liquid state. For convenience, the preferred embodiment will be described with reference to a latex material. The latex material may be fashioned as a glove, condom, diaphragm, slipper, overshoe, sterile bands, catheters, latex or plastic tubing, diaphragms, drapes, gut openings, mouthpieces, baby nipples, intra gastric nasal tubes, nasal gastric tubes, kidney shunts, rubber dams for teeth, plastic braces for teeth, sub-clavian vein and artery shunts, colostomy bags, or any other product. Normally these latex products will be adapted for use in juxtaposition to a person's or animal's skin.

As used in the instant patent application, the term "biocide" means that the disease-producing characteristic or harm-causing characteristic is rendered ineffective substantially upon contact or shortly after the microbe or harmful agent contacts the biocide material. A few suitable biocides are believed to be dextran sulphate, nonoxynol-9, benzalkonium, betadyne, gentian violet, acriflavine and acridine dyes, mercurochrome, silver salts, and an extract of blue green algae. Additionally, a very lengthy list of what are believed to be suitable biocides is being filed concurrently with this patent application and forms part of the file wrapper.

Latex products, such as latex gloves and condoms, are conventionally formed by either a single dip or double dip process. A mold or former in the shape of the desired latex product is initially covered with a chemical coagulant, which allows a relatively thick, uniform, continuous layer of latex to be deposited on the former. The coagulant is dried on the former, and then the former is dipped into a vat of liquid latex for an appropriate period of time, whereby a film of latex is picked up on the surface of the former. The latex is allowed to wet gel into a sticky or tacky state, and while in the gel state, is leached in a warm water rinse or bath. The rinse removes the coagulant as well as any residual ammonia or potassium hydroxide which might be present. In order to increase the thickness of latex, the process may be repeated so that a second film of latex is built up integrally over the first layer of latex. Usually the second layer is less thick than the first layer.

A biocide barrier has been incorporated into a latex product in the following experiment. After the first dip of the former into the liquid latex and after the warm water leach in the conventional manner, the former (with the liquid latex in a wet gel state) is dipped into a solution of gentian violet, at a concentration of 0.33% by weight in water. The biocide solution coats the liquid latex. The biocide solution coating is then dried. Thereafter, the former is dipped again into a vat of liquid latex, may be leached again, and then the entire coating on the former is cured by drying.

It appears that the biocide solution acts as a secondary coagulant, and causes the second layer of latex to be relatively thicker than is normally achieved without any biocide solution.

A solution of 1.5% by weight of gentian violet in water has also been used in this process, with slightly less desireable uniformity in thickness of the coatings. Nevertheless, it is believed that the concentrations of up to about 5% by weight of gentian violet in water or water and alcohol with other cosolvents can be advantageously used in the process.

It has been observed that the maximum amount of biocide solution picked-up by the wet gel latex coating the former is about 0.2 grams of solution per gram of latex.

It is believed that the biocide is bonded to and is permanently diffused within the surface of the latex, thereby substantially filling the pores and other imperfections of the latex.

The present invention also contemplates that the biocide solution may be sprayed or otherwise applied to the wet gel latex, instead of being applied by dipping.

Although particular embodiments of the present invention have been described and illustrated herein, it should be recognized that modifications and variations may readily occur to those skilled in the art and that such modifications and variations may be made without departing from the spirit and scope of our invention. Consequently, our invention as claimed below may be practiced otherwise than as specifically described above.