Solid gel dispensers for achieving controlled release of volatile liquid materials and method for preparing same

Claim 1

In a dispenser for achieving controlled release over an extended period of time of a volatile liquid into the environment adjacent to the dispenser, the dispenser comprising a hydrogel formed from an aqueous solution of polyvinyl alcohol, the improvement comprising (1) the presence in said hydrogel of from 1 to 20 percent, based on the total weight of said hydrogel, of a polyelectrolyte as a finely divided dispersed phase within a continuous phase of said hydrogel and a monohydric alcohol containing from one to four carbon atoms in an amount sufficient to solubilize said volatile liquid and without precipitating the polyvinyl alcohol, (2) a method for preparing said dispenser whereby at least a portion of said volatile liquid is incorporated into said dispenser by immersing it in an aqueous solution of said volatile liquid and (3) a free standing dispenser possessing an exterior surface that is initially dry to the touch and remains so throughout the useful life of said dispenser.

Claim 4

A method for preparing a free standing dispenser for the controlled release of a volatile liquid material, said method comprising the following steps: 1) heating under atmospheric pressure a mixture comprising from 5 to 25 weight percent of polyvinyl alcohol, a polyelectrolyte, water and at least one water-miscible liquid selected from the group consisting of monohydric alcohols and dimethyl sulfoxide, the concentration of water-miscible liquid being sufficient to maintain said polyelectrolyte as a dispersed phase in a solution of said polyvinyl alcohol, 2) placing said dispersion in a container corresponding in contour to the shape of the final dispenser and cooling the resultant dispersion to below room temperature to form a hydrogel in the shape of the final dispenser, 3) when said water-miscible liquid is dimethyl sulfoxide, placing said hydrogel in contact with methanol or ethanol for a period of time sufficient to replace substantially all of the dimethyl sulfoxide with said methanol or ethanol, 4) placing said dispenser in an aqueous solution of said volatile liquid for a period of time sufficient to absorb an amount of said solution equivalent to at least 95 weight percent of the final dispenser, replace at least a portion of the water present in said dispenser with said solution, and 5) removing the final dispenser from said aqueous solution.

Claim 5

A method for preparing a free standing dispenser for the controlled release of a volatile liquid material, said method comprising the following steps: 1) heating under atmospheric pressure a mixture comprising from 5 to 25 weight percent of polyvinyl alcohol, a polyelectrolyte, water and at least one water-miscible liquid selected from the group consisting of monohydric alcohols and dimethyl sulfoxide, the concentration of water-miscible liquid being sufficient to maintain said polyelectrolyte as a dispersed phase in a solution of said polyvinyl alcohol, 2) placing said dispersion in a container corresponding in contour to the shape of the final dispenser and cooling the resultant dispersion to below room temperature to form a hydrogel in the shape of the final dispenser, 3) when said water-miscible liquid is dimethyl sulfoxide, placing said hydrogel in contact with methanol or ethanol for a period of time sufficient to replace substantially all of the dimethyl sulfoxide with said methanol or ethanol, 4) placing said dispenser in an aqueous solution of said volatile liquid for a period of time sufficient to absorb an amount of said solution equivalent to at least 95 weight percent of the final dispenser, replace at least a portion of the water present in said dispenser with said solution, and 5) removing the final dispenser from said aqueous solution.