Osmotically-driven fluid dispenser and composition

Abstract

Improvements in a mini-osmotic pump and coating compositions are described. The dispensing pump includes an inner fluid-filled bag encased by an osmotic layer and outer, semi-permeable membrane. The inner bag is formed with an arcuate edge at the open end of the bag to inhibit formation of fissures in the outer membrane in this edge region. The coating compositions include cellulose acetate butyrate, cellulose acetate propionate, and polymethylmethacrylate polymers, optionally mixed with ethyl cellulose in acetone based solvent systems.

What is claimed is:  
     
         1 . A dispenser comprising: 
 (i) a flexible container having a closed end and an opposed open end;    (ii) an osmotically-effective solute composition encapsulating at least a portion of the container;    (iii) a shape-retaining, semipermable membrane encapsulating the osmotically-effective solute composition;    (iv) a cap having a surface adapted for sealing engagement with the open end of the container;    (v) a port extending from the interior of the container and through the cap; the container having an arcuate, outer edge formed at its open end adjacent its junction with the sealing surface of the cap.    
     
     
         2 . The dispenser of    claim 1   , wherein the arcuate edge has a radius of curvature between 0.01 inches (0.254 mm) and 0.09 inches (2.29 mm).  
     
     
         3 . The dispenser of    claim 2   , wherein the arcuate edge has a radius of curvature between 0.01 inches (0.254 mm) and 0.08 inches (2.03mm).  
     
     
         4 . The dispenser of    claim 2   , wherein the arcuate edge has a radius of curvature between 0.01 inches (0.254 mm) and 0.07 inches (1.78 mm).  
     
     
         5 . The dispenser of    claim 1    wherein the semipermeable membrane comprises a polymer selected from the group consisting of cellulose acetate butyrate, cellulose acetate propionate, polymethylmethacrylate, mixtures thereof, and mixtures of any of the foregoing with ethyl cellulose.  
     
     
         6 . The dispenser of    claim 5    wherein the polymer is selected from the group consisting of cellulose acetate butyrate and mixtures of cellulose acetate butyrate and ethyl cellulose.  
     
     
         7 . The dispenser of    claim 5    wherein the polymer is selected from the group consisting of cellulose acetate propionate and mixtures of cellulose acetate propionate and ethyl cellulose.  
     
     
         8 . The dispenser of    claim 5    wherein the polymer is selected from the group consisting of polymethylmethacrylate and mixtures of polymethylmethacrylate and ethyl cellulose.  
     
     
         9 . A coating composition comprising a mixture of (i) polymer selected from the group consisting of cellulose acetate butyrate, cellulose acetate propionate, polymethylmethacrylate, mixtures thereof, and mixtures of any of the foregoing with ethyl cellulose, (ii) solvent selected from the group consisting of acetone, mixtures of acetone and water and mixtures of acetone and lower alkanols having 1-8 carbon atoms, and optionally (iii) one or more additives selected from the group consisting of plasticizers and flux enhancers.  
     
     
         10 . The composition of    claim 9    wherein the solvent is selected from the group consisting of acetone, a mixture of acetone and water, a mixture of acetone and methanol, and a mixture of acetone and ethanol.  
     
     
         11 . The composition of    claim 10    wherein the concentration of acetone in the solvent is at least 80% by volume.  
     
     
         12 . The composition of    claim 11    wherein the concentration of acetone in the solvent is at least 90% by volume.  
     
     
         13 . The composition of    claim 9    wherein the polymer concentration in the solvent is between 1-15% (w/v).  
     
     
         14 . The composition of    claim 13    wherein the polymer concentration in the solvent is between 2-8% (w/v).  
     
     
         15 . The coating composition of    claim 9    adapted to coat a semipermeable membrane exhibiting a water transmission rate of between 1-60 cc.mil/cm 2  .hr.  
     
     
         16 . The coating composition of    claim 10    adapted to coat a semipermeable membrane exhibiting a water transmission rate of between 3-45 cc.mil/cm 2 .hr.  
     
     
         17 . The coating composition of    claim 9    wherein the polymer is selected from the group consisting of cellulose acetate butyrate and mixtures of cellulose acetate butyrate and ethyl cellulose.  
     
     
         18 . The coating composition of    claim 9    wherein the polymer is selected from the group consisting of cellulose acetate propionate and mixtures of cellulose acetate propionate and ethyl cellulose.  
     
     
         19 . The coating composition of    claim 9    wherein the polymer is selected from the group consisting of polymethylmethacrylate and mixtures of polymethylmethacrylate and ethyl cellulose.