WO1989003860A1

WO1989003860A1 - Moisture sensitive elastomer compositions

Info

Publication number: WO1989003860A1
Application number: PCT/US1988/003577
Authority: WO
Inventors: Ellsworth E. Faust; Charles K. Kliment; Francis E. Gould
Original assignee: Tyndale Plains-Hunter, Ltd.
Priority date: 1987-10-14
Filing date: 1988-10-12
Publication date: 1989-05-05
Also published as: AU2812389A

Abstract

Elastomer compositions, having water absorptive properties, are produced by subjecting a homogeneous blend of a curable rubber latex and a hydrophilic polyurethane polymer, to curing conditions. Moisture permeable membranes, water swellable sealants, extruded shapes and active agent media are produced from the composition.

Description

MOISTURE SENSITIVE ELASTOMER COMPOSITIONS

Technical Field

This invention relates to el astomer composi tions. More particul arly, the invention pertains to moisture sensitive el astomer compositions comprising a composite of a rubber polymer and a hydrophil ic polyurethane polymer.

Background of the invention

It is wel l known that rubber, incl uding natural and synthetic types, as a class is highly resistant to the ef fects of moisture. In fact, rubber is the material of choi ce for fabri cating a great variety of water repellant articles, particularly fabrics and coatings. However, there are some applications for which a moisture sensitive rubber is desirable. For instance, rubber films and membranes having increased moisture permeability and transmission would be useful in fabricating prophylatic devices such as condoms as well as bandages, finger cots and surgical gloves. Rubber that absorbs water accompanied by swelling would be useful as self-sealing caulks and gaskets in an aqueous environment. Because of their relatively high water absorbency, these materials would also be suitable for holding and controlling the release of active ingredients as exemplified by medications, flavors, fragrances, insecticides, germicides, spermicides and the like.

Disclosure of the invention

It has now been discovered that moisture sensitive rubber compositions can be realized by combining rubber with a hydrophilic polyurethane polymer. The provision of such compositions and their preparation and uses constitute the principal objects and purposes of the invention. Other objects and purposes will become apparent in the ensuing description.

As employed herein, the expression "moisture sensitive" means that the rubber compositions of the invention undergo changes in physical behavior such as swelling on exposure to a moist environment such as body fluids or tissues. Examples of these changes and how they can give rise to useful properties are described above and hereinafter.

The moisture sensitive rubber compositions of the invention are prepared by first forming a homogeneous blend of a curable rubber component and a hydrophilic polyurethane and then subjecting the blend to curing conditions to effect curing of the rubber component. In some formulations, the curing conditions may cause crosslinking of the polyurethane component as well.

In preparing the blends, efforts should be made to ensure that the two basic components are thoroughly mixed. A generally suitable procedure consists in mixing the curable rubber component (in the form of a rubber latex or as a solution or dispersion in an organic solvent) with a solution or water-based emulsion of the hydrophilic polyurethane polymer. Curing of the composition is performed in the usual manner, i.e., by heating in the presence of rubber curing agents. Exemplary and satisfactory curing agents include sulfur, zinc oxide, dimethyl zinc and methyl or ethyl dithiocarbamate or any mixture thereof. In a typical curing operation, the uncured blends including the curing system are first stripped of volatile components such as water or solvents. The stripped blends can then be pressure formed or extruded to give the desired shape. In the case of films or membranes such as condoms or gloves, dipping or casting is the usual forming method. The foregoing and other rubber shaping techniques are well known in the art and therefore need not be described in detail. Once the final configuration is obtained, curing is effected by applying heat.

As understood herein, the term "curable rubber component" includes uncured natural rubber as well as various synthetic curable rubber components commonly used in the preparation of synthetic rubbers and elastomers. Representative synthetic rubber components include those derived from unsaturated hydrocarbon monomers and mixtures thereof, such as isoprene, chloroprene, butadiene, SBR (styrene/butadiene rubber), isobutene/isoprene and EPDM (ethylene/propylene/butadiene). Synthetic rubber monomers and latices produced therefrom, as well as other chemicals used in the manufacture of rubber and useful in the invention, are well known and are commercially available from a number of chemical suppliers. A lengthy description of these materials is, therefore, unnecessary for the practice and understanding of the invention. For a comprehensive review of rubber and rubber technology, describing rubber components and methods useful herein, see Kirk- Othmer, Encyclopedia of Chemical Technology, Third Edition, Vol. 20, particularly pages 337 to 489 (incorporated herein by reference).

The hydrophilic polyurethane polymers employed in carrying out the invention are known materials, the description and preparation of which are set forth, for example, in U. S. Patent Nos. 3,822,238, 3,975,350, 4,156,066, 4,156,067, 4,255,550, 4,359,558 and 4,451,635, incorporated herein by reference. Such polymers are resins obtained by reacting a polyisocyanate with a resin having two or more reactive terminal hydrogens and containing various polar sites which appear in the final polymer product and are responsible for its hydrophilic character. Illustrative polar sites include ether groups, carboxylic acid groups, sulfhydryl groups, sulfonium groups, sulfonic groups and quaternary ammonium groups.

Representative resin systems from which the hydrophilic polyurethane polymers can be derived are:

1. An adduct of dihydroxy compounds such as ethylene glycol or propylene glycol with ethylene oxide, propylene oxide, ethylene imine, propylene imine, dioxolane or any mixtures of same; 2. An adduct of trihydroxy compounds such as glycerol or trimethylol propane with ethylene oxide, propylene oxide, ethylene imine, propylene imine, dioxol ane or any mixtures of same ;

3. An adduct of tetrahydroxy compounds such as erythritol or pentaerythritol with ethylene oxide, propyl ene oxide, ethyl ene imine, propylene imine, dioxolane or any mixtures of same;

4. An adduct of polyhydroxy compounds such as anhydroenneaheptitol , sorbitol, mannitol , hydrolyzed l ow molecul ar weight polyvinyl acetate, sucrose or lactose wi th ethylene oxide, propylene oxide, ethyl ene imine, propylene imine, dioxolane or any mixtures of same;

5. An adduct of polybasic acids such as trimellitic acid, pyromell itic acid, mel litic acid, pyrophosphoric acid, and low mol ecul ar wei ght polyacrylic and methacrylic acids with ethylene oxide, propylene oxide, ethylene imine, dioxol ane or any mixtures of same;

6. An adduct of hydroxy acids such as mal eic acid, citric acid or sugar acids wi th ethylene oxide, propylene oxide ethylene imine, dioxolane or mixtures of same. Sugar aci ds are defined in "Carbohydrate Chemistry, " Volume 5 and more specifically. Chapter 17 (a review of literature published during 1971), The Chemical Society, Burlington House, London, Great Britain (1972) and in other sources as well;

7. An adduct of amino compounds, such as ammonia, ethylene diamine, diethylene triamine, triethylene tetraamine with ethylene oxide, propylene oxide, ethylene imine, dioxolane or any mixtures of same;

8. Hydrammonium or quaternary ammonium salts of 7;

9. A sulfonated polyester resin of maleic acid, itaconic acid, mesaconic acid, fumaric acid and a glycol of 2 to 6 carbon atoms;

10. A polyester of a lower alkyl dialkanolamine and a diacid wherein the diacid is adipic, sebacic, azelaic, maleic, phthalic, fumaric acid or mixtures of same, the amine group being converted to an hydra ammonium or quaternary ammonium group;

11. A linear or slightly branched polyamide of an alkyl amine and a diacid wherein the amine is diethylene triamine, triethylene tetraamine, tetraethylene pentamine or polyloweralkylene imines such as ethylene imine or propylene. Suitable diacids include maleic, adipic, azelaic, sebacic, phthalic, itaconic acid or any mixture of same. The term "slightly branched" indicates only methyl or ethyl substituents on the polyamide backbone, the ethyl substituent being less than 1%;

12. Hydrammonium or quaternary ammonium salts of 11;

13. Polysulfhydryl resin having in the backbone sulfonium, sulfoxide, or sulfone groups;

14. Hydrammonium or quaternary ammonium salts of ethylene or propylene imine adducts of polyhydroxy compounds from categories 1 to 4; and

15. Polyesters of polethylene oxides with maleic acid, adipic acid, sebacic acid, phthalic acid, azelaic acid, fumaric acid or any mixtures of same.

In general, the resins of classes 1-15 above will fall within an equivalent weight range above 140, preferably above 170 and up to about 2000. In addition, a ratio of carbon atoms to oxygen and/or amine and/or imine nitrogen atoms ranging from about 1.2:1 to about 2.8:1 is required. Preferably, the ratio is 1.33:1 to 2.8:1, more preferably 1.33:1 to 2.5:1. The aforedescribed polyurethane polymers may vary in their hydrophilicity from polymers that are water soluble to polymers which are water insoluble but which nevertheless will absorb water (e.g., at least 10% by weight), usually accompanied by swelling. Hydrophilic character can be controlled by balancing the type and number of polar sites against the type and size of the inert portion of the polymer molecule following the guide lines given in the cited patents.

A representative polyurethane useful in the invention is prepared by reacting a diisocyanate with a mixture of one or more low molecular weight alkylene glycols such as diethylene glycol and one or more long-chain poloxyalkylene glycol resins in which the oxyalkylene units contain 2 to 4 carbon atoms. Hydrophilic character in these polyurethanes is determined by varying the ratio of low molecular weight alkylene glycol and long-chain polyoxyalkylene glycol. Extreme hydrophilicity of the polymer, even water solubility, is achieved by employing a predominant amount of the highly polar polyoxyethylene glycol. Minimal hydrophilicity results when employing a predominant amount of a poly oxyalkylene glycol in which the oxyalkylene contains higher numbers of carbon atoms, that is, three or more. Intermediate hydrophilicity can be realized by using a mixture of the polyoxyalkylene glycol s or glycols having varying ratios of high to low oxyalkylene units in the resin chain.

A highly suitable hydrophilic polyurethane polymer for preparing the moisture sensitive rubber compositions of the invention comprises the reaction product of a mixture of an organic diisocyanate, a low molecular weight alkylene glycol, such as ethylene glycol and/or diethylene glycol, a water-soluble poloxy ethylene glycol having a number average molecular weight of from about 400 to about 20,000, and water, the reaction mixture having an NCO/OH ratio of from about 0.5 to 1.0, preferably about 0.8 to 0.98 and wherein the percent by weight in the reaction mixture of the low molecular weight glycol is no more than about 20%, the water content is no more than about 0.5% and the weight percent of the diisocyanate is from about 5% to about 60%.

An especially preferred polymer is produced by reacting on a 100% weight basis from about 12% to about 55% of methylene bis (cyclohexy 1-4,4'-isocyanate), from about 2% to about 20% of the low molecular weight alkylene glycol such as diethylene glycol, from about 25% to about 85% of a polyoxy ethylene having a number average molecular weight of from about 1000 to about 8000 and from about 0.1% to about 0.5% water. In addition to methylene bis(cyclohexyl4,4'-isocyanate) other diisocyanates can be used in preparing suitable hydrophilic polyurethane polymers. These other diisocyanates include both aliphatic and aromatic types although the aliphatics are preferred. Representative members are tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexylene 1,2-diisocynate, cyclohexylene 1,4-diisocyanate, and aromatic diisocyanates such as 2,4- and 2,6-tolylene diisocyanates. Also suitable are the isocyanate equivalents which form urethane linkages as exemplified by nitrile carbonates, such as adiponitrile carbonate.

The alkylene glycols and poly oxyalkylene glycols are known entities which can be purchased from chemical supply houses. Typical commercial products are the polyoxy ethylene glycols manufactured by the Union Carbide Corporation, such as CARBCWAX^® 1450, CARBOWAX^® 4500 and CARBOXWAX^® 8000. The numbers refer to average molecular weights.

In preparing the hydrophilic polyurethane polymers, the glycol components and water are formed into a homogeneous mixture which is then reacted with the diisocyanate. The reaction is catalyzed by known catalysts, examples of which are tin salts and organic tin esters such as dibutyl tin dilaurate, tertiary amines such a triethyl diamine (DABCO), N,N,N,N'-tetramethyl-1,3-butane diamine, and other recognized catalysts for urethane polymer synthesis.

The presence of water in the reaction mixture causes evolution of carbon dioxide, resulting in the polymer being obtained as a foam. This is an advantage in that the foamed polymer, owing to its large surface area, exhibits a high rate of dissolution, thereby facilitating the preparation of solutions of the polymer.

In adding the requisite quantity of water to the reaction mixture, allowance should be made for any moisture that may be present in the glycol components.

It is not unusual for commercial grades of alkylene glycols and poly oxyalkylene glycols to contain varying amounts of water. Moreover, such glycols tend to be hygroscopic and even if free of water, may become contaminated with moisture from atmospheric exposure.

Preferably, however, sufficient water will be present or added to cause foaming of the polyurethane polymer as it is formed. Generally, from about 0.1 to about 0.5 part by weight of water based on 100 parts by weight of the total reaction mixture will be effective.

So far as can be ascertained, the compositions of the invention should generally contain at least about 50% by weight of the hydrophobic rubber component in order to provide the requisite elasticity or rubbery character. Such formulations are preferred when the compositions of the invention are used in the manufacture of prophylatic devices and other film articles requiring a high rate of water vapor transmission.

Depending on their chemical configuration, the hydrophilic polyurethane polymers may be insoluble in water but soluble in organic solvents. The water sensitive rubber compositions of the invention preferably contain on a solids weight basis from about 5% to about 50% of the solvent soluble polyurethane, and [polyurethane is used] from about 5% to 20% when a water soluble polyurethane is used.

The moisture sensitive rubber compositions of the invention are particularly useful in the manufacture of film products having controlled moisture transmission such as prophylatic devices (pessaries, condoms), surgical gloves, surgical membranes and dressings, and the like. Coatings can be prepared by spraying a substrate or article with a solvent solution or emulsion (latex) of the uncured composition which is then cured in place.

The rubber compositions of the invention can also be cast, extruded, pressed, calendered or molded into a variety of useful shapes and configurations such as rods, bulk articles and tubing (for example, surgical catheters). Other applications are caulking and sealant materials.

A further use of the rubber compositions of the invention is as an active agent release medium. This is effected by adding an active agent to the uncured composition followed by curing. On exposure of such formulations to aqueous conditions, the active agents are slowly leached out in a controlled manner. Active agents which can be dispersed by this technique include biostats or biocides such as germicides, insecticides and spermicides; insect repellants; detergents including soaps; various drugs and medicines, cosmetics, fragrances, flavors and the like.

A general procedure for producing the aforedescribed articles and materials comprises stripping water or solvents from the uncured polyurethane polymer/rubber blend and then pressure forming or extruding to the desired shape. Films and membranes are produced by dipping or casting, followed by curing.

The rubber compositions of the invention when cured usually exhibit an equilibrium water content of at least about 10% by weight. Equilibrium water content is determined by immersing a sample of the composition in water at 20°C for 24 hours and weighing the composition in the dry state and after removal from water, and expressing the gain as % (by weight of composition) of water absorbed. The elastomer compositions thus are hydrophilic despite the inherent hydrophobicity of the rubber component.

The invention is illustrated further by the following examples in which components are given in parts by weight unless stated otherwise.

PREPARATION OF ELASTOMER/HYDROPHILIC POLYURETHANE

POLYMER COMPOSITIONS AND CURED FILMS THEREFROM

Example I

A rubber latex formulation was prepared as follows. To 80.0 parts of a 62.5% solids natural rubber latex were added with agitation 1.3 parts of a 68% solids sulfur dispersion, 0.3 parts of a 60% solids zinc oxide dispersion and 1.0 part of a 50% solids zinc dimethyldithiocarbamate dispersion (sold as Methyl Zimate^® by R.T. Vanderbilt Co.). Water, 45.0 parts was then added to reduce the latex solids level to 40%.

A polyurethane solution was prepared by dissolving and reacting in 588 parts of water, a hydrophilic polyurethane formed from 59.2 parts of CARB0WAX^® 8000, 25.0 parts of CARBOWAX^® 1450, 2.6 parts of diethylene glycol and 13.1 parts of methylene bis (4-cyclohexylisocyanate).

To 37.5 parts of the 40% solids rubber latex described above was added with stirring 25.7 parts of a solution of the water soluble, hydrophilic polyurethane polymer described above and 61.8 parts of water. The total solids content of the resulting mixture was 15.0% (calculated). A film was cast from this blend, air dried and cured for 20 minutes at 110°C.

The cured film exhibited tensile strength of 3,667 psi and an ultimate elongation of 740%. After immersion in water overnight at ambient temperature, the tensile strength measured 1,799 psi with ultimate elongation of 840%.

0.75 inch diameter disks were die cut from the dry film ad kept under water for 2 days. The disks exhibited a water content of 30% and a linear expansion of 9%. Specimens kept immersed for 12 days showed no further uptake of water.

For comparison purposes, a film was cast from the rubber latex alone, air dried and cured at 110°C for 30 minutes. This film had a tensile strength of 2,489 psi and ultimate elongation of 867%. The water content of this film after two days immersion in water was determined to be 4.5% with a linear expansion of 2.3%.

Example II

To 37.5 parts of the formulated rubber latex of Example I was added 11.4 parts of the aqueous solution of the polyurethane of Example I along with 62.1 parts of water. A film was cast, air dried and cured as in Example I. Tensile strength of the dry film was determined to be 3,966 psi with ultimate elongation of 868%. After hydrating the film for 24 hours in water at ambient temperature, the wet tensile strength was 2,658 psi and ultimate elongation 960%. Water content after two days immersion in water was found to be 21% and the linear expansion was 7%.

Water vapor transmission rates were determined on the films from Examples I and II, and compared to the values for straight natural rubbers as set forth in Table I appended. The results show the greater permeability of moisture vapors through the blend films as compared to natural rubber.

Exampl e III

A styrene/butadiene latex was prepared as follows. To 72.4 parts of a 69% solids Pliolite^® 5356 synthetic styrene/butadiene rubber latex (Goodyear Co.) were added 1.1 parts of a 68% solids sulfur dispersion, 0.6 part of a 60% solids zinc oxide dispersion, 0.8 part of a 50% solids Ethyl .pa Zimate^® dispersion (R.T. Vanderbilt Co.) and 56. 2 parts water.

To 40.0 parts of the styrene/butadiene latex prepared above were added 11.8 parts of a 14.5% solids solution of the aqueous water soluble polyurethane of Example I along with 125.0 parts of water. A film was cast, air dried and then cured for 120 minutes at 120°C.

The water content of the film was determined to be 19% after two days immersion in water at ambient temperature. A film cast from the formulated and cured latex alone exhibited a water content of 9% after two days of water immersion.

To 38.3 parts of the rubber latex of Example I were added 23.2 parts of an aqueous sol ution containing 7.2% of a polyurethane formed from 57.6 CARBOWAX^® 8000, 24.4% of CARBOWAX^® 1450, 3.0 parts of diethylene glycol, 0.15% water and 14.9 parts of methylene bis(cyclohexylisocyanate).

A film was cast from the mixture, air dried and cured as described in Example I. The water content of the film, after two days water immersion at ambient temperature, was found to be 24% while the linear expansion was measured at 10%. Tensile strength of the wet film was 2,638 psi and ultimate elongation 840%. The water content and linear expansion values of the film remained constant after 39 days of water immersion.

Example V

To 25 parts of the rubber latex of Example I were added 75 parts of a 50/50 (by wt.) ethanol/water mixture and 18.7 parts of a polyurethane solution prepared by dissolving in 70 parts of a 90/10 (vol.) ethanol water mixture a polyurethane polymer formed from 54.4 parts CARBCWAX^® 1450, 7.2 parts of diethylene glycol, 2.4 parts of gluconic acid delta lactone, 0.3 part water and 35.8 parts of methylenebis(cycloexylisocyanate), followed by the addition of 70 parts of water to reduce the solids level of the solution to 17.6% and the ethanol content of the volatile portion to 45%. A film was cast from the mixture, air dried and cured for 30 minutes at 110° C. After a two day water immersion at ambient temperature, the water content and linear expansion of the polymer were found to be 27% and 11%, respectively.

The tensile strength of the dry film was 2,054 psi and the ultimate elongation 1,100%. After two days immersion in water, the tensile strength of the wet film was determined to be 2,146 psi and the ultimate elongation 1,000%.

Example VI

To 37.5 parts of a rubber solution, formed by dissolving in 190 parts of toluene 10 parts of dry rubber produced by casting a film from the latex of Example I and drying under vacuum at 40°C, was added the following:

A. 12.5 parts of a 5% polyurethane solution prepared by dissolving in 95 parts of toluene, 5 parts of a polyurethane produced from 39.0 parts of CARBOWAX^® 1450, 5.2 parts of ethylene glycol, 20.9 parts of polytetramethylene glycol having an average molecular weight of 2000 (available as TERATHANE^® 2000 from the DuPont Co.), 0.2 part of water and 34.8 parts of methylene bis(cyclohexyl-4,4¹-isocyanate). B. 1.9 parts of a dispersion of curing agents prepared by blending 2.5 parts of sulfur, 0.6 part of zinc oxide and 1 part of Methyl Zimate^® curative in 95.1 parts of toluene on a roller mill.

A film was cast from the mixture, air dried and cured at 110°C for 30 minutes. After immersion for two days in water at ambient temperature, the water content of the film was found to be 18% and the linear expansion 6%.

Example VII

A nonaqueous blend of 70% SBR synthetic rubber and 30% water insoluble hydrophilic polyurethane was prepared by mixing the following components:

A. 70 parts of a synthetic rubber solution obtained by dissolving 5 parts of a cast rubber film from the Pliolite^® 5356 SBR of Example III in 95 parts of toluene.

B. 3.5 parts of a curing agent obtained by forming a dispersion of 1.5 parts sulfur, 0.75 part of zinc oxide nd 0.75 part of Methyl Zimate^® dispersion in 97 parts of toluene. C. 30 parts of the 5% polyurethane solids solution of Example VI.

A film was cast from the mixture, air dried and then heated to 120°C for 20 minutes. After two days immersion in water at ambient temperature, the water content of the film and its linear expansion were found to be 23% and 11%, respectively.

Example VIII

A film was cast from the blend of natural rubber latex and the aqueous solution of the water soluble polyurethane of Example I and air dried in vacuum at room temperature. The resulting uncured dried film was subjected to 5,000 psi at 50°C in a hydraulic press to form a plate 1.2 mm in thickness. After curing at 120°C for 40 minutes, the plate was immersed in water for two days. The water content and linear expansion of the plate were then measured and found to be 29% and 9%, respectively.

A key property of elastomers for many applications is good tear resistance. Table II appended summarizes the wet tear propagation resistance values found for some of the rubber/hydrophilic compositions of the invention. These values were determined following ASTM 1938. As will be observed from the Table II data, the rubber/hydrophilic polyurethane compositions of the invention exhibited wet tear propagation resistance approximating that of cured natural rubber. Yet, at the same time the hydrophilic character of such composition was retained, greatly exceeding that of rubber alone as demonstrated by the high water absorption capacity of the compositions. Hydrophilic properties mean good water vapor transmission rate, a highly desirable quality of such film products as condoms and surgical gloves.

OTHER USES OF THE ELASTOMER/BYPROPHILIC

COMPOSITIONS

EXAMPLE A - Extruded Tube

A blend of the rubber latex and water insoluble hydrophilic polyurethane of Example V was cast as a film and air dried under vacuum at 30°C to constant weight. The resulting dry uncured film was cut into small (5x5 mm) pieces and the pieces fed into a laboratory hand extruder preheated to 60°C. A tube having an OD of 7 mm and an ID of 4 mm was extruded at

12,000 psi. The tube was suspended in an oven and cured at 120°C for 60 minutes. After immersion in water for two days at ambient temperature, the water content and linear expansion were determined and found to be 26% and 10%, respectively. The tube is suitable for use as a urinary catheter or drain tube for body fluids.

EXAMPLE B - CONDOM

To the rubber latex and hydrophil ic polymer bl end described in Exampl e V was added 0.2 parts of nonylphenoxypoly (ethyl eneoxy) ethanol nonioni c surfactant (IGEPAL^® CO 630, GAF Corp.) . Glass mandrel s used for forming l atex condoms were used to dip condoms from the above solution. After each dip, the latex sol ution was ai r-dried at room temperature. After the fourth dip, the condoms were cured at 100 °C for 20 minutes. When put into water, 20 mg of the

IGEPAL^® CO 630 surfactant was rel eased during the first hour.

EXAMPLE C - Active Agent Release Medium

To the mixture of rubber latex and hydrophilic polymer of Example A was added 0.5 parts of tetracycline. The mixture was processed, dried and extruded as described in Example A. The resulting tube was placed in distilled water at 37°C and the elution of tetracycline was monitored every hour by taking samples from the mixed solution. It was found that the tetracycline elution was fairly steady at 4-6 mg/hour during the 24 hour period. TABLE I

Film Hydrophilic Moisture Vapor Thickness Polyurethane Transmission Rate

Film ( inch) % (g/m²/24 hours)

Example I 0.0129 20 454

Example II 0.0231 10 120

Rubber 0.0174 0 69

Rubber 0,0260 0 53

TABLE II

Film % HydroThickness Tear PropagaResisTested philic (inch) tion Average tance Polyurethane (lb/in) Maximum

Example II 10 0.0134 35.1 97.3

Example IV 10 0.0165 34.9 92.3

Example V 25 0.0152 35.9 98.5

Cured rubber 0 0.0229 35.3 110.8

Claims

Claims:

1. A moisture sensitive elastomer composition comprising a homogenous blend of a curable rubber component and a hydrophilic polyurethane, said composition upon curing having an equilibrium water absorption of at least 10% by weight.

2. The composition of claim 1 wherein the rubber component is a natural or synthetic rubber.

3. The composition of claim 1 wherein the hydrophilic polyurethane is formed by reacting a diisocyanate with a mixture of a low molecular weight alkylene glycol and one or more water-soluble polyoxy alkylene (C²-C⁴) glycols having a number average molecular weight of from about 400 to about 20,000, and wherein the equivalent ratio of isocyanate to hydroxyl groups is from about 0.5:1 to about 1:1 and the percent by weight of isocyanate is from about

5% to about 60%.

4. The composition of claim 1 wherein the polyurethane is insoluble in water but soluble, in organic solvents, and is present in the composition in an amount of from about 5% to 50% by weight.

5. The composition of claim 1 wherein the polyurethane is soluble in water and organic solvents, and is present in the composition in an amount of from about 5% to about 30% by weight, the said composition having an equilibrium water content of at least 15% by weight.

6. The composition of claim 2 wherein the synthetic rubber is selected from the group consisting of polyisoprene, polybutadiene, polychloroprene, butadiene/styrene copolymer, isobutene/isoprene copolymer and ethylene/polypropylene/butadiene terpolymer.

7. A cured composition as in claim 1 in the form of a prophylactic.

8. A cured composition as in claim 1 in the form of a pessary.

9. A cured composition as in claim 1 in the form of a film.

10. A cured composition as in claim 1 in the form of a sealant.

11. The composition of claim 9 wherein the film is in the form of a bandage.

12. The composition of claim 9 wherein the film is in the form of a glove.

13. A cured composition as in claim 1 in the form of an extruded shape.

14. The composition of claim 13 wherein the extruded shape is in the form of a tube.

15. An active agent release medium comprising an active agent and a moisture sensitive elastomer composition as in claim 1.

16. The active agent release medium of claim 15 wherein the active agent is a drug.

17. The active agent release medium of claim 15 wherein the active agent is a fragrance.

18. The active agent release medium of claim 15 wherein the active agent is a cosmetic.

19. The active agent release medium of claim 15 wherein the active agent is a biocide.

20. The active agent release medium of claim 19 wherein the biocide is a germicide, an insecticide or a spermicide.

21. The active agent release medium of claim 15 wherein the active agent is an insect repellant.

22. The active agent release medium of claim 15 wherein the active agent is a detergent.

23. A process of producing a moisture sensitive elastomer composition having, upon curing, an equilibrium water absorption of at least 10% by weight comprising forming a curable homogeneous blend of a rubber latex and a hydrophilic polyurethane and subjecting the blend to curing conditions.

24. The process of claim 23 wherein the rubber latex is natural rubber latex.

25. The process of claim 23 wherein the rubber latex is a synthetic rubber latex.

26. The process of claim 23 wherein prior to curing the blend is subjected to shaping.

27. The process of claim 26 wherein the blend is shaped by injection molding, extrusion, pressing or calendering.

28. The elastomer composition prepared by the process of claim 23.