IE46628B1 - Vaginal diaphragm and a method for the production thereof - Google Patents

Abstract

The vaginal diaphragm comprises a cap (3) and an annular, fairly rigid and yet elastic edge (4) for sealing against the vaginal walls. At the same time, the diaphragm (2) is made so flexible that mutually opposite sides of the edge (4) thereof can be folded together. For this purpose, the diaphragm is made of at least one thermoplastic elastomer. Such a vaginal diaphragm has no toxic effects.

Description

The present invention relates to an improved vaginal diaphragm and to a method- for the production thereof. In particular, the present invention relates to diaphragms prepared from thermoplastic elastomers.

A vaginal diaphragm commonly comprises an imperforate cup-shaped member made of a thin rubber-like material having a round, somewhat stiff but resilient rim.

A spring is generally incorporated into the rim to maintain the shape of the diaphragm. Opposite sides of the rim can be -0 folded together to form a compact diaphragm unit to facilitate insertion of the diaphragm into the vagina.

The presence of the spring causes the diaphragm to assume a bow shape when folded. Without the spring the diaphragm would not be rigid enough to form the bow** .3 shape and would, therefore, be difficult to insert. When the folded diaphragm is fully inserted within the vagina, release of the diaphragm establishes the round shape of the diaphragm rim which then makes sealing engagement with the inner walls of the vagina around the cervix, which fits within the diaphragm. The seal formed by the rim prevents ingress of sperm cells into the cervical region.

Present day diaphragms generally consist of a latex membrane and a metal spring encapsulated in latex. They are generally prepared by compression molding. Generally, the latex membrane comprises a molded rim and dome both of which are molded separately from the spring. -246628 Latex has certain properties which make it less than ideal as a material from which to make diaphragms.

Xt has been shown that because of its poiyisoprenic Structure latex will undergo some decomposition by autooxidation.

Latex materials by their very nature have a tendency to form pinholes in a free film such as that commonly used in the preparation of diaphragms.

Xt has also been shown that some of the stabilizers, emulsifiers and decomposition by-products associated with the use of latex are potential cytotoxicological agents.

Rubber or rubber-like materials and certain thermoplastic substances such as plasticized polyvinyl chloride and polyethylene, for example, have also been employed in the production of diaphragms but these too have certain dis15 advantages connected with their use. There is a need, therefore, for a material which can be made into films for use in the fabrication of diaphragms which has the resiliency and flexibility of the prior art materials but does not have the disadvantages inherent in the prior art materials.

We have now produced a vaginal diaphragm formed from a thermoplastic elastomer which has sufficient resiliency and flexibility to allow easy insertion of the diaphragm by the user without the aid of an instrument. - 3 46628 According to the present invention there is provided a vaginal diaphragm comprising a thin cup-like member which is dome-shaped having an annular somewhat stiff but resilient rim for making sealing engagement with the walls of the vagina, the diaphragm being sufficiently flexible to enable opposite sides of the rim to be folded to facilitate insertion thereof into the vagina, wherein the dome-shaped member and the rim are formed from the same or different thermoplastic elastomers.

By the term 'elastomer' as used herein is meant a material which at room temperature can be stretched under low stress to at least twice its original length and, upon immediate release of the stress, will return with force to its approximate original length.

The present invention will be further described with reference to the accompanying drawings in which:Figure 1 is a perspective view of one embodiment of the invention; Figure 2 is a perspective view of the diaphragm of Figure 1 wherein the opposite peripheral portions are squeezed together in preparation for insertion and use; Figure 3 is a top-plan view of the diaphragm of Figure 1 with a spring ring embedded within the rim; Figure 4 is a sectional view taken at line 4 of the diaphragm of Figure 1.

Figure 5 is a top-plan view of the spring ring which is embedded within the rim of the diaphragm of Figure 3^. -446628 Referring now specifically to the drawings, there is shown in Figure 1 a diaphragm 2 having a cup portion 3 and a rim 4. Figure £ shows a rim and film formed by injection molding. As shown in' Figure 2, when the rim is thus squeezed together, the cup takes on something of a draped. condition between the two ends of the bow formed by the rim. This facilitates insertion and proper placement of the diaphragm.

Xn accordance with the present invention, there is provided a vaginal diaphragm comprising a film and rim made from a thermoplastic elastomer. Both the film and the rim may be made from the same or different elastomers.

The film amd rim can be formed individually or they can be made and formed in one piece employing the appropriate molding techniques. In the former method, the rim is formed individually by means of injection molding and sealed to a film of the thermoplastic material. The two parts can be joined together by various means such as radio frequency techniques, heat sealing or solvent or. adhesive bonding, for example. Alternatively, the film and rim can be formed simultaneously by injection molding. The properties of thermoplastic elastomers are such that the rim once formed has the required rigidity but remains freely flexible. When the diaphragm 2 is in position, the rim 4 lies flat against adjacent organ surfaces and its flexibility permits it to accommodate itself to the contour of the surfaces. However, the rim 4 is rigid enough to hold the cup portion 3 of the diaphragm 2 in its extended position and is completely flexible throughout.

This not only adds to the comfort, but ensures the proper fitting of the diaphragm.

The squeezing of the rim causes the diaphragm to assume a bow shape, which is also arcuate. When the rim is thus squeezed together, the cup takes on something of a draped condition between the two ends of the bow formed by the rim. This facilitates insertion and proper placement of the diaphragm.

Thermoplastic elastomers are known in the art to be bioeompatible and their long-term tissue compatibility is well known. Prior to the present invention, however, thermoplastic elastomers have not been employed in the preparation of diaphragms.

Any thermoplastic elastomer may be employed to form the films used to prepare the diaphragm of the present • * invention. However, in order to achieve a certain degree of softness for the dome and flexibility for the rim, it is preferred to use thermoplastic elastomers having an average Shore A hardness of about 50 to about 90. The most preferred range is from about 75 to 90. However, softer or harder thermoplastic elastomers can be employed; they can be compounded with compatible polymers such as ethylene propylene elastomers, plasticized polyvinyl chloride, or acrylonitrile-butadiene-styrene terpolymer, for example, to introduce the desired modulus. Suitable thermoplastic elastomers whioh may be employed in preparing the diaphragms include styrene-butadiene block copolymer, styrene-isoprene block copolymer, ethylene vinylacetate, ethylene propylene copolymer and ethylene propylene terpolymer. The preferred - 6 46628 thermoplastic elastomers are the thermoplastic polyurethanes having a polyester or polyether linkage. Suitable thermoplastic polyurethanes whioh can be employed include , Pellethane (Registered Trade Mark—an Upjohn polyether based urethane 5 elastoplastic polymer), Cyanoprene (an American Cyanamid Company fully-reacted polyester or polyether type urethane tlioxmoplastic elastcner), Estane (Registered Trade Mark-a Β. F. Goodrich Company thermoplastic polyurethane made from polyester or polyether based urethanes), floylar (Registered Trade Mark - a Uniroyal Gaipany thermoplastic polyurethane elastomer), Ruoothane (a Hooker Chemical Company polyurethane thermoplastic elastomer), Q-Thane (a Quinn Company polyurethane thermoplastic elastomer) and Texin (Registered Trade Mark—a Mobay Chenical Company polyurethane thermoplastic elastcmer).

Thermoplastic elastomers and the thermoplastic polyurethanes in particular have been found to be superior to the prior art materials in physical strength. Films made from thermoplastic elastomers exhibit superior abrasion resistance and tear resistance properties and have greater tensile strength than the prior art materials.

In addition, the thermoplastic elastomers generally do not show a significant amount of absorption of materials like body enzymes or other proteins; these are properties which make them more desirable materials for the preparation of vaginal diaphragms. - 7 46628 In a preferred embodiment of the invention, the diaphragm consists of a dome-shaped thermoplastic polymeric film and a thermoplastic polymeric rim. The dome-shaped film and the rim can be made from the same or from different types of thermoplastic elastomers. In another embodiment of the invention, a spring comprising, a flexible polymeric ring or metal coil may be embedded in the rim to give it added rigidity. One suitable form of metal coil comprises a helical spring which is bent into ah annulus. The ends of the spring can be joined by any suitable means. They may be intermeshed, welded, or otherwise secured together so that the spring is annular.

The spring itself may be made from any material from which a spring of suitable characteristics may be formed. The spring, however, is an optional feature of this invention since the physical properties of the thermoplastic elastomers are sufficient to give the rim and diaphragm the rigidity required to assure proper fitting of the diaphragm after insertion. - 8 46628 When using a diaphragm of this type, it is common practice to place within the cup a quantity of spermacidal cream or jelly or other spermacide and the diaphragm is then inserted into the vagina. One end of the how formed when the rims are squeezed together is then easily inserted rearwardly into the vagina, and the diaphragm is readily moved into position. Ones the diaphragm has been moved into its proper position, the rim is released and the diaphragm is allowed to return to its original shape.

As previously indicated, the flexible rim readily accommodates itself to the contour of the adjacent organ surfaces.

As indicated above, the vaginal contraceptive diaphragms in use today are made of rubber or rubber-like materials and are generally manufactured by compression molding. Flexible springs, where employed, are placed in the mold so that during compression in combination with heat, the molten rubber encases the spring and the dome and rim become fused. according to one embodiment The diaphragm/jf the present invention can be produced by injection molding. The method consists of melting the thermoplastic elastomer and injecting it into a split diaphragm mold containing one or more cavities each consisting of a ring and a thin dome-shaped area. The softened polymeric material is injected into the ring portion of the cavity and then forced into the dome area. The amount of each shot injected is proportional to cavity ' size. The cycle time from injection to separation of the 6 6 28 diaphragm from the mold can vary according to the speed of injection, temperatures used and efficiency of cooling the mold. Xn a typical process, the thermoplastic polyurethane is heated prior to injection to a temperature high enough to soften the polymer but low enough to prevent chemical breakdown. Thia is generally accomplished at a temperature between about 400-450°?. The mold, temperature is generally maintained at about 70-120°? during the operation. For a single cavity aold, a cycle time of about 5-10 seconds for.filling, 5-10 seconds for holding and about 30 seconds for setup time prior to ejection of the diaphragm from the mold may generally be employed. The temperature and time employed in the molding step are not critical. The particular temperature range and cycle time employed in the molding step, however, will depend upon the particular thermoplastic elastomer employed and the time allowed for the elastomer to set.

Xn the fabrication of a 'diaphragm, according to another , method of this invention, the first step involves the formation of the rim portion. The rim is prepared by injection molding the thermoplastic elastomer.

As indicated above, it is preferred that the diaphragm be capable of assuming a bow* shape when the rim is squeezed on the sides to facilitate easy insertion. Conventional injection molding comprises side injection of softened polymeric material into the ring mold. This results in - 10 46628 only two stress points in the ring thus making it difficult to foxm the bow on all sides when squeezing the rim of the the embodiment of diaphragm. According to/the present invention, the rim is prepared by center injection molding, i.e.softened thermoplastic elastomer is injected from the center of the mold through a number of outlets simultaneously. It is preferred to use four or more outlets in this step.

This procedure results in the formation of a multitude of stress points in the finished rim. Thus when the rim of the finished diaphragm is squeezed, the bow shape is obtained in each instance because of the more even distribution of the stress points around the rim. The temperature at which the molding step is carried out is not critical; however, it is preferred to heat the polymer to a temperature high enough to soften the material, but low enough to prevent chemical breakdown of the elastomer. The specific temperature employed in the molding step will depend upon the particular polymer employed and tha time allowed for the mold to set. After formation of the rim, the flash is removed from the side and ’center portions of the rim prior to attaching the rim to the dome. The rim may be heated for a short period before placing it into the annular groove of the diaphragm mold used to foxm the dome. This can be accomplished by placing the rim in an oven at a temperature below the melting point of the thermoplastic elastomer; however, any suitable means can be employed to heat the ring. The preheating step is only a preferred step, however, and is not critical to the process. A film of the thermoplastic 6 6 2 8 elastomer is then preheated on some suitable support to a ' temperature below its melting point prior to being placed on the dome portion of the mold. The film itself may be prepared by blow molding, by extrusion or casting or by other techniques known in the art. It is preferred to maintain the rim and mold at a temperature at which the elastomer ia softened but below its melting temperature prior to bringing the mold in contact with the film. This step can be performed by beating the rim and the mold in a single heating unit or in separate units or in any other suitable fashion. To form the dome-shaped portion of the diaphragm, the mold and film are brought into contact with each other; the heated mold thus causes the film to conform to its dome-like shape and acts as a heat sealing element to seal the film to the preformed diaphragm { ring. In an alternate step, either vacuum or pressure may be applied to the entire mold at the same time that the film comes into contact with the'mold and the rim. In this way the dome forms a tight seal with the ring, and the resulting diaphragm is free of pinholes. A vacuum between 2 psi and 20 psi is suitable, although it is preferred to apply a vacuum of between 4 psi and 5 psi.

Where pressure is applied, a pressure between 1 mm. and 32 mm. is suitable, although it is preferred to apply a pressure between 20-25 mm. Alternatively, the rim and dome may be joined together by means of other techniques such as, for example, by radio frequency techniques or by solvent or adhesive bonding.

The mold and the diaphragm are- held in place only momentarily after the sealing has been accomplished, generally in the order of 25-60 seconds. The fusing or sealing of the membrane to the rim portion of the diaphragm is accomplished almost instantaneously on contact, and tha mold is separated from the diaphragm. The formed diaphragm is then quenched by techniques known in the art which cause the dome-shaped portion of the diaphragm to set in the shape of the mold.

I The following example illustrates the process for making a diaphragm from a thermoplastic elastomer: a) The thermoplastic resin (Pellethane #2363-90A) is heated at 115°F for 3 hours and is vacuum dried for an additional 2 hours. The resin i3 then heated at 410°F and tha softened resin is center injection molded in a ring mold at a temperature of 155°F. The injection time is approximately 5 seconds. The ring is allowed to cure for 20 seconds after which the flash is removed from the center and the side. b) A sheet of thermoplastic resin (Pellethane ♦2363-80A) is cut into a 6-inch square, clamped on a clamping frame and heated at 460°F for 11 seconds. The ring formed in a) above is first heated at 410°F for 90 seconds after which it is placed on the diaphragm mold.

The ring and mold are preheated at 180°F for 11 seconds. The mold is then moved up into the film, and when the mold meets the film, vacuum is applied (25 mm./Hg.).

The parts are held in place for 30 seconds after which the formed diaphragm is removed and placed in water for 30 seconds.

Claims (18)

1. CLAIMS:1. A vaginal diaphragm comprising a thin cup-like member which is dome-shaped having an annular somewhat stiff but resilient rim for making sealing engagement with the walls of the vagina, said diaphragm being sufficiently flexible to enable opposite sides of the rim to be folded to facilitate insertion thereof into the vagina, wherein the dome-shaped member and the rim are formed from the same or different theromplastic elastomers.

2. A vaginal diaphragm as claimed in Claim 1 wherein the rim and dome are formed from the same thermoplastic elastomer.

3. A vaginal diaphragm as claimed in Claim 1 wherein the rim and dome are formed from different thermoplastic elastomers.

4. A vaginal diaphragm as claimed in any one of the preceding claims wherein the thermoplastic elastomer or one of the thermoplastic elastomers is a thermoplastic elastomer having a Shore A hardness in the range of from 50 to 90.

5. A vaginal diaphragm as claimed in Claim 4 wherein the thermoplastic elastomer has a Shore A hardness in the range of from 75 to 90.

6. A vaginal diaphragm as claimed in any one of the preceding claims wherein the thermoplastic elastomer or one of the thermoplastic elastomers is a polyurethane. -1546628

7. A vaginal diaphragm as claimed in any one of the preceding claims wherein a spring is molded integrally within the rim.

8. A vaginal diaphragm as claimed in claim 1 5 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

9. A method for making a vaginal diaphragm which comprises molding a rim for the diaphragm and integrally molding a dome with the rim, the rim and the dome being 10. Formed from the same or different thermoplastic elastomers

10. A method as claimed in claim 9 wherein the thermoplastic elastomer or one of the thermoplastic elastomers is a thermoplastic polyurethane having a Shore A hardness in the range of from 50 to 90. 15

11. A method as claimed in claim 10 wherein the thermoplastic elastomer has a Shore A hardness in the range of from 75 to 90.

12. A method as claimed in any one of claims 9 to 11 wherein the thermoplastic elastomer or one of the 2o thermoplastic elastomers is a polyurethane.

13. A method as claimed in any one of the preceding claims wherein the dome and the ring are formed from the same thermoplastic elastomer.

14. A method as claimed in any one of claims 9 to 25 12 wherein the dome ahd the ring are formed from different -1646628 thermoplastic elastomers.

15. A method as claimed in any one of claims 9 to 14 which comprises center injection molding a rim from a thermoplastic elastomer, deforming a sheet of a 5 thermoplastic elastomer into a dome at an elevated temperature, the sheet having a diameter greater than the ring, and sealing the dome to the ring, whereby a diaphragm is formed having a continuous rim integral with a flexible dome-shaped membrane. 10 16. A method as claimed in claim 15 wherein the rim is heat sealed to the dome. 17. A method as claimed in claim 15 wherein vacuum is applied to the mold during the sealing step. 18. A method as claimed in claim 15 wherein pressure 15 is applied to the mold during the sealing step. 19. A method as claimed in any one of claims 15 to

16. 18 wherein the rim and dome are formed from a thermoplastic polyurethane having a Shore A hardness in the range of from 50 to 90.

17. 20 20. A method as claimed in claim 9 substantially as hereinbefore described.

18. 21. A method as claimed in claim 9 substantially as hereinbefore described with reference to the Example.