DK151179B - VAGINAL MEMBRANE AND METHOD FOR PRODUCING THE SAME - Google Patents

Description

151179

The present invention relates to a vaginal membrane and to a method for its preparation. In particular, the invention relates to membranes made of thermoplastic elastomers.

A vaginal membrane generally contains a non-perforated 05 and bowl-shaped member made of a thin rubber-like material with a round and somewhat stiff but elastic resilient rim. A spring is usually incorporated therein to maintain the shape of the membrane. Opposite sides of the rim can be folded to form a compact membrane unit to facilitate the insertion of the membrane 10 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 stiff enough to form this "bow" shape and therefore the diaphragm would be difficult to insert. When the folded membrane is fully inserted into the vagina, a release of the membrane will re-establish the round shape of the membrane rim, which then forms the sealing contact with the inner walls of the membrane around the cervix that fits into the membrane. The seal formed by the rim prevents the penetration of sperm into the cervical region.

Contemporary membranes or pessaries generally consist of a latex membrane and a metal spring encased in latex and are generally made by compression molding. In general, the latex membrane contains a molded rim and a vault, both of which are molded separately relative to the spring.

Latex has certain properties which make this material not ideal as a material for making such membranes. It has been found that latex will undergo some degradation of auto-oxidation due to the polyisoprene structure of the material. Because of their intrinsic nature, latex materials tend to form 15 micro holes in a free film, such as the film commonly used to make pessaries.

It has also been found that some of the stabilizers, emulsifiers, and degradation by-products associated with the use of latex are potential cytotoxic agents. Rubber or 20 rubber-like materials, as well as certain thermoplastic materials, such as plasticized polyvinyl chloride and polyethylene, have also been used to make pessaries, but these materials are also subject to certain disadvantages associated with their use. Therefore, there is a need for a material which can be designed into films for use in the production of pessaries, which has the elasticity and flexibility of known materials, but which does not suffer from the disadvantages associated with known materials.

According to the invention, a vaginal membrane or pessary is provided which has sufficient elasticity and flexibility to allow easy insertion of the pessary by the user without the aid of an instrument, but without the tendency to form micro-holes and without the disadvantages associated with prior art. materials.

Furthermore, a method of preparing a pessary having the above advantages is provided.

This is achieved with a vaginal membrane and a method with the features set forth in the claims. In the following, the invention will be explained in more detail with reference to the drawing, in which figure 1 is a perspective view of an embodiment of the vaginal membrane or pessary according to the invention, figure 2 is a perspective view of the pessary in figure 1, but where opposite edge parts are squeezed together under Fig. 3 is a top plan view of the pessary of Fig. 1 showing a spring ring embedded in the rim; Fig. 4 is a sectional view taken along line 4-4 of Fig. 1; and Fig. 5 is a plan view of that spring ring. , which is embedded in the pessary ring as shown in Figure 3.

10 is now referred to the drawing, in which Figure 1 shows a vaginal membrane or a pessary 2 with a bowl portion 3 and a rim 4. Figure 4 shows a border with films made by injection molding. When the rim is squeezed as shown in Figure 2, the bowl portion assumes a draped state between the two ends of the arc or arc formed by the rim.

15 This facilitates the insertion and correct placement of the pessary.

According to the invention there is provided a pessary containing a film with a rim made of a thermoplastic polyurethane elastane. The film and brim may be made of seam or various polyurethane elastomers, and the film and brim may be individually designed or they may be made and formed in one piece using appropriate casting techniques.

In the former case, the rim is formed individually by injection molding and the rim is sealed into a film of the thermoplastic material. The two parties can be joined together using various means, such as radio frequency welding, heat sealing or bonding using solvent or adhesive.

Alternatively, film and rim can be formed simultaneously by injection molding. The properties of the thermoplastic polyurethane elastomers are such that once the rim is formed, it has the necessary rigidity, but the rim remains freely flexible. When the pessary 2 is in position, the rim 4 50 is flat against adjacent organ surfaces and the flexibility of the rim allows it to adapt to the contour of the surfaces. However, the rim 4 is sufficiently rigid to hold the bowl portion 3 of the pessary in its extended position, and the rim is completely and completely flexible. This partly contributes to comfort and also ensures the correct fit of the pessary.

The clamping of the rim causes the pessary to assume a "bow" shape that is also curved. When the rim is squeezed, the bowl portion, as previously mentioned, assumes a somewhat draped state between the two ends of the belly formed by the rim. As mentioned, this facilitates the insertion and correct placement of the pessary 40.

Thermoplastic polyurethane elastomers are known to be biocompatible, and their long-term tissue compatibility is well known. However, to date, thermoplastic elastomers have not been used for the production of pessaries.

Any thermoplastic polyurethane elastones can be used to form the films used to make the pessary of the invention. However, to achieve a degree of softness for the vault as well as flexibility for the rim, it is preferable to use thermoplastic polyurethane elastomers having an average Shore A hardness of between 50 and 90.

The most preferred range is from 75 to 90. However, softer or 10 harder thermoplastic elastomers can be used, and they can be compounded or blended with compatible polymers such as ethylene-propylene elastomers, plasticized polyvinyl chloride or acrylonitrile butadiene styrene polymer to give the material the desired modulus. . Suitable thermoplastic elastomers which can be used to make pessaries include styrene butadiene block copolymer, styrene isoprene block copolymer, ethylene vinyl acetate, ethylene propylene copolymer and ethylene propylene terpolymer. The preferred thermoplastic elastomers are the thermoplastic polyurethanes which have a polyester or polyether bond. Applicable thermoplastic polyurethanes include Pellathan (an upjohn polyether-based and elastoplastic urethane polymer), cyanoprene (an American Cyanamid Company polyester or polyether type thermoplastic and fully reacted polyurethane elastomer), Estane (a GoodFop polyurethane thermoplastic company, and from polyester ester or polyether based urethanes), Roylar (a thermoplastic polyurethane elastomer from Uniroyal Company), Rucothane (a thermoplastic polyurethane elastomer from Hooker Chemical Company), Q-Thane (a thermoplastic polyurethane elastomer from Quinn Company), and Texin (a thermoplastic polyurethomer). Mobay Chemical Company).

30 The thermoplastic polyurethanes have been found to be superior to known physical strength materials. Films made of thermoplastic elastomers have better abrasion resistance, tear resistance and have greater tensile strength than known materials. Furthermore, thermoplastic elastomers generally do not exhibit a significant degree of absorption of materials such as body enzymes or other proteins. These properties make the materials more suitable for the preparation of vaginal membranes or pessaries.

In a preferred embodiment of the invention, the pessary 40 consists of a vaulted thermoplastic polymer film as well as a thermoplastic polymer rim. The vaulted film and rim may be made of the same or different thermoplastic polyurethane elastomers.

When using a pessary of the present type, it is common practice to place a portion of spermicidal cream or gel or other spermacidal agent in the bowl portion, and the peso is then inserted 05 into the vagina. One end of the arch or arch formed when the rim is squeezed can then be easily inserted backwards into the vagina and the pessary can be easily moved into position. When the pessary is moved to its correct position, the border is released and the pessary is allowed to return to its original shape. As previously indicated, the flexible rim readily adapts to the contour of the adjacent body surfaces.

As indicated above, they are currently in use in contraceptive vaginal membranes or pessaries made of rubber or rubber-like materials, and are generally manufactured by compression molding. When used, flexible springs are placed in the mold so that the molten rubber surrounds the spring during compression combined with heat and the vault and rim are fused.

The pessary according to one embodiment of the invention can be prepared by injection molding. The process consists of a melting of the thermoplastic polyurethane elastomer as well as an injection thereof into a divided mold containing one or more mold cavities, each consisting of an annular region and a thin vault or dome region. The amount of material in each injection is proportional to the size of the mold cavity 25. The time from the injection to the pessary's withdrawal from the mold may vary according to the injection rate, the temperatures used and the efficiency of the mold cooling. In 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 degradation. This is usually achieved at a temperature between 205 and 230 ° C. The mold temperature is generally maintained at 21 - 49 ° C during the operation. With a mold with a single mold cavity, a filling time of 5-10 seconds, a holding time of 5-10 seconds and a hardening time of approx. 30 seconds 35 before the pessary's ejection from the mold. The used temperature and time during the casting operation is not critical. However, the actual temperature range and period used during the casting operation will depend on the particular thermoplastic elastomer used and the time during which the elastomer is allowed to cure.

During the preparation of a pessary in carrying out a second embodiment of the method according to the invention, a first step includes the configuration of the rim part. The rim is made by injection molding the thermoplastic elastomer. As indicated above, it is preferred that the pessary is capable of assuming a "bow" shape when the rim 10 is scrutinized on the sides to facilitate insertion. Conventional injection molding comprises a side injection of plasticized polymer material into an annulus. This results in only two points of tension in the ring, making it difficult to form the bow shape on all sides when clamped on the rim of the pessary. According to the present embodiment of the invention, the rim is produced by central injection molding, i.e., the softened thermoplastic elastomer is injected from the center of the mold and simultaneously through multiple outlets.

It is preferred to use four or more outlets during this operation step. This procedure results in the formation of several 20 voltage points in the finished rim. Thus, when the rim of the finished pessary is squeezed, the "oven shape" is obtained in each case due to the more uniform distribution of the points of tension around the rim.

The temperature at which the casting 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 degradation of the elastomer. The particular temperature used during the molding step will depend on the polymer used and the time allowed for curing. After forming the rim, the pendant is removed from the side and center areas of the rim before attaching the rim to the vault or dome. The rim may be heated for a short period of time before being placed in the annular gutter in the pessary shape which is used to form the vault. This can be achieved by placing the rim in an oven at a temperature below the melting point of the thermoplastic elastomer. However, any suitable means for heating the rim ring may be used. However, the preheating is only a preferred step which is not critical to the process.

A film of the thermoplastic elastomer is then preheated on some suitable support to a temperature below the melting point of the elastomer before the film is applied to the vaulted or dome-shaped portion of the mold. The film itself may be made by blow molding, by extrusion or molding or by other prior art.

It is preferred to maintain the rim and mold at a temperature whereby the elastomer is softened, but lying below the melting temperature, before contacting the mold with the film. This operation may be performed by heating the rim and mold in a single heating unit or in separate units or in any other suitable manner.

To form the vaulted or dome-shaped part of the pessary, the mold and the film are brought into contact with each other. Thus, the heated mold 20 causes the film to assume the dome-like shape and further functions as a heat sealing member for joining the film and the pre-formed rim ring. As an alternative operation, the entire mold can be put under vacuum or pressure at the same time as the film comes into contact with the mold and the rim. In this way, the dome forms a tight seal with the rim ring, and the resulting pessary 2 is free of micro holes. A vacuum of between 0.14 kp / cm and 2 1.4 kp / cm is suitable, although a vacuum 2 of between 0.28 kp / cm and 0.35 kp / cm is preferred. When pressure is used, a pressure between 1 mm and 32 mm is suitable, although it is preferable to use a pressure between 20 and 25 mm. Alternatively, the rim and the dome may be joined by other techniques, such as radio frequency welding or by solvent or adhesive bonding.

The mold and pessary are held in place only a short time after the seal has been completed, usually of the order of 25-60 seconds. The fusion or sealing of the diaphragm and the rim of the pessary is achieved almost immediately by contact, and the mold is separated from the pessary. The produced pessary is then quenched using known techniques, whereby the dome-shaped portion of the pessary is 40 cured in the formed form.

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Claims (7)

A vaginal membrane containing a thin bowl-like portion having an annular and somewhat rigid but elastic resilient rim adapted to establish tight-fitting contact with the walls of the vagina, which membrane is sufficiently flexible to allow opposing sides of the rim to fold together to form a slight insertion into the vagina, characterized in that said dome-shaped portion and said rim are made of the same or of different thermoplastic polyurethane layers. 2. A vaginal membrane according to claim 1, characterized in that the thermoplastic polyurethane elastomer has a Shore A hardness of between 75 and 90. 3. A method of making a vaginal membrane or pessary according to claim 1 or 2, characterized in that an edge of the pessary is cast and that a dome is cast together with the rim, the rim and the dome being made of the same or of different thermoplastic polyurethane elastomers. 151179 4. A method according to claim 3, characterized in that a rim is injection molded with a central inlet of a thermoplastic polyurethane elastomer, that a sheet or plate of a thermoplastic polyurethane elastomer is deformed into a dome at an increased temperature, which sheet has a diameter. , which is larger than that of the rim ring, and the AT dome is sealed to the rim ring in such a way that a pessary with a continuous rim is formed together with a flexible and dome-shaped membrane. 5. A method as claimed in claim 4, characterized in that the rim is heat sealed to the dome. 6. A process as claimed in claim 4, characterized in that the mold is put under vacuum during the sealing operation. 15 Process according to claim 4, characterized in that the mold is pressurized during the sealing operation.