JPS6340101B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method of making vaginal diaphragms, particularly vaginal diaphragms containing thermoplastic elastomers.

Vaginal diaphragms are usually made of thin trash-like material and consist of a nonporous cup-shaped membrane with a round, somewhat rigid, elastic rim. A spring is generally incorporated therein to maintain the shape of the diaphragm. The sides of the rim can be folded together to form a compressed diaphragm unit to facilitate insertion of the diaphragm into the vagina. When the spring is present, the diaphragm collapses into a "bow" shape. Without the spring, the diaphragm is not stiff enough to form a "bow" shape, making it difficult to do so.
When the folded diaphragm is fully inserted into the vagina, upon release of the diaphragm, the rim of the diaphragm assumes a rounded shape which then sealingly engages the inner walls of the vagina around the cervical canal, and the cervix closes around the diaphragm. interlock with The seal formed by the rim prevents sperm cells from entering the cervical region.

Today, diaphragms generally consist of a latex membrane and a metal spring encapsulated in the latex.
Such diaphragms are generally manufactured by compression molding. Generally speaking, the latex membrane consists of a molded rim and dome, both of which are molded separately from the spring.

Latex has certain properties that make it not ideal as a material for making diaphragms.
The latex was shown to degrade somewhat due to autoxidation due to its polyisoprene structure. Latex materials, by their very nature, have a tendency to form pinholes in loose films such as those commonly used in diaphragm manufacture.
It has also been shown that some of the degradation byproducts associated with the use of stabilizers, emulsifiers, and latexes are potential cytotoxic agents. Rubber or rubber-like materials and certain plastics, such as plasticized polyvinyl chloride and polyethylene, have also been used in the fabrication of diaphragms;
These also have certain drawbacks associated with their use. Therefore, there is a need for a material that has the elasticity and flexibility of prior art materials, but without the inherent disadvantages of prior art materials, and that can be made into films for use in making diaphragms.

A primary object of the present invention is to provide a vaginal diaphragm constructed from a thermoplastic elastomer with sufficient elasticity and flexibility to permit easy insertion of the diaphragm without the use of instruments.

A second object of the invention is to provide a method of manufacturing a diaphragm in which portions of the diaphragm are molded from thermoplastic elastomer.

Another object of the present invention is to provide an improved method of fabricating pinhole-free diaphragms from thermoplastic elastomers.

These and other objects of the invention will be better understood upon reference to the following description and accompanying drawings.

Referring now to the drawings in detail, FIG. 1 shows a diaphragm 2 having a cup portion 3 and a rim 4. As shown in FIG. FIG. 4 shows a rim and film formed by injection molding. As shown in FIG. 2, when the rim is squeezed in this manner, the cup assumes a somewhat sagging position between the two ends of the bow formed by the rim. This facilitates insertion and proper placement of the diaphragm.

According to the present invention, there is provided a vaginal diaphragm comprising a film and a rim made of a thermoplastic elastomer. Both the film and rim can be the same, or they can be made from different elastomers. The film and rim can be molded individually, or they can be fabricated and molded together using suitable molding techniques. In the former method, the rim is formed separately by injection molding and sealed to a film of thermoplastic material. The two parts can be joined together by various means, such as radio frequency techniques, heat sealing, solvent or adhesive bonding. Alternatively, the film and rim can be formed simultaneously by injection molding. The properties of the thermoplastic elastomer are such that once formed, the rim has the required stiffness but remains free and flexible. When the diaphragm 2 is in place, the rim 4 lies flat against the adjacent organ surface and its flexibility allows the diaphragm to conform itself to the contours of the surface. However, the rim 4 is sufficiently rigid to hold the cup portion 3 of the diaphragm 2 in its extended position and is completely flexible throughout. This not only provides comfort, but also ensures proper engagement of the diaphragm.

When the rim is squeezed, the diaphragm assumes a ``bow'' shape, which is also arcuate. That is, when this rim is squeezed together, the cup assumes a sagging position 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 biocompatible, and their long-term tissue compatibility is well known. However, prior to this invention, thermoplastic elastomers have not been used in the manufacture of diaphragms.

Any thermoplastic elastomer can be used to form the film used to make the diaphragm of the present invention. However, in order to impart some degree of softness to the dome and flexibility to the rim, it is preferred to use a thermoplastic elastomer having an average Shore A hardness of about 50 to about 90. The most preferred range is about 75-90. However, softer or harder thermoplastic elastomers can be used; they can be blended with compatible polymers such as ethylene propylene elastomer, plasticized polyvinyl chloride, or acrylonitrile-butadiene-styrene terpolymers to achieve the desired modulus. Can be introduced. Examples of suitable thermoplastic elastomers that can be used to make the diaphragm are styrene-butadiene block copolymers, styrene-isoprene block copolymers, ethylene-vinyl acetate, ethylene-propylene copolymers and ethylene-propylene terpolymers. Preferred thermoplastic elastomers are thermoplastic polyurethanes with polyester or polyether linkages. Examples of suitable thermoplastic polyurethanes that can be used are: Pellathane (urethane elastoplastic polymer based on Upjohn polyether), Cyanoprene.
(American Cyanamid Company fully reacted polyester- or polyether-type urethane thermoplastic elastomers), Estane (BFGoodrich Company thermoplastic polyurethanes made from polyester- or polyether-based urethanes), Roylar (Uniroyal Company thermoplastic polyurethane elastomer), Rucothan
(Hooker Chemical Company polyurethane thermoplastic elastomer), Q-Thane
(Quinn Company polyurethane thermoplastic elastomer) and Texin (Mobay
Chemical Company Polyurethane Thermoplastic Elastomer).

In particular, thermoplastic elastomers and thermoplastic polyurethanes have been found to have superior physical strength over prior art materials. Films made from thermoplastic elastomers exhibit excellent abrasion and tear resistance and have greater tensile strength than prior art materials. Additionally, thermoplastic elastomers generally do not absorb significant amounts of substances such as body proteins and other proteins; these properties make these materials highly desirable as materials for the manufacture of vaginal diaphragms.

In a preferred embodiment of the invention, the diaphragm consists of a dome-shaped thermoplastic polymer film and a thermoplastic polymer rim. The domed film and rim can be made from the same or different types of thermoplastic elastomers.

When using this type of diaphragm, a quantity of spermicidal cream or jelly or other spermicidal agent is dispensed into the cup as is conventional practice, and the diaphragm is then inserted into the vagina. One end of the bow formed when the rims are squeezed together is then easily inserted into the back of the vagina, and the diaphragm is easily moved into position. Once the diaphragm has moved into its proper position, releasing the rim will cause the diaphragm to return to its original shape. As previously mentioned, the flexible rim easily conforms itself to the contours of the adjacent vessel.

As indicated above, vaginal pregnancy diaphragms in use today are made from rubber or rubber-like materials and are generally fabricated by compression molding. When using a flexible spring, place it in a mold,
During compression combined with heat, the molten rubber surrounds the spring and the dome and rim become fused.

In making the diaphragm, according to the method of the invention, the first step involves forming the rim portion. The rim is made by injection molding a thermoplastic elastomer. As indicated above, the diaphragm is preferably capable of assuming a "bow" shape when squeezing the sides of the rim to facilitate insertion. Conventional injection molding consists of side injection of softened polymeric material into a ring mold. This creates only two stress points in the ring, which makes it difficult to create a bow on all sides when squeezing the rim of the diaphragm. According to an aspect of the invention, the rim is manufactured by center injection molding, ie, by simultaneously injecting the softened thermoplastic elastomer from the center of the mold through multiple outlets. It is preferred to use four or more outlets in this step.
This method creates a large number of stress points in the finished rim. Therefore, when squeezing the rim of the finished diaphragm, the stress points are distributed so evenly around the rim that in each case a "bow" shape is obtained. The temperature at which the forming 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 destruction of the elastomer. The particular temperature used in the molding process will depend on the particular polymer used and the time for curing of the molded article. After the rim is formed, flash is removed from the sides and center of the rim before the rim is attached to the dome. After the rim is briefly heated, it is placed into the annular groove of the diaphragm mold used to form the dome. This can be accomplished by placing the rim in a furnace at a temperature below the melting point of the thermoplastic elastomer, but any suitable means can be used to heat the ring. However, this preheating step is only a preferred step and is not required in this method. The thermoplastic elastomer film is then preheated on some suitable support to a temperature below its melting point before being placed in the dome portion of the mold. The film itself can be made by blow molding, extrusion or cast molding, or other methods known in the art. Preferably, the rim and mold are maintained at a temperature at which the elastomer softens but is below its melting point before contacting the mold with the film. This step can be carried out by heating the rim and mold in a single heating unit or in separate units, or in any other suitable manner. The mold and film are brought into contact with each other to form the dome-shaped portion of the diaphragm; the heated mold thus conforms the film to its dome shape and acts as a heat-sealing element to preform the film. Seal to the diaphragm ring. In another step, vacuum or pressure can be applied across the mold at the same time that the film contacts the mold and rim. In this way,
The dome forms a tight seal with the ring and the resulting diaphragm is free of pinholes. 2~
A reduced pressure of 20 psi (0.14-1.41 Kg/cm ² ) is appropriate, but
It is preferred to apply a reduced pressure of 4 to 5 psi (0.28 to 0.35 Kg/cm ² ). When applying pressure, a pressure of 1 to 32 mm is appropriate, but it is preferable to apply a pressure of 20 to 25 mm. Alternatively, the rim and dome can be joined together by other techniques, such as radio frequency techniques or solvent or adhesive bonding.

The mold and diaphragm are held in place for a short period of time, typically on the order of 25 to 60 seconds, after the seal is achieved. Fusing or sealing of the membrane to the rim portion of the diaphragm is accomplished almost instantaneously upon contact and separates the mold from the diaphragm. The formed diaphragm is then cooled by methods known in the art, thereby hardening the dome-shaped portion of the diaphragm to the shape of the mold.

The following examples illustrate methods of fabricating diaphragms from thermoplastic elastomers: (a) Thermoplastic (Pellethane #2363-90A)
was heated to 115°C (46°C) for 3 hours and dried under reduced pressure for an additional 2 hours. Next, apply this resin to 410〓
(210℃) and soften the resin to 115〓(68℃).
Center injection molding in a ring mold at a temperature of 100°F (°C). The injection time is approximately 5 seconds. this ring
After curing for 20 seconds, remove the burr from the center and sides.

(b) Thermoplastic resin (Pellethane #2363−80A)
Cut the seal into 6 inch (15 cm) square pieces, fasten to the clamping frame, and heat to 460° (238°C).
Heat for 11 seconds. The ring formed in (a) above is first heated to 410℃ (21℃) for 90 seconds, and then placed on the diaphragm mold. Ring and mold 180〓
Preheat to (82°C) for 11 seconds. The mold is then moved into the film and when the mold is facing the film, vacuum (25 mm/Hg) is applied. After holding these parts in place for 30 seconds, remove the formed diaphragm and place it in water for 30 seconds.

Although preferred embodiments of the invention have been described, it should be understood that various changes can be made without departing from the scope of the invention as disclosed and claimed herein.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of one embodiment of the present invention. 2 is a perspective view of the diaphragm of FIG. 1 with opposing peripheral portions of the diaphragm squeezed together in preparation for insertion and use; FIG. Figure 3 shows
Figure 2 is a top view of the diaphragm of Figure 1 with a spring ring embedded within the rim; FIG. 4 is a cross-sectional view taken at line 4 of the diaphragm of FIG. 5 is a top view of a spring ring embedded within the rim of the diaphragm of FIG. 3; FIG. 2...Diaphragm, 3...Cup part, 4...
...Rim, 5...Spring.

Claims (1)

Claims: 1. Center injection molding of a rim from a thermoplastic elastomer, transforming a sheet of thermoplastic elastomer into a dome at elevated temperature, the sheet having a larger diameter than the rim, and forming the dome into a dome. 1. A method of making a vaginal diaphragm, comprising sealing to said rim, thereby forming a diaphragm having a continuous rim incorporating a flexible dome-shaped membrane. 2. The method according to claim 1, wherein the rim is heat-sealed to the dome. 3. The method according to claim 1, wherein reduced pressure is applied to the mold during the sealing process. 4. The method according to claim 1, wherein pressure is applied to the mold during the seal ring process. 5. The method of claim 1, wherein the dome and ring contain the same thermoplastic elastomer. 6. The method of claim 1, wherein the dome and ring contain different thermoplastic elastomers. 7. The method of claim 1, wherein the rim and dome contain thermoplastic polyurethane having a Shore A hardness of 50 to 90.