JPH0717548A - Rubber stopper and production thereof - Google Patents

Abstract

PURPOSE:To make a stopper not easily uncorked from the mouth part of a bottle, keep its surface free from adhesion of mold release agent and prevent the deterioration of liquid by forming a fluororubber layer on the surface of a leg part which is inserted into the mouth part of the bottle. CONSTITUTION:A leg part 2 is formed integrally with a lid part 1 at its lower part to insert it into the mouth part of a bottle. The leg part 2 is made into a cylindrical form and, when pressed into the mouth of the bottle, stays in there and is swollen outwardly, so that it will not easily come off. The upper side faces 2a of the leg part 2 are curved smoothly to conform with the curved chamfer face of the inner edge part of the bottle mouth for receiving a rubber stopper. Moreover, the leg part 2 is forked into two parts and a fluororubber layer 3 is formed on their surfaces. This makes a stopper uncorked easily from the mouth part of a bottle to improve chemical resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a rubber stopper and a rubber which, for example, seal a bottle containing a freeze-dried chemical solution or a chemical product, avoid contact between the chemical solution and rubber, and do not use a release agent. The present invention relates to a method for manufacturing a stopper.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Publication No. 57-53184 discloses a method for producing a laminated rubber stopper as a rubber stopper attached to a chemical solution storage bottle.

This "method for producing a laminated rubber stopper" is
"A lower die having a bottle insertion part molding recess is at least larger than the outer diameter of the finished product, and is sequentially polymerized with an unvulcanized butyl rubber sheet and a resin film having a property to withstand the medicine or medical drug to be packaged. The process of heating and pressurizing with a mold to form an element body whose lower surface is covered with a resin layer and whose upper surface is a rubber surface, and "the top end contact surface of the bottle mouth of the element body is
A step of forming a blank plug by cutting it to a width of 3 or less, and then "polymerizing an unvulcanized butyl rubber sheet on the upper surface of the blank plug loaded in the lower mold to make a bottle of a finished product. And the upper die having an enlarged head forming recess having the same diameter as the outer diameter of the upper end contact surface is heated and pressed to form a finished product.

In the case of the laminated rubber stopper manufactured by Japanese Patent Publication No. 57-53184, rubber is exposed on the upper surface of the stopper and the lower surface of the stopper is covered with a resin film.

If the inner edge of the mouth of the bottle is sharply pointed at a right angle, the tip of the rubber plug may be damaged when the rubber plug is inserted, and the rubber chips may fall into the bottle. The inner edge of the bottle mouth is usually rounded and chamfered. Therefore, the bottle mouth insertion portion and the bottle mouth upper end contact surface of the laminated rubber stopper are usually formed so as to be rounded in conformity with the chamfered shape of the inner edge portion of the bottle mouth portion.

[0006] In the case of the laminated rubber stopper for freeze-dried preparations of Japanese Utility Model Publication No. 2-44750, the legs are bifurcated from the connecting portion with the lid, and the inside and outside of the bottle are connected via the forked portion. The rubber stopper is temporarily fixed to the mouth of the bottle so that they can communicate with each other, and after the chemical solution is injected into the bottle via the bifurcated part, the bottle into which the chemical solution has been injected is stored in the low temperature vacuum device, and the internal chemical solution The rubber stopper is completely tightened by freeze-drying and vacuuming. However, when a fluororesin film is attached to the legs, the friction resistance is small, so the legs freeze and contract when kept at low temperature, and the rubber stopper completely enters the bottle mouth, and the chemicals inside the bottle Lyophilization may be inadequate. Therefore, in order to avoid such a situation, in Japanese Utility Model Publication No. 2-44750, a protrusion is provided on the surface of the leg portion so that it is caught in the mouth of the bottle, and the rubber stopper is completely sealed in vacuum. .

[0007]

However, the Japanese Patent Publication No. 57-
Like the laminated rubber stopper of No. 53184, when a resin film is attached to the peripheral surface of the leg, a bottle mouth that holds the leg of the lower die in order to make it easier to remove the leg from the lower die of the primary process. The present situation is that the release agent is sufficiently applied to the inner surface of the insertion portion molding cavity (cavity).

For this reason, an unvulcanized butyl rubber sheet is placed on the fluorine resin film and the upper mold and the lower mold are heated.
When the vulcanized butyl rubber sheet under pressure is removed, a large amount of release agent adheres to the surface of the fluorine resin film on the leg. This release agent is mostly washed when the legs are separated, but it may not be able to get into the scratches formed when the fluororesin film is stretched by a large pressure in the vulcanization process of the butyl rubber sheet. For this reason, there is a possibility that some of the chemicals contained in the bottle may react with the release agent.

In addition, "the peripheral portion of the plug is at most 2
In the step of "cutting with a width of / 3 or less", a method of punching with a cylindrical punch with the leg portion of the plug as a guide is adopted in order to avoid wrinkling of the resin film. Therefore, the planar projection shape of the leg portion becomes the punching shape of the peripheral edge portion of the plug.

However, when the unvulcanized rubber sheet is overlaid on the upper surface of the metal plug through the cutting process and the secondary processing is performed by heating and pressing, the peripheral edge of the resin film shrinks due to heating. As a result, the boundary between the bottle mouth insertion portion of the rubber stopper and the bottle upper end contact surface portion may be contracted.

When the peripheral edge of the resin film shrinks to the boundary between the bottle insertion portion and the bottle upper end contact surface in this manner, a gap is created between the resin film and the rubber, and the resin film and the rubber. There is a problem that the chemical solution enters through the gap between the and, the rubber dissolves in the chemical solution, and the chemical solution deteriorates.

In addition, in the case of the laminated rubber stopper for freeze-dried preparations of Japanese Utility Model Publication No. 2-44750, since the protrusions are formed on the legs in addition to the above-mentioned damage to the resin film, the mold is complicated to form the protrusions. In addition, there is a problem that the protrusion and the resin film are difficult to adhere to each other.

[0013]

SUMMARY OF THE INVENTION The rubber stopper according to the present invention has been made by paying attention to such a problem, and it is premised that the rubber stopper does not easily come off from the mouth portion of the bottle, and the release agent on the surface. It is an object of the present invention to provide a rubber stopper that does not adhere to the container, does not change the quality of a liquid such as a drug solution therein, and does not need to form a protrusion even when used in a bottle for a freeze-dried preparation.

[0014]

In order to solve the above-mentioned problems, the rubber plug according to claim 1 of the present invention is characterized in that a fluorine rubber layer is formed on the leg surface of the rubber plug.

According to a second aspect of the present invention, in the method for producing a rubber plug, the vulcanized butyl rubber sheet is coated with fluorine rubber on the surface from which the leg portions are projected, and after the coating layer of fluorine rubber is dried,
It is characterized in that a rubber plug in which a leg portion and a lid portion are integrated is separated from the butyl rubber sheet.

A method of manufacturing a rubber stopper according to a third aspect of the present invention is characterized in that the fluorine rubber is applied by masking.

According to a fourth aspect of the present invention, there is provided a method for producing a rubber plug, which comprises an unvulcanized butyl rubber sheet having a coating layer of fluorine rubber formed on the front and back surfaces, a lower mold having a cavity for molding a leg portion, It is characterized in that it is arranged between an upper mold having a cavity for forming a lid and heated and pressurized.

According to a fifth aspect of the present invention, in the method for producing a rubber stopper, a film of fluorine rubber is formed on the surface of the leg portion of the rubber stopper in the primary step, and in the preliminary step, the concave portion of the lower mold for the secondary step is formed. , The leg is inserted so that there is a gap between the upper side surface of the leg and the peripheral edge of the opening of the recess, and the leg is positioned on the upper surface of the lower mold for the secondary process in the secondary process. Laying a thin unvulcanized butyl rubber sheet with an opening,
Place the thick unvulcanized butyl rubber sheet that forms the lid on this thin unvulcanized butyl rubber sheet and integrally mold it with the upper mold for integral molding that has a cavity for forming the lid of the rubber plug. It is characterized by performing.

The method for manufacturing a rubber stopper according to claim 6 of the present invention is
In the primary process of claim 5, an unvulcanized butyl rubber sheet having a fluorine rubber layer formed on the lower surface is placed on the upper surface of the lower mold for the primary process, and the butyl rubber sheet vulcanized by the lower mold and the upper mold is used. It is characterized in that the leg portion of the rubber stopper is taken out by separating the peripheral portion of the protruding portion.

[0020]

According to the rubber stopper according to the first aspect of the present invention and the method for manufacturing the rubber stopper according to the second and third aspects, it is necessary to use a release agent without fear of causing scratches due to stretching of the fluorine resin film. Nor. Further, since the surface is made of fluorine rubber, it has good chemical resistance and can sufficiently shield the surface of butyl rubber.

According to the method for producing a rubber plug according to claim 4 of the present invention, in addition to the actions of claims 2 and 3, if a fluorine rubber layer is previously formed on an unvulcanized butyl rubber sheet, this butyl rubber sheet By performing vulcanization and punching, rubber plugs can be easily mass-produced.

According to the method of manufacturing a rubber plug according to claim 5 of the present invention, in addition to the effects of claims 2 and 3, the butyl rubber in a vulcanized state at the time of integrally molding in the secondary step is provided on the upper side surface of the leg portion. The fluorescein rubber that adheres to the surface of the fluorescein rubber and covers the surface of the leg extends inside the butyl rubber of the lid, so that the fluorescein rubber does not separate from the boundary between the fluorescein rubber and the butyl rubber.

According to the method for producing a rubber plug of claim 6 of the present invention, in the primary step of claim 5, the fluorine-containing rubber layer is previously formed on the unvulcanized butyl rubber sheet for the primary step. Similar effects can be obtained.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rubber plug according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a rubber stopper according to the present invention.

The rubber stopper of this embodiment is used as a cold-resistant rubber stopper for a bottle that stores a freeze-dried drug solution, but the rubber stopper may be used for other chemicals, beverages and the like. . Also, what is stored in the bottle is not limited to liquid,
Granules, powders, solids such as pellets, or gas may be used.

FIG. 1 shows a sectional structure of a rubber plug according to an embodiment of the present invention. Reference numeral 1 is a lid portion made of butyl rubber, reference numeral 2 is a leg portion made of butyl rubber, and reference numeral 3 is a fluorine rubber (for example, The product name is Daiel, manufactured by Daikin Industries, Ltd.).

The lid portion 1 extends horizontally so as to come into close contact with the upper end surface of the mouth portion of a bottle (not shown), and the thickness of the lid portion 1 is about 4 mm. Below the lid portion 1, a leg portion 2 to be inserted into the mouth portion of the bottle is integrally formed. The surface portion of the leg portion 2 inserted into the mouth of the bottle is covered with the fluorine rubber 3 through the primer, but in this embodiment, the lower surface 1a of the flange portion of the lid portion 1 is also covered with the fluorine rubber 3. In the present embodiment, the leg portion 2 is formed in a cylindrical shape and bulges outward so that the leg portion 2 stays in the bottle mouth when pressed into the bottle mouth and does not easily fall out. The side surface upper portion 2a of the leg portion 2 is smoothly curved in accordance with the chamfered curve of the inner edge portion of the mouth of the bottle to which the rubber plug is attached. The radius of this curve is approximately 1.5 mm, but since the lower surface 1a of the lid portion 1 is covered with the fluorine rubber 3, there is no possibility that the butyl rubber of the lid portion 1 will come into contact with the chemical liquid inside the bottle. The surface of the lid 1 is covered with a fluorine rubber layer 5 through a primer.
Even if the chemical solution of the bottle comes into contact with the surface of the lid 1, the butyl rubber inside the lid 1 does not change and the chemical or butyl rubber does not change. Although the leg portion 2 is formed in a cylindrical shape in this embodiment, when the leg portion 2 is used for a bottle of a freeze-dried preparation, the leg portion 2 is bifurcated to form a fluorine rubber layer on the surface.

According to the rubber plug of this embodiment, the fluorine rubber 3
Covers the surface portion of the leg portion 2, so that the chemical solution or the like contained in the bottle is prevented from coming into contact with the butyl rubber of the leg portion 2, and the peripheral edge portion of the fluorine rubber 3 is not peeled off.
In addition, even if the bottle chemical solution comes into contact with the surface of the lid portion 1, the butyl rubber inside the lid portion 1 does not come into contact with the chemical liquid or the butyl rubber. Further, when the leg 2 is branched into two to form a rubber stopper for use in a bottle for a freeze-dried preparation, since the surface is coated with a fluorine rubber film, the rubber stopper is temporarily halved during freeze-drying. Even if it is stopped, the rubber stopper is prevented from completely blocking the bottle from the temporarily fixed state and impeding the drying.

Next, a method of manufacturing the rubber stopper according to the embodiment of the present invention will be described.

FIG. 2 shows a method of manufacturing a rubber stopper according to this embodiment. The rubber stopper has an upper mold 4 and a lower mold 5.
It is molded by and. The upper mold 4 is formed with a cavity 6 for forming the lid portion 1 of the rubber stopper, and the lower mold 5 is formed with a cavity 7 for forming the leg portion 2 of the rubber stopper. An unvulcanized butyl rubber sheet 8 is arranged between the upper mold 4 and the lower mold 5.

In this embodiment, the unvulcanized butyl rubber sheet 8 is first sprayed with a primer to obtain 50 ° c to 70 ° c.
After heating for 10 to 20 minutes at the temperature of 10 to 20 minutes to dry, for example, a fluorine rubber having a trade name of "DAIEL" manufactured by Daikin Industries, Ltd. is sprayed and dried.

After the unvulcanized butyl rubber sheet 8 is arranged between the upper mold 4 and the lower mold 5, the heated upper mold 4 and the lower mold 5 are clamped and pressed. As a result, a large number of rubber plug bodies are formed on the vulcanized rubber sheet. Therefore, open the lower mold 4 and the upper mold 5 to remove the rubber sheet, and punch the rubber plug with a punch to complete the rubber plug. .
Since the unvulcanized butyl rubber sheet 8 on which the coating film of the fluorine rubber layer 9 is formed can be mass-produced and stored in advance, the heated upper mold 4 and the lower mold 4 can be used to form the rubber plug of this embodiment. By placing the unvulcanized butyl rubber sheet 8 between the molds 5 and applying pressure, rubber plugs can be easily mass-produced.

In the above embodiment, the fluorine rubber layer 3 is formed on the lower surface 1a of the flange portion of the lid portion 1. However, as shown in FIG. 3, a butyl rubber sheet which has not been vulcanized and whose both surfaces are not coated is formed. A method is also available in which the butyl rubber sheet is prepared and vulcanized between the upper mold 4 and the lower mold 5, and then the perforated plate 11 is attached to the leg portion 2 of the vulcanized rubber sheet 10 for masking. is there. In this case, since only the leg 2 is exposed from the perforated plate 11, if a primer is spray-dried on this surface and then fluorine rubber is sprayed on the primer and dried by heat treatment, only the surface of the leg 2 of the rubber plug is exposed. The fluoro rubber layer 12 is formed. After the fluorine rubber layer 12 is formed, the perforated plate 11 is removed from the rubber sheet 10 and the rubber stopper is punched with a punch.

Next, a second embodiment of the method for manufacturing a rubber stopper according to the present invention will be described.

The method of manufacturing a rubber plug according to the second embodiment includes a primary step for forming legs of a rubber plug having a film of fluorine rubber formed on a surface portion to be inserted into a bottle, and a lower step for the secondary step. It consists of a preliminary step of mounting the legs of the rubber stopper in the concave portion of the mold, and a secondary step of vulcanizing the butyl rubber sheet double-set on the lower mold for the secondary step.

The primary step is a step of obtaining the leg portion 2 having a butyl rubber layer formed on the lower surface to be inserted into the bottle. Specifically, a lower mold and an upper mold (not shown) that form the leg portion 2
And prepare. The lower mold has a cavity forming a leg. The upper mold for the primary process preferably has a cavity forming the peripheral edge contour of the leg. On one surface of the butyl rubber sheet used for the vulcanization in the primary step, a fluorine rubber layer is formed with or without a primer.
The fluorine rubber layer is formed by various means such as spraying or coating and dried. When this butyl rubber sheet is disposed between the lower mold and the upper mold for the primary process and vulcanized, the leg portions 2 of the rubber plug are formed as convex portions on the butyl rubber sheet. Usually, in order to form many legs at once,
A large number of cavities are formed in the mold of the primary process. The leg portion 2 is obtained by punching out the peripheral edge portion of the convex portion of the butyl rubber sheet.

In the preliminary step, as shown in FIG. 4, the punched leg portion 2 is set in the lower die 13 for the secondary step. The lower mold 13 for the secondary process is formed with a large number of recesses 18 for mounting legs. The lower mold 13 for the secondary process holds the leg portion 2 during integral molding. The heating temperature of the lower mold 13 at the time of integral molding is set to about 100 ° C. to 120 ° C. in order to remove the legs without using the release agent. If the temperature is higher than this temperature, the leg portion 2 adheres to the concave portion 13, so that the separation without the release agent becomes difficult.

In the secondary step, a thin unvulcanized butyl rubber sheet 15 and a thick unvulcanized butyl rubber sheet 16 are placed on the lower mold 13 before the integral molding. The thickness of the thin unvulcanized butyl rubber sheet 15 is almost the same as the height from the upper surface of the lower mold 13 to the upper surface 2b of the upper end of the leg 2 held in the recess 18. As shown in FIG. 7, the thin butyl rubber sheet 15 has a large number of circular holes 15a in which the legs 2 are located. The lower die 1 is attached to the edge of the hole 15a.
The peripheral portions of the leg portions 2 of 3 are located close to each other, and the melted butyl rubber sheet immediately enters between the leg portions 2 and the concave portions 18. The thick unvulcanized butyl rubber sheet 16 is for forming a lid. In order to form the fluorine rubber layer on the upper surface of the lid portion 1, in this embodiment, the fluorine rubber layer 17 is formed on the upper surface of the thick unvulcanized butyl rubber sheet 16 through the primer. When the unvulcanized butyl rubber sheets 15 and 16 are double laid on the lower die 13, 160
The upper mold 14 heated to about C to 180 ° C. is pressed against the unvulcanized butyl rubber sheet 16 to apply pressure to integrally mold it.

As a result, the surface of the leg portion 2 is covered with the fluorine rubber layer 3 and the rubber stopper in which the fluorine rubber layer 3 is advanced into the butyl rubber of the lid portion 1 is formed. According to such a rubber stopper, the fluorine rubber layer 3 is formed from the surface of the leg portion 2 to the lid portion 1.
Since it extends inside, it is possible to completely prevent the fluorine rubber layer 3 from peeling off. Therefore, it is possible to prevent contact between the chemical liquid and butyl rubber. When it is attached to a bottle for a freeze-dried preparation, the leg portion 2 of the rubber stopper is bifurcated. When filling the bottle with the freeze-dried preparation, in order to freeze-dry after filling, the rubber stopper is not completely closed, and a gap is provided between the bifurcated portion and the opening of the bottle. Freeze-drying is performed in this state, and the rubber stopper is pressed in the vacuum device to close the gap between the forked portion and the opening. When the bottle is taken out from the vacuum device, the rubber stopper completely adheres to the mouth of the bottle. In the case of a rubber stopper with a fluorine resin film attached to the surface, the surface friction resistance is small,
The legs may fall into the bottle when frozen and dried, but in the case of the rubber stopper of this embodiment, the surface of the legs 2 is covered with the fluorine rubber layer 3, so that the rubber stopper may be removed during freeze-drying. There is no danger of falling inside the bottle. In addition, since the film is not stretched unlike the fluororesin film, the barrier property is not deteriorated due to scratches on the film.

[0040]

According to the rubber stopper according to the first aspect of the present invention and the method for producing the rubber stopper according to the second and third aspects, a mold release agent is used without fear of causing scratches due to stretching of the fluorine resin film. You don't even have to. Also, because the surface is fluorine rubber,
It has good chemical resistance and can sufficiently shield the surface of butyl rubber.

According to the rubber plug of claim 4 of the present invention, in addition to the effects of claims 2 and 3, if a fluorine rubber layer is previously formed on an unvulcanized butyl rubber sheet, the vulcanization of this butyl rubber sheet is achieved. By performing punching and punching, rubber plugs can be easily mass-produced.

When a leg is branched into two to form a rubber stopper for use in a bottle for a freeze-dried preparation, since the surface of the rubber stopper is formed with a coating film of fluorine rubber, the rubber stopper should be about half when freeze-dried. Even if it is temporarily fixed, the rubber plug is prevented from completely blocking the bottle from the temporarily fixed state and hindering the drying, and it is not necessary to form a protrusion or the like.

Further, according to the method for producing a rubber plug according to claims 5 and 6 of the present invention, in addition to the effects of claims 2 and 3, butyl rubber in a vulcanized state at the time of integral molding in the secondary step is Since the fluorine rubber attached to the surface of the fluorine rubber on the upper side surface of the leg portion and covering the surface of the leg portion extends inside the butyl rubber of the lid portion, the fluorine rubber is not separated from the boundary portion between the fluorine rubber and the butyl rubber.

[Brief description of drawings]

FIG. 1 is a sectional view of a rubber plug according to an embodiment of the present invention.

FIG. 2 is a sectional view of a method for manufacturing a rubber plug according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a modified example of the method for producing a rubber plug of the present invention.

FIG. 4 is a cross-sectional view of another embodiment of the method for manufacturing a rubber stopper according to the present invention.

5 is a sectional view of a secondary step of integrally molding the rubber plug shown in FIG.

6 is a cross-sectional view of the rubber stopper shown in FIG.

FIG. 7 is a plan view of the thin unvulcanized rubber sheet shown in FIG.

[Explanation of symbols]

 1 Lid part 2 Leg part 3 Fluoro rubber 4 Upper mold 5 Lower mold 6 Cavity of lid part 7 Cavity of leg part 8 Unvulcanized butyl rubber sheet 9 Fluoro rubber layer 10 Vulcanized rubber sheet 11 Perforated plate 12 Fluoro rubber layer 13 Lower mold for secondary process 14 Upper mold for secondary process 15 Thin unvulcanized butyl rubber sheet 16 Thick unvulcanized butyl rubber sheet 17 Fluoro rubber layer 18 Cavity

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuichi Hiraizumi Inventor Yuichi Hiraizumi 4-2-22 Higashiyotsugi, Katsushika-ku, Tokyo Kazusa Hard Chrome Co., Ltd.

Claims (6)

[Claims] 1. A rubber stopper in which a leg portion inserted into the mouth of the bottle protrudes from a lid portion that closely adheres to an upper end surface of the bottle mouth, and a fluorine rubber layer is formed on a surface of the leg portion inserted into the mouth of the bottle. A rubber stopper that is characterized by 2. An unvulcanized butyl rubber sheet is placed between a lower die having a cavity for forming a leg portion and an upper die having a cavity for forming a lid portion, and is heated and pressed to produce the lower portion. Remove the vulcanized butyl rubber sheet that was opened by removing the mold and the upper mold, apply fluorine rubber to the surface from which the legs of this vulcanized butyl rubber sheet project, and after drying the coating layer of the fluorine rubber, the butyl rubber sheet A method of manufacturing a rubber stopper, characterized in that a rubber stopper having a leg portion and a lid portion integrated with each other is separated. 3. The method of manufacturing a rubber stopper according to claim 3,
A method of manufacturing a rubber stopper, characterized in that the surface of the vulcanized butyl rubber sheet on which the leg portion is projected is masked to expose the leg portion and the fluorine rubber is applied. 4. An unvulcanized butyl rubber sheet having a coating layer of fluorine rubber formed on the front and back surfaces of a lower mold having a cavity for forming a leg and an upper mold having a cavity for forming a lid. The vulcanized butyl rubber sheet, which was placed in between and heated and pressed to open and remove the lower mold and upper mold, was removed, and the rubber plug with the leg and lid integrated was separated from this butyl rubber sheet. A method for producing a rubber stopper, comprising: 5. A primary step for forming a leg portion of a rubber stopper having a film of fluorine rubber formed on a surface portion to be inserted inside a bottle, and a lower metal for a secondary step having a concave portion for holding the leg portion. The upper side surface of the leg portion is exposed above the upper surface of the lower mold in the concave portion of the mold, and the leg of the rubber stopper is provided with a gap between the upper side surface of the leg portion and the peripheral edge portion of the opening of the concave portion. A preliminary step of inserting a portion, and a thin unvulcanized having a wall thickness approximately equal to the height from the upper surface of the lower mold for the secondary step to the upper surface of the leg portion and having an opening larger than the leg portion. A butyl rubber sheet is prepared, and this thin unvulcanized butyl rubber sheet is placed on the upper surface of the lower mold for the secondary step so that the legs are located in the opening. Place the thick unvulcanized butyl rubber sheet that forms the lid on the A secondary step of performing integral molding an upper die for integral molding having a cavity for the lid part forming a plug of the manufacturing method of the rubber plug, characterized in that it comprises. 6. The method of manufacturing a rubber plug according to claim 5, wherein the primary step includes a step of forming a fluorine rubber layer on a lower surface of an upper surface of a lower mold for a primary step having a cavity for molding the leg portion. Placing a vulcanized butyl rubber sheet, closing the lower mold for the primary process and the upper mold for the primary process facing it, and vulcanizing the unvulcanized butyl rubber sheet; and the lower mold for the primary process. Open the mold and upper mold, remove the vulcanized butyl rubber sheet with the above-mentioned fluorine rubber attached to the surface, separate the peripheral edge of the protruding part from the removed vulcanized butyl rubber sheet, and take out the leg part of the rubber plug. A method of manufacturing a rubber stopper, comprising: