RUBBER PLUG FOR MEDICAL SERVICE

Abstract

 A rubber plug (2) provided with a leg (4) fitted into the mouth of a vial (1) and a flange (6) in contact with an upper edge surface (5) of the vial mouth, wherein projections (8) for preventing close contact of a top face (7) of a head of the rubber plug (2) are shaped into an arcuate shape and positioned at the portions of the upper edge surface (5) on the outer side of the inner diameter of the vial mouth so that the lower parts of the arcuate projections (8) of the top face (7) come into contact with the upper edge surface (5) on the outer side of the vial mouth and compressive deformation of the arcuate projections (8) is suppressed with the upper edge surface (5) acting as the base. When a pharmaceutical preparation is freeze-dried in a vacuum inside the vial (1), the top face (7) does not completely contact the push surface of the freeze-drying rack when the rubber plug (2) is inserted, and a space is defined between the push surface and the top face (7) of the rubber plug (2) and a close contact can be prevented.

Description

TECHNICAL FIELD

[0001] The present invention relates to a medical rubber plug for sealing or stopping a mouth of a container (or receptacle) for medical use, particularly for sealing or stopping the mouth of a vial which stores freeze-drying preparation.

BACKGROUND ART

[0002] A conventional medical rubber plug for sealing or stopping a mouth of a vial which stores preparation such as antibiotics, has a leg 22 that is fitted into the mouth of the vial 21 and a flange 24 that contacts with a top edge surface 23 of the mouth of the vial 21, as shown in Fig. 2. In general, projections 26 are provided on the top surface 25 of the mushroom-cap-like part of the medical rubber plug in order to prevent rubber plugs from adhering (or sticking) each other during its cleaning, disinfection and drying, and/or in order to prevent the rubber plug from adhering to an aluminum cap to be fitted around the rubber plug. The shape and position of the projection 26 on the top surface 25 of the mushroom-cap-like part of the rubber plug are not limited, for example, as shown in Fig. 3 illustrating T-shaped projections 27, and as shown in Figs. 4 and 5 illustrating semicylindrical (or semicircular) projections 28 and 29.

[0003] Meanwhile, preparation, such as antibiotics, is frozen, evacuated (or made vacuous) and dried, by filling up a specified quantity of medicament (or medication liquid) in a vial, by half-inserting into the opening (or mouth) of the vial a rubber plug the leg of which has an opening to facilitate a passage of aqueous vapor from the medicament, by placing the vial in a shelf (or rack) inside a freeze dryer, and by maintaining a specified temperature and a specified degree of vacuum inside the freeze dryer. The freeze vacuum drying of the preparation in the freeze dryer includes a primary drying step and a secondary drying step. In the primary drying step, normally, the medicament is frozen at temperature of -30 to -45°C, and then it is kept at the degree of vacuum of 1 to 0.03 Torr and at temperature of -20 to +30°C for 12 to 36 hours. The freeze vacuum drying of the medicament is completed after the medicament is kept at temperature of +20 to +40°C for 1 to 6 hours in the secondary drying step.

[0004] Next, nitrogen is supplied to the freeze dryer to raise the inside pressure to the normal level (-300 mmH₂O to 0), and a stainless steel press panel of the shelf inside the freeze dryer is employed to press (or bias) the rubber plug and to fit it completely in the vial mouth. The general condition for plugging it therein is: the pressing force (or biasing force) per vial is 1 to 5 kg; the pressing duration is 1 to 10 minutes; and the frequency of pressing it is once or twice. Once the insertion of the rubber plug thereto is completed, the vial is moved out of the freeze dryer, and then it is transferred to the succeeding process for winding an aluminum cap around the rubber plug tightly, thus gaining the preparation with the vial being plugged therewith.

[0005] For preparation in the freeze vacuum drying, butyl rubber such as isobutylene-isoprene copolymer is generally employed as material of the rubber plug, in order to prevent water, air and the like from stealing in from outside while the preparation is hermetically kept therein, or in order to maintain air-tightness inside the vial. Butyl rubber, however, shows a high degree of unsaturation, and shows a low degree of bridge density; namely, the butyl rubber is inferior in elasticity, and the viscosity of the rubber surface is greater. Accordingly, when the rubber plug, made of butyl rubber, is pressed to plug the mouth with the press panel of the freeze dryer after the freeze vacuum drying is completed, the top surface of the rubber plug may stick to the press panel due to the stickiness, and the vial may be hung upwards together with the rubber plug sticking to the press panel when the press panel is lifted. If the vial is dropped down in a few seconds, it may cause the surrounding vials to overturn, which hinders a removal of the vials from inside the freeze dryer and which blocks a transfer thereof to the following step (or process).

[0006] To solve the problem, oil, or reacting type of silicone, is coated on the top surface of the butyl rubber plug in order to reduce adhesion to the press panel of the freeze dryer. Also, as rubber plugs with no adhesion to the press panel of the shelf inside the freeze dryer, there have been proposed rubber plugs such as ones 51 in which the top surface 52 thereof, or both of the top surface 52 and the leg 53 thereof, is/are laminated with resin film, as shown in Figs. 6 and 7. Namely, there have been proposed the rubber plug 51 in which the whole part of the top surface 52 and leg 53 thereof, or a part thereof, is laminated with fluoroplastic film 54 (Patent Publication No. 2,545,540), and the rubber plug 51 in which the top surface 52, or the leg 53, or the whole surface thereof, is laminated with a surface, processed by corona discharging, of ultra high polymer polyethylene film 55 (Japanese Laid-Open Patent Publication No. 4-22,362 ), and the like.

[0007] However, the shape, number and position of the projections which are provided on the top surface of the rubber plug for the purpose of preventing the adhesion, are not specified. Therefore, even if the adhesion between the rubber plugs is prevented by the silicone coat on the surface of the rubber plug, the actual situation is that the complete prevention thereof from sticking to the press panel of the shelf inside the freeze dryer has not been realized. Therefore, generally, silicone is coated on the surface of the press panel of the shelf inside the freeze dryer to prevent the adhesion between the top surface of the rubber plug and the press panel. This method, however, requires an extra work for coating silicone onto the surface of the press panel of the shelf inside the free dryer, and it may cause contamination inside the freeze dryer.

[0008] A technique for laminating the resin film onto the top surface of the rubber plug has an advantage that the top surface of the rubber plug is prevented from sticking to the press panel of the shelf inside the freeze dryer. However, the top surface of the rubber plug has a double-layer construction in which the soft rubber thereof is laminated with a resin film. Therefore, not only the method for molding the rubber plug is complicated, but also it is difficult to prevent a generation of film fragments or coring, thus making difficult its quality assurance as a rubber plug for medical use. Furthermore, the rubber plug in which the resin film is coated on the top surface thereof has a disadvantage that it is not possible to provide the rubber plug at low cost, because the resin film is relatively expensive, and because not a few manufacturing processes (or steps) are required.

[0009] An object of the present invention is to provide a rubber plug for medical use that solves the problems of the aforementioned prior art, in which it satisfies various characteristics including a low gas permeability, a low water permeability (or low moisture permeability), an air tightness (or hermetic property), an easiness of needling (or pricking) it, a nature (or property) of heat resistance, a nature (or property) of resistance against aging, a nature (or property) of low coring, and the like, which complies with the Japan Pharmacopoeia, which satisfies the Rubber Plug Testing Standard for Infusion, and which prevents the top surface of the rubber plug from sticking (or adhering) to the press panel when the rubber plug, being kept half-inserted inside an opening of a vial that is placed inside the freeze dryer, is completely plugged into the opening of the vial by the press panel of the shelf inside the freeze dryer after the preparation is frozen, evacuated and dried inside the vial.

DISCLOSURE OF THE INVENTION

[0010] The inventor et al. repeated various tests and discussed on shape, number and quantity, and mounting position, of projections on the top surface of the mushroom-cap-like part of the rubber plug, in order to achieve the aforementioned object. As a result, the inventor et al. found that the adhesion of the top surface of the rubber plug to the press panel of the shelf inside the freeze dryer can be prevented, by positioning the projection for preventing the adhesion thereto of the rubber plug which is to be plugged in the mouth of the vial for medical use, on an upper part of an edge surface which locates outside the internal diameter of the mouth of the vial, and found that the rubber plug is easier in manufacturing and less expensive than the conventional rubber plug having the double-construction which is formed by laminating with the resin film.

[0011] The medical rubber plug in accordance with claim 1 of the present invention comprises: a leg part which is inserted into a mouth of a vial; and a flange part which contacts an upper edge surface of the mouth of the vial, in which a projection which is provided on a top surface of a mushroom-cap-shaped part of the medical rubber plug and which prevents an adhesion of the top surface thereof, is arc-shaped, and in which the projection is provided on an upper part of an edge surface locating outside an inner diameter of the mouth of the vial. With the construction that the projection which is provided on the top surface of the mushroom-cap-shaped part of the medical rubber plug and which prevents the adhesion of the top surface thereof, is arc-shaped, and with the construction that the projection is provided on the upper part of the edge surface locating outside the inner diameter of the mouth of the vial, the lower part of the arc-shaped projection on the top surface of the mushroom-cap-shaped part of the rubber plug comes to contact the edge surface locating outside the mouth of the vial, and the compressive deformation of the arc-shaped projection is suppressed by the edge surface functioning as a base. Namely, the whole top surface of the rubber plug does not contact the press surface closely, and a space is formed between the press surface and the top surface of the rubber plug. Therefore, the adhesion therebetween is prevented.

[0012] In the medical rubber plug in accordance with claim 2 of the present invention, there are provided six to twelve projections each of which is the projection that is provided on the top surface of the mushroom-cap-shaped part of the medical rubber plug and that prevents the adhesion of the top surface thereof. With the construction that there are provided six to twelve projections each of which is the projection that is provided on the top surface of the mushroom-cap-shaped part of the medical rubber plug and that prevents the adhesion of the top surface thereof, it is possible to completely prevent the adhesion between the press surface of the shelf inside a freeze dryer, and the top surface of the rubber plug; at the same time, it is possible to keep in good condition the tightness with which the aluminum cap is wound around the flange of the rubber plug. Therefore, it is possible to prevent the rubber plug from dropping in the vial.

BRIEF DESCRIPTION OF DRAWINGS

[0013] 

Fig. 1 shows a medical rubber plug according to the present invention, where Fig. 1a is a plan view thereof, and Fig. 1b is a vertical cross-sectional view showing a state in which the rubber plug is fully inserted into a mouth of a vial;

Fig. 2 shows a conventional medical rubber plug, where Fig. 2a is a plan view thereof, and Fig. 2b is a vertical cross-sectional view showing a state in which the rubber plug is fully inserted into a mouth of a vial;

Fig. 3 is a plan view of the conventional medical rubber plug on a top surface of which T-shaped projections are formed;

Fig. 4 is a plan view of the conventional medical rubber plug on a top surface of which semi-cylindrical projections are formed;

Fig. 5 is a plan view of the conventional medical rubber plug on a top surface of which other semi-cylindrical projections are formed;

Fig. 6 is a vertical cross-sectional view of the conventional medical rubber plug on a top surface and a leg part of which a fluoroplastic film is laminated; and

Fig. 7 is a vertical cross-sectional view of the conventional medical rubber plug on a top surface of which an ultra high polymer polyethylene film is laminated.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] A medical rubber plug in accordance with the present invention has a leg to be fitted into a mouth of a vial, and a flange to come to contact with an upper edge surface of the mouth of the vial, which is similar to the conventional rubber plug, and the medical rubber plug has a size and a shape, each of which does not change especially. The medical rubber plug is different from the conventional one in that each of projections provided on a top surface of a mushroom-cap-shaped part (or mushroom-pileus-shaped part or lamp-shade-like part) of the rubber plug of the present invention is arc-shaped (or arcuate in shape), and in that the projections are arranged on an upper part of an edge surface locating outside an internal diameter of the mouth of the vial. Thus, even if the arc-shaped projections according to the present invention are added to the conventional rubber plug so that the arc-shaped projections are positioned on the upper part of the edge surface outside the internal diameter of the mouth of the vial, there is no particular difference in function and effect. The material which the rubber plug of the present invention is made of, is butyl rubber with a low gas permeability and a low vapor (or moisture) permeability, which has been conventionally utilized.

[0015] The size of the projection provided on the top surface of the mushroom-cap-shaped part of the medical rubber plug in accordance with the present invention, is determined by the size of the medical rubber plug, and is not specifically determined. The desirable size thereof is 1.0 to 2.0 mm in its base and 0.4 to 0.8 mm in its height. It is preferable to provide six to twelve arc-shaped projections, and it is preferable that the arc-shaped projections are provided on the same circumference (or circle) at an equal interval. If the number of the arc-shaped projections is less than six, the adhesion between the top surface of the rubber plug and the aluminum cap can be prevented, but the adhesion between the pressing surface of the shelf inside the freeze dryer and the top surface of the rubber plug can not be prevented completely. Meanwhile, if the number of the arc-shaped projections exceeds twelve, the adhesion between the pressing surface of the shelf inside the freeze dryer and the top surface of the rubber plug can be prevented completely, but the tightness between the flange of the rubber plug and the aluminum cap becomes deteriorated, thus easily allowing the rubber plug to drop in the vial at time of piercing a needle therethrough.

[0016] The usage of the medical rubber plug in accordance with the present invention is the same as that in accordance with the conventional medical rubber plug. Namely, a specified quantity of medicament liquid is filled up in the vial; the rubber plug is half-inserted (or half-engaged) into the mouth of the vial; plural vials are arranged inside each of the shelves inside the freeze dryer in alignment; they are frozen, evacuated and dried under a predetermined condition (in respect of temperature, degree of vacuum, and time); they are dried at a specified temperature for a specified duration of time; they are pressed down by the press panels of the shelves in the freeze dryer; and then the rubber plugs are completely fitted and inserted in the mouths of the vials.

EMBODIMENT 1

[0017] The medical rubber plug of the present invention is explained below in detail based on Fig. 1, which illustrates an embodiment thereof. Fig. 1a is a plan view of the medical rubber plug of the present invention, and Fig. 1b is a vertical cross-sectional view showing a state in which the rubber plug is completely inserted inside the mouth of the vial.

[0018] In Fig.1, a reference number 1 points to a vial; and 2 to a rubber plug which has a leg 4 having an opening 3 and being inserted into the mouth of the vial 1 and which has a flange 6 contacting the upper edge part 5 of the mouth of the vial 1. On the top surface 7 of the flange 6 of the rubber plug 2, there are provided the arc-shaped projections 8 which locate above the upper edge part 5 of the mouth of the vial 1. The distance "D" between centers of the arc-shaped projections 8 is greater than the internal (or inner) diameter "d" of the mouth of the vial 1. There are provided six to twelve arc-shaped projections 8 (eight projections 8 in Fig. 1) on a circumference (or circle) corresponding to a part "a" which is equal to a difference between an external (or outer) diameter of the rubber plug 2 and the aforementioned internal diameter "d". With the construction, the rubber plugs 2 are prevented from closely adhering (or sticking) to each other at time of cleaning, disinfecting (or sterilizing) and drying the rubber plugs; an unshown aluminum cap tightly wound around the rubber plug 2 is prevented from closely adhering (or sticking) to the rubber plug 2; and the adhesion between the press surface (or biasing surface) of the shelf inside the freeze dryer and the top surface 7 is prevented after the medicament liquid therein is frozen, evacuated and dried.

[0019] According to the aforementioned structure, when the rubber plug 2 is half-inserted into the mouth of the vial 1 for the purpose of the freeze vacuum drying of the medicament liquid therein, and then when the top surface 7 of the rubber plug 2 is pressed by the press panel of the shelf inside the freeze dryer, not shown in the figure, in order to completely put the rubber plug 2 inside the mouth of the vial 1, a lower surface of the flange 6 of the rubber plug 2 comes to contact with the upper edge part 5 of the mouth of the vial 1. Namely, the arc-shaped projection 8 on the top surface is securely supported on the upper edge surface 5 which functions as a base. Therefore, the contact of the entire top surface of the rubber plug 2 with the press panel is prevented, resulting in no adhesion of the top surface of the rubber plug 2 with respect to the pressing surface. Also, it goes without saying that the adhesion between the rubber plugs 2 is prevented during their cleaning, disinfecting and drying, and that the tightness of the unshown aluminum cap being wound on the rubber plug 2 is kept in good condition.

EMBODIMENT 2

[0020] The vial made of glass has a capacity of 10 ml, an internal (or inner) diameter being 12.5 mm of the mouth, an external (or outer) diameter being 20mm of the edge surface of the mouth, and a height of 50 mm. The rubber plug in accordance with the present invention has an construction in which 4 to 14 arc-shaped projections are symmetrically provided on the top surface on the upper part of the edge surface that locates outside the inner diameter of the mouth of the vial where the arc-shaped projection has a base of 1.5mm, a height of 0.6mm and where the distance "D" between the centers of the projections is 15.5mm, and has the construction in which silicone coat of 30 to 50 mg/piece is applied to the top surface thereof. For comparison, there is prepared a rubber plug that has a construction in which 8 or 12 arc-shaped projections are symmetrically provided on the top surface on the upper part thereof that locates inside the inner diameter of the mouth of the vial, or symmetrically provided on the top surface on the upper part thereof that locates on a boundary with the edge surface, where the arc-shaped projection has a base of 1.5mm, a height of 0.6mm and where the distance "D" between the centers of the projections is 10.5mm or 12.5mm, and has the construction in which silicone coat of 30 to 50 mg/piece is applied to the top surface thereof. Both of the rubber plugs were half-inserted into the mouths of the vials, and then each of the rubber plugs was pressed with a pressure of 5 kg for 10 minutes by a stainless steel press panel. Under the condition, the degrees of adhesion between the press surfaces and the top surfaces of the rubber plugs, were measured while video-recording the situation at time of raising the pressure plate. Using 50 specimens of both of the rubber plugs respectively, measurements were made in order to seek for the time during which they sticked to the pressure panels. Together with the measurements, the tightness with which the aluminum caps were wound around the flanges of the rubber plugs was also tested. Table 1 shows the results. By the way, how to evaluate the tightness is based upon a procedure in which a plastic needle with its tip being cut to a diameter of 5 mm was pressed against the part of each of the rubber plugs which a needle is pierced through, and in which the number of rubber plugs that were dropped down into the vial with a pressure of 5 kg, or less, was counted.

[Table 1]

	Present Invention Example					Example in Contrast
	1	2	3	4	5	1	2	3
Number of Projections (pcs)	4	6	8	12	14	8	12	8
Inter-projection distance D (mm)	15.5	15.5	15.5	15.5	15.5	12.5	12.5	10.5
Adhesion Duration: 0 sec.	45	50	50	50	50	-	-	-
Adhesion Duration< 0.5 sec.	4	-	-	-	-	-	-	-
Adhesion Duration< 1.0 sec.	1	-	-	-	-	2	6	3
Adhesion Duration< 2.0 sec.	-	-	-	-	-	6	8	7
Adhesion Duration< 3.0 sec.	-	-	-	-	-	33	29	19
Adhesion Duration< 4.0 sec.	-	-	-	-	-	9	7	14
Adhesion Duration≧ 4.0 sec.	-	-	-	-	-	-	-	7
Tightness with Aluminum Cap	0/50	0/50	0/50	0/50	15/50	0/50	0/50	0/50

[0021] As shown in Table 1, regarding the rubber plug according to the present invention, no adhesion between the press panel and the top surface of the rubber plug was recorded, and a favorable result was also gained of the tightness with which the aluminum cap was wound around the flange of the rubber plug, when there were provided six to twelve arc-shaped projections. When there were provided four arc-shaped projections, slight adhesion therebetween was recorded. When there were provided 14 arc-shaped projections, it was observed that the nature of the tightness between the aluminum cap and the flange of the rubber plug became deteriorated, and that some rubber plugs were dropped off by the needle's piercing therethrough. On the other hand, it was observed that the rubber plugs, employed for comparison, respectively, showed the adhesion between the press panels and the flanges of the rubber plugs.

EMBODIMENT 3

[0022] Regarding the rubber plug of "Present Invention Example 6" which is the same as the rubber plug of "Present Invention Example 3" in "EMBODIMENT 2", regarding the rubber plug of "Prior Example 1" in which the rubber plug has a double-layer structure where a resin film is laminated, regarding the rubber plug of "Prior Example 2" that has a construction in which three projections are radially arranged at an equal interval between adjacent projections on the same circumference (or periphery or circle) where the projection has a width being 1.2mm of a base, a length of 3.0mm, a height of 0.4mm and where the distance between the centers of the projections is 11.5mm, and has the construction in which silicone coat of 30 to 50 mg/piece is applied to the top surface thereof, regarding the rubber plug of "Prior Example 3" that has a construction in which four projections are radially arranged at an equal interval between adjacent projections on the same circumference (or periphery or circle) where the projection has a width being 1.0mm of a base, a length of 2.5mm, a height of 0.4mm and where the distance between the centers of the projections is 12.5mm, and has the construction in which silicone coat of 30 to 50 mg/piece is applied to the top surface thereof, and regarding the rubber plug of "Prior Example 4" that has a construction in which four projections, being T-shaped as shown in Fig. 3, are radially arranged at an equal interval between adjacent projections on the same circumference (or periphery or circle) where each projection has a width of 1.2mm, a length of 4.0mm, a height of 0.6mm and where the distance between the centers of the projections is 13.0mm, and has the construction in which silicone coat of 30 to 50 mg/piece is applied to the top surface thereof, the degrees of adhesion between the press panels and the top surfaces of the rubber plugs, were measured while video-recording the situation at time of raising the pressure plate, under the same condition as the condition of "EMBODIMENT 2." Using 50 specimens of both of the rubber plugs respectively, measurements were made in order to seek for the time during which they sticked to the pressure panels. Together with the measurements, the tightness with which the aluminum caps were wound around the flanges of the rubber plugs was also tested. Table 2 shows the results. By the way, The method in which the tightness was evaluated, complied with the method of evaluation which was used in "EMBODIMENT 2".

[Table 2]

	Present Invention Example 6	Prior Example 1	Prior Example 2	Prior Example 3	Prior Example 4
Number of projections (pcs)	8	0	3	4	4
Inter-projection Distance (mm)	15.5	-	11.5	12.5	13.0
Adhesion Duration: 0 sec.	50	50	-	-	-
Adhesion Duration< 0.5 sec.	-	-	-	-	-
Adhesion Duration< 1.0 sec.	-	-	-	2	10
Adhesion Duration< 2.0 sec.	-	-	3	15	19
Adhesion Duration< 3.0 sec.	-	-	6	14	13
Adhesion Duration< 4.0 sec.	-	-	24	13	8
Adhesion Duration≧ 4.0 sec.	-	-	17	6	-
Tightness with Aluminum Cap	0/50	0/50	0/50	0/50	0/50

[0023] As shown in Table 2, regarding the rubber plug of "Present Invention Example 6" and the same of "Prior Example 1", there was no adhesion between the press panels and the top surfaces of the rubber plugs respectively, and the nature of the tightness between the aluminum cap and the flange of the rubber plug was in good condition. Meanwhile, regarding the rubber plugs of "Prior Example 2," "Prior Example 3," and "Prior Example 4," the nature of the tightness between the aluminum cap and the flange of the rubber plug was in good condition; however, it was observed that there was adhesion between the press panel and the top surface of the rubber plug.

[0024] The medical rubber plug according to claim 1 has a construction in which the projection for preventing the adherence of the top surface of the flange of the rubber plug is formed arc-shaped (or in arc) and in which the projection is arranged on the upper part of the edge surface outside the internal diameter of the mouth of the vial. With the construction, the lower part of the arc-shaped projection on the top surface of the flange of the rubber plug comes to contact with the edge surface outside of the mouth of the vial, and the compressive deformation of the arc-shaped projection is suppressed by the edge surface serving as a base. Namely, the whole top surface of the flange of the rubber plug does not adhere to the press surface, and a space is formed between the press surface and the top surface of the flange, thus preventing the adhesion therebetween.

[0025] The medical rubber plug according to claim 2 has six to twelve pieces of the arc-shaped projections for preventing the adherence of the top surface of the flange of the rubber plug. With the construction, it is possible to completely prevent the adhesion between the press surface of the shelf of the freeze dryer, and the top surface of the rubber plug; at the same time, it is possible to keep in good condition the property of the tightness with which the aluminum cap is wound around the flange of the rubber plug.

Claims

1. A medical rubber plug comprising:

a leg part which is inserted into a mouth of a vial; and

a flange part which contacts an upper edge surface of the mouth of the vial,
characterized in that a projection which is provided on a top surface of a mushroom-cap-shaped part of the medical rubber plug and which prevents an adhesion of the top surface thereof, is arc-shaped, and

that the projection is provided on an upper part of an edge surface locating outside an inner diameter of the mouth of the vial.

2. The medical rubber plug as claimed in claim 1, wherein there are provided six to twelve projections each of which is the projection that is provided on the top surface of the mushroom-cap-shaped part of the medical rubber plug and that prevents the adhesion of the top surface thereof.

Drawing