JPS60250921A - Molding method of synthetic resin container cap - Google Patents

Abstract

PURPOSE:To make possible molecular orientation of a pilferproof bottom part by a structure wherein when a container cap is molded by the cooperation of a male and a female mold assembly resin flows in a circular space in the circumferential direction and part of the female mold moves relatively to the male mold. CONSTITUTION:The container cap 2 having the weakening line 12 and the pilferproof skirt part 16 with several slits 18 and bridges 20 on the cylindrical skirt wall 6 of the circumference of the ceiling wall 4 and the female thread 24 inside the cylindrical skirt wall 6 is compression-molded in one body out of synthetic resin material. When resin material 62 is molded by the cooperation of the major diameter end 40 of the plunger member 34 of the male mold assembly and the circular movable members 54, 56 of the female mold assembly, the material 62 is circulated in a circular space part for the pilferproof skirt part 16 in the circumferential direction through the cavity 58 and the groove 44 provided on the member 54 and the end part 40. In this manner, it is possible to obtain a synthetic resin container cap which is in a circumferential molecular orientation on the pilferproof skirt part.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for molding a synthetic resin container lid, and more particularly to a method for compression molding a synthetic resin container lid having pilfer-proof properties.

BACKGROUND ART As is well known to those skilled in the art, metal lids made from thin metal sheets such as aluminum-based alloys have recently been used as container lids with pilfer-proof properties for containers such as food and beverage bottles. In place of the container lid, a synthetic resin container lid made of a suitable synthetic resin material such as polyethylene or polypropylene has been proposed.

A typical example of such a synthetic resin container lid includes a top wall and a cylindrical skirt wall that hangs down from the periphery of the top wall.

The skirt wall is formed with a weakened line consisting of a plurality of slits extending in the circumferential direction at intervals in the circumferential direction and a plurality of bridge sections located between these slits, and the skirt wall has a weakened line formed in the skirt wall. It is divided into a main portion located above the weakening line and a pilfer-proof hem portion located below the weakening line. Furthermore, a female thread is formed on the inner surface of the main portion. In the container lid described above, the female thread is screwed into the male thread formed on the outer circumferential surface of the mouth and neck of the container, and after being screwed together, the pilfer-proof hem is heated and heated in the circumferential direction. By being deflated, it is attached to the mouth and neck of the container lid in the required hole.

Therefore, when molding the above-mentioned synthetic resin container lid, it is necessary to mold the container lid in the same manner as in the case of ordinary synthetic resin container lids that do not have the weakened line, that is, do not have pilfer-proof properties. A male mold assembly defining an inner surface and a female mold assembly defining an outer surface of the container lid are used, and a synthetic resin material is compressed between the male mold assembly and the female mold assembly. intended. However, in the compression molding of the synthetic resin container lid, there is the following problem that must be solved due to the weakened line.

That is, since the cross-section of the space for the bridge defined by the cooperation of the male and female assemblies is small, the synthetic resin material passes through this space during compression molding. The annular space for the pilfer-proof hem, which is defined by the cooperation of the mold assembly and the female mold assembly and which follows the above-mentioned space, is not filled sufficiently, and the required throughput is therefore reduced. A problem arises in that it is not possible to form a pilfer-proof hem.

In order to solve this problem, the cross section of the space for the bridge section described above may be made larger. However, if it is hidden, the strength of the bridging part is large, and a considerable amount of force is required to break the bridging part when separating the container lid from the mouth and neck of the container. It becomes impossible or extremely difficult for a young person to remove the container lid.

Furthermore, in order to solve the above-mentioned problem, it would be possible to partially cut off a part of the bridge after forming the container lid, but this would require a cutting device for cutting, and the forming A cutting process is required after the process, which increases manufacturing costs and reduces manufacturing efficiency.

On the other hand, as a method for molding a synthetic resin container lid, a male assembly that defines the inner surface of the container lid and a female assembly that defines the outer surface of the container lid are used. A molding method has also been proposed in which the synthetic resin material is compressed between a solid body and at least a portion of the female mold assembly is moved relative to the male mold assembly during the compression.

In this method, the flow of the synthetic resin material is promoted by the movement of the female mold assembly during compression, and therefore the container lid can be formed relatively easily, and the container lid can also be made thinner. I can do it.

However, when the synthetic resin container lid is molded by the method described above, the pilfer-proof hem is heated and heat-shrinked after molding, so the following problem must be solved. A problem arises. In the above method, as is easily understood, as the female mold assembly moves, the synthetic resin material flows from the top wall side of the container lid toward the pilfer-proof bottom side, and the bridge portion is Therefore, within the annular space, there is almost no flow in the circumferential direction and an axial flow (i.e., the flow from the top wall side to the annular space for the pilfer-proof hem). (direction toward the hem of the proof) is the main direction. It is generally known that in synthetic resin materials, when resin flows during compression molding, molecular orientation occurs in the direction of the flow, and when heated after molding, thermal contraction occurs in the direction of the molecular orientation. However, in a synthetic resin container lid that is compression molded by the method described above, when the pilfer-proof hem is heated and heat-shrinked after molding, the flow of resin is mainly axial at the pilfer-proof hem. Because of this, there is heat shrinkage in the axial direction, but almost no heat shrinkage in the circumferential direction. After the container lid is screwed onto the neck of the container, the pilfer-proof hem is heated, and the resulting heat shrinkage engages the lower surface of the locking jaw formed on the outer circumferential surface of the neck of the container. However, as mentioned above, if the heat shrinkage in the circumferential direction of the hem of the pilfur-proof is small, the attachment of the hem of the pilfur-proof to the above-mentioned locking jaws will be insufficient, and therefore a weakened line will occur. There is a risk that the container lid will be separated from the mouth and neck of the container without the bridging portion being broken, and the pilfer-proof property will be impaired.

<Object of the Invention> The present invention has been made in view of the above facts, and its main purpose is to avoid deterioration of the performance of the container lid itself, and to avoid the problems associated with increased manufacturing costs and decreased manufacturing efficiency. It is an object of the present invention to provide a new and excellent method for molding which skillfully solves the above-mentioned problems.

<Summary of the Invention> As a result of intensive studies, the present inventors have discovered that a synthetic resin material is injected into an annular space for a pilfer-proof hem defined by cooperation between a female assembly and a male assembly. If a resin flow path is provided to allow the synthetic resin material to flow into the annular space during compression molding, prior to molding the main part of the container lid, the synthetic resin material will flow into the annular space. flows in the circumferential direction and its molecular orientation is mainly in the circumferential direction, and when this pilfer-proof part is heated after compression molding, it undergoes a relatively large heat shrinkage in the circumferential direction.
In this way, it has been found that the pilfer-proof hem can be reliably engaged with the locking mark formed on the outer peripheral surface of the mouth and neck of the container.

That is, according to the present invention, there is provided a top wall and a cylindrical skirt wall that hangs down from the periphery of the top wall, and the skirt wall includes:
A weakened line is formed that includes a plurality of circumferentially spaced slits extending in the circumferential direction and a bridge section located between the slits, and the skirt wall is also located above the weakened line. The main part is divided into a main part and a pilfer-proof hem located below the weakened line, and a female thread is formed on the inner surface of the main part. A container lid having a configuration in which the combined hindlimb pilfer-proof hem is heated and heat-shrinked is provided by a male assembly defining an inner surface of the container lid and a female assembly defining an outer surface of the container lid. in a method of compression molding integrally from a synthetic resin material using; A resin channel for introducing a resin material is provided in at least one of the male assembly and the female assembly, and during compression molding, the synthetic resin material passes through the resin channel. flowing into the annular space and flowing circumferentially through the annular space, and at least a portion of the female assembly being moved relative to the male assembly. A method is provided.

<Preferred specific examples of the invention> A more detailed explanation will be given below with reference to the accompanying drawings.

First, an explanation will be given with reference to FIG. 1, which shows an example of a synthetic resin container lid molded by the molding method according to the present invention. 4 and a cylindrical skirt wall 6 that hangs down from the periphery of the top wall 4.

An annular projection 8 having an appropriate cross-sectional shape is integrally formed on the inner surface of the top wall 4, and a seal member 10 of an appropriate shape is disposed on the inner surface of the top wall 4 defined by the annular projection 8. This sealing member 10 is mounted by compression molding the container lid 2 as described below and then positioning it on the inner surface of the top wall 4 in a required manner. If desired, instead of the annular projection 8 and the seal member 10, an annular seal portion having an appropriate cross-sectional shape may be integrally formed on the inner surface of the top wall 4.

The skirt wall 6 is formed with a weakened line 12 extending in the circumferential direction, and the skirt wall 6 has a main portion 14 located above the weakened line 12 and a pill located below the weakened line 12. It is divided into a fur-proof hem portion 16. The weakened lines 12 include a plurality of slits 18 (eight in the specific example) extending in the circumferential direction at intervals in the circumferential direction, and a plurality of slits 18 located between these slits 18 (corresponding to the slits 18 in the specific example). 8) bridging parts 20
It consists of The outer surface of the main portion 14 is formed with an uneven shape or a knurled shape 22 to prevent fingers from slipping thereon.

A female thread 24 is formed on the inner surface of the main portion 14 and is screwed into a male thread formed on the outer peripheral surface of the mouth portion of the container (not shown).

In the container lid 2 described above, the female thread 24 of the main portion 14 is screwed into a male thread (not shown) formed on the neck of the container lid, and then the pilfer-proof hem 16 is heated. Ru. As a result, the pilfer-proof hem 16 shrinks due to heating, and thus engages the locking jaw formed at the mouth of the container.

According to a specific example of the molding method according to the present invention, the container lid 2 shown in FIG. 1 is formed into an inverted state, that is, in FIG. Compression molding is performed in an upside-down state compared to the state shown in the figure.

Explaining with reference to FIG. 2-A, the illustrated molding apparatus is as follows:
It includes a male assembly, generally designated 30, and a female assembly, designated generally 32.

The illustrated male assembly 30 is comprised of a plunger member 34 . The plunger member 34 includes a large-diameter main portion 36 , a small-diameter portion 38 that is adjacent to the large-diameter main portion 36 and has a somewhat smaller diameter than the large-diameter main portion 36 , and a small-diameter portion 38 that is adjacent to the small-diameter portion 38 . It has a large diameter end portion 4o having a diameter substantially equal to that of the large diameter main portion 36. The plunger member 34 is configured to be movable up and down by a fluid pressure cylinder mechanism or the like.
As will become clear from the following description, one end of the large diameter main portion 36 defines the lower inner surface of the main portion 14, the subsequent inner surface of the weakened line 12, and the inner surface of the pilfer-proof hem 16; The end portion 4o defines the inner surface of the top wall 4 and the upper inner surface of the main portion 14, and the small diameter portion 38 existing between the large diameter main portion 36 and the large diameter end portion 40 defines the inner surface of the intermediate portion of the main portion 14. do. An annular recess 42 for defining the yielding protrusion 8 is provided on the end surface of the large diameter end 40, and a portion existing inside the annular recess 42 (i.e., a central portion of the end surface) is annular. recess 4
2 (i.e., the peripheral edge of the end face) is also slightly protruded. A plurality of grooves 44 (constituting resin flow paths) are carved at intervals in the circumferential direction on the circumferential surface of this large diameter end. Each of the grooves 44 extends from the end surface of the large diameter end 4o toward the small diameter portion 38.

Furthermore, a threaded groove 46 for defining the female thread 24 in the main portion 14 is carved on the outer circumferential surface of the small diameter portion 38 .

The illustrated female assembly 32 includes a central member 48, a first annular movable member 50, and a second annular movable member 52, with the first annular movable member 5o being an intermediate annular movable member 54 and an upper annular movable member 56. It is composed of The center member 48 has a cylindrical shape, is arranged below the plunger member 34, and has a first annular movable member 50 (an intermediate annular movable member 54, an upper annular movable member 56''BL and The second annular movable member 52 is disposed around the center member 48 and the plunger member 34, and is configured to be movable up and down.

In the female assembly 32 described above, the upper end surface of the central member 48 defines the outer surface of the top wall 4, and the second annular movable member 52 defines the outer surface of the main portion 14, as will become clear from the description later. However, the intermediate annular movable member 54 is connected to the outer surface of the weakened line 12 and the weakened line 12 of the pilfer-proof hem 16.
defines an outer surface of a region adjacent to the upper annular movable member 56;
defines the outer surface of the remaining area of the pilfer-proof hem 16. The diameter of the center member 48 is the same as that of the plunger member 34.
The diameter is made somewhat larger than that of the large-diameter main portion 36, and its upper end surface is somewhat concave. Referring also to FIG. 3, the inner diameter of the second annular movable member 52 is substantially equal to the diameter of the central member 48. In addition, the intermediate annular movable member 5
The inner diameter of the plunger member 4 is substantially equal to the diameter of the large-diameter main portion 36 of the plunger member 34, and a plurality of (eight in the specific example) bridge portions 20 are provided on the inner surface thereof at intervals in the circumferential direction. A recess 58 is provided for defining the . Each recess 58 is formed from one end to the other end of the intermediate annular movable member 54, and as is clear from FIGS. 2-A and 3, its width gradually increases upward and its depth increases. The depth increases upward to Lg. These recesses 58 are provided at circumferential positions corresponding to the grooves 44 provided in the plunger member 34, that is, at positions facing the grooves 44 when the plunger member 34 is lowered as described later. . The inner circumferential edge of the upper surface of the intermediate annular movable member 54 is inclined inwardly and downwardly, and the inner circumferential edge of the upper surface thereof is further inclined downwardly inwardly than the inner circumferential edge. Further, the inner diameter of the upper annular movable member 56 is substantially equal to the diameter of the large diameter main portion 36 of the plunger member 34. The inner circumferential edge of the lower surface of the upper annular movable member 56 is inclined inwardly and downwardly in accordance with the shape of the inner circumferential edge of the upper surface of the intermediate annular movable member 54. An annular notch 60 whose defining surface is arcuate is provided. Therefore, as can be easily understood from FIG. defining an outer surface and further cooperating with the plunger member 34 to form a pilfer-proof hem 1;
6. Define an annular space for 6.

Next, mainly referring to FIGS. 2-A to 2-0,
A molding procedure for compression molding the container lid 2 using the above-mentioned continuous molding apparatus will be explained.

At the start of molding, the male mold assembly 30 and the female mold assembly 32 are in the state shown in FIG. 2-A. That is, the second annular movable member 52 abuts the intermediate annular movable member 54, and the intermediate annular movable member 54 abuts the upper annular movable member 56, causing the female mold assembly 32 to be in a so-called mold-clamped state. ing. In this state, by the action of an appropriate synthetic resin material supply mechanism (not shown), on the upper surface of the central member 48 of the female mold assembly 32,
A suitable synthetic resin material 62 (indicated by a two-dot chain line in FIG. 2-A), which may be polyethylene or polypropylene, is supplied in a predetermined amount in a softened and molten state.

Next, the male mold assembly 30, ie, the plunger member 34, begins to descend and compression molding begins.

When the plunger member 34 is lowered to the position shown in FIG. 2-B, the end surface of the plunger member 34 comes into contact with the synthetic resin material 62 and compresses it, as shown in an enlarged view in FIG. . Further, the large diameter end portion 40 of the plunger member 34 is connected to an intermediate annular movable member 54 and an upper annular movable member 56.
The inner peripheral edge of the upper surface of the intermediate annular movable member 54 and the inner peripheral edge of the lower surface of the upper annular movable member 56 cooperate with the large-diameter end 40 of the plunger member 34 to prevent pilfer-proofing. An annular space is defined for the skirt 16. Therefore, when the synthetic resin material 62 is compressed by the lowering of the plunger member 34, the synthetic resin material 62 is compressed by the plunger member 34 as shown by the arrow in FIG.
A portion of the synthetic resin material 62 flows into the annular space through the groove 44 formed in the large diameter end 40 of the intermediate annular movable member 54, as can be easily understood from FIG.
The liquid flows into the annular space through the recess 58 formed in the annular space) and is caused to flow in the circumferential direction within the annular space. Thus, prior to forming the main portion 14 of the container lid 2,
The weakened line 12 (the inner surface of the intermediate annular movable member 54 excluding the recess 58 directly contacts the outer peripheral surface of the large diameter end 40 of the plunger member 34 to define the slit 18 of the weakened line 12, and the recess 58 Since the pilfer-proof hem 16 is molded together with the bridging portion 20 of the weakened line 12, and the flow of the synthetic resin material 62 within the annular space is mainly in the circumferential direction, the molecular orientation in the pilfer-proof hem 16 is is the circumferential direction.

After that, as shown in FIG. 2-c, the plunger member 3
4, while the pressurized state of the synthetic resin material 62 is maintained, the upper annular movable member 56 and the intermediate annular movable member 54
And the second annular movable member 52 is moved in the direction toward the plunger attachment 34, that is, raised. In the event of such an increase,
The upward flow of the compressed synthetic resin material 62, more specifically, the outer peripheral surface of the plunger member 34 and the second annular movable member 52
The upward flow that flows between the inner surface of the skirt wall 6 and the main portion 14 of the skirt wall 6 is promoted, whereby the main portion 14 is formed together with the top wall 4. In this manner, the container lid 2 is compression-molded in an inverted state, as shown in FIG. 2-C. In the specific example, since a groove 44 is formed in the large diameter end 40 of the plunger member 34, when compression molding is performed, the main portion adjacent to the inner surface of the top wall 4 corresponds to the groove 44. 14
A protrusion 64 (FIG. 1) is formed at the upper end of the inner surface.

After the container lid 2 is compression-molded, the second annular movable member 52 is lowered and the upper annular movable member 5 is lowered.
6 is raised, whereby the second annular movable member 52 and the upper annular movable member 56 are separated from the molded container lid 2. Next, the plunger member 34 is raised together with the intermediate annular movable member 54, and the central member 48 is removed from the molded container lid 2. Next, after a predetermined period of time has passed after the intermediate annular movable member 54 stops rising, the plunger member 34
is stopped from rising, thereby causing the plunger member 34 to separate from the molded container lid 2.

Thereafter, the intermediate annular movable member 54 is separated from the molded container lid 2 by the action of a removal mechanism (not shown), and
The container lid 2 is removed from the molding device.

In the above-mentioned container lid 2 which is compression-molded, the molecular orientation in the pilfer-proof hem 16 is in the circumferential direction. It can be heat-shrinked to a large extent and is suitable for a configuration in which the pilfer-proof hem 16 is heated and engaged with a locking jaw formed at the neck and neck of the container.

Although a specific example of the molding method according to the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to this specific example, and various modifications and modifications can be made without departing from the scope of the present invention. is possible.

<Examples and Comparative Examples> Example A synthetic resin container lid having the form shown in FIG. 1 was compression molded as described above using the chopstick compression molding apparatus shown in FIG. 2-A. The dimensions of the main parts of the male assembly and the female assembly are as follows: Eight grooves are formed at equal intervals in the circumferential direction on the plunger member constituting the male assembly.
On the other hand, a recess was formed in the intermediate annular member of the female assembly at a location corresponding to the groove.

Regarding the plunger member, outer diameter of large diameter main part...approximately 28.1m outer diameter of small diameter part...approximately 26.3m11 length of small diameter part...approximately 6.2m outer diameter of large diameter end ...approximately 28.11111 Length of large diameter end...approximately 3.2 Width of groove...approximately 0.9 m Groove length...approximately 2.4n Depth of groove... - Approximately 0.7 m Regarding the second annular movable member, Inner diameter: Approximately 29.9 m Knurling bottom diameter: Approximately 29. f) Regarding the I11 intermediate annular movable member, Inner diameter: Approximately 28.11!1 Height of inner peripheral end: 1.0 Width at the lower end of the recess: Approximately 0.5 m Upper end of the recess Width at...approximately 1.3 m (deepest point of recess)...approximately 0.3W Angle of inclination of the bottom of the four parts...1
゜Inclination angle of the inner peripheral edge of the upper surface...45゜Regarding the upper annular movable member, Inner diameter...approximately 28.11111 Width of the annular notch at the inner peripheral edge...approximately 1.2 fi Center of the radius of curvature of the arcuate surface Regarding the parts, outer diameter: approx. 29.9, cod rollet bottom diameter: approx. 29.6M, and the synthetic resin material used has a melt index of 1.
．． 5 El/10 min polypropylene (Mitsubishi Noblen EC-8).

At the time of starting molding, the second annular movable member, the intermediate annular movable member, and the upper annular movable member are brought into a mold-clamped state, and the lower surface of the plunger member is placed above the upper surface of the central member. I placed it in the Om position. Further, the temperature of each member (male assembly and female assembly) was set at 35°C.

Then, in the above-mentioned state, polypropylene was extruded using an extruder with a nozzle diameter of 1211L and a screw diameter of 6511m+ so that the temperature of the extrudate reached 190°C. Immediately after cutting, the molten pellets were placed on the top surface of the center member.

Compression molding was started immediately after placing the molten pellets. During compression molding, first, the plunger member has an average weight of 10 wx.
/sec to pressurize the molten pellets on the central member. The plunger member was lowered by a hydraulic mechanism, the maximum pressure of which was approximately 170 K9/ad. When the plunger member descends and the distance between its lower surface and the upper surface of the center member becomes 3.51311, then the upper annular movable member, the intermediate annular movable member, and the second annular movable member are averaged by the hydraulic mechanism. It was raised at a rate of 5 Qm/BeC, and the rise was stopped when these rose by 10 units. Then, this state was maintained for 3 seconds. During this time, the plunger member continued to be pressurized and its pressure was maintained at approximately 140 Kp/cd.

Next, the second annular movable member was lowered and the upper annular movable member was raised. Next, the intermediate annular movable member and the granger member are raised, and after a predetermined period of time has elapsed after the intermediate annular member is stopped from rising, the plunger member is stopped from rising, and then the container lid, which has been molded with the required opening, is removed. I put it out.

The pilfer-proof hem of each of the five container lids obtained through the above-mentioned process was cut at the bridging portion and separated from the main portion, and immersed in an oil bath at 165° C. for 5 seconds. Then, the total length of the Pilfa-Pulle-87 hem before and after the dipping treatment was measured, and the shrinkage rate S was calculated using the following formula.

S: Shrinkage rate (q6) La: Total length after treatment Lb: Total length before treatment The results obtained are shown in Table 1.

Comparative Example For comparison, a plunger member with no large-diameter end and no groove formed at the tip (i.e., except that the small-diameter portion extends to the tip and no groove is formed) was used. A synthetic resin container lid is compression molded in the same manner as in the above embodiment using a granger member that is substantially the same as the plunger member in the above embodiment and a female assembly that is substantially the same as in the above embodiment. did. The synthetic resin material used had a melt index of 1.59710 m1 as in the example.
n polypropylene.

For each of the five container lids thus obtained,
The shrinkage rate S was determined in the same manner, and the results are shown in Table 1.

Table 1 Note that the container lid used in this experiment has a pilfer-proof hem with an inner diameter of 27.3 m+ and has eight bridges, but this container lid is not formed on the container to which it is attached. The outer diameter of the locking jaws is 24.6 m, so the calculated shrinkage required to obtain sufficient pilfer-proof properties is at least 7 m.

[Brief explanation of drawings]

FIG. 1 is a side view, partially in cross section, of an example of a synthetic resin container lid molded by the molding method according to the present invention. 2-A to 2-c are simplified cross-sectional views showing the main parts of a molding device used in a specific example of the molding method according to the present invention in various states. FIG. 3 is a partially enlarged sectional view showing a part of the female die assembly in the molding apparatus shown in FIGS. 2-A to 2-c. FIG. 4 is a partially enlarged sectional view showing the state shown in FIG. 2-B in a partially enlarged manner. 2... Container lid 4... Top wall 6... Skirt wall 12... Weakening line 14... Main part 16... Pilfer proof hem 18... Slit 20... Bridge Part 24...Female thread 30...Male assembly 32...Female assembly 34...Plunger member 44...Groove 50...First annular movable member 52...No. 2 annular movable member 54...middle annular movable member 56...upper annular movable member Patent applicant Akira Kishimoto Attorney Patent attorney Hisashi Ono Figure 2-B Figure 2-C

Claims (1)

[Claims] 1. A top wall and a cylindrical skirt wall that hangs down from the periphery of the top wall, and the skirt wall has a plurality of slits extending in the circumferential direction at intervals in the circumferential direction. A weakened line consisting of a bridge portion located between the slits is formed,
The skirt wall is divided into a main part located above the weakened line and a pilfer-proof hem part located also below the weakened line, and a female thread is formed on the inner surface of the main part. and a male assembly defining the inner surface of the container lid, which is screwed onto the mouth and neck of the container after molding, and the pilfer-proof hem is heated and heat-shrinked. and a female molding assembly defining an outer surface of the container lid; A companion resin channel is provided in at least one of the male assembly and the female assembly for allowing the synthetic resin material to flow into the annular space for the pilfer-proof hem; During compression molding, the synthetic resin material is flowed into the annular space through the resin channel and flows circumferentially through the yield space, and at least a portion of the female mold assembly is in contact with the male mold assembly. A method characterized in that: being moved relative to a mold assembly. 2. The resin flow path is composed of a plurality of grooves provided at intervals in the circumferential direction at the tip of the male assembly;
A method according to claim 1. 3. The female mold assembly is formed with a plurality of four parts for defining the bridge part, and the recessed part is arranged at a part corresponding to the groove provided in the male mold assembly. 3. The method of claim 2, wherein: 4. The female assembly includes a first annular movable member defining an outer surface of the line of weakness and an outer surface of the pilfer-proof hem, and a second annular movable member defining an outer surface of the main portion; a central member defining an outer surface of the top wall; a large-diameter end defining the inner surface of the top wall and the upper inner surface of the main portion; and a large-diameter end that defines the inner surface of the middle portion of the main portion, and and a plurality of grooves are provided on the circumferential side of the large diameter end, and the container lid has a small diameter portion that connects the male assembly to the female assembly. The synthetic resin material is compressed between the male assembly and the female assembly by moving in a direction approaching the central member of the solid body, and during compression molding, the synthetic resin material is compressed between the male assembly and the female assembly. an annular movable member cooperates with the large diameter end of the male assembly to define the annular space, and the synthetic resin material is flowed into the annular space through the resin channel. the first annular movable member and the second annular movable member of the female assembly are moved in a direction toward the male assembly; 4. The method according to claim 2, wherein the synthetic resin material is caused to flow in the direction of movement of the first annular movable member and the second annular movable member as the synthetic resin material moves. 5. the first annular movable member of the female assembly includes an intermediate annular movable member defining an outer surface of the weakened line and an outer surface of a region of the pilfer-proof hem adjacent to the weakened line; 5. The method of claim 4, further comprising an upper annular movable member defining the outer surface of the remaining area of the pilfer-proof hem.