JP6885761B2 - Synthetic resin cap and cap unit - Google Patents

Description

The present invention relates to a technique for sealing a container mouth portion, and more particularly to a synthetic resin cap and a cap unit.

As drinking containers for water, tea, soft drinks, etc., bottle containers such as PET bottles and paper carton containers with spouts that can be opened and closed are widely used. As the cap used for these containers, for example, a synthetic resin cap formed by injection molding a resin into a desired shape is used.

Further, in recent years, a pouch capable of containing a jelly-like food or the like by a flexible sheet has also been widely used. As the spout of such a pouch, the container mouth is formed by a spout that is heat-welded to the container body, and the container mouth is opened or closed by using a synthetic resin cap.

There is a type of such a cap that is fitted into the container mouth by a stopper, but there are also many screw types that are attached by screw engagement with a screw portion formed on the outer surface of the tubular side wall of the container mouth. ..

For example, Patent Documents 1 to 3 disclose a screw-fitting type bottle cap that suppresses liquid leakage by forming an inner ring and a contact ring on the inner wall of the top plate of the bottle cap.

Japanese Unexamined Patent Publication No. 8-40444 Jitsufuku No. 5-31078 Gazette Patent No. 4393092

However, the technology including the above-mentioned patent documents cannot be said to meet the needs of the market yet, and at least the following problems exist.
That is, it is effective to use a contact ring in addition to the inner ring in order to improve the sealing property (sealing property) of the cap with respect to the container mouth.

However, since friction is generated at the portion where the contact ring comes into contact with the container mouth, there is a problem that the opening torque tends to increase in the tightening of the screw after the contact ring comes into contact with the container mouth.

In this regard, the retightening angle of the cap with respect to the container mouth is also important for quality control when the cap is wound around the container mouth, and the conventional structure allows for obtaining an appropriate opening torque value. The retightening angle range is narrowed, and as a result, capping management may become difficult.

The above-mentioned problems are particularly remarkable in recent low-height caps (the height in the spindle direction is small), but a cap structure capable of obtaining an appropriate opening torque value that is easy to manage has not yet been proposed.
Therefore, one of the objects of the present invention is to provide a synthetic resin cap capable of obtaining an appropriate opening torque value that is easy to manage and a cap unit including the synthetic resin cap.

In order to solve the above-mentioned problems, the cap unit in one embodiment of the present invention is (1) screwed into the container mouth portion formed of the first resin and the container mouth portion, and is more than the first resin. A cap unit including a synthetic resin cap made of a second resin having a high hardness, wherein the container mouth portion is a tubular side wall provided with an inner surface into which the contents are poured out, and a tubular side wall of the tubular side wall. It has a screw portion formed on an outer surface, and a protruding portion that protrudes outward in the radial direction is formed at the upper end of the outer surface of the tubular side wall, and the container mouth portion is formed by the protruding portion and the screw portion. The synthetic resin cap is provided with an inner ring on the lower surface, which is in close contact with the inner surface of the tubular side wall to form a seal. When, with drops from the edge of the top plate portion is formed between the screw portion and engaged with the skirt wall screw bar is formed to the lower surface and a by said skirt wall and the inner ring of the top plate portion was top comprising a contact ring, a, when said synthetic resin cap is screwed into the container opening, that the top contact ring in contact with the projecting portion on the upper side than the lightening portion The arranged protruding portion is elastically deformed, and the inner ring is brought into close contact with the inner surface of the tubular side wall below the lightening portion .

Further, in the cap unit according to (1) described above, it is preferable that (2) the elastic deformation of the protruding portion is released when the synthetic resin cap is opened from the container mouth portion.

Further, in the cap unit according to (1) or (2) described above, (3) the position where the top contact ring contacts the protruding portion is outside the root of the protruding portion in the radial direction. It is preferable to have.

Further, in the cap unit according to any one of (1) to ( 3 ) described above, ( 4 ) the protruding portion is the tubular side wall between the screw portion and the protruding portion in the radial direction. It is preferable that the surface protrudes outward from the outer surface of the.

Further, in the cap unit according to any one of (1) to ( 4 ) described above, ( 5 ) the protruding portion is arranged above the seal point at which the inner ring is in close contact with the inner surface of the tubular side wall. It is preferable to be done.

Further, in the cap unit according to any one of (1) to ( 5 ) described above, ( 6 ) the first resin is preferably low-density polyethylene, and the second resin is preferably high-density polyethylene.

To further achieve the above object, the cap unit according to one embodiment of the present invention, the container opening is characterized spout der Rukoto.

According to the synthetic resin cap and the cap unit of the present invention, it is possible to prevent an excessive opening torque from being generated even in the retightening after the top contact ring comes into contact with the container mouth portion, and as a result, the proper opening is performed. The permissible retightening angle range for obtaining the plug torque value can be widened.

It is an external front view of the cap unit 100 which concerns on embodiment. It is a front view (half cross section) of the appearance of the container mouth portion 10A of the cap unit 100, and a partially enlarged view thereof. It is an external front view (half cross section) of the synthetic resin cap 20 of the cap unit 100. It is a schematic diagram explaining the cross-sectional structure of a cap unit 100. It is a schematic diagram explaining the state transition when the synthetic resin cap 20 is fitted in the container mouth portion 10A. It is a front view which shows the container mouth part 10B which concerns on modification 1. FIG. It is a front view which shows the container mouth part 10C which concerns on modification 2. FIG.

Hereinafter, embodiments for preferably carrying out the present invention will be described. For convenience of explanation, the X direction, the Y direction, and the Z direction are appropriately defined in the following description, but it goes without saying that the scope of rights of the present invention is not reduced.
For matters other than the features of the present invention described in detail below, a known cap structure such as Japanese Patent No. 4393092 may be referred to as appropriate.

[Cap unit]
FIG. 1 shows a cap unit 100 according to this embodiment.
As shown in the figure, the cap unit 100 includes a container mouth portion 10A and a synthetic resin cap 20.

The container mouth portion 10A is a portion where the contents are poured out from a container for accommodating the contents such as food and drink and chemicals, for example. The container mouth portion 10A may have a structure integrated with, for example, a container body in which the contents are housed, or may be a separate body from the container body. Further, as such a container, various known containers such as a resin bottle and a paper pack may be applied as long as the container mouth portion 10A of the present embodiment is applicable.

Examples of the container mouth portion 10A having an integral structure with the container body include the mouth portion of a bottle container such as a PET bottle. On the other hand, examples of the container mouth portion 10A separate from the container body include a pouch and a spout that is heat-welded to a paper container.
Hereinafter, the description will be continued by exemplifying a spout as an example of the container mouth portion 10A and a paper container as the container body, but the present invention is not limited to this embodiment.

The synthetic resin cap 20 has a function of being screwed into the container mouth portion 10A formed of the first resin, and is formed of a second resin having a hardness higher than that of the first resin.
Here, as the first resin and the second resin, various known resins can be applied as long as the second resin is harder than the first resin as described above. Examples of such a resin include low-density PE (polyethylene), high-density PE, PP (polypropylene), and a mixed resin of PE and PP.
As a non-limiting example, the combinations of the first resin and the second resin suitable for this embodiment are shown in Table 1 below.

[Container mouth]
Next, with reference to FIG. 2, the detailed structure of the container mouth portion 10A in the present embodiment will be described. Note that FIG. 2 (1) is an external front view (half cross section) of the container mouth portion 10A, and FIG. 2 (2) is a partially enlarged view of the P portion in FIG. 2 (1).
As an example, the container mouth portion 10A in the present embodiment is a synthetic resin spout formed separately from the container body. As shown in FIG. 2 (1), the container mouth portion 10A includes a tubular side wall 11 and a flange portion 12.

The tubular side wall 11 is a tubular portion having an inner surface 11a in which the inside is hollow and the contents are poured out. On the other hand, a screw portion 11c is formed on the outer surface 11b of the tubular side wall 11, and the screw portion 11c is screwed with the screw 22a of the synthetic resin cap 20 described later when the cap is closed.

In the present embodiment, the screw portion 11c is a so-called multi-threaded screw. For example, when water or the like is the content, a multi-thread screw is often used from the viewpoint of easy openness. In the present embodiment, a three-threaded screw is used as the screw portion 11c, but the present invention is not limited to this form, and a single-threaded screw or a two-threaded screw may be used.

Further, in the present embodiment, a protruding portion 11d is formed at the upper end of the outer surface of the tubular side wall 11 so as to project outward in the radial direction (X direction in FIG. 2). The protruding portion 11d is provided at the open end of the tubular side wall 11, and can be brought into contact with the top contact ring 23 of the synthetic resin cap 20, which will be described later.

In the present embodiment, the protruding portion 11d has a shape that extends horizontally outward from the upper end of the outer surface of the tubular side wall 11. However, the top surface side (upper surface in the Z direction) of the protruding portion 11d may extend horizontally from the upper end of the outer surface of the tubular side wall 11, or may have a curved surface such that the tip hangs downward in the Z direction. Alternatively, the curved surface may be such that the tip is inclined upward in the Z direction.

Further, the thickness of the protruding portion 11d in the Z direction is preferably smaller than the thickness of the tubular side wall 11 in the X direction at the portion where the lightening portion 11e described later is formed. In any case, the thickness of the protruding portion 11d in the Z direction may be appropriately set within a range in which the protruding portion 11d can be flexed (elastically deformed) after the top contact ring 23 comes into contact with the top contact ring 23.

Further, it is preferable that the amount of protrusion of the protruding portion 11d to the outside in the radial direction (the size from the root in the radial direction) does not protrude more than the outer diameter of the thread of the screw portion 11c. Further, the protruding portion 11d may protrude from the outer diameter of the screw valley of the screw portion 11c.
Here, the root of the protruding portion 11d means the vicinity of the outer surface 11b of the tubular side wall 11 on which the protruding portion 11d protrudes, and the tip of the protruding portion 11d means a tip extending outward in the radial direction.

Further, it is preferable that the protruding portion 11d protrudes outward from the outer surface of the tubular side wall 11 between the screw portion 11c and the protruding portion 11d in the radial direction. For example, in the case of the protruding portion 11d in FIG. 2 (1), a lightening portion 11e is formed between the screw portion 11c and the protruding portion 11d, and the bottom of the lightening portion 11e (the tubular side wall 11). It has a form that protrudes outward in the radial direction from the outer surface).

As described above, in the present embodiment, the lightening portion 11e is formed between the screw portion 11c and the protruding portion 11d on the outer surface 11b of the tubular side wall 11. _{The lightening portion 11e is a portion that is cut out so that the bottom surface 11e 2} is recessed from the outer surface 11b toward the inside (toward the center of the tubular side wall 11).
Therefore, it can be said that the container mouth portion 10A has a lightening portion 11e recessed inward in the radial direction between the protruding portion 11d and the screw portion 11c.

As shown in FIG. 2 (2), when the above-mentioned lightening portion 11e is provided, _{it is preferable that the root 11d 1} of the protruding portion 11d and the upper end portion 11e ₁ of the lightening portion 11e coincide with each other.
Further, when the lightening portion 11e described above is provided, the thickness of the protruding portion 11d in the Z direction (the average thickness in the protruding direction (X direction) or the thickness in the Z direction at an arbitrary portion of the protruding portion 11d) is determined. It is preferable that the thickness of the upper end portion 11e ₁ of the lightening portion 11e is smaller than the thickness in the X direction.
On the other hand, when the lightening portion 11e described above is not provided, the thickness of the protruding portion 11d in the Z direction (the average thickness in the protruding direction (X direction) or the thickness in the Z direction at an arbitrary portion of the protruding portion 11d) is , It is preferable that the thickness of the protruding portion 11d _{is smaller than the thickness of the root 11d 1 in the X direction.}

As a method of forming the lightening portion 11e, for example, it may be formed at the same time as the injection molding for forming the container mouth portion 10A, or a part of the lightening portion 11e may be scraped off after the injection molding to form the lightening portion 11e. May be good.
Further, the depth of the lightening portion 11e (the depth of the recess in the X direction) is not particularly limited, and the protruding portion 11d can be bent (elastically deformed) after the top surface contact ring 23 comes into contact. It may be set appropriately within the above range.
Further, the size of the lightening portion 11e in the Z direction is preferably such that the elastically deformed protruding portion 11d does not come into contact with _{the lower surface 11e 3 of the lightening portion 11e when the cap is retightened.}
It should be noted that the lightening portion 11e does not have to be formed as described in the modified example described later.

The flange portion 12 is a portion that is heat-welded to the container body described above. For example, a part of the container body such as a paper container (such as a paper container coated with resin) or a pouch is brought into close contact with the welding surface 12a. To. The welding mode of the container body and the flange portion 12 is not particularly limited, and a known welding mode may be applied. For example, the upper surface (upper side in the Z direction) of the flange portion 12 may be welded to the container body, the lower surface may be welded, or if there is a length in the Z direction, the side surface may be welded to the container body. It may be in the form.

[Synthetic resin cap]
Next, the detailed structure of the synthetic resin cap 20 in the present embodiment will be described with reference to FIG.
As shown, the synthetic resin cap 20 includes at least a top plate portion 21, a skirt wall 22, and a top contact ring 23.

The top plate portion 21 is provided with an inner ring 21b on the lower surface 21a which is in close contact with the inner surface 11a of the tubular side wall 11 of the container mouth portion 10A to form a seal. Further, in the present embodiment, the outer ring 24 may be formed on the lower surface 21a of the top plate portion 21 on the outer side of the inner ring 21b and on the inner side of the skirt wall 22.

The skirt wall 22 is formed so as to descend from the peripheral edge of the top plate portion 21 and to have a screw portion 22a screwed with a screw portion 11c formed on the outer surface 11b of the tubular side wall 11. As shown in FIG. 3, on the outer surface of the skirt wall 22, for example, a knurl portion (also referred to as a so-called vertical rib or knurl) extending in the axial direction (Z direction) extends in the circumferential direction (θz direction). A plurality may be formed.

The top contact ring 23 is a lower surface 21a of the top plate portion 21 and is formed so as to hang down between the skirt wall 22 and the inner ring 21b. Then, as will be described later, when the synthetic resin cap 20 is screwed into the container mouth portion 10A, the protruding portion 11d or the like is elastically deformed when the top surface contact ring 23 comes into contact with the protruding portion 11d. On the other hand, when the synthetic resin cap 20 is opened from the container mouth portion 10A, the elastic deformation of the protruding portion 11d is released and the state returns to the state before closing.
The height of the top surface contact ring 23 (height from the top plate portion 21) is set to be lower than, for example, the inner ring 21a and the outer ring 24.

Further, in the synthetic resin cap 20 of the present embodiment, an opening history explicit band (TE band) 25 may be provided via a bridge that can be broken at the lower end of the skirt wall 22. In such a case, when the synthetic resin cap 20 is opened from the container opening 10A for the first time, the TE band 25 remains in the accommodating groove 11g of the container opening 10A.

Next, with reference to FIGS. 4 and 5, a state when the synthetic resin cap 20 is fitted to the container mouth portion 10A and a mode of its transition will be described.
When the synthetic resin cap 20 is closed to the container mouth 10A, when the synthetic resin cap 20 is rotated in the closing direction (for example, clockwise) in the θz direction, the screw 22a of the skirt wall 22 becomes the screw portion of the container mouth 10A. It is screwed with 11c.

When the screw 22a continues to be screwed with respect to the screw portion 11c, the top contact ring 23 of the synthetic resin cap 20 comes into contact with the protruding portion 11d of the container mouth portion 10A, as shown in FIG. In the present embodiment, the synthetic resin cap 20 is further rotated in the closing direction by a predetermined angle from this contacted state to perform retightening.

In the present embodiment, the predetermined angle at which the synthetic resin cap 20 is further turned in the closing direction from this contact state is also referred to as "tightening angle", but this retightening angle is set within an appropriate range without increasing the opening torque. Containment is an important factor in improving manufacturing quality.

Therefore, in the present embodiment, in order to suppress an increase in the opening torque during retightening, the protruding portion 11d in contact with the top surface contact ring 23 is elastically deformed, and the synthetic resin cap is detached from the protruding portion 11d. At the time (when opening the cap), the elastic deformation of the protruding portion 11d is released.

FIG. 5 (1) shows a state transition when the synthetic resin cap 20 is fitted to the container mouth portion 10A.
First, as shown in FIG. 3A, when closing the synthetic resin cap 20 with respect to the container mouth portion 10A, for example, the synthetic resin cap 20 is rotated clockwise in the θz direction. At this time, although the top contact ring 23 is not yet in contact with the protruding portion 11d, the maximum outer diameter portion below the inner ring 21b is in close contact with the inner surface 11a of the tubular side wall 11 to form a seal point SP.

Next, when the state changes from (a) to (b) in the figure, the top contact ring 23 comes into contact with the protruding portion 11d.
At this time, the position where the top surface contact ring 23 comes into contact with the protruding portion 11d is preferably outside the root of the protruding portion 11d in the radial direction (X direction in the cross section in FIG. 5).
Further, in the present embodiment, the position where the top surface contact ring 23 comes into contact with the protruding portion 11d is preferably outside _{the bottom surface 11e 2 of the lightening portion 11e in the radial direction.}

Further, in the present embodiment, when the top surface contact ring 23 comes into contact with the projecting portion 11d, the projecting portion 11d is arranged above the seal point SP in which the inner ring 21b is in close contact with the inner surface 11a of the tubular side wall 11. Is preferable. In other words, the protruding portion 11d is preferably arranged above the upper end of the screw portion 11c (the upper end of the region where the screw is formed) on the tubular side wall 11. Further, the seal point SP of the inner ring 21b is preferably arranged below the lightening portion 11e in the height direction (Z direction), and in addition, the seal point SP is arranged in the height direction (Z direction). In the above, the arrangement form may be closer to the screw portion 11c than to the protruding portion 11d.
As a result, the elastic deformation described above does not affect the portion forming the seal point SP, and the seal state can be properly maintained.

When the top contact ring 23 comes into contact with the protruding portion 11d, in the present embodiment, the outer ring 24 does not come into contact with the protruding portion 11d and is separated from each other by a predetermined distance. As a result, an increase in the opening torque generated by the contact between the outer ring 24 and the protruding portion 11d is suppressed.

As described above, the outer ring 24 of the present embodiment also functions as a protective wall when the top surface contact ring 23 is excessively laterally displaced with respect to the protruding portion 11d, for example, when a large impact is applied to the cap unit 100. doing.
Next, when the state changes from (b) to (c) in the figure, retightening is performed and the protruding portion 11d is elastically deformed.

As a result, even if retightening is performed, the frictional force generated between the top contact ring 23 and the protruding portion 11d does not excessively increase, and an increase in the opening torque is suppressed.
Further, when the retightening is performed, the radial pressure generated between the screw portion 22a and the screw portion 11c due to the contact between the top surface contact ring 23 and the protruding portion 11d also increases. In particular, since a multi-threaded screw is used in this embodiment, when the retightening angle is increased, the opening torque generated between the screw 22a and the screw portion 11c is likely to increase as compared with the single-threaded screw.

On the other hand, according to the present embodiment, since the protruding portion 11d can be elastically deformed at the time of retightening, an excessive pressure is not generated between the top surface contact ring 23 and the protruding portion 11d, which causes the opening. It is also possible to suppress an increase in plug torque.

As shown in FIG. 5 (2), the top surface contact ring 23 of the present embodiment may have a shape that hangs down from the top plate portion 21 and is asymmetrical with respect to the height direction (Z direction). More specifically, the top surface contact ring 23 may be inclined on the inside of the portion in contact with the protrusion 11d at an angle from the outside.

Further, assuming that the angle of the gradient with respect to the horizontal direction is the gradient angle α, the gradient angle α is preferably, for example, 30 to 80 degrees. As described above, in the present embodiment, the shape of the top contact ring 23 is asymmetric with respect to the Z direction and the inner side surface is inclined so that the protruding portion 11d and the tubular side wall 11 are easily elastically deformed at the time of retightening.
After the state shown in FIGS. 5 (1) and 5 (b), a seal is formed not only at the seal point SP but also at the contact portion between the protruding portion 11d and the top surface contact ring 23.

As described above, in the present embodiment, the protruding portion 11d in contact with the top surface contact ring 23 is elastically deformed at the time of retightening, and the top surface contact ring 23 is separated from the protruding portion 11d at the time of opening the cap. This elastic deformation is released by.

In particular, since water-based beverages and paper carton-based beverages are required to have quick openness, multi-threaded screws may be used to increase the lead angle of the screws. In this case, the opening torque per retightening angle tends to be high, but there are cases where the cap height cannot be sufficiently secured, and it is desired to reduce the opening torque as much as possible while maintaining an appropriate retightening angle.

In this regard, for example, it can be assumed that a lubricant is put in the cap, but when the content is milk, for example, the lubricant cannot be put in the cap in order to satisfy the strict requirements stipulated in the Ordinance of the Ministry of Milk, etc.

As described above, in the conventional structure, it is extremely difficult to suppress the increase in the opening torque while maintaining the retightening angle, but according to the present embodiment, the increase in the opening torque is suppressed and an appropriate retightening angle is suppressed. Has become possible.

The above-described embodiment can be modified in various ways without departing from the spirit of the present invention. Hereinafter, a modified example that can be appropriately applied to the embodiment will be described. In each of the following modifications, the configurations having the same functions as those of the above-described embodiment are designated by the same reference numbers and the description thereof will be omitted as appropriate.

<Modification example 1>
FIG. 6 is a schematic view of the container mouth portion 10B according to the first modification.
The difference between this modification 1 and the above-described embodiment is that the lightening portion 11e is mainly enlarged. Therefore, the configuration having the same function / operation as the above-described embodiment is designated by the same reference number and the description thereof is omitted (the same applies to the following modification 2).

As shown in the figure, the lightening portion 11e of the modified example 1 is formed so as to fill the space between the protruding portion 11d and the screw portion 11c. In other words, the size of the lightening portion 11e of the first modification in the Z direction is larger than that of the lightening portion 11e in the above-described embodiment.
The size of the bottom of the lightening portion 11e (size in the Z direction) in the modified example 1 may be about the same as the size of the screw valley (size in the Z direction) of the screw portion 11c.

Further, in the present modification 1, the depth of the lightening portion 11e is uniform and the bottom surface hangs down along the Z direction, but the present invention is not limited to this embodiment. For example, the bottom surface of the lightening portion 11e may hang diagonally so as to intersect the Z direction, or the bottom of the lightening portion 11e may be a two-stage bottom (multi-stage bottom). It may be.

<Modification 2>
FIG. 7 is a schematic view of the container mouth portion 10C according to the modified example 2.
The difference between this modification 2 and the above-described embodiment and modification 1 is that the lightening portion 11e is not formed mainly on the tubular side wall 11.

That is, as shown in the figure, in the modified example 2, the lightening portion 11e is not formed between the protruding portion 11d and the screw portion 11c, and the region has the same outer diameter as the screw valley of the screw portion 11c. ing. Therefore, in the present embodiment, it can be said that the position where the top surface contact ring 23 comes into contact with the protruding portion 11d is outside the outer surface 11b of the tubular side wall 11.

Also in this modification 2, the protruding portion 11d in contact with the top contact ring 23 is elastically deformed at the time of retightening, thereby suppressing an increase in the opening torque.
Further, according to the second modification, since the lightening portion 11e is not formed, it is possible to further maintain the rigidity of the tubular side wall 11 while suppressing the increase in the opening torque.

As described above, the synthetic resin cap and the cap unit of the present invention are suitable for providing a structure capable of suppressing an increase in opening torque while maintaining an appropriate retightening angle.

100 Cap unit 10A, 10B, 10C Container mouth 11 Cylindrical side wall 12 Flange 20 Synthetic resin cap 21 Top plate 22 Skirt wall 23 Top contact ring 24 Outer ring 25 TE band

Claims (7)

The container mouth made of the first resin and
A cap unit comprising a synthetic resin cap that is screwed into the container mouth and is made of a second resin having a hardness higher than that of the first resin.
The container mouth is
A tubular side wall with an inner surface from which the contents are poured,
It has a screw portion formed on the outer surface of the tubular side wall, and has.
A protrusion protruding outward in the radial direction is formed at the upper end of the outer surface of the tubular side wall.
The container mouth portion further has a lightening portion recessed inward in the radial direction between the protruding portion and the screw portion.
The synthetic resin cap is
A top plate section having an inner ring on the lower surface to form a seal in close contact with the inner surface of the tubular side wall,
With decreases from the periphery of the top plate portion, a skirt wall screw bar is formed to be screwed with the screw portion,
It is provided with a top contact ring which is the lower surface of the top plate portion and is formed between the skirt wall and the inner ring.
When the synthetic resin cap is screwed into the container opening, that the top contact ring in contact with the projecting portion, with the projecting portion disposed on the upper side than the lightening portion is elastically deformed A cap unit in which the inner ring is in close contact with the inner surface of the tubular side wall below the lightening portion . The cap unit according to claim 1, wherein when the synthetic resin cap is opened from the container mouth portion, the elastic deformation of the protruding portion is released. The cap unit according to claim 1 or 2, wherein the position where the top contact ring comes into contact with the protruding portion is outside the root of the protruding portion in the radial direction. The cap unit according to any one of claims 1 to 3 , wherein the protruding portion projects outward from the outer surface of the tubular side wall between the screw portion and the protruding portion in the radial direction. The cap unit according to any one of claims 1 to 4 , wherein the protruding portion is arranged above a seal point at which the inner ring is in close contact with the inner surface of the tubular side wall. The cap unit according to any one of claims 1 to 5 , wherein the first resin is low-density polyethylene and the second resin is high-density polyethylene. The container mouth portion is spout, cap unit according to any one of claims 1-6.

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