JP6210360B2 - Synthetic resin cap - Google Patents

Description

The present invention relates to a synthetic resin cap body having a laminated structure used to seal a mouth tube portion of a synthetic resin container.

Polyethylene terephthalate (hereinafter abbreviated as “PET”) resin-made biaxially stretched casing, so-called PET bottles have excellent gas barrier properties, high transparency, and toughness that does not crack even when dropped. It has various advantages such as non-adsorption that does not transfer the odor of the product and low odor that does not generate the odor of the resin itself, and is widely used for drinks such as drinking water, carbonated drinks, tea, and fruit juice. Has been.
And in the case product filled with the content liquid, the quality due to air, especially oxygen, in the period until the cap body is removed and used by sealing the mouth tube with the cap body after storing the content liquid The decrease can be suppressed.
For applications where the oxygen barrier property of PET resin alone is insufficient, for example, a casing in which an oxygen barrier resin such as ethylene vinyl alcohol copolymer resin or nylon resin is laminated as an intermediate layer is used.

However, even if the oxygen barrier resin is laminated as an intermediate layer as described above, there is a limit in suppressing the permeation of oxygen, and there is a demand for more severely suppressing the deterioration of the content liquid due to oxygen. For the above, it is necessary to adopt a method of capturing oxygen permeated from the outside through the peripheral wall.
In Cited Document 1, an intermediate layer is formed from a resin composition in which an oxygen barrier resin is mixed with a transition metal complex, and this intermediate layer not only suppresses oxygen permeation, but also can capture oxygen. Is described.

Further, in Cited Document 2, a liner containing a hydrogen generator such as sodium borohydride that generates hydrogen by reaction with moisture is attached to the inner surface of the top wall of the cap, and the moisture in the container is the hydrogen generator. The invention relating to the method for capturing permeated oxygen is described in which hydrogen generated by reaction with oxygen and oxygen permeated from the air into the container are reacted to form water.

JP-A-1-278344 Special table 2012-523354 gazette

As a method of disposing a hydrogen generator on the cap body, a method of sticking a liner containing a hydrogen generator as described in Patent Document 2 to the inner surface of the top wall, or in a synthetic resin forming the cap body There is a method in which a molten resin lump encapsulating a synthetic resin in which a hydrogen generator is dispersed is supplied to a cavity mold, and the cap body is formed by compression molding with a core mold to disperse the hydrogen generator in the cap body. is there.
However, the method of sticking the liner to the inner surface of the top wall has problems such as the need for a sticking process and the concern that the liner may fall off. It is difficult to reproducibly laminate an intermediate layer made of a resin in which the resin is dispersed in a predetermined position, and the generated hydrogen is likely to escape to the outside because the intermediate layer is laminated near the outer surface of the top wall. There is a problem that it cannot be effectively used to capture oxygen permeated into the container.

An object of the present invention relates to an arrangement mode of the above-described hydrogen generating agent in a cap body, and effectively uses hydrogen generated by the hydrogen generating agent to capture oxygen permeated into the container. It is possible to create an arrangement mode of a hydrogen generating agent that can be manufactured with high productivity.

The main configuration of the present invention related to the means for solving the above technical problem is:
In the synthetic resin cap body,
It is made of synthetic resin and has a cylindrical injection molding with a top.
In the top wall, an intermediate layer in which a hydrogen generating agent that reacts with moisture to generate hydrogen is dispersed in a matrix resin is laminated,
The intermediate layer is positioned closer to the inner surface side than the central position in the thickness direction of the top wall, and in the vicinity of the flat inner surface from the central part of the top wall toward the outer peripheral edge. It is said that the taper shape changes from the center toward the center in the thickness direction.

Described above, the stacking position of the intermediate layer, and a position close to the inner surface side of the thickness direction of the center position of the top wall, and, toward the outer periphery from the center of the top wall, relative to the flat inner surface The cap body having a laminated aspect of an intermediate layer that changes from the vicinity to the central position in the thickness direction is formed by using an injection molding method using a multilayer nozzle as described later. Unlike the compression molding method described above, the intermediate layer can be laminated with high accuracy at a predetermined lamination position with high productivity.

Then, with the multilayer embodiment of the intermediate layer of the structure, in a region where the intermediate layer formed by dispersing hydrogen generating agent in the top wall are laminated, the intermediate layer is sandwiched main material layer to form the main body of the cap body, In the thickness direction, it has a laminated structure of two types and three layers such as outer main material layer / intermediate layer / inner main material layer.
Then, moisture from the container permeates the inner main material layer and reaches the intermediate layer. In this intermediate layer, moisture reacts with the hydrogen generating agent , and the generated hydrogen passes through the inner main material layer and moves into the container. and, the water reacts with the oxygen in the vessel, and the referred mechanism, capturing function is exerted against the oxygen having passed through the vessel from the air.

In view of this, the inner main material layer becomes a so-called barrier layer against the movement of moisture from the container to the intermediate layer, so that when the inner main material layer becomes thicker, the moisture arrival speed to the intermediate layer increases. The oxygen scavenging function is not fully exhibited due to a decrease in size.
In particular, polyolefin resins such as polyethylene resin and polypropylene resin, which are used in many cap bodies, have low moisture permeability. Therefore, the inner main material layer is made as thin as possible, that is, the intermediate layer is laminated at the inner position. It needs to be close to the surface side.

Further, with the hydrogen generated from the intermediate layer of the cap member moves into the vessel through the inner main material layer, since the escape to the outside through the outer main material layer, moving the generated hydrogen as possible in the vessel, it pointed transmitted from the outside the order to the capture oxygen effectively, by increasing the thickness of the outer main material layer, it is necessary to reduce the thickness of the inner main material layer.
The lamination mode of the intermediate layer having the above configuration is based on such a mechanism related to the movement of moisture and the movement of hydrogen, and the lamination position of the intermediate layer is brought closer to the inner surface side than the center position in the thickness direction of the top wall. By setting the position, the hydrogen generated by the hydrogen generating agent can be effectively used to capture permeated oxygen.
And according to the lamination | stacking aspect of the intermediate | middle layer arrange | positioned taper-shaped with respect to the above flat inner surfaces, it is the inner side from an inner surface to an intermediate | middle layer toward the outer periphery from the center of a top wall As the distance through the main material layer gradually increases , the time until the moisture in the container passes through the inner main material layer and reaches the intermediate layer is gradually delayed according to the distance. By utilizing the aspect, the oxygen scavenging function can be stably exhibited over a long period of time.

  According to another configuration of the present invention, in the main configuration described above, a gate mark by a pin gate of an injection molding apparatus is provided at the center of the outer surface of the top wall.

  With the above configuration, the intermediate layer is laminated at a position close to the inner surface side of the top wall by using an injection molding device in which a pin gate is disposed at a position corresponding to the center of the outer surface of the top wall as described later. Is possible.

  Still another configuration of the present invention is that the main configuration is made of polypropylene (PP) resin including the matrix resin.

  Still another configuration of the present invention is that the main configuration is made of a polyethylene resin including a matrix resin.

  The above two configurations relate to the synthetic resin to be used, and polypropylene resin and polyethylene resin are used in many cap bodies, but the matrix resin forming the intermediate layer also has the same kind of polypropylene resin or By using the polyethylene resin, peeling of the intermediate layer can be prevented, injection molding is easy, and molding distortion can be suppressed.

  Still another configuration of the present invention is that, in the above main configuration, the hydrogen generating agent is sodium borohydride.

  Sodium borohydride has good thermal stability. If the moisture content is kept low by drying, etc., it will be decomposed in the process of dispersing into a matrix resin by a twin screw extruder and the injection molding process of the cap body. And can be used stably.

Here, the above-described “inner layer stacking position is a position closer to the inner surface side than the central position in the thickness direction of the top wall, and the flat inner surface from the central part of the top wall toward the outer peripheral edge” On the other hand, the injection molding method for realizing the lamination mode is assumed to be changed in a taper shape from the vicinity to the center position in the thickness direction.
Of course, the injection molding method described below is an example, and various variations can be made as necessary.

First, an injection molding apparatus having the following configuration is used.
(1) A multilayer nozzle that forms a merged resin body by joining an intermediate layer resin that forms an intermediate layer in a main material resin that forms a main layer of a cap body, and a mold disposed at the tip of the nozzle. Shall have.
(2) The nozzle has a cylindrical outer flow path, an intermediate flow path, an inner flow path, and a cylindrical combined flow path that extends to the tip of the nozzle in communication with the three flow paths in order from the outside. Shall have.
(3) An opening adjustment mechanism that can block or open the opening end of the inner flow path to the combined flow path and further adjust the opening is provided.
(4) The mold cavity has a configuration in which the cavity is injected and filled via a pin gate disposed at a position facing the center of the outer surface of the top wall of the cap body of the cap body.

Using the above-described injection molding apparatus, injection molding is performed along the following steps 1 to 5.
Step 1: Supply main material resin from the outer channel and the inner channel to the combined channel.
Step 2: After a predetermined time from the start time of Step 1, the intermediate layer resin is supplied from the middle channel to the combined channel.
Step 3: After a predetermined time from the start time of Step 2, the supply of the main material resin from the inner flow path is shut off by adjusting the opening degree of the open end.
Step 4: After a predetermined time from the start time of Step 3, the supply of the intermediate layer resin is stopped.
Step 5: After a predetermined time from the start time of Step 4, the open end is opened and a pressure holding step is performed.

And according to the above injection molding method,
Among the main material resins, the main material resin supplied from the outer flow path forms the outer surface side (outer main material layer) of the cap body, and the main material resin supplied from the inner flow path is the inner surface side of the cap body. (Inner main material layer) is formed.
Then, when the intermediate layer resin is supplied from the middle flow path to the combined flow path in Step 2, the intermediate layer resin is interposed between the main material resins supplied from the internal and external flow paths in the cylindrical flow path from the combined flow path to the pin gate. It flows in and is laminated in a cylindrical shape.

Here, the supply amount of the main material resin from the inner channel to the outer channel is reduced by adjusting the opening degree of the opening end, so that the outer wall as described above When a layered structure of two types and three layers called the main material layer / intermediate layer / inner main material layer is formed, the inner main material layer is made thin, and “the intermediate layer is laminated in the thickness direction of the top wall. It is possible to realize a stacking mode in which the position is closer to the inner surface side than the center position. Then, the supply of the main layer resin after the supply of the intermediate layer resin is stopped and the flow of the main material resin from the pin gate to the center of the cavity and the pressurization to the main material resin in the subsequent pressure holding process, The central part is pushed, and it is assumed that “from the central part of the top wall toward the outer peripheral edge, the flat inner surface changes from the vicinity thereof toward the central position in the thickness direction in a tapered shape. It is possible to realize an intermediate layer stacking mode.
In addition, the supply amount of the main material resin from the inner flow path can be adjusted according to the degree of adjustment of the opening degree of the opening end, so that the intermediate layer can be laminated with high accuracy and good reproducibility at a predetermined position. it can.

Since the present invention has the above-described configuration, the following effects can be obtained.
In the top wall of the cap body of the present invention, “the stacking position of the intermediate layer is a position closer to the inner surface side than the center position in the thickness direction of the top wall, and from the center portion of the top wall toward the outer peripheral edge. It is assumed that the flat inner surface changes in a tapered shape from the vicinity thereof toward the center position in the thickness direction. ”The lamination mode is formed using an injection molding method using a multilayer nozzle. Unlike the compression molding method, the intermediate layer can be laminated with high accuracy at a predetermined lamination position with high productivity.
And according to the lamination | stacking aspect of the said intermediate | middle layer, while the movement of the water | moisture content from a container to an intermediate | middle layer is achieved smoothly, the quantity of the hydrogen which permeate | transmits the top wall of a cap body and escapes outside is suppressed. It is possible to effectively use the generated hydrogen to effectively exert the function of capturing permeated oxygen. Moreover, the oxygen scavenging function can be stably exhibited over a long period of time by utilizing a taper-like laminated form of the intermediate layer with respect to the flat inner surface .

It is a front view which cuts and shows one Example of the cap body of this invention longitudinally. It is explanatory drawing which shows the lamination | stacking aspect of the intermediate | middle layer in the top wall of the cap body of FIG. It is explanatory drawing which shows the lamination | stacking aspect of the intermediate | middle layer in the top wall of the cap body of a comparative example. It is explanatory drawing which shows the lamination | stacking aspect of the cap body of another comparative example. (A) which shows the measurement result of the amount of dissolved oxygen is a table | surface, (b) is a graph. It is a schematic explanatory drawing which shows the principal part longitudinally about an example of an injection molding apparatus. It is explanatory drawing which shows the movement position of the shut-off pin in the apparatus of FIG. It is explanatory drawing which shows the example of an injection pattern. It is a schematic explanatory drawing which shows the filling process of the molten resin to the metal mold cavity by the injection pattern of FIG. It is explanatory drawing which shows the other lamination | stacking aspect of the intermediate | middle layer in a top wall. It is a schematic explanatory drawing which shows the other filling process of the molten resin to the metal mold cavity by the injection pattern of FIG.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described along examples with reference to the drawings.
1 and 2 show an embodiment of the cap body of the present invention, FIG. 1 is a longitudinal front view, and FIG. 2 is an enlarged view of the laminated mode of the intermediate layer 11 on the top wall 2 of the cap body 1 of FIG. It is explanatory drawing shown.

The cap body 1 is an injection molded product made of PP resin and has a top wall 2 and a side peripheral wall 3 in which the outer surface 2t and the inner surface 2u are formed flat, respectively , and the outer diameter is A gate mark 5 is formed at the center of the top wall 2 on the outer surface 2t side by a tip of a pin gate of the injection molding apparatus.
An intermediate layer 11 is laminated on the top wall 2, and this intermediate layer 11 is obtained by dispersing 25 mg of sodium borohydride (NaBH4) as a hydrogen generator in a PP resin matrix.

Referring to FIG. 2, the lamination mode of the intermediate layer 11 in the main material layer 10 will be described.
The average thickness of the top wall 2 is 1.6 mm. In FIG. 2, an alternate long and short dash line Ltc indicates a center position Ptc in the thickness direction of the top wall 2 (in the present embodiment, from the outer surface 2t and the inner surface 2u to 0. 0). The intermediate layer 11 is located on the inner surface 2u side from the one-dot chain line Ltc corresponding to 1/2 the thickness of the top wall 2 over the entire range.
Further, the lamination mode of the intermediate layer 11 will be described in detail. The lamination position of the intermediate layer 11 is closest to the inner surface 2 u in the vicinity of the center where the gate mark 5 of the top wall 2 is formed , and from the center to the top wall 2. It is laminated | stacked in the main material layer 10 in the state changed to the taper shape so that it may leave | separate from the inner surface 2u toward the center position Ptc of the thickness direction toward the outer periphery. That is, when the distance from the inner surface 2u to the intermediate layer 11 gradually increases from the center toward the outer peripheral edge (outward in the radial direction), the moisture in the container causes the main material layer 10 (inner main material layer 10b) to move. Since the time until the light passes through and reaches the intermediate layer 11 is sequentially delayed, it is possible to stably exhibit the oxygen scavenging function over a long period of time by using this tapered lamination mode.

And the lamination | stacking position in the center vicinity and outer periphery vicinity of the intermediate | middle layer 11 is a position about 0.1 mm and about 0.6 mm from the inner surface 2u, respectively, and the average value of a lamination | stacking position is 0.4 mm from the inner surface 2u. And 0.8 mm which is the central position Ptc in the thickness direction of the top wall 2, and is located sufficiently on the inner surface 2 u side.
Moreover, the average value of the layer thickness t of the intermediate layer 11 is 0.12 mm, and the thickness is reduced to about 7.5% of the average thickness 1.6 mm of the top wall 2.

Here, the cap body 1 of the above embodiment is based on an injection molding method to be described later. As described above, the lamination position of the intermediate layer 11 is flattened from the central portion of the top wall 2 toward the outer peripheral edge. It is said that the outer surface 2t on the opposite side is changed from the vicinity of the formed inner surface 2u , that is , changes in a taper shape away from the inner surface 2u.
Moreover, it has the characteristic which the cap layer which laminated | stacked the intermediate | middle layer by the conventional compression molding said that the average layer thickness of the intermediate | middle layer was thinned to about 0.1 mm.

And according to the lamination | stacking aspect of the taper-shaped intermediate | middle layer 11 as mentioned above, it is the intermediate | middle via the main material layer 10 (inner main material layer 10b) from the inner surface 2u toward the outer periphery from the center of the top wall 2. FIG. As the distance to the layer 11 is gradually increased, the time for the moisture in the container to reach the intermediate layer 11 is sequentially delayed. Therefore, the oxygen scavenging function can be stabilized over a long period of time using this tapered layered form. Can be demonstrated.
Further, if the thickness of the intermediate layer 11 is 0.5 mm or more, it is difficult to bring the stacking position of the intermediate layer 11 closer to the inner surface 2u side than the center position with the top wall 2 having a thickness of about 1.6 mm. However, by reducing the thickness of the intermediate layer 11 as described above, the intermediate layer 11 can be brought closer to the inner surface 2u side, and the matrix resin in the intermediate layer 11 according to the moisture moving speed can be obtained. The influence of can be reduced.
Further, by reducing the thickness of the intermediate layer 11, it is possible to reduce the molding distortion caused by the lamination of the intermediate layer 11, and to suppress the deformation due to the molding distortion of the cap body 1.

Next, FIG. 3 is an explanatory view showing a lamination mode of the intermediate layer 11 on the top wall 2 of the cap body 31 prepared as a comparative example of the cap body 1 of the above-described embodiment.
The cap body 31 of this comparative example is made of PP resin and has the same shape as the cap body 1 of the above embodiment, and only the lamination mode of the intermediate layer 11 is different.
The intermediate layer 11 shown in FIG. 3 will be described in detail. The intermediate layer 11 has a semicircular convex shape in the direction of the inner surface 2u in the vicinity of the center where the gate mark 5 of the top wall 2 is formed and a diameter of about 10 mm. It is laminated, and on the outside, it is located at a position slightly closer to the outer surface side than the center line Ltc.
In the intermediate layer 11, the amount of sodium borohydride dispersed in the PP resin matrix is 25 mg, similar to the cap body 1 of the example.

And the average value of the lamination | stacking position of the intermediate | middle layer 11 is a position which approached 0.1 mm outer surface side from the center position Ptc of the thickness direction of the top wall 2 shown by the dashed-dotted line Ltc.
The average value of the layer thickness t of the intermediate layer 11 is 0.15 mm.

Next, in addition to the cap body 1 of the embodiment having the lamination mode shown in FIG. 2 and the cap body 31 of the comparative example shown in FIG. 3, the shape is the same as the cap body 1 of the embodiment and the intermediate layer 11 is not laminated. A single layer cap body of PP resin single layer, and a disk 21 in which sodium borohydride is dispersed in a matrix resin as a hydrogen generator is attached to the inner surface 2u of the top wall 2 of the single layer cap body shown in FIG. The disc-attached cap body 32 was prepared, and a test related to the permeation property of the permeated oxygen was performed on these four types of cap bodies.
The disk 21 used for the cap body 32 shown in FIG. 4 has a lower surface and a side surface of the hydrogen generation layer 22 in which 25 mg of sodium borohydride is dispersed in an ethylene-vinyl acetate copolymer (EVA) resin as a matrix resin. It is coated with a coating layer 23 made of an olefinic thermoplastic elastomer (TPO) resin. The layer thickness of the hydrogen generation layer 22 is 0.7 mm, and the layer thickness of the coating layer 23 on the lower surface side is 0.3 mm.

The test contents and measurement conditions are as follows.
(1) Water that has been deaerated until the amount of dissolved oxygen (Dissolved Oxygen: DO value) is 0.7 to 0.8 ppm using a PET bottle having a diameter of about 63 mm and an inner volume of 720 ml as a container. Are fully filled and sealed with each cap body.
At this time, in order to react hydrogen and oxygen, a bottle in which palladium acetate is added so that the concentration of palladium (Pd) is about 5 ppm is formed and used.
The catalyst is not limited to palladium, but unless a reaction catalyst is added, the reaction is not accelerated and the function of capturing oxygen is not effectively exhibited.
(3) Using the oxygen concentration meter Fibox-3 manufactured by PreSens, Germany, the DO value in the bottle after storage at 60 ° C. for 3 days, 5 days, and 7 days is measured.

FIG. 5 shows a table (FIG. 5 (a)) and a graph (FIG. 5 (b)) summarizing the DO value measurement results. The test body S is the cap body 1 of the example, and C1 is the cap of the comparative example. The bodies 31 and C2 use a single-layer cap body, and C3 uses a cap body 32 with a disk.
In addition, () DO value (dissolved oxygen increase amount) calculated by the following formula (1) is shown in parentheses in the table.
ΔDO value = DO value after elapse of a predetermined number of days−DO value at start (1)
This ΔDO value can be used as an index of oxygen scavenging performance, and it can be said that the greater the negative value, the better the oxygen scavenging performance.

From the measurement results, the following can be understood.
(1) In test body C2, that is, a test body that does not use a hydrogen generator, the DO value rises in proportion to the number of days elapsed, and oxygen in the air permeates the peripheral wall of the plastic bottle and dissolves in the water of the plastic bottle. You can see that it is dissolved.
(2) In the test body C3 using the cap body 32 with a disk, the ΔDO value was −0.58 ppm on the third day of the test, and this value was maintained until the seventh day, so that oxygen was stably captured. The function is demonstrated.
(3) In the test body S using the cap body 1 of the example, the ΔDO value is −0.44 ppm on the third day from the start of the test, and this value is maintained until the seventh day. Although the oxygen scavenging performance is slightly lower as compared, it can be said that the permeated oxygen scavenging function is sufficiently exhibited.
(4) In the test body C1 using the cap body 31 of the comparative example, it can be seen that the oxygen scavenging function is exhibited as compared with the test body C2, but the ΔDO value does not reach a negative value, and the DO The value gradually increases, the oxygen scavenging function is not sufficient, and oxygen permeating from the peripheral wall of the PET bottle to the inside cannot be captured sufficiently.

When comparing the results of the test body S and the test body C1, the difference between the two is in the position where the intermediate layer 11 in which the hydrogen generator is dispersed is obtained. As shown in FIG. It is laminated at a position approaching the inner surface 2u from the central position Ptc in the thickness direction of the wall 2, and with respect to the outer main material layer 10a laminated on the outer surface 2t side of the intermediate layer 11 of the main material layer 10, Since the inner main material layer 10b laminated on the inner surface 2u side is thin,
From the inside of the PET bottle, the rate of moisture that reaches the intermediate layer 11 through the inner main material layer 10b is large, and it can be seen that a considerable amount of hydrogen was generated from the initial stage of measurement due to the reaction between this moisture and the hydrogen generator. .
Furthermore, since the outer main material layer 10a is thick and the inner main material layer 10b is thin, the escape of generated hydrogen to the outside through the outer surface 2t is suppressed, and more hydrogen is absorbed. It can be presumed that the inside of the bottle could be transmitted through the surface 2u, and that the oxygen scavenging effect could be sufficiently exhibited from the early stage of measurement as described above.

On the other hand, in the cap body 31 of the comparative example used for the test body C1, the outer main material layer 10a is thin and the inner main material layer 10b is opposite to the cap body 1 of the embodiment as seen in FIG. Since the layer thickness is thick, the arrival speed of moisture from the inside of the PET bottle through the inner main material layer 10b to the intermediate layer 11 is small.
In addition, it is presumed that the oxygen scavenging function was not sufficiently exhibited due to the small suppression effect related to the outward escape of hydrogen through the outer surface 2t.
In the test described above, the amount of sodium borohydride dispersed in the cap body 1 of the example used for the test body S, the cap body 31 of the comparative example used for C1, and the cap body 32 with a disk used for C3. The oxygen scavenging function was comparatively examined.
Here, the amount of hydrogen generated can be increased or decreased depending on the amount of sodium borohydride added, but when the amount of sodium borohydride added is increased or decreased in this way, the above three cap bodies are used. It is clear that a similar trend of comparison results can be obtained with respect to the oxygen scavenging function.

Next, an injection molding apparatus and an injection molding method for molding the cap body 1 of the embodiment shown in FIG. 2 and the cap body 31 of the comparative example shown in FIG. 3 will be described.
6 and 7 schematically show an example of an injection molding apparatus. FIG. 6 is a longitudinal sectional view in the vicinity of the nozzle 111, showing a state in which a mold 101 is attached on the downstream side, and FIG. It is explanatory drawing for demonstrating the position of the front-end | tip 120p of the shut-off pin 120 in the apparatus of FIG.

The nozzle 111 has a cylindrical first mandrel 121, a second mandrel 122, and a third mandrel 123 that are arranged in the same central axis shape from the inside, and a cylindrical shut-off pin inside the first mandrel 121. 120 is slidably inserted and disposed.
The tip of each mandrel has a tapered cylindrical shape with a diameter reduced toward the downstream side.
A cylindrical outer flow path 115 a through which the main material resin Ra flows is formed between the third mandrel 123 and the second mandrel 122, and the intermediate layer resin Rb flows between the second mandrel 122 and the first mandrel 121. A cylindrical inner flow path 115b is formed, and a cylindrical inner flow path 115c through which the main material resin Ra flows is formed between the first mandrel 121 and the shut-off pin 120 in the same manner as the outer flow path 115a. .

The main material resin Ra is supplied from a first supply portion Sa such as a screw-type extruder or an accumulator having a plunger attached to the tip of the extruder, and passes through the introduction passage 112a and is connected to the outside through the manifolds 114a1 and 114a2. It is introduced into the channel 115a and the inner channel 115c.
Further, the intermediate layer resin Rb is supplied from the second supply part Sb, and is introduced into the middle flow path 115b through the introduction path 112b and the manifold 114b.

The main resin Ra is from the reduced diameter channel 115as disposed at the tip of the outer channel 115a and the reduced diameter channel 115cs disposed at the tip of the inner channel 115c, and the intermediate layer resin Rb is the middle channel. The reduced diameter flow path 115bs disposed at the front end of 115b is supplied to the cylindrical merged flow path 119, and the main material resin Ra and the intermediate layer resin Rb merge in the merged flow path 119 to form a merged resin body.
The joined resin body is disposed at a position corresponding to the center of the outer surface of the top wall 2 of the cap body 1 in the cavity 104 formed by the core mold 102 and the cavity mold 103 of the mold 101. The cavity 104 is injected and filled through the pin gate 105.

Further, in this device, the shut-off pin 120 is configured to slide on the inner peripheral surface of the reduced diameter tip portion of the first mandrel 121 that forms the inner flow path 115c together with the shut-off pin 120.
In addition to the normal function of blocking or opening the tip of the nozzle 111, the shut-off pin 120 moves the position of the tip 120p to a predetermined position in the vicinity of the opening end 117c to the combined channel 119 of the inner channel 115c. By controlling and positioning the opening end portion 117c, the opening degree of the opening end portion 117c is adjusted between the fully opened state and the blocked state, and the supply amount of the main material resin Ra from the inner flow path 115c to the combined flow path 119 is adjusted. Have
Then, the sliding movement (in the vertical direction in FIG. 6) of the shut-off pin 120 is controlled by a servo mechanism using a servo motor (not shown) so that the advanced flow path adjustment function as described above is exhibited. Like to do.

Here, FIG. 7 is a view for explaining the position of the tip 120p of the shut-off pin 120 in the apparatus of FIG.
Here, the position P0 is the tip of the nozzle 111, the position P3 is the upstream end of the reduced diameter flow path 115cs, the position P2 is near the lower end of the reduced diameter flow path 115cs, and the position P1 is a position corresponding to the lower end of the inner flow path 115c. The position P3 corresponds to a state in which the opening degree of the opening end portion 117c is fully opened, the position P2 corresponds to a state in which the opening degree is reduced, and the position P1 corresponds to a state in which the opening degree is blocked.
The opening degree of the open end 117c is adjusted between the fully open state and the shut off state between the position P1 and the position P3, and the supply amount of the main material resin Ra from the inner flow path 115c to the combined flow path 119 can be adjusted. .

Next, an injection molding method using the above-described apparatus will be described.
FIG. 8 shows the injection pattern when the cap body 1 of the embodiment shown in FIG. 2 and the cap body 31 of the comparative example shown in FIG. Is an explanatory diagram schematically showing the time axis and the vertical axis as the molten resin supply rate,
The solid line shows the injection pattern of the PP resin, which is the main resin Ra, and the PP resin in which sodium borohydride is dispersed as a hydrogen generator in the PP resin, which is the intermediate layer resin Rb, shown by the broken line.

In FIG. 8, along with the above-described injection patterns of both resins, along the passage of time when the cap body 1 of the example is formed by the one-dot chain line Sp1 and the cap body 31 of the comparative example is formed by the two-dot chain line Sp31. The fluctuation pattern of the position of the tip 120p of the shut-off pin 120 is shown.
In the formation of the cap body 1 indicated by the one-dot chain line Sp1, the position of the tip 120p is moved from the position P2 → P1 → P2 shown in FIG. 7, and in the formation of the cap body 31 indicated by the two-dot chain line Sp31, the position P3 → P1 → It is moved with P3.

The injection molding process of the cap body 1 according to the embodiment of the injection pattern of FIG. 8 along with the passage of time is as follows.
(1) The position of the tip 120p of the shut-off pin 120 is set to P2 (see FIG. 7), the opening degree of the opening end portion 117c of the inner flow path 115c is reduced, and the main material resin Ra is removed from the first supply portion Sa. Then, it is supplied to the combined channel 119 through the outer channel 115a and the inner channel 115c.
(2) At time tb1, the intermediate layer resin Rb is supplied from the second supply section Sb to the combined flow path 119 via the intermediate flow path 115b, and flows between the main material resin Ra from the outer flow path 115a and the inner flow path 115c.
(3) At time ts1, the position of the tip 120p of the shut-off pin 120 is set to P1, and the supply of the main material resin Ra from the inner flow path 115c is shut off.
(4) The supply of the intermediate layer resin Rb from the second supply unit Sb is stopped at time tb2.
(5) At time ts2, the position of the tip 120p of the shut-off pin 120 is returned to P2, and the supply speed of the main material resin Ra from the inner flow path 115c is returned to the original speed.
(6) The mold pressure is reduced to a predetermined pressure at time ta2 (as a result, the supply speed Va of the main material resin Ra from the first supply unit Sa is reduced), and the pressure holding process is performed until time ta3. .

FIG. 9 shows the filling process of the main resin Ra and the intermediate layer resin Rb into the cavity 104 of the mold 101 in the process as described above by the injection pattern of FIG. 8 when molding the cap body 1 of the embodiment. FIG. 9 is a schematic explanatory diagram for explaining the above, and the filling into the cavity 104 proceeds in the order of FIG. 9 (a) → (b) → (c).
Cross-sectional views along lines J1-J1 and J3-J3 on FIGS. (A) and (c), and cross-sectional views along lines J2a-J2a and J2b-J2b on FIG. (B). Is shown.
In addition, here, the main material resin Ra supplied from the outer flow path 115a is referred to as an outer main material resin Ra1, and the main material resin Ra supplied from the inner flow path 115c is referred to as an inner main material resin Ra2.

  In this example, the position of the tip 120p of the shut-off pin 120 is P2, and the opening amount of the opening end portion 117c is reduced to reduce the supply amount of the inner main material resin Ra2 supplied from the inner flow path 115c. When the intermediate layer resin Rb is supplied from the middle flow path 115b, the intermediate layer resin Rb in the pin gate 105 has a relatively large diameter in the outer main material resin Ra1 and the inner main material resin Ra2 as seen in FIG. And flow in a circular shape from the center of the cavity 104 toward the outer periphery.

Further, as indicated by a one-dot chain line Sp1 in FIG. 8, the supply of the inner main material resin Ra2 from the inner flow path 115c is cut off at time ts1 to ts2 with the position of the tip 120p of the shutoff pin 120 as P1. As shown in FIG. 9B, in the pin gate 105, the intermediate layer resin Rb is laminated in the outer main material resin Ra1 in the shape of a narrow cylindrical tail at the upstream end Rbu.
Further, the flow of the main material resin Ra from the pin gate 105 toward the central portion of the cavity 104 and the main material in the supply process of the main material resin Ra at the subsequent time ts2 to ta2 and the pressure holding process at the time ta2 to ta3. By pressurizing the resin Ra, the intermediate layer 11 made of the intermediate layer resin Rb is pressed against the center of the mold surface forming the cavity 104 as shown in FIG. 9C, and the intermediate layer 11 is pressed as shown in FIG. It becomes a taper-shaped lamination | stacking aspect.

Then, as shown in FIG. 9 (a), when filling the intermediate layer resin Rb in the state of FIG. 9 (c) through the state of FIG. The intermediate layer 11 made of the intermediate layer resin Rb can be laminated at a position close to the inner surface 2u side of the cap body 1 as seen in FIG.
Further, as shown in FIG. 9B, the supply of the inner main material resin Ra2 is cut off at the upstream end Rbu of the intermediate layer resin Rb, and the upstream end of the intermediate layer resin Rb is changed from a cylindrical shape to a columnar shape. Thus, the intermediate layer 11 can be laminated in the entire region from the central portion of the top wall 2 of the cap body 1 to the outer peripheral edge.

  Here, as shown in FIG. 9 (b), the supply of the intermediate layer resin Rb is not interrupted, and the upstream end of the intermediate layer resin Rb remains in a thin cylindrical shape as shown in FIG. 9 (a). Then, as shown in FIG. 10, the central portion of the top wall 2 becomes a non-laminated region Rn in which the intermediate layer 11 is not laminated, but in consideration of productivity related to injection moldability and the like, such a non-laminated region Rn. It can also be set as the laminated aspect which has.

Next, FIG. 11 is a schematic explanatory diagram for explaining a filling process of the main material resin Ra and the intermediate layer resin Rb into the cavity 104 of the mold 101 at the time of molding the cap body 31 of the comparative example. Filling into the cavity 104 proceeds in the order of (a) → (b) → (c).
11A and 11C are cross-sectional views taken along lines K1-K1 and K3-K3, and FIG. 11B is taken along lines K2a-K2a and K2b-K2b. A cross-sectional view is shown.

In this example, since the position of the tip 120p of the shut-off pin 120 is P3 and the opening degree of the opening end 117c is fully open, the intermediate layer resin Rb at the pin gate 105 is the outer main resin as shown in FIG. The material resin Ra1 and the inner main material resin Ra2 are laminated in a cylindrical shape having a larger diameter than that in FIG.
For this reason, when the filling in the state of FIG. 11C is completed through the state of FIG. 11B, the lamination position of the intermediate layer 11 by the intermediate layer resin Rb is a cap as a whole as seen in FIG. The body 31 is laminated at a position close to the outer surface side.
Further, the flow of the main material resin Ra from the pin gate 105 toward the central portion of the cavity 104 and the main material resin Ra in the supply process of the main material resin Ra at the time ts2 to ta2 and the pressure holding process at the time ta2 to ta3. As shown in FIG. 3, the intermediate layer 11 is laminated in a semicircular convex shape in the direction of the inner surface 2u in the vicinity of the center where the gate mark 5 of the top wall 2 is formed. Yes.

As mentioned above, although embodiment of this invention was described along the Example, this invention is not limited to these Examples.
In the cap body 1 of the above embodiment, the matrix resin for forming the intermediate layer 11 is made of PP resin, but an appropriate synthetic resin can be used depending on the purpose of use.
Also, when using the same type of resin as the matrix resin and the resin that forms the main body of the cap body, considering the lamination of the intermediate layer, for example, a resin having a low melt viscosity may be used as the matrix resin. It is also possible to select a resin different from the resin forming the main body as the matrix resin.
Further, the amount of the hydrogen generating agent can be appropriately adjusted in consideration of the purpose of use of the container.

The above-described injection molding apparatus and injection molding method are merely examples for molding the cap body of the present invention, and the detailed apparatus configuration and injection molding process can be variously modified.
For example, in the sliding pattern of the shut-off pin 120 indicated by the one-dot chain line Sp1 in FIG. 8, the supply amount of the inner main material resin Ra2 is narrowed from the beginning with the tip 120P as the position P2, but initially the position P3 is fully opened. An appropriate pattern can be adopted from various variation patterns such that the supply amount is narrowed at the position P2 immediately before the injection start time tb1 of the intermediate layer resin Rb.

As described above, the lamination mode of the intermediate layer on the top wall of the cap body of the present invention can be molded with high productivity using an injection molding method using a multilayer nozzle, and moisture from the container to the intermediate layer can be formed. Can be achieved smoothly, and the amount of hydrogen that permeates the top wall of the cap body and escapes to the outside can be suppressed, and the generated oxygen is effectively used to effectively capture the permeated oxygen. In addition, the oxygen scavenging function can be demonstrated stably over a long period of time , and it can be used in a wide range of applications where it is required to more strictly suppress the deterioration of the content liquid due to oxygen. Use expansion is expected.

DESCRIPTION OF SYMBOLS 1; Cap body 2; Top wall 2t; Outer surface 2u; Inner surface 3; Side peripheral wall 5; Gate trace 10; Main material layer 10a; Outer main material layer 10b; Hydrogen generation layer 23; coating layer
31; Cap body (comparative example)
32; Cap body (comparative example)
Ptc; central position 101 (in the thickness direction); mold 102; core mold 103; cavity mold 104; cavity 105; pin gate 111; nozzle 112a, 112b; introduction path 114a1, 114a2, 114b; Channel 115b; Middle channel 115c; Inner channels 115as, 115bs, 115cs; Reduced diameter channel 117c; Open end 119; Combined channel 120; Shutoff pin 120p; Tip 121; First mandrel 122; Mandrels P0, P1, P2, P3; position Ra (at the tip of the shut-off pin); main material resin (PP resin)
Ra1; outer main resin Ra2; inner main resin Rb; intermediate layer resin Rbu; upstream end (of intermediate layer resin)
Rn; non-stacked region Sa; first supply unit Sb; second supply unit

Claims (5)

It is a cylindrical injection-molded product,
In the top wall (2), an intermediate layer (11) in which a hydrogen generating agent that reacts with moisture to generate hydrogen is dispersed in a matrix resin is laminated,
The intermediate layer (11) is laminated at a position closer to the inner surface (2u) side than the central position (Ptc) in the thickness direction of the top wall (2), and from the central part of the top wall (2). A synthetic resin cap body characterized in that it changes in a tapered shape from the vicinity thereof toward the center position (Ptc) in the thickness direction with respect to the flat inner surface (2u) toward the outer peripheral edge.
The synthetic resin cap body according to claim 1, wherein a gate mark (5) by a pin gate of an injection molding device is provided at the center of the outer surface (2t) of the top wall (2). The cap body made of a synthetic resin according to claim 1 or 2 made of a polypropylene resin including a matrix resin. The synthetic resin cap body according to claim 1 or 2 made of polyethylene resin including a matrix resin. The synthetic resin cap body according to claim 1, 2, 3, or 4, wherein the hydrogen generator is sodium borohydride.

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