JP6641793B2 - Synthetic resin container - Google Patents

Description

  The present invention relates to a synthetic resin container having a raised bottom shape in which legs are formed on a peripheral side of a container bottom.

  Conventionally, a synthetic resin container obtained by forming a bottomed cylindrical preform using a thermoplastic resin such as polyethylene terephthalate, and then molding the preform into a bottle shape by biaxial stretching blow molding, etc. It is generally used in a wide field as a container containing various beverages and the like.

Further, in this type of synthetic resin container, attempts have been made to form the container as thin as possible in order to reduce the weight and the cost by reducing the amount of resin used.
For example, Patent Literature 1 discloses that a bottom mold of a blow molding die can be moved up and down, a preform is stretched in a state where the bottom mold is lowered, and then a bottom side of the preform stretched by raising the bottom mold is used. Disclosed is a method in which, after being pushed up, blow air is further supplied so that the stretched preform is brought into close contact with a molding surface of a blow mold and molded into a bottle shape. According to such a method, the container bottom can be made thinner.

JP 2008-254244 A

Meanwhile, the synthetic resin container molded in Patent Document 1 has a raised bottom shape in which legs are formed on the peripheral side of the container bottom.
According to the study of the present inventors, the finding that when trying to mold a synthetic resin container having such a bottom shape by blow molding, a trace generally called sink mark is likely to be formed on the outer peripheral surface of the leg portion. However, when such sink marks occur, not only the appearance of the container is impaired, but also the strength of the container is reduced, so improvement is required.

  Therefore, the present inventors have conducted intensive studies to determine the cause of sink marks on the outer peripheral surface of the legs formed on the bottom when blow molding the synthetic resin container having the bottom shape. Thus, the present invention has been completed.

  That is, the present invention provides a leg bottom extending along the circumferential direction, an outer peripheral wall connected to an outer peripheral edge of the leg bottom and a lower end edge of the container body, and an inner peripheral wall rising from the inner peripheral edge of the leg bottom. In molding a synthetic resin container having a raised bottom-like bottom shape formed on the peripheral edge side by blow molding, the leg portion having the following structure is used, and the occurrence of sink marks on the outer peripheral wall portion of the leg portion is suppressed. The purpose is to provide.

The synthetic resin container according to the present invention is a synthetic resin container including a mouth, a shoulder, a trunk, and a bottom, wherein the bottom includes a bottom plate that exhibits reduced pressure absorption performance, and the bottom plate includes Around the leg bottom extending along the circumferential direction, an outer peripheral wall connected to an outer peripheral edge of the leg bottom and a lower end edge of the trunk, and an inner peripheral wall rising from the inner peripheral edge of the leg bottom. The raised leg portion is formed in a raised bottom shape, and a concave groove is formed on the outer peripheral wall portion continuously or intermittently along a circumferential direction, and formed so as to be juxtaposed along a height direction. There is a configuration.

  According to the present invention, when molding by blow molding a synthetic resin container having a raised bottom-like bottom shape in which legs are formed on the peripheral edge side of the container bottom, on the outer peripheral wall of the legs formed on the bottom, By forming at least one concave groove continuously or intermittently in the circumferential direction, the occurrence of sink marks on the outer peripheral wall portion can be suppressed.

It is a front view showing the outline of the container made of a synthetic resin concerning the embodiment of the present invention. It is a bottom view showing the outline of the container made of synthetic resin concerning the embodiment of the present invention. It is AA sectional drawing of FIG. It is a principal part expanded sectional view which shows the outline of the leg part formed in the bottom part of the synthetic resin container which concerns on embodiment of this invention. It is explanatory drawing which shows an example of the molding method of the synthetic resin container which concerns on embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  In the present embodiment, the container 1 is formed into a cylindrical preform having a bottom by, for example, injection molding or compression molding using a thermoplastic resin. It is manufactured by molding into a predetermined container shape having a mouth portion 2, a shoulder portion 3, a trunk portion 4, and a bottom portion 5 as shown.

  In manufacturing such a container 1, as the thermoplastic resin to be used, any resin capable of forming the container 1 as described above can be used. Specifically, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, polylactic acid or copolymers thereof, and those blended with these resins or other resins are preferable. It is. In particular, an ethylene terephthalate-based thermoplastic polyester such as polyethylene terephthalate is preferably used. Further, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene and the like can also be used.

The mouth portion 2 is a cylindrical portion on which a screw portion 21 for attaching a lid (not shown) is formed. The mouth portion 2 includes a portion having substantially the same diameter immediately below a support ring 22 generally formed in a container of this type, and has a frustoconical shoulder portion expanding in diameter toward the body portion 4. It is connected to 3.
FIG. 3 shows a cross section taken along the line AA in FIG. 1, but the thickness of a portion of the mouth portion 2 below the support ring 22 is omitted.

  In the present embodiment, the container 1 is provided in a so-called hot pack in which the contents sterilized by heat are filled and sealed at a high temperature. For this reason, when the inside of the container is cooled to room temperature after the hot pack and the inside of the container is decompressed, the body 4 is deformed inward to reduce the volume of the container 1 and absorb the reduced amount of the internal pressure. The reduced pressure absorbing panels 6 on the surface are arranged at predetermined intervals along the circumferential direction.

  Also, when hot-packing the contents, the weight and heat of the contents, and the pressure associated with the filling (filling fine pressure), make the inside of the container a positive pressure, and try to deform the container so as to expand outward. Load works. At this time, the decompression absorption panel 6 is expanded to the outside of the container, and then cooled to room temperature so as to be smoothly inverted when the inside of the container is in a reduced pressure state, so that the inward deformation of the container is not hindered. If so, the specific panel shape is not particularly limited. For this reason, in the example shown in FIG. 1, the illustration of the specific panel shape of the reduced-pressure absorption panel 6 provided on the peripheral surface of the body 4 is omitted.

  The body 4 is a portion that occupies most of the height direction of the container 1, and has a hexagonal cross-sectional shape orthogonal to the height direction of the portion where the decompression absorption panel 6 is provided, and a shoulder. The upper end connected to the portion 3 is an upper cylindrical portion 41, and the lower end connected to the bottom 5 is a lower cylindrical portion 42. Thereby, the container 1 of the present embodiment has a so-called round bottle-like container shape in which the cross-sectional shape is rounded as a whole.

  In the present embodiment, by providing a horizontal bead 43 extending annularly along the circumferential direction in each of the upper cylindrical portion 41 and the lower cylindrical portion 42 of the body 4, the lateral direction ( Although the load bearing strength in the direction perpendicular to the height direction is increased, these lateral beads 43 can be omitted as appropriate.

Here, the height direction refers to a direction perpendicular to the horizontal plane when the container 1 is erected on a horizontal plane with the mouth 2 up, and in this state, the vertical, horizontal, and vertical directions of the container 1 Shall be stipulated.

  In the present embodiment, as shown in FIGS. 2 and 3, the bottom 5 includes a bottom plate 50 that is indented into the container, and has a raised bottom shape in which a leg 51 is formed around the bottom plate 50. Have been. The leg portion 51 formed around the bottom plate portion 50 is connected to the leg bottom portion 51 c extending annularly with a predetermined width along the circumferential direction, and to the outer peripheral edge of the leg bottom portion 51 c and the lower end edge of the body portion 4. And an inner peripheral wall 51a rising from the inner peripheral edge of the leg bottom 51c.

The leg portion 51 can secure a sufficient ground contact area by setting the width W of the leg bottom portion 51c to 0.1 to 5.0 mm. However, the leg bottom portion 51c itself functions as a ground contact portion. Alternatively, as shown in FIG. 2, the grounding portions 51d may be provided at regular intervals in the circumferential direction.
Further, in order to ensure the load bearing strength of the leg portion 51, the upper end of the outer peripheral wall portion 51b (the outermost diameter portion of the leg portion 51), the radial distance L ₃ between the upper end of the inner circumferential wall 51a is 2 It is preferable that the inner peripheral wall portion 51a rises from the leg bottom portion 51c at an angle θ of 1 to 10 ° with respect to the height direction, and is connected to the bottom plate portion 50 via the connection portion 50a.

The container 1 having such a bottom shape can be formed using, for example, a blow mold as shown in FIG.
The blow mold 100 shown in FIG. 5 has a bottom mold 101 that can move up and down between a first blow mold position and a second blow mold position.
In order to mold the container 1 using such a blow mold 100, first, as shown in FIG. 5 (a), with the bottom mold 101 lowered to the first blow mold position, the blow mold 100 Is closed and heated and softened to set a preform P in a state in which blow molding is possible. Next, as shown by a two-dot chain line in the figure, the stretching rod 102 is moved down, and blow air is blown into the inside of the preform P from a blow air supply source (not shown) to perform first blow molding.

  At this time, the preform P can be uniformly stretched by appropriately adjusting the downward movement speed of the stretching rod 102, the pressure of the blow air, and the like. The mold 101 is raised to the second blow molding position, and the bottom side of the stretched preform P is pushed up. At this time, the stretching rod 102 is moved upward in synchronization with the movement of the bottom mold 101 so that the bottom side is sandwiched and pushed up by the bottom mold 101 and the stretching rod 102. Then, if necessary, second blow molding is performed by increasing the pressure of the blow air, and the stretched preform P is brought into close contact with the molding surface of the blow mold 100 to shape the shape (FIG. 5). (B)). Thereby, the bottom part 5 can be molded sufficiently and the container 1 thinned.

  Thereafter, cooling air CA for cooling is blown out from a blowout hole (not shown) provided in the stretching rod 102 to take out the molded container 1 after post-processing such as cooling treatment. In 1, a trace generally called sink is likely to be formed on the outer peripheral wall 51 b of the leg 51 formed on the bottom 5. The occurrence of such sink marks not only impairs the appearance of the container 1 but also causes the strength of the container 1 to decrease.

  There are various possible causes of such sink marks, but if there is a portion where a smooth flat surface or a curved surface exists in a relatively wide range, the portion tends to stick to the molding surface, and the portion tends to stick to the molding surface. When the mold is released, a load is applied to the attached portion so that the portion is deformed so as to be bent and peeled off from the molding surface. Then, if such a load is applied while the part adhered to the molding surface is not sufficiently cooled, it is considered that the trace is left as sink marks.

  Further, as described above, since the stretching rod 102 moves upward in synchronization with the movement of the bottom mold 101 and is located at a position away from the legs 51 formed on the bottom 5 of the container 1, the stretching rod 102 The cooling air CA that has been blown out cannot reach the leg portion 51 easily. Further, the leg portion 51 includes an inner peripheral wall portion 51a rising from the leg bottom portion 51c, and the inner peripheral wall portion 51a makes it difficult for the cooling air CA to reach the inside of the leg portion 51.

From these facts, the present inventors believe that the container 1 can be taken out without sufficiently cooling the outer peripheral wall 51b of the leg 51 attached to the molding surface. I came to think that this was the cause of sink marks.
Therefore, in the present embodiment, even when the container 1 is taken out without sufficiently cooling the outer peripheral wall portion 51b of the leg portion 51 at the time of blow molding, the outer peripheral wall portion 51b hardly sticks to the molding surface. Based on the idea of suppressing sink marks, the following configuration was adopted.

  That is, in the present embodiment, four concave grooves 52 formed along the circumferential direction are arranged in the outer peripheral wall portion 51b of the leg portion 51 formed on the bottom portion 5 of the container 1 along the height direction. Is formed. Thereby, the unevenness is provided on the outer peripheral wall portion 51b so that sticking to the molding surface is effectively avoided, and unnecessary load is not applied when the molded container 1 is removed from the blow mold 100. Thus, the occurrence of sink marks on the outer peripheral wall 51b can be suppressed.

  As long as such an effect is achieved, at least one concave groove 52 may be formed in the outer peripheral wall portion 51b, and the number of the concave grooves 52 formed in the outer peripheral wall portion 51b depends on the design of the entire container. Can be set as appropriate while taking into account the balance of. Furthermore, the concave grooves 52 may be formed continuously along the circumferential direction, or may be formed at regular intervals or intermittently at irregular intervals.

  In the present embodiment, the concave groove 52 is formed in a V-groove shape having a linear groove bottom, so that the outer peripheral wall portion 51b has a vertical cross-sectional shape along the height direction outside the container. It is preferable to be formed so as to be divided into a plurality of curved surfaces 53 each having a convex arc shape. In this case, the line of intersection of two vertically adjacent curved surfaces 53 becomes the groove bottom of the concave groove 52.

FIG. 4 is an enlarged view of a portion surrounded by a chain line in FIG. 3. As shown in FIG. 4, a curved surface 53 formed above and below the concave groove 52 has a vertical cross-sectional shape along the height direction outside the container having a radius of curvature of 2 to 5 mm. It is preferable to form the convex arc.
If the ratio is less than the above range, the shapeability is poor, and it tends to be difficult to form the curved surface 53 into a desired shape. On the other hand, if it exceeds the above range, the effect of suppressing the occurrence of sink marks on the outer peripheral wall 51b tends to be weakened.

Further, of at least one of the grooves 52 formed in the outer peripheral wall portion 51b, a radial distance between the lowest groove 52 and the leg bottom portion 51c (the concave portion along the direction orthogonal to the height direction). distance) _{L 0} between the groove 52 and the Ashisoko portion 51c is preferably a 1.5 to 3.0 mm.
If the ratio is less than the above range, the shapeability is poor, and it tends to be difficult to form the curved surface 53 into a desired shape. On the other hand, if it exceeds the above range, the effect of suppressing the occurrence of sink marks on the outer peripheral wall 51b tends to be weakened.

Further, it is preferable that the height H (the separation distance from the leg bottom portion 51c along the height direction) H of the connecting portion 50a between the bottom plate portion 50 and the inner peripheral wall portion 51a of the leg portion 51 is 4 to 12 mm.
If the thickness is less than the above range, the thickness of the bottom plate portion 50 and the inner peripheral wall portion 51a of the leg portion 51 tends to be increased during blow molding. On the other hand, if the thickness exceeds the above range, the thickness of the bottom plate portion 50 and the inner peripheral wall portion 51a of the leg portion 51 becomes too thin during blow molding, and the durability tends to be poor. Can be

  In the present embodiment, the above numerical range is set by taking the container 1 having a capacity of 500 ml as an example, and these numerical values can be appropriately adjusted according to the capacity of the container 1.

  Further, the container 1 of the present embodiment is subjected to a hot pack, and when hot-packing the contents, the inside of the container is subjected to a positive pressure due to the weight and heat of the contents, and furthermore, the pressure accompanying the filling (filling small pressure). As described above, the load acting to deform the container 1 so as to swell outward acts as described above.

For this reason, when the pressure in the container decreases after the hot pack, the bottom plate portion 50 deforms inwardly of the container, reduces the volume of the container 1 together with the above-described reduced pressure absorbing panel 6, and absorbs the decrease in the internal pressure. It is preferable to configure as follows.
Here, in the present embodiment, the peripheral edge side of the bottom plate portion 50 is connected to the inner peripheral wall portion 51a while rising up into the container, and the vertical cross-sectional shape along the height direction of the connecting portion 50a is set to be inward of the container. The shape is curved so as to be convex. Thereby, the connecting portion 50a is used as a hinge so that the bottom plate portion 50 can be deformed inward of the container.
Note that if the bottom plate portion 50 can deform to the inside of the container to exhibit a sufficient reduced pressure absorbing function, the reduced pressure absorbing panel 6 provided on the body portion 4 can be omitted as necessary.

When the bottom plate 50 is deformed inward to exhibit reduced pressure absorption performance, the larger the area of the bottom plate 50, the more the reduced pressure absorption performance can be exhibited. For this reason, the ratio L ₂ / L ₁ of the radial distance L ₂ from the center of the bottom plate 50 to the upper end of the inner peripheral wall 51a to the radial distance L ₁ from the center of the bottom plate 50 to the upper end of the outer peripheral wall 51b. Is preferably 0.70 to 0.95 so that the area of the bottom plate 50 can be sufficiently secured.

  As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the above-described embodiments, and it is needless to say that various modifications can be made within the scope of the present invention. Nor.

  For example, in the above-described embodiment, an example is described in which the present invention is applied to a round bottle-shaped synthetic resin container, but the present invention is not limited to this. The present invention can be applied to various synthetic resin containers having a raised bottom shape in which legs are formed on the peripheral side of the container bottom, and a so-called rectangular or rectangular cross-sectional shape is used. The present invention can also be applied to a square bottle-shaped synthetic resin container or a synthetic resin container having an elliptical cross section.

  Further, in the above-described embodiment, the example in which the container is formed by the blow mold having the movable bottom mold has been described, but the embodiment is not limited thereto. Even when the blow mold does not have a movable bottom mold, when blow molding a bottom-shaped container with a raised bottom, cooling air ejected from a stretching rod located at a position away from the legs, The legs may not be reachable. In such a case, the present invention can be suitably applied.

  INDUSTRIAL APPLICABILITY The present invention as described above can be applied to a synthetic resin container generally used in a wide field as a container containing various beverages and the like.

DESCRIPTION OF SYMBOLS 1 Container 2 Mouth part 3 Shoulder part 4 Body part 5 Bottom part 50 Bottom plate part 50a Connecting part 51 Leg part 51a Inner peripheral wall part 51b Outer peripheral wall part 51c Leg bottom part 52 Recessed groove 53 Curved surface

Claims (9)

A synthetic resin container having a mouth, a shoulder, a trunk, and a bottom,
The bottom portion includes a bottom plate portion exhibiting a reduced pressure absorbing performance, and is connected around a circumference of the bottom plate portion, a leg bottom portion extending along a circumferential direction, and an outer peripheral edge of the leg bottom portion and a lower end edge of the trunk portion. An outer peripheral wall portion, and a leg portion having an inner peripheral wall portion rising from the inner peripheral edge of the leg bottom portion is formed as a raised bottom shape,
A synthetic resin container , wherein a concave groove is formed in the outer peripheral wall portion continuously or intermittently in a circumferential direction and is formed so as to be juxtaposed in a height direction .   The synthetic resin container according to claim 1, wherein the concave groove divides the outer peripheral wall portion into a plurality of curved surfaces whose vertical cross-sectional shape along the height direction is formed into an arc shape convex outwardly of the container. . The synthetic resin container according to claim 2 , wherein a vertical cross-sectional shape of the curved surface is an arc having a radius of curvature of 2 to 5 mm.   The synthetic resin according to any one of claims 1 to 3, wherein a radial distance between the lowest one of the grooves and the bottom of the leg is 1.5 to 3.0 mm. container.   The synthetic resin container according to any one of claims 1 to 4, wherein a height of a connecting portion between the bottom plate portion and the inner peripheral wall portion is 4 to 12 mm.   The synthetic resin container according to any one of claims 1 to 5, wherein the bottom plate portion is deformable inward of the container.   The ratio of the radial distance from the center of the bottom plate portion to the upper end of the inner peripheral wall portion with respect to the radial distance from the center of the bottom plate portion to the upper end of the outer peripheral wall portion is 0.70 to 0.95. The container made of a synthetic resin according to any one of claims 6 to 6.   The synthetic resin container according to any one of claims 1 to 7, wherein a radial distance between an upper end of the outer peripheral wall and an upper end of the inner peripheral wall is 2 to 8 mm. The synthetic resin container according to any one of claims 1 to 8, wherein an angle of the inner peripheral wall portion with respect to a height direction is 1 to 10 °.