JP6691655B2 - Synthetic resin container - Google Patents

Description

  The present invention relates to a synthetic resin container having a reduced pressure absorption performance at the bottom, more specifically, having a bottom structure capable of coping with changes in internal pressure due to hot filling and subsequent reduced pressure absorption, and The present invention relates to a synthetic resin container which is excellent in self-sustaining property, bottom portion, and shape stability of the container.

  BACKGROUND ART Containers made of synthetic resin are widely used as packaging containers for various liquids because they are lightweight and have excellent impact resistance. In particular, a stretch-molded container formed by stretch-blow molding polyethylene terephthalate (PET) has a combination of transparency, gas barrier property, light weight, impact resistance, appropriate rigidity, etc., and is used for containing a liquid content. Widely used as a packaging container.

  Hot filling of the contents to enhance the storability of the contents is widely performed in synthetic resin containers such as polyester, but in the synthetic resin containers due to volumetric shrinkage of the contents due to cooling. Decompression deformation always occurs. In order to prevent this, various synthetic resin containers having a bottom portion provided with a reduced-pressure absorption performance have been proposed (Patent Documents 1 to 3).

JP2012-91830A Japanese Patent No. 5408501 JP, 2013-144560, A

All of the synthetic resin containers having the bottom shape described in Patent Documents 1 to 3 above exhibit the decompression performance by deforming the bottom-bottomed bottom surface of the bottom part toward the inside of the container during decompression. Various improvements such as increasing the amount of movement of the bottom surface have been made in order to exert a better reduced-pressure absorption performance.
However, at the bottom having a structure that is greatly deformed inward of the container, the contents are filled by hot filling, and when the weight and heat of the contents act on the bottom of the raised bottom, the bottom of the raised bottom forms. The container may protrude below the ground plane of the container, impairing the self-supporting property of the container.
In addition, due to the thickness distribution of the bottom surface, the filling conditions and the surrounding environment, when the internal pressure changes after filling and the inside of the container is depressurized and the bottom surface deforms inward of the container, the desired deformation is obtained. However, there is a possibility that it may be deformed unevenly and the shape stability of the bottom or the container may be impaired.

  Therefore, the object of the present invention is to have an excellent decompression absorption performance, and also to have a bottom structure capable of coping with changes in internal pressure due to hot filling and subsequent decompression absorption. An object of the present invention is to provide a synthetic resin container having excellent properties.

  According to the present invention, the bottom is a synthetic resin container having reduced pressure absorption performance, wherein the bottom is formed with a leg including an outer peripheral wall continuous with the body, a grounding part and an inner peripheral wall. A movable bottom portion, which is located above the ground contact portion, is formed inside the inner peripheral wall, and between the outer edge of the movable bottom portion and the inner edge that is in contact with the central portion, radially protrudes, and a plurality of them are formed in the circumferential direction. There is provided a container made of synthetic resin, which is provided with a curved portion and a groove portion that connects the inner edge of the movable bottom portion so as to be located above the outer edge in the container axial direction between the curved portions.

In the synthetic resin container of the present invention,
1. The groove portion is formed radially,
2. The groove portion has a curved bottom portion protruding downward,
3. The depth of the groove portion is 0.1 to 3.0 mm at the center position between the inner and outer edges of the movable bottom portion,
4. The angle of inclination of the curved bottom with respect to the horizontal direction is 2 to 15 ° at the center position between the inner and outer edges of the movable bottom,
5. The radius of curvature R of the curved bottom is 30 to 300 mm,
6. The width of the groove portion is wider or narrower than the width of the inner and outer edges at the center position between the inner and outer edges of the movable bottom portion,
7. At the boundary between the inner edge of the movable bottom portion and the outer edge of the central portion, an annular projection protruding downward is formed,
8. A folded-back portion is formed at an upper end of an inner peripheral wall of the leg portion, and an inner edge of the folded-back portion is connected to the movable bottom portion so as to coincide with a position of an outer edge of the movable bottom portion.
9. The central portion of the movable bottom portion projects upward or downward,
Is preferred.

In the synthetic resin container of the present invention, the leg portion formed at the bottom of the container is radially inwardly projected, and a plurality of curved portions formed in the circumferential direction and inclined upward toward the central portion between the curved portions. A movable bottom formed of a groove is formed. According to such a configuration, it is possible to increase the distance (height distance) between the movable bottom portion and the ground contact surface, and when the movable bottom portion projects downward due to the heat of the contents or its own weight during hot filling, It is possible to prevent the movable bottom from protruding beyond the ground contact surface.
Also, when the weight and heat of the contents are applied due to hot filling or the like, the groove that inclines upward absorbs the bending that occurs in the radial direction of the bottom part, while the stress that tries to return to the original shape (upward inclined state) acts. Therefore, when the contents are cooled and the inside of the container is depressurized, it is possible to smoothly move the entire movable bottom portion upward by utilizing the above-described action.
In the synthetic resin container of the present invention, the leg portion that does not contribute to absorption of reduced pressure is formed in the bottom portion, and as described above, since the downward deformation amount of the movable bottom portion is controlled, the internal pressure changes. In addition, the height of the container can always be kept constant, the self-supporting property of the container is maintained, and the transportability is excellent.

It is a side view which shows an example of the synthetic resin container of this invention. FIG. 2 is a bottom view (A) and a partial sectional view (B) of the synthetic resin container shown in FIG. 1. It is a partial expanded sectional view of the bottom part for demonstrating the movable behavior of the synthetic resin container shown in FIG. 2A is a sectional view taken along the line aa in FIG. 2A, and FIG. 2B is a sectional view taken along the line bb in FIG. 2A. 2A and 2B are partial cross-sectional views for explaining the behavior of the bottom portion of the synthetic resin container shown in FIG. 1, in which (A) is an empty state, (B) is a state immediately after hot filling, and (C) is a hot state. It is a figure which shows the pressure-reduced state after filling and (D) which piled up (A)-(C), respectively. It is a side view which shows another embodiment of the synthetic resin container of this invention. FIG. 6 is a bottom view (A) and a partial sectional view (B) of the synthetic resin container shown in FIG. 5. FIG. 6 is a partially enlarged cross-sectional view of a bottom portion for explaining the movable behavior of the synthetic resin container shown in FIG. 5. 6A is a sectional view taken along line aa in FIG. 6A, and FIG. 6B is a sectional view taken along line bb in FIG. 6A. FIG. 6 is a bottom view showing another example of the synthetic resin container shown in FIG. 5.

The synthetic resin container of the present invention will be described based on a specific example shown in the accompanying drawings.
The synthetic resin container 1 of the present invention shown in FIG. 1 comprises a mouth part 2, a shoulder part 3, a body part 4 and a bottom part 5, and the body part 4 is an upper body part 4 a connected from the shoulder part 3 and a lower part connected to the bottom part. It comprises a body 4b, an upper body 4a and a central body 4c located between the lower body 4b.
The central body portion 4c has three circumferential ribs 6, 6, 6 formed in parallel and at equal intervals, so that the mechanical strength of the body portion and the shape-retaining property against internal pressure deformation are secured. The outer peripheral surface excluding the ribs 6 is formed straight in the axial direction, and it is possible to wind a label (not shown) around the body part once.
In the specific example shown in the figure, ribs 7 are also formed between the lower body portion 4b and the bottom portion 5 to clearly define the body portion 4 and the bottom portion 5, but the body portion and the bottom portion are not always clearly defined. You don't have to.

  The bottom part 5 roughly comprises an annular leg part 8 and a movable bottom part 9 located inside the leg part 8. The leg portion 8 is located below the rib 7 and is composed of an outer peripheral wall 8a continuous from the body portion 4, a ground contact portion 8b, and an inner peripheral wall 8c that rises upward from the ground contact portion 8b. As is clear from FIGS. 2B and 3, the movable bottom portion 9 is located above the ground contact portion 8b and is connected to the upper end of the inner peripheral wall 8c of the leg portion 8.

At the center of the movable bottom portion 9, there is formed a substantially flat central portion 12 defined by an annular projection 11 projecting downward, and the central portion 12 is located at the highest position in the axial direction of the container as a whole in the movable bottom portion 9. is doing. Although the annular protrusion 11 is not necessarily formed, it is formed at the boundary between the inner edge of the movable bottom portion 9 and the outer edge of the central portion 12 as in the present embodiment, so that the movable bottom portion 9 can be moved in accordance with the movement of the movable bottom portion 9. It is possible to absorb the bending in the radial direction that occurs as a result.
Further, as is clear from FIG. 2 (A), in the movable bottom portion 9, between the outer edge of the movable bottom portion 9 and the inner edge in contact with the central portion 12 (the outer edge of the annular protrusion 11 when the annular protrusion 11 is formed), A plurality of curved portions 13 protruding downward in the radial direction are formed at equal intervals in the circumferential direction (16 radially in FIG. 2), and an inner edge that is in contact with the central portion 12 between the adjacent curved portions 13 and 13. A plurality (16 in FIG. 2) of groove portions 14 extending from (the outer edge of the annular protrusion 11) toward the outer edge of the movable bottom portion 9 are formed at equal intervals. As shown in the figure, it is desirable that the curved portions 13 and the groove portions 14 are formed in a uniform shape and radially at equal intervals in order to ensure uniform deformation when the contents are filled or when the pressure is reduced.

As is clear from FIG. 2, the groove portion 14 has a curved bottom portion 14 a protruding downward, is inclined upward from the outer edge of the movable bottom portion 9 toward the central portion 12, and is located at the central portion 12 more than the outer edge of the movable bottom portion 9. The inner edge (outer edge of the annular projection 11) that contacts with is formed so as to be located above in the axial direction of the container.
The groove portion 14 absorbs the bending that occurs in the radial direction of the bottom portion when the weight of the contents, or further heat due to hot filling or the like, and smoothly restores the original shape (upward tilted state) when decompressing. It is preferable to set the depth and width of the groove, the inclination angle of the curved bottom portion, and the radius of curvature so that the shape restoring action can be exhibited.
As shown in FIG. 3A, the depth D of the groove is near the center position M1 between the inner and outer edges of the movable bottom 9 (in the specific example shown, the inner edge is the outer edge of the annular projection 11). It is preferably the deepest, and the depth D is preferably in the range of 0.1 to 3.0 mm, and the depth D can be appropriately adjusted in the radial direction of the groove. Note that, as shown in FIG. 3A, the center position M1 is specifically defined by drawing a line segment X1 connecting the inner and outer edges of the movable bottom 9 in the groove 14 and passing through the midpoint of the line segment X1. It means a point where a straight line Y1 perpendicular to and the curved bottom portion 14a of the groove portion intersect. The depth D is represented by the difference between the distance D1 between the line segment X1 and the point M1 and the distance D2 between the line segment X2 and the point M2, that is, D2-D1 with reference to FIGS. To be done. The line segment X2 is a line segment that connects the inner and outer edges of the movable bottom portion 9 in the bending portion 13, and M2 is a straight line Y2 that passes through the midpoint of the line segment X2 and is perpendicular to the line segment X2 and the bending portion 13. It is the point of intersection.
Further, in the specific example shown in FIG. 2A, the circumferential width of the groove portion is formed in a substantially spindle shape having the largest width in the vicinity of the central position M1, but the inner and outer edges of the movable bottom portion 9 are formed. Even if it is formed to have a wide width in the vicinity and the narrowest width in the vicinity of the center position M1, the above-described convex deformation and restoration are facilitated, which is preferable.
The inclination angle θ of the curved bottom portion 14a of the groove with respect to the horizontal direction is preferably in the range of 2 to 15 ° at the center position M1. Specifically, as shown in FIG. 3A, the inclination angle θ is expressed by an angle of the tangent Z with respect to the horizontal direction by drawing the tangent Z of the curved bottom portion 14a of the groove at the center position M1. .
Furthermore, the curvature radius R of the curved bottom portion 14a of the groove portion is preferably in the range of 30 to 300 mm. As a result, when the movable bottom portion 9 moves from the outer edge of the movable bottom portion 9 as a starting point, it is possible to reduce the bending that occurs in the radial direction as compared with the case of the linear shape.

  By making the thickness of the groove portion 14 that absorbs the bending generated in the radial direction of the bottom portion thin, when the weight and heat act due to hot filling or the like, the adjacent curved portions 13 widen their intervals, Further, when the pressure is reduced, the adjacent curved portions 13 are easily bent so as to narrow the space between them, and the entire movable bottom portion 9 can be uniformly and gently moved upward.

In FIG. 4 for explaining the fluctuation of the bottom portion of the synthetic resin container according to the present invention in accordance with the change of the internal pressure, (A) is an empty state, (B) is a state immediately after hot filling (for example, 87 ° C.), ( (C) is a partial cross-sectional view showing a reduced pressure state after filling (B), and (D) is a view in which (A) to (C) are superimposed.
In the synthetic resin container 1 of the present invention, regardless of the filling temperature, immediately after the contents are filled (B), the movable bottom portion 9 moves below the empty state (A) due to the weight of the contents. However, even if it is filled and sealed at a high temperature of 87 ° C., the movable bottom portion does not move excessively downward due to the formation of the groove portion 14 as described above. Further, in the case of being cooled after hot filling and being in a reduced pressure state (C), the movable bottom 9 is smoothly moved upward by utilizing the shape restoring action of the groove portion 14, and after the reduced pressure is absorbed. The movable bottom portion 9 is located above the empty state (A).
As is clear from FIG. 4 (D) which is a superposition of these figures, the synthetic resin container of the present invention is movable even when the contents are filled at a high temperature and the weight and heat of the contents act. The bottom portion 9 does not move excessively downward, and even when it is in a depressurized state thereafter, the bottom portion 9 is gently deformed and rises inward of the container, thereby exhibiting a desired depressurized absorption performance. be able to.

Next, another embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, as is clear from FIG. 5, particularly FIG. 6 (B) and FIG. 7, the upper end of the inner peripheral wall 8c of the leg portion 8 projects upward from the upper end of the inner peripheral wall 8c, and then goes downward. An annular folded-back portion 15 that is folded back is formed, and an inner edge 15a of the folded-back portion 15 is connected to match the position of the outer edge of the movable bottom portion 9, so that the synthetic resin container 1 of the present invention shown in FIG. Is different from
Although the depth of the folded-back portion 15 is not limited to this, the vertical distance from the upper end of the folded-back portion to the inner edge 15a of the folded-back portion is preferably in the range of 0.5 to 3.0 mm. If the folded-back portion is shallower than the above range, the inner peripheral wall 8c of the leg portion 8 is more likely to fall inward when the movable bottom 9 moves downward, as compared with the case where the folded back portion is in the above range. When it is larger than the above range, the moldability becomes inferior to that in the above range.

  As described above, since the movable bottom portion 9 is connected to the inner peripheral wall 8c of the leg portion 8 via the folded-back portion 15 having an appropriate depth, the weight and heat of the contents due to hot filling or the like can be applied to the movable bottom portion. Even when acting on 9, the inner peripheral wall 8c of the leg portion 8 is prevented from being excessively retracted (inwardly collapsed) toward the center of the movable bottom portion 9, and the inner edge 15a of the folded portion 15 is also excessively retracted. Is effectively prevented. As a result, even if it is subjected to hot filling or the like, the movable bottom portion 9 does not excessively project downward, or uneven deformation does not occur. It can also be used for hot filling.

The synthetic resin container of the present invention is not limited to the specific examples described above, and various modifications can be made.
That is, in the specific example shown in the drawing, the curved portions 13, 13 ... And the groove portions 14, 14 ... Are formed in 16 pieces respectively, but the invention is not limited to this. Although it depends on the diameter of the movable bottom portion 9, a range of 3 to 36 pieces is preferable in order to increase the movable area of the movable bottom portion and to exert a greater reduced pressure absorption performance. desirable. If the number is less than 3, the bending width at the time of decompression may be smaller than that in the above range, and the decompression performance may be deteriorated. If the number exceeds 36, the above range may be exceeded. .., the width of the groove portions 14, 14, ... Is smaller, which may make molding difficult.
Further, the curved portions 13, 13 ... Are not limited to the shapes shown in the figures as long as the adjacent groove portions 14, 14 ... Can be restored, but ensure a movable region capable of coping with a large change in internal pressure. In order to do so, it is preferable that the shape projects downward as in the specific example shown in the figure.
Further, although not shown, an annular groove portion formed concentrically from the center of the central portion 12 is formed to divide the curved portions 13, 13, ... And the groove portions 14, 14 ... In the radial direction. As a result, the movable bottom portion 9 can be further easily bent and can be smoothly moved in the vertical direction. The intervals at which the above-mentioned annular groove portions are arranged are not particularly limited, but equal intervals are preferable.
Further, the groove portion 14 may be formed so that the inner edge of the movable bottom portion 9 is located above the outer edge in the container axial direction, and has a portion that is inclined downward in the radial direction of the bottom portion. Good.

Further, although the folded-back portion 15 shown in the drawing is formed in an annular shape, when the rigidity is insufficient due to a problem such as wall thickness, the folded-back portion 15 is formed in the curved portion 13 as shown in FIG. It is preferable not to form the corresponding portions, but to form them at intervals corresponding to the groove portions 14. As a result, it is possible to effectively prevent the inner edge 15a of the folded-back portion 15 from inclining in accordance with the movement of the movable bottom portion.
Further, in the specific example shown in the drawings, the central portion 12 of the movable bottom portion 9 is formed to be substantially flat, but it may be projected outward or inward of the movable bottom portion 9, whereby the central portion 12 is formed. Can be made thinner, and a greater reduced pressure absorption performance can be exhibited. Further, as described above, the annular protrusion 11 is not always necessary, but since the annular protrusion is formed at the boundary between the inner edge of the movable bottom portion 9 and the outer edge of the central portion 12, a radial direction generated according to the movement of the movable bottom portion 9 is generated. It becomes possible to absorb the bending.
Furthermore, in the specific example shown in the drawings, the outer edge of the movable bottom portion 9 is formed in a circular shape, but the present invention is not limited to this, and depending on the shape and width of the curved portion and the groove portion, a polygonal shape, a petal shape, or the like. Can be changed appropriately.

It is preferable that the movable bottom portion 9 has an outer diameter of 85 to 95% of the diameter of the ground contact portion of the bottom portion in order to secure the self-supporting property of the container and the vacuum absorbing performance. The central portion 12 of the movable bottom portion 9 preferably has an outer diameter of 20 to 35% of the outer diameter of the movable bottom portion 9.
Further, it is preferable that the circle connecting the tops of the curved portions 13, 13 ... Has a diameter of 60 to 90% of the outer diameter of the movable bottom portion 9. If it is less than 60% of the outer diameter of the movable bottom portion 9, there is a possibility that the bending width at the time of depressurization becomes smaller than that in the above range, and the depressurization absorption performance is reduced. If it exceeds%, the angle with the inner peripheral wall becomes steeper than in the above range, and molding may be difficult.
Further, in the synthetic resin container of the present invention, it is preferable that the thickness of the bottom portion is equal to or less than the thickness of the thinnest portion of the body portion, and depending on the diameter of the movable bottom portion 9, It is desirable that the thickness is reduced to within the range of 0.15 to 0.4 mm, preferably 0.2 to 0.3 mm.
Furthermore, it is preferable to increase the degree of crystallinity in order to suppress inward collapse of the inner peripheral wall 8c of the leg portion 8. Specifically, when at least the inner peripheral wall 8c of the leg portion 8 and the folded portion 15 are formed, The crystallinity including the folded-back portion 15 is preferably 30% to 50%.

In the synthetic resin container of the present invention, as long as it has the above-mentioned bottom shape, it can be molded by a conventionally known synthetic resin container manufacturing method, but it is possible to move the movable bottom part 9 up and down due to a change in internal pressure of the container. In this regard, since it is important that the movable bottom portion 9 is thin, it is preferable to form the movable bottom portion 9 by a stretch blow molding method capable of forming the thin portion.
In the stretch blow molding, a preform made of a thermoplastic polyester resin such as polyethylene terephthalate is molded using a bottom mold capable of shaping the bottom shape described above on the bottom of the container.
At this time, since the concave-convex shape including the folded-back portion 15, the curved portions 13, 13, ... And the groove portions 14, 14 ... Is formed on the bottom portion, the bottom die is improved in order to improve releasability. It is preferable that the mold has a rough surface. Therefore, even in the molded synthetic resin container, the surface of the movable bottom portion 9 that comes into contact with the bottom mold, and further the surface of the inner peripheral wall 8c of the leg portion 8 is formed into a rough surface.

In the synthetic resin container of the present invention, a thermoplastic polyester resin which has been conventionally used for stretch blow molding, particularly an ethylene terephthalate thermoplastic polyester is advantageously used, but of course, polybutylene terephthalate, polyethylene naphthalate, etc. It is also possible to use a blend with another polyester or a polycarbonate, an arylate resin, or the like.
Further, not only a single layer of the above thermoplastic polyester resin but also a multilayer structure of the above thermoplastic polyester resin and a gas barrier resin or an oxygen absorbing resin may be used, and heat resistance capable of withstanding hot filling at high temperature may be obtained. For the purpose of application, the mouth of the preform used is preferably thermally crystallized.
As for the stretch blow molding conditions, as long as a bottom mold capable of imparting the above-mentioned shape to the bottom can be used, molding can be performed under conventionally known molding conditions, and one-stage blow molding as well as two-stage blow molding can be performed. It is preferable that it is heat-fixed from the viewpoint of heat resistance.

In the synthetic resin container of the present invention, the bottom portion which does not affect the appearance of the container is provided with the reduced-pressure absorption performance, and thus can be effectively used as a container for seasonings and the like filled by hot filling.
In addition to such contents, the present invention can be applied to contents filled at a relatively high temperature.

  DESCRIPTION OF SYMBOLS 1 synthetic resin container, 2 mouth parts, 3 shoulder parts, 4 body parts, 5 bottom parts, 6 ribs, 8 leg parts, 9 movable bottom parts, 11 annular protrusions, 12 central parts, 13 curved parts, 14 groove parts, 14a curved bottom parts , 15 Folded part.

Claims (6)

The bottom portion 5 that closes the lower end of the body portion 4 is a synthetic resin container having reduced pressure absorption performance,
The bottom portion 5 has a ring-shaped leg portion 8 and a movable bottom portion 9 surrounded by the leg portion 8,
The leg portion 8 includes a ground portion 8b, an outer peripheral wall 8a extending upward from the outer peripheral edge of the ground portion 8b and connected to the lower end of the body 4, and an inner peripheral wall 8c rising from the inner peripheral edge of the ground portion 8b. ,
The movable bottom portion 9 is located above the ground contact portion 8b,
The movable bottom portion 9 has a circular central portion 12 and an annular movable wall portion that extends from the central portion 12 and is continuous with the upper end of the inner peripheral wall 8c of the leg portion 8,
The movable wall portion is inclined upward toward the central portion 12,
The movable wall portion has a curved portion 13 that is curved downward in a convex shape,
The movable wall portion has a groove portion 14 extending in the radial direction,
The groove portions 14 are formed in the movable wall portion at regular intervals in the circumferential direction ,
A synthetic resin container having an annular projection 11 extending from the central portion 12 and connected to an upper end of the movable wall portion . Said movable wall portion within the synthetic resin container according to claim 1 wherein the continuous to the upper end of the peripheral wall 8c of the legs 8 via the folded portion 15. The groove 14, the synthetic resin container according to claim 1 or 2 has a curved bottom portion protruding downward.   The synthetic resin container according to claim 1, wherein the groove portion 14 has a depth of 0.1 to 3.0 mm at a central position between inner and outer edges of the movable bottom portion 9. The synthetic resin container according to claim 3 or 4 , wherein an inclination angle of the curved bottom portion with respect to the horizontal direction is 2 to 15 ° at a central position between inner and outer edges of the movable bottom portion 9. The synthetic resin container according to any one of claims 3 to 5 , wherein a radius of curvature R of the curved bottom portion is 30 to 300 mm.