JP6143213B1 - Plastic bottle - Google Patents

Abstract

An object of the present invention is to provide a plastic bottle having a pressure resistance that has a simple structure and hardly deforms the bottom even when pressure is generated inside the bottle. A plastic bottle having a body part (40) and a bottom part (50), wherein the bottom part is an annular bottom grounding part (51), an annular outer wall surface (52) connecting the bottom grounding part and the trunk part, and An inner wall surface 53 connecting the bottom grounding portion and the center of the bottom portion is provided, the outer wall surface is reduced in diameter downward from the trunk portion toward the bottom grounding portion, and the inner wall surface extends from the center of the bottom portion to the bottom. The diameter is expanded downward toward the grounding portion, and the outer wall surface and the inner wall surface are connected at the bottom grounding portion to form a convex portion 57 that is convex downward in the bottle, and the convex portion is formed on the inner wall surface side. A plastic bottle having a curvature radius of 1.0 mm or more and 3.0 mm or less, an inner wall angle of 20 degrees or more and 70 degrees or less, and a thickness of the bottom grounding portion of more than 0.35 mm and 0.80 mm or less. [Selection] Figure 2

Description

  The present invention relates to a plastic bottle for filling a liquid, and more particularly to a plastic bottle for filling a beverage, especially an alcoholic beverage.

  In recent years, plastic bottles obtained by stretch blow molding plastics such as polyethylene terephthalate and polyethylene naphthalate are widely used as containers for filling various beverages because they are superior in impact resistance and lightweight compared to glass. ing. Moreover, it is used also as a container filled with beverages containing volatile components such as carbonated beverages and alcoholic beverages by improving the strength by biaxial stretch blow molding and heat setting.

Patent Document 1 discloses a plastic bottle having a rib structure at the ends of a plurality of legs at the bottom as a plastic bottle having high pressure resistance and impact resistance, even when it is thinned for weight reduction. Have been described.
Patent Document 2 describes a container capable of adjusting the vacuum pressure generated by hot pack filling.
Further, in Patent Document 3, the concave portion of the bottom of the container is prevented from reversing outward even when affected by the increase in internal pressure due to the temperature rise of the stored liquid, so that the container does not fall down during heating or the like. A plastic container is described.

JP 2011-20686 A JP 2011-79585 A Japanese Patent Laid-Open No. 9-240651

However, the bottom part of the plastic bottle of Patent Document 1 has a petaloid shape, and the leg shape tip tends to have insufficient mold shape fidelity due to overstretching. The bottle is tilted and the appearance is liable to be impaired.
The plastic bottle of Patent Document 2 is a plastic container having a bottom that can absorb negative pressure when the inside of the bottle is negative pressure, and does not have pressure resistance when the inside of the bottle is positive pressure. When the pressure is applied, the bottle bottom center part protrudes from the grounding part, and the bottle cannot easily stand upright.
In addition, the plastic container of Patent Document 3 gives heat resistance by increasing the degree of biaxial stretching in the side wall part of the bottom part and heat setting, but it is required to reduce the weight of the entire container in recent years. When responding to the above, there is a possibility that the thinning of the bottom side wall portion may lead to insufficient strength. In addition, in order to obtain a target function in the manufacturing method, it is necessary to heat (heat set) the bottom of the bottle, so that the blow mold temperature control circuit of the bottle molding machine becomes complicated and the utility cost increases.

  In addition, when filling a beverage with a high temperature of 50 ° C. or higher, the inside of the bottle may be decompressed after being allowed to cool, and a body dent may be formed. The pressure may be increased. This method can reduce the amount of oxygen that enters the inside of the bottle, so it is preferable from the viewpoint of maintaining the quality of the beverage. However, when the internal pressure during filling is high, the grounding part and the recess at the bottom of the bottle jump out of the bottle. There was a case. In this case, not only can the bottle not stand upright, but the pressure inside the bottle is reduced by the amount of protrusion, and there is a case in which the bottle body is recessed after cooling the bottle and the aesthetic appearance is impaired.

  As described above, it is an object of the present invention to provide a plastic bottle having a pressure resistance that has a simple structure and hardly deforms the bottom even when a pressure is generated inside the bottle.

  As a result of intensive studies, the present inventor has found that the above problem can be solved by making the bottom of the plastic bottle a predetermined shape. Hereinafter, for reference, reference numerals of the corresponding drawings are shown in parentheses. The present invention is not limited to the form described in the drawings.

The first embodiment is a plastic bottle (100) having a barrel (40) and a bottom (50),
The bottom part (50) includes an annular bottom grounding part (51), an annular outer wall surface (52) connecting the bottom grounding part (51) and the body part (40), and the bottom grounding part (51). An inner wall surface (53) connecting the center (55) of the bottom,
The outer wall surface (52) is reduced in diameter downward from the trunk portion (40) toward the bottom grounding portion (51), and the inner wall surface (53) extends from the bottom center (55) to the bottom grounding portion ( 51), and the outer wall surface (52) and the inner wall surface (53) are connected to form a convex portion (57) that is convex downward in the bottle. And
The convex portion (57) has an inner wall surface (53) side radius of curvature of 1.0 mm to 3.0 mm and an inner wall angle of 20 degrees to 70 degrees,
It is a plastic bottle whose thickness of the bottom grounding part (51) is more than 0.35 mm and less than 0.80 mm.

Here, the “body part” means that the bottle body part includes a shape in which a rib or panel for imparting strength is provided.
The “bottom ground contact portion” refers to a portion where the plastic bottle and the horizontal surface are in contact with each other in the state where the bottom portion of the plastic bottle is placed on a horizontal surface, and is an annular portion.
The “center of the bottom” refers to the intersection of the central axis of the plastic bottle and the bottom.
“Bottle downward direction” refers to a vertically downward direction in a state where the bottom portion of the plastic bottle is placed on a horizontal plane. The upward direction of the bottle refers to the opposite direction.
The diameter-reducing direction refers to the direction from the bottle body portion toward the center axis of the bottle, and the diameter-enlargement direction refers to the direction from the center axis of the bottle toward the bottle body portion.
The “outer wall surface” is an annular portion that decreases in diameter downward from the trunk portion toward the bottom grounding portion.
The “inner wall surface” is a portion that expands downward from the center of the bottom toward the bottom grounding portion.
In the present specification, the outer surface of the bottle (the surface in contact with the outside air) is referred to as the outer surface, and the inner surface of the bottle (the surface in contact with the contents such as beverage) is referred to as the “inner surface”.

As shown in FIG. 3, the bottom grounding portion (51) has a reduced diameter direction end portion (532) and an expanded diameter direction end portion (522) and is in contact with the horizontal plane P, and the reduced diameter direction end portion ( 532), the center position of the end portion (522) in the diameter expansion direction is set as the grounding point. Note that when the bottom ground contact portion (51) is viewed microscopically, it can be said that the predetermined surface including the reduced diameter direction end portion (532) and the expanded diameter direction end portion (522) is in contact with the horizontal plane P. When visually observed, the diameter-reducing end (532) and the diameter-enlarging end (522) coincide with each other, and the convex portion 57 and the horizontal plane P appear to be in point contact in FIG. There is. The present invention also includes a form that appears to be in point contact.
The “curvature radius on the inner wall surface side” refers to the curvature radius of the convex portion (57) on the inner wall surface side from the ground contact point.
The “inner wall angle” refers to an angle formed by a predetermined inner wall surface (53) and a horizontal plane (P) constituting the convex portion (57), and includes an inner wall angle α and an inner wall angle α ′ which will be described later. Meaning.

  In 1st Embodiment, it is preferable that the ratio of the height of the said bottom part with respect to the radius of the said bottom grounding part is 0.20 or more and 0.50 or less. Thereby, the pressure resistance of the plastic bottle can be further improved.

As shown in FIG. 2, the “radius of the bottom grounding portion” refers to the plastic bottle center axis (X) and the horizontal plane (X) in the state where the bottom (50) of the plastic bottle is placed on the horizontal plane (P). The distance (r) from the intersection (P1) with P) to the grounding point in the bottom grounding part.
The “bottom height” is the distance (h) from the intersection (P1) between the central axis (X) of the plastic bottle and the horizontal plane (P) to the outer surface of the center (55) of the bottom in the same state. Say.

In 1st Embodiment, it is preferable that the shape of the said bottom part is a stacked saddle type. Thereby, the pressure resistance of the plastic bottle according to the present invention can be further improved.
Here, the “overlapping saddle type” means that the inner wall surface of the bottom portion has at least one inflection point in the longitudinal section including the central axis of the plastic bottle.

In 1st Embodiment, it is preferable that the maximum diameter of the said trunk | drum is 65 mm or more and 75 mm or less, and the ratio of the thickness of the said bottom grounding part with respect to the thickness of the said trunk | drum is 1.0 or more and 5.0 or less. The weight of the plastic bottle is preferably 45 g or less. In the present invention, the bottle of a predetermined capacity having the body diameter can be a lightweight bottle having a predetermined thickness while having high pressure resistance.
In addition, the diameter of a trunk | drum is a diameter with respect to the periphery of the outer surface of a trunk | drum.

  In 1st Embodiment, it is preferable that the said trunk | drum is cylindrical. This makes it possible to improve the design of the plastic bottle, and in particular, when a high-grade beverage such as wine is filled, it is possible to give a high-quality design.

In the first embodiment, in the plastic bottle filled with a liquid at 50 ° C. so that the gauge pressure is 80 kPa, the bottom protrusion immediately after filling is preferably 1.0 mm or less, and the upright inclination is 0.5 mm or less. Preferably there is.
Here, “bottom pop-out” means that the inner wall surface (53) of the bottle bottom portion (50) is displaced downward from the bottom ground contact portion (51) before popping out, and the bottle height increases.
Further, “upright tilt” means that the bottle tilts after pressurization in the measurement of the bottom protrusion.

  The plastic bottle of the first embodiment may have a gas barrier thin film. Thereby, in addition to nitrogen filling for maintaining the quality of the filling, it is possible to further prevent gas from entering from the outside through the bottle, so that the quality of the filling can be maintained at a higher level.

  According to the present invention, even when a plastic bottle having a simple structure at the bottom is thinned and lightened, the bottom is hardly deformed due to a high internal pressure, and the body is not easily dented due to a change in the internal pressure. A plastic bottle having pressure resistance can be provided.

It is a front view which shows the whole plastic bottle of one Embodiment of this invention arrange | positioned on the horizontal surface. It is the expanded sectional view which expanded bottom 50 vicinity in the longitudinal section containing the central axis of the plastic bottle of FIG. It is a figure explaining the method of calculating the inner wall angle (alpha) and outer wall angle (beta) of the convex part in a bottom grounding part. The upper drawing is an enlarged cross-sectional view similar to FIG. 2, and the lower drawing is a bottom view of the bottle. Note that corresponding portions in the upper view and the lower view are connected by a broken line. It is a figure for demonstrating bottom protrusion and an upright inclination. It is a figure explaining the curvature radius of an inner wall surface side and an outer wall surface side. It is a figure explaining the method of calculating the inner wall angle (alpha) and inner wall angle (alpha) 'of a convex part in a bottom grounding part in case an inflection point exists between the end point 534 and the point 536. FIG.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to the embodiment. In addition, the figure shown below shows the structure schematically and does not show the magnitude | size and shape of each component accurately.

<Plastic bottle 100>
FIG. 1 is a front view showing an entire plastic bottle 100 according to an embodiment of the present invention. A plastic bottle 100 shown in FIG. 1 includes an opening 10, a neck 20, a shoulder 30, a body 40, and a bottom 50. Further, FIG. 1 shows the central axis X and the horizontal plane P of the plastic bottle 100. The central axis X refers to the axis of a cylinder that constitutes the body portion 40.

The bottle downward direction refers to a vertically downward direction in a state where the bottom of the plastic bottle is placed on a horizontal plane, and refers to a downward direction on the paper surface in FIG. The bottle upward direction means the opposite direction.
The diameter-reducing direction refers to the direction from the bottle body 40 toward the center axis X of the bottle, and the diameter-enlargement direction refers to the direction from the center axis X of the bottle to the bottle body 40 horizontally.

  The opening 10 has a liquid injection outlet and has irregularities that engage with a known cap. The neck portion 20 is a portion that connects the opening portion 10 and the shoulder portion 30 and is formed in a cylindrical shape. The shoulder portion 30 is a portion that connects the neck portion 20 and the trunk portion 40 and has a portion that increases in diameter toward the trunk portion.

(Torso 40)
The trunk | drum 40 is a site | part which connects the shoulder part 30 and the bottom part 50, and is shape | molded by the cylindrical shape. The maximum diameter of the body portion 40 is preferably 65 mm or greater and 75 mm or less. The thickness of the trunk is preferably 0.20 mm or greater and 0.60 mm or less. The thickness of the neck and shoulder is not particularly limited, but the neck is preferably 0.30 mm to 0.70 mm and the shoulder is preferably 0.25 mm to 0.50 mm.

  The body 40 may be reinforced with ribs, panels, etc. to give strength, but as a preferred form, the body 40 has a cylindrical shape without ribs, panels, etc. preferable. By forming the body portion 40 in a cylindrical shape, it becomes possible to provide a high-class design in combination with the simple shape of the bottom portion 50 shown below. In particular, a bottle for filling a high-grade beverage such as wine. It becomes suitable as.

(Bottom 50)
FIG. 2 shows an enlarged view in which the vicinity of the bottom 50 is enlarged in a longitudinal section including the central axis X of the plastic bottle 100. The bottom portion 50 includes an annular bottom grounding portion 51, an annular outer wall surface 52 that connects the bottom grounding portion 51 and the body portion 40, and an inner wall surface 53 that connects the bottom grounding portion 51 and the center 55 of the bottom portion 50. The bottom grounding portion 51 is a portion where the plastic bottle 100 and the horizontal plane P are in contact with each other in a state where the plastic bottle 100 is placed on the horizontal plane P with the bottom 50 of the plastic bottle 100 facing down, and is an annular portion. As shown in FIG. 3, the bottom grounding portion 51 has a reduced diameter direction end portion 532 and an expanded diameter direction end portion 522 and is in contact with the horizontal plane P. The reduced diameter direction end portion 532 and the expanded diameter direction The center position of the end 522 is set as a grounding point.

  The outer wall surface 52 is an annular portion that decreases in diameter downward from the trunk portion 40 toward the bottom ground contact portion 51. Further, the inner wall surface 53 is a portion that expands downward from the center 55 of the bottom portion 50 toward the bottom ground contact portion 51, and is a substantially bowl-shaped portion having an opening in the downward direction. The center 55 of the bottom 50 refers to the intersection of the central axis X of the plastic bottle 100 and the bottom 50.

The outer wall surface 52 and the inner wall surface 53 are connected at the bottom grounding portion 51 to form a convex portion 57 that is convex downward in the bottle. The convex portion 57 is an annular portion including the bottom grounding portion 51 described above.
The convex portion 57 has a radius of curvature of 1.0 mm to 3.0 mm, more preferably 1.5 mm to 2.5 mm, on the inner wall surface 53 side. By setting the curvature radius to 1.0 mm or more, it can be formed into a stable shape with high fidelity to the mold shape, and the production yield is also good. Moreover, sufficient pressure resistance is obtained when it is 3.0 mm or less.
FIG. 6 shows a method of measuring the radius of curvature on the inner wall surface 53 side.
The curvature radius on the inner wall surface 53 side refers to the curvature radius of the convex portion 57 on the inner wall surface side with respect to the ground contact point. Specifically, as shown in FIG. 6, when the arc of the radius of curvature on the inner wall surface side is set to an end point 534 that is tangent to the inner wall surface of the bottle, the reduced diameter direction end portion 532 and the end point 534 are included. The radius of the arc.
The curvature radius on the outer wall surface 52 side refers to the curvature radius of the convex portion 57 on the outer wall surface side with respect to the ground contact point. Specifically, as shown in FIG. 6, when the arc of the radius of curvature on the outer wall surface side is set to an end point 524 that is tangent to the inner wall surface of the bottle, it includes an end portion 522 in the diameter increasing direction and an end point 524. The radius of the arc.

Further, the inner wall angle of the convex portion 57 is preferably 20 degrees or more and 70 degrees or less, and the lower limit is more preferably 30 degrees or more, and further preferably 35 degrees or more. Further, the upper limit of the inner wall angle is more preferably 65 degrees or less, and further preferably 60 degrees or less. When the inner wall surface 53 is formed so as to rise with respect to the horizontal plane, the pressure resistance of the bottom grounding portion 51 is increased, and the force that pushes the bottom grounding portion 51 vertically downward is the component force in the vertically downward direction of the pressure of the content liquid. This reduces dispersion and suppresses bottom out. In addition, when the inner wall angle is set to 70 degrees or less, the plastic bottle can be easily molded, and the bottom grounding portion can be easily molded with a necessary thickness even if the bottle is lightened.
The above “inner wall angle” means to include an inner wall angle α and an inner wall angle α ′ which will be described later.

The measuring method of the inner wall angle of the convex part 57 is demonstrated using FIG.
In the longitudinal section including the central axis X of the plastic bottle in the state of standing upright on the horizontal plane P with the bottom 50 of the plastic bottle down, an end point 534 where the arc of the radius of curvature on the inner wall surface side is tangent to the inner wall surface of the bottle, An angle α formed from a straight line L2 connecting the end point 534 to a point 536 on the inner wall surface located in the diameter reduction direction 2.5 mm and the horizontal plane P was measured, and this was defined as the inner wall angle α.

FIG. 3 shows an example in which there is no inflection point between the end point 534 and the point 536 on the inner wall surface 53 of the convex portion 57. In this form, the space between the two points has a substantially linear structure.
In addition, an example in which there is an inflection point between the end point 534 and the point 536 is illustrated in FIG.
In FIG. 7, when there is an inflection point between the end point 534 and the point 536, a straight line L2 ′ connecting the end point 534 to the point 536 ′ on the inner wall surface located in the diameter reducing direction 1.0 mm, and the horizontal plane The angle α ′ formed from P was measured, and this was defined as the inner wall angle α ′. Thereby, even when there is an inflection point between the end point 534 and the point 536, it can be determined whether or not the inner wall surface 53 is formed so as to rise with respect to the horizontal plane P.
The inner wall angle α is preferably 20 degrees or more and 70 degrees or less, and the lower limit is more preferably 30 degrees or more, and further preferably 35 degrees or more. The upper limit of the inner wall angle is more preferably 65 degrees or less, more preferably 60 degrees or less, more preferably 55 degrees or less, more preferably 50 degrees or less, and 45 degrees or less. More preferably.
Further, the inner wall angle α ′ is preferably 20 degrees or more and 70 degrees or less, and the lower limit is more preferably 30 degrees or more, more preferably 35 degrees or more, and more preferably 40 degrees or more. Preferably, it is 45 degrees or more, more preferably 50 degrees or more, and further preferably 55 degrees or more. Further, the upper limit of the inner wall angle is more preferably 65 degrees or less, and further preferably 60 degrees or less.
By having the convex part 57 which the bottle bottom part 50 combines such a curvature radius and inner wall angle by the side of the inner wall surface 53, the pressure resistance with respect to the internal pressure of the plastic bottle 100 can be improved.

Further, the outer wall angle β of the convex portion 57 is preferably 30 degrees or more and 85 degrees or less, the lower limit is more preferably 40 degrees or more, and the upper limit is more preferably 80 degrees or less.
As shown in FIG. 3, the outer wall angle β of the convex portion 57 is a vertical cross section including the central axis X of the plastic bottle in an upright state on the horizontal plane P with the bottom 50 of the plastic bottle facing down. An angle formed by a horizontal plane P and a straight line L1 that connects an end point 524 that is tangent to the inner wall surface of the bottle and a point 526 of the outer wall surface that is located 2.5 mm from the end point 524 in the diameter-expanding direction. β. When the outer wall angle β is in such a range, the bottom grounding portion is not excessively stretched and the wall thickness can be secured, and sufficient bottom strength can be obtained.
The shape of the plastic bottle can be measured with a commercially available contour shape measuring machine, for example, Contracer CV-3000 (conditions: stylus diameter 25 μm, scanning speed 0.1 mm / second) manufactured by Mitutoyo Corporation.

  In the present invention, the thickness of the bottom ground contact portion 51 is more than 0.35 mm and not more than 0.80 mm. The lower limit is more preferably 0.38 mm or more, and the upper limit is more preferably 0.70 mm or less, still more preferably 0.60 mm or less. When the lower limit exceeds 0.35 mm, the strength of the bottom ground contact portion 51 is improved, the pressure resistance of the plastic bottle is improved, and the molding stability of the bottom portion can be ensured. When the upper limit is 0.80 mm or less, the occurrence of bottle deformation due to insufficient cooling can be suppressed, which is also effective for weight reduction.

In the plastic bottle 100, the ratio of the thickness of the bottom grounding portion 51 to the thickness of the body portion 40 is preferably 1.0 or more and 5.0 or less, more preferably 1.1 or more and 3.0 or less. More preferably, it is 5 or more and 2.5 or less. Thus, by forming the thickness of the bottom grounding portion thicker than the thickness of the body portion, it is possible to combine the lightness of the plastic bottle and the pressure resistance of the bottom portion.
The trunk thickness means that the length of the trunk 40 is divided into four equal parts, and the average value of the thickness at four points every 90 degrees in the circumferential direction at a quarter height from the top of the trunk 40. Say. The thickness of the plastic bottle including the thickness of the bottom grounding portion 51 and the thickness of the body portion 40 can be measured by a magnetic thickness meter MAGNA-MIKE manufactured by OLYMPUS.

  Next, the ratio of the height of the bottom part 50 to the radius of the bottom grounding part 51 will be described with reference to FIG. The radius of the bottom grounding portion refers to the installation point in the bottom grounding portion 51 from the intersection P1 between the central axis X of the plastic bottle 100 and the horizontal plane P in the state where the bottom 50 of the plastic bottle 100 is placed on the horizontal plane P. Distance r. Further, the bottom height refers to a distance h from the intersection P1 between the central axis X of the plastic bottle and the horizontal plane P to the outer surface of the center 55 of the bottom 50 in the same state.

In the plastic bottle 100 of the present invention, the ratio (h / r) of the height h of the bottom 50 to the radius r of the bottom ground contact 51 is preferably 0.20 or more and 0.50 or less, and is 0.25 or more. More preferably, it is 0.40 or less.
When h / r is 0.20 or more, the convex portion 57 is formed so as to stand with respect to the horizontal plane, and the pressure resistance is increased. Moreover, when h / r is 0.50 or less, the inner wall surface 53 is suppressed from being unnecessarily stretched toward the center of the bottom portion 50 and thinning. By adopting such a structure, the pressure resistance of the plastic bottle 100 can be further improved, and the stability of standing the plastic bottle can be increased.

  In the plastic bottle 100 of the present invention, it is preferable that the shape of the bottom 50 is a stacked bowl shape. Thereby, the pressure resistance of the PET bottle 100 of the present invention can be further improved.

  Here, the stacked saddle type will be described with reference to FIG. 4 is an enlarged cross-sectional view in which the vicinity of the bottom 50 is enlarged in a vertical cross section including the central axis X of the plastic bottle 100, and the lower view of FIG. 4 is a bottom view of the plastic bottle 100. Note that corresponding portions in the upper view and the lower view are connected by a broken line. In the bottom view of the bottom portion 50 in the lower side view of FIG. 4, the outermost circle Q1 is the surface of the body portion 40, and the circle Q2 inside one represents the bottom grounding portion 51. Further, inner circles Q3 and Q4 represent inflection points of the inner wall surface 53 in the longitudinal section including the central axis X.

As illustrated in FIG. 4, the overlapping saddle type means that a curve representing the inner wall surface 53 of the bottom 50 has at least one inflection point in a longitudinal section passing through the central axis X of the plastic bottle 100. Say. The curvature radius of the inflection point is preferably 1 mm or more and 10 mm or less. Since the bottom surface has a stacked bowl shape, strength and pressure resistance are improved even in a lightweight bottle.
In the illustrated embodiment, the two inflection points Q3 and Q4 are provided. However, the plastic bottle 100 of the present application may have at least one inflection point. In the present specification, a configuration in which the inner wall surface 53 of the bottom 50 has no inflection points in a longitudinal section passing through the central axis X of the plastic bottle 100 is referred to as a bowl shape.

(Pressure resistance)
The plastic bottle 100 of the present invention has pressure resistance when the bottom portion 50 has the above-described preferred form. Specifically, the plastic bottle 100 is filled with a liquid at 50 ° C. so that the gauge pressure becomes 80 kPa, and the bottom protrusion immediately after filling can be preferably 1.0 mm or less, more preferably 0.5 mm or less. The upright inclination is preferably 0.5 mm or less, more preferably 0.3 mm or less.
A method of evaluating the bottom protrusion and the upright inclination will be described with reference to FIG. (A) shows the state before pressurization, and (B) shows the state when the bottom of the bottle after pressurization protrudes and tilts (the cap is omitted in the figure).
First, as shown in (A), the bottom line is drawn by drawing a horizontal line L3 around the body of the upright bottle 100, and the height of the horizontal line L3 is set to the reference position P2. Next, after applying a predetermined gauge pressure inside the bottle, it is measured how much the horizontal line L3 is displaced from the reference position P2. Specifically, the distance (mm) by which the horizontal line L3 is displaced vertically upward from the reference position P2 is measured and averaged at four positions every 90 degrees in the body circumferential direction.
Further, for the upright inclination, the difference between the maximum height and the minimum height from the reference position P2 of the horizontal line L3 after pressurization in the measurement of the bottom protrusion was measured. Specifically, the maximum displacement distance and the minimum displacement distance of the distance (mm) where the horizontal line L3 is displaced vertically upward from the reference position P2 are measured, and the difference (mm) is calculated.

(material)
As a material of the plastic bottle 100, polyethylene terephthalate, polyethylene naphthalate or a mixture thereof, or a thermoplastic resin such as cyclic polyolefin, polypropylene, or the like is preferably used.

  The plastic bottle 100 can be a multilayer molded bottle having two or more layers. For example, it can be set as the plastic bottle which has a gas barrier property thin film in order to provide gas barrier property. Examples of the gas barrier thin film include a thin film made of an ethylene vinyl alcohol copolymer (EVOH) and an inorganic thin film. Examples of the inorganic thin film include a diamond-like carbon (DLC) film and a Si-containing film such as SiC, SiO, SiN, SiOC, SiON, and SiONC, which can be formed using a known chemical vapor deposition method. .

(Production method)
As a manufacturing method of the plastic bottle 100, a known method such as injection blow molding or direct blow molding can be employed. Above all, the thermoplastic resin as described above is injection-molded to prepare a test tubular preform, which is heated to a temperature higher than the glass transition temperature and lower than the crystallization temperature at the time of temperature rise, and a high-pressure fluid is produced in the blow mold. A method of manufacturing by injection blow molding (biaxial stretch blow molding) by blowing is preferred.
The stretch ratio by biaxial stretch blow molding is not particularly limited, but it is preferable to set the stretch ratio so as to be the thickness of the bottom ground portion 51 described above. It is preferable to set the draw ratio so that the thickness ratio is in the above range.
For example, the stretch ratio by the biaxial stretch blow molding is to set the thickness and shape of the preform so that the surface ratio becomes 7 to 11 times when the thickness of the bottom ground contact portion 51 is reached. It is done.

  Hereinafter, the present invention will be described using examples and comparative examples, but the present invention is not limited to the following examples.

720 mL liquid plastic bottles according to Examples 1 to 4 and Comparative Examples 1 to 4 were produced by biaxial stretch blow molding using polyethylene terephthalate (intrinsic viscosity IV value 0.8). The results are shown in Table 1.
In Examples 3 and 4, since an inflection point exists between the end point 534 and the inner wall surface point 536 located in the diameter reducing direction 2.5 mm, the inner wall angle α ′ was different from the inner wall angle α.
In addition, the curvature radius and angle of a convex part, and the height of the bottom part were measured using Mitutoyo Corporation tracer CV-3000 (conditions: stylus diameter 25 micrometers, scanning speed 0.1mm / sec). The thickness of the trunk portion and the bottom grounding portion was measured using a magnetic thickness meter MAGNA-MIKE 8500 manufactured by OLYMPUS.

  A pressure resistance test and a drop test were performed using the plastic bottles obtained in the examples and comparative examples. The results are also shown in Table 1.

<Pressure resistance test>
The method of the pressure resistance test is as follows.
The bottle was injected with 720 mL of 50 ° C. water, liquid nitrogen was added dropwise so that the bottle internal pressure was 80 kPa, and the cap was tightly sealed. The bottom protrusion of the bottle and the upright inclination were evaluated according to the following criteria.
"Jump out the bottom"
A: 0.5 mm or less,
○: More than 0.5 mm and 1.0 mm or less,
Δ: more than 1.0 mm and 1.5 mm or less,
×: Over 1.5 mm “upright tilt”
○: 0.5 mm or less,
Δ: more than 0.5 mm and 1.0 mm or less,
X: More than 1.0 mm In addition, when Examples 3 and 4 were evaluated in the case of a gauge pressure of 90 kPa in the <pressure resistance test>, in both cases, “bottom protrusion” was 0.5 mm or less, and “upright inclination” was 0.5 mm. It was the following.

<Drop test>
The method of the drop test is as follows.
After filling the bottle with water according to the internal volume and capping it, it was dropped vertically from the bottom onto a concrete plate from a height of 0.9 m and examined for cracks.

It was found that the plastic bottles of Examples 1 to 4 have good evaluation results of the bottom protrusion and the upright inclination, and have pressure resistance. Further, it was found that there was no cracking caused by dropping and it had impact resistance.
On the other hand, it was found that the plastic bottles of Comparative Examples 1 to 3 had poor evaluation results of the bottom protrusion and the upright inclination, and the pressure resistance was inferior. Further, the plastic bottle of Comparative Example 4 having a large radius of curvature, a small inner wall angle, and a thick bottom ground contact portion had poor bottom protrusion and upright inclination as compared with Examples 1-2.

DESCRIPTION OF SYMBOLS 10 Opening part 20 Neck part 30 Shoulder part 40 Body part 50 Bottom part 51 Bottom grounding part 52 Outer wall surface 53 Inner wall surface 57 Convex part 100 Plastic bottle

Claims (7)

A plastic bottle having a body and a bottom,
The bottom portion includes an annular bottom grounding portion, an annular outer wall surface connecting the bottom grounding portion and the body portion, and an inner wall surface connecting the bottom grounding portion and the center of the bottom portion,
The outer wall surface is reduced in diameter downward from the trunk portion toward the bottom grounding portion, and the inner wall surface is expanded in diameter downward from the center of the bottom portion toward the bottom grounding portion, and The wall surface and the inner wall surface are connected to form a convex portion that is convex downward in the bottle,
The convex portion has a curvature radius on the inner wall surface side of 1.0 mm or more and 3.0 mm or less, and an inner wall angle of 20 degrees or more and 70 degrees or less,
A plastic bottle, wherein the bottom grounding portion has a thickness of more than 0.35 mm and not more than 0.80 mm.   The plastic bottle according to claim 1, wherein a ratio of a height of the bottom part to a radius of the bottom grounding part is 0.20 or more and 0.50 or less.   The plastic bottle according to claim 1 or 2, wherein the shape of the bottom portion is a stacked bowl shape.   The maximum diameter of the trunk is 65 mm or more and 75 mm or less, the ratio of the thickness of the bottom grounding part to the thickness of the trunk is 1.0 or more and 5.0 or less, and the weight of the plastic bottle is 45 g or less. The plastic bottle of any one of Claims 1-3.   The plastic bottle of any one of Claims 1-4 whose said trunk | drum is cylindrical shape.   6. The plastic bottle filled with a liquid at 50 ° C. so that the gauge pressure is 80 kPa has a bottom protrusion immediately after filling of 1.0 mm or less and an upright inclination of 0.5 mm or less. The plastic bottle according to item.   The plastic bottle according to any one of claims 1 to 6, wherein the plastic bottle has a gas barrier thin film.