JP2560929B2 - Method for manufacturing PET bottle - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a biaxially stretch blow-molded PET (polyethylene terephthalate) bottle having excellent grounding stability and good suitability on a high-speed filling line.

[0002]

2. Description of the Related Art A method for manufacturing a PET bottle by biaxially stretch blow molding is a pre-heated bottomed cylindrical preform in a mold composed of a neck mold, a body part and a bottom mold which are divided into left and right parts. -A method of inserting a foam, fixing the neck of the preform, stretching the body of the preform in the stretching lot in the longitudinal direction, and then blowing air into the preform to form a PET bottle The air between the expanding preform and the mold cavity during molding is successively discharged to the outside of the mold through the gaps in the parting line with the mold of each part. However, in the mold used in this case, conventionally, the bottom parting line between the body part mold and the bottom part mold is generally provided at a portion corresponding to the innermost periphery of the bottle bottom part grounding surface of the mold part. Therefore, depending on the shape of the bottle, the air discharge between the expanding preform and the mold cavity surface is insufficient, and the reproducibility of the mold shape near the grounding surface at the bottom of the bottle is impaired. However, a bottle with so-called sitting (grounding stability) is often generated, causing an accident such as a fall on the high-speed filling line, which is a problem.

In order to solve the problem of grounding stability on the filling line, bottles are usually supported by three-point or four-point support provided with three or four convex portions on the grounding surface at the bottom of the bottle. A method was taken to improve the grounding stability of the. Further, as another improvement method, a method of previously correcting the shape of the mold by an extent that the shape reproducibility is impaired at the time of molding has been taken.

[0004]

However, the above-mentioned method of providing three or four convex portions on the bottom of the bottle is
There is no problem of grounding stability during general use, but there is a problem that troubles such as inversion bottles easily occur due to the small grounding area at the bottom of the bottle on the high-speed filling line when filling contents. Was becoming. In addition, the method of correcting the shape of the mold in advance causes uneven shape reproducibility of the molded product due to variations in molding conditions during molding of the bottle,
There is a problem in that the suitability on a high-speed filling line becomes unstable because the grounding stability of the molded bottle varies.

Further, when a PET bottle is molded using a conventional mold, the body parting lines of the left and right body parts, in which air easily escapes between the preform that expands during molding and the mold cavity. The shape of the bottom part of the PET bottle with a long diameter direction is easy to show the shape of the bottom part because the reproducibility of the mold shape is good. Was hard to come by. For this reason, when the PET bottle is viewed from the side as shown in FIG. 4, a bottle having a bottom whose shape protrudes from the outside to the center is formed, and the ground stability of the bottle is impaired. It was often seen to fall. The present invention is 2
It is intended to provide a method for producing a PET bottle in which the structure of the bottle mold in the axial stretch blow molding is improved to improve the grounding stability and the suitability on a high-speed filling line is improved.

[0006]

The present invention relates to a method for manufacturing a biaxially stretch blow molded bottle having a flat cross-sectional shape, as shown in FIG. 1, as shown in FIG. 11) is provided with a bottom parting line (30) for the bottom mold (10) and the body part mold (20), and two body parts for dividing the bottom parting line (30) and the body part mold. Width 5 to 20 centered on each of the two intersections with the parting line (21)
Two protrusions (14) with a height of 0.1 to 0.5 mm in mm
, Using the mold provided in the corresponding portion of the bottom bottom grounding surface (12) of the bottom mold, if necessary, the air in the mold from the gap of the bottom parting line (30). By sucking, the shape reproducibility of the mold near the grounding portion at the bottom of the PET bottle was improved and the suitability for high-speed filling line was improved.
It is a method of manufacturing an ET bottle.

The mold of the present invention comprises a neck mold, a body mold which is divided into left and right parts, and a bottom mold.

The raised portion provided on the portion corresponding to the bottom ground contact surface of the bottom type bottle of the present invention is a raised portion having a gentle curve as shown in FIG. 2 and having a height of 0.1 to 0.5 mm. It is (14), and in the molded bottle, it is the same plane as the ground contact surface of the other bottom portion or has a recess.

The bottom parting line between the bottom mold and the body part of the present invention is provided with a clearance of 0.05 to 0.5 mm. If necessary, the bottom parting line The air in the mold is sucked through the gap. For this method, as shown in FIG. 3, an ordinary vacuum pump is connected to the air vent hole (15) of the bottom die to remove the air provided in the bottom die. Through the passage (16) and the bottom passage (10), the body portion die (20), and the gap passage (31) formed by the heat resistant silicone rubber packing (40) at the time of molding the bottle, the parting is performed. Line (30)
The air in the mold is sucked from the gap by reducing the pressure to 50 to 400 mmHg.

The PET bottle targeted by the present invention has a width of the ground contact surface at the bottom of the bottle of 4 mm or less.

[0011]

In the biaxially stretched blow molding method for PET bottles, when the preform expanding in the mold is cooled by the inner surface of the mold and the air in the mold, the melt viscosity of the preform becomes Due to the large dependence on
Adhesion of the expanding preform to the inner surface of the mold deteriorates.
For this reason, it is preferable that the expanding preform is brought into close contact with the inner surface of the mold as soon as possible and without cooling, and the air between the expanding preform and the inner surface of the mold is preformed. It is necessary to discharge it out of the mold as soon as possible according to the expansion of the frame.

According to the mold of the present invention, the bottom part of the bottom mold and the body part mold are located at the outermost peripheral portion of the bottom grounding part of the bottle where the air between the expanding preform and the inner surface of the mold is the most difficult to escape. A coating line is provided, and if necessary, by suction from the gap of the bottom parting line,
The air in the mold is effectively and forcibly discharged out of the mold to improve the mold shape reproducibility in the vicinity of the grounded portion at the bottom of the PET bottle. Further, a width 5 to 5 is centered around two intersections of the body part line of the body part in the major axis direction of the PET bottle and the bottom part and the bottom parting line of the body part.
A protrusion having a height of 20 mm and a height of 0.1 to 0.5 mm is provided in a portion corresponding to the bottom-bottom grounding surface of the bottom mold, and as a result, the easily-protruded portion of the molded bottle bottom is the other grounding surface. The surface of the PET bottle is the same as or flat, and the ground stability of the PET bottle is improved.

[0013]

1 is a partial front view of a bottom mold and a partial sectional view of a body mold of a PET bottle used in an embodiment of the present invention, and FIG. 2 is a partial side view of the bottom mold. It is a fragmentary sectional view of a body type.

First, a mold for a flat bottle of a liquid detergent having a full water capacity of 630 ml was prepared. In this mold, a bottom parting line (30) between the bottom mold (10) and the body part mold (20) is provided in the outermost peripheral part (11) of the bottle bottom grounding surface, and the gap between them is set to 0.
2 mm, and a width 15 centered on each of the two intersections of the bottom parting line (30) and the two body parting lines (21) dividing the body part mold (20).
Two protrusions (14) having a height of 0.3 mm and a height of 0.3 mm are respectively provided on the corresponding portions (12) of the bottom surface of the bottom type bottom bottle.

Then, in a Nissei ASB-250 machine, a polyethylene terephthalate (PET) having IV (intrinsic viscosity) 0.74 was used as a molding material, and then a cylindrical preform having a bottom was injection-molded. A PET bottle was molded using the above mold under the molding conditions of preform preheating temperature of 120 ° C., blow pressure of 25 kg / cm ² , and suction pressure of 140 mmHg.

Next, in order to evaluate the grounding stability of the PET bottle molded in this example, 600 ml of room temperature water was put in the bottle and the bottle was placed in the direction of 90 ° (minor axis direction) with respect to the side surface of the bottle. With the center of the bottom of the bottle as a fulcrum, the neck of the bottle was tilted 7 ° with a finger and the finger was released, and the number of seconds until the shaking of the bottle left and right stopped was measured. In addition, the center of gravity of the bottle of this embodiment is about 10 mm from the bottom with respect to the total height of 235 mm.
It is located at the position of 3 mm, and the flatness is 66 mm at the bottom.
Minor diameter 49 mm, maximum length of the body 96 mm: Minor diameter 58 m
It was m.

As a result of the evaluation test, the time to stand still was 4.0 seconds. The correlation between this evaluation test and the suitability of the bottle on the actual high-speed filling line is 7 seconds or less from the result of analysis of the data accumulated from the past until the bottle sways in this evaluation test. If so, the bottle was judged to have good suitability on the fast fill line. From this, it was determined that the PET bottle molded according to the present invention had good suitability on a high-speed filling line.

Further, the PET bottles molded in this example were filled with 30,000 bottles at a filling rate of 80 bottles / minute in a liquid detergent high-speed filling line as a practical test. There were no troubles such as an overturned bottle due to a defective shape of the bottom ground contact surface of the bottle.

[0019]

As shown in the above examples, the PET bottles obtained by the production method of the present invention contain water at room temperature in an amount equivalent to the content of the PET bottles, and the direction of 90 ° to the side surface of the bottle (direction of minor axis). In the evaluation method of the grounding stability of the bottle, the center of the bottom of the bottle is used as a fulcrum, the neck of the bottle is tilted by 7 ° with a finger and the finger is released, and the number of seconds until the left and right shakes of the bottle stop is measured. The number of seconds until the shaking of the bottle left and right stopped was 7 seconds or less, and it was confirmed that the grounding stability of the bottle was good. Furthermore, a PET bottle obtained by the production method of the present invention was subjected to a practical filling test in a liquid detergent high-speed filling line, and the bottle collapsed due to a defective shape of the bottom ground contact surface of the bottle on the filling line. No troubles such as these occurred, and the suitability on the high-speed filling line was good.

Further, in the mold according to the present invention, two protrusions are provided in the part corresponding to the grounding part of the bottle in order to improve the grounding stability of the PET bottle. Unlike the conventional mold in which the part corresponding to the ground contact surface of the body part is in the body part, since it is in the bottom mold, it is easy to manufacture the mold and the manufacturing cost is low.

Moreover, according to the method for producing a PET bottle of the present invention, the shape stability of the molded bottle is improved, so that the molding loss is greatly reduced as compared with the conventional manufacturing method, and 0.3%. I was able to hold it down.

[Brief description of drawings]

FIG. 1 is a partial front view of a bottom mold and a partial sectional view of a body mold of the present invention.

FIG. 2 is a partial side view of a bottom mold and a partial cross-sectional view of a body mold of the present invention.

FIG. 3 is an explanatory view showing a method of sucking air in a mold through a gap between bottom parting lines of a bottom mold and a body part mold according to the present invention.

FIG. 4 is an explanatory view showing a state of a bottom portion of a flat bottle formed by a conventional mold as seen from a side surface thereof.

[Explanation of symbols]

 10 …… Bottom type 11 …… Equivalent to the outermost circumference of the bottle bottom contact surface 12 …… Equivalent to the contact area of the bottle bottom 13 …… Equivalent to the innermost circumference of the bottle bottom contact surface 14 …… Protruded part 15 …… Bottom Air vent hole of mold 16 …… Air vent passage provided in the bottom mold 20 …… Body part 21 …… Body parting line 30 …… Bottom parting line between bottom mold 31… … Gap passage 40 …… Packing

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Claims (2)

(57) [Claims] 1. A method for producing a biaxially stretched blow-molded bottle having a flat cross-sectional shape, wherein a bottom parting line between a bottom mold and a body part mold is provided at a portion corresponding to the outermost periphery of a bottle bottom grounding surface of a mold. The width is 5 to 20 mm and the height is 0.1 with the two intersections between the bottom parting line and the two body parting lines dividing the body part mold as centers.
A method of manufacturing a PET bottle, characterized in that two raised portions having a diameter of 0.5 mm are provided at respective portions corresponding to the bottom-side ground contact surface of the bottom type bottle. 2. The method for producing a PET bottle according to claim 1, wherein air in the mold is sucked through the gap between the parting lines.