JPH0423622B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for manufacturing a bottle, and more specifically, the present invention relates to a method and apparatus for manufacturing a bottle, and more specifically, after adjusting the temperature of a molding section of a polyester bottomed parison, this molding section is stretch-blow-molded. The present invention relates to a method and apparatus for manufacturing bottles.

(Prior art) Japanese Patent Publication No. 53-22096 discloses that an injection mold,
A technique has been proposed in which a bottomed parison is formed from a molten resin, the parison is heated to a desired temperature from the inside and outside by electric heaters on a heating stage, and then the parison is stretch blow molded to produce a bottle.

(Problems to be solved by the invention) In recent years, stretch blow molded bottles made of polyester resin,
Especially when the contents contained in biaxially stretched blow-molded polyethylene terephthalate bottles and the shape of the bottles (e.g. due to the setting of the bead) are diversified, and therefore the wall thickness distribution of the bottle is required to be very precise. has been increasing. For example, in the case of bottles that store carbonated beverages, beer, etc., in order to prevent deformation and breakage due to positive internal pressure and to improve gas barrier properties (especially against carbon dioxide gas), some wall portions are locally thinner than the specified wall thickness. On the other hand, from the point of view of material cost, it is necessary to avoid creating wall sections that are thicker than necessary. Furthermore, when items such as jewelry are hot-packed, similar precautions must be taken to prevent deformation due to negative internal pressure.

In other words, the thickness of each part of the bolt, such as the shoulder, body, and bottom, is adjusted to a predetermined value with high precision, depending on the bottle shape, dimensions, material strength, internal pressure, required gas barrier properties, etc. It is desirable to do so. The wall thickness of each part of this bottle, that is, the stretchability, is determined by the temperature of the part of the parison corresponding to the bolt part immediately before stretch blow molding (this temperature is the moldable temperature, that is, the temperature above the glass transition point of the polyester). is largely dominated by

That is, in order to control the wall thickness distribution of the bolt to a predetermined value with high precision, it is necessary to adjust the temperature distribution of the parison immediately before stretch blow molding with high precision.

However, with conventional heating methods, it has been difficult to control the temperature distribution of the parison with high precision. Therefore, it has been difficult to produce stretch-blown polyester bottles in which the wall thickness distribution is controlled with high precision.

(Objective of the Invention) An object of the present invention is to provide a method and apparatus for manufacturing a bottle having a highly accurate wall thickness distribution from a polyester bottomed parison by stretch blow molding.

(Structure of the Invention) The present invention provides a method for manufacturing a bottle by stretch blow molding a molded part of a polyester bottomed parison, in which the molded part is relatively higher than the glass transition point of the polyester than an injection mold. The parison is taken out in a high temperature state, and gas is simultaneously blown onto the molded part of the taken out parison from the circumferential direction,
The object of the present invention is to provide a method for manufacturing a bottle, characterized in that stretch blow molding is performed immediately after the molded part is cooled to a predetermined temperature equal to or higher than the glass transition point.

Furthermore, the present invention provides an apparatus for manufacturing a bottle by stretch blow molding a molded part of a polyester bottomed parison, the apparatus comprising: a through hole into which the molded part can be inserted; an annular high pressure chamber surrounding the through hole; A guide hole extending substantially tangentially to the annular high-pressure chamber that guides the pressurized gas into the annular high-pressure chamber, and a plurality of discontinuous slits located radially inside the annular high-pressure chamber along the circumferential direction. an annular low pressure chamber connected to the annular high pressure chamber;
The molded part is connected to the annular low-pressure chamber through an annular constriction part, and is inserted into the through hole, which expands radially inward to have a trapezoidal cross section. The present invention provides a bottle manufacturing apparatus characterized by comprising a cooling block having an annular gas outlet for cooling to a predetermined temperature.

(Example) In FIG. 1, 1 is a bottomed parison made of polyester, for example polyethylene terephthalate, and 1a is a retaining ring. The part below the retaining ring 1a of the bottomed parison 1 is the molded part 2
The upper part 2a of the molding part 2, the lower part thereof,
The cylindrical portion 2b, which becomes slightly smaller in diameter toward the bottom, and the bottom portion 2c should each form the shoulder, body, and bottom of the bottle (see Figure 6) formed by stretch blow molding. It is a part.

The bottomed parison 1 is taken out of the injection mold at a relatively high temperature, higher than the glass transition point of the resin, and is immediately suspended into the cooling device 4 while the retaining ring 1a is held by the holder 3. As shown in the figure, the molded part 2 is inserted into a cooling block 5, which will be described later, and held in that position.

The cooling device 4 includes a cooling block 5 and a drive mechanism 6 that moves the cooling block 5 up and down at predetermined timing. The drive mechanism 6 is connected to the cooling block 5
A vertical worm gear 7 engaged with the worm gear 7, a stepping motor 8, and gears 9 and 10 for transmitting the rotation of the stepping motor 8 to the worm gear 7 are provided. That is, the cooling block 5 is configured to move up and down via the worm gear 7 in accordance with the rotation of the stepping motor 8.

The cooling block 5 is made of, for example, an aluminum alloy, and as shown in FIGS. 2 and 3,
Slightly between 11 (width w is preferably between 3 and 10
mm), a through hole 12 with a circular cross section into which the molded part 2 can be inserted, and an annular high pressure chamber 1 surrounding the through hole 12
3, and an annular low-pressure chamber 15 separated from the high-pressure chamber 13 by an annular barrier portion 14 and located radially inside the high-pressure chamber 13.

As shown in FIGS. 3 and 4, the upper end of the barrier portion 14 has a plurality of slits 16a, preferably six or more (eight in the figure), preferably equally spaced along the circumference. It is provided. As clearly shown in FIG. 3, the lower end of the barrier portion 14 is also provided with a plurality of slits 16b, preferably at alternate positions with the upper slits 16a.

In addition, a plurality of (two in the figure) guide holes for introducing pressurized air 18 from a pressurized gas (usually air, hereinafter referred to as air) source to the high pressure chamber 13 via a conduit and a flow rate solenoid valve. 17 are provided. Each guide hole 17 is formed to be centrally symmetrical and to extend substantially tangentially to the high pressure chamber 13, so that the pressurized air 18 flows as uniformly and smoothly as possible within the high pressure chamber 13. ing. That is, a substantially uniform primary pressure (for example, 1 kg/cm ² ) is generated in the high pressure chamber 13 along the circumferential direction.

The pressurized air 18 in the high pressure chamber 13 is fed through the slit 16
The air flows into the low pressure chamber 15 through the slits 16a and 16b, and since the slits 16a and 16b are formed at equal intervals along the circumference as described above, they are also used to temporarily store the air in the low pressure chamber 15. Since the annular constriction part 19 described later is provided, the low pressure chamber 15
A substantially uniform secondary pressure (for example 0.5 kg/cm ² ) is created within the circumferential direction.

An annular constriction portion 1 is provided inside the low pressure chamber 15 in the radial direction.
9 and an annular air outlet 20 are provided, and the outlet 20 widens radially inward to have a trapezoidal cross section. Relatively low pressure air 2 in the low pressure chamber 15
1 is once squeezed by the constriction part 19, and then blown out from the blow-off port 20, and simultaneously and substantially uniformly hits the forming part 2 of the parison 1 in the circumferential direction, so that it hits the inside of the through hole 12. The molded part 2 is cooled substantially uniformly along the circumferential direction to a predetermined temperature equal to or higher than the glass transition point of the polyester. Since the air 21 has a relatively low pressure and the outlet side of the blow-off port 20 is widened, there is no risk of deformation of the molded part 2 when the air 21 hits the molded part 2.

The degree of cooling of a specific portion in the axial direction of the molding section 2, that is, the temperature after cooling, is determined by the cooling block 5 to the specific portion.
It is adjusted by the amount of air 21 blown out per unit time and the blown out time.

FIG. 5 shows an example of the above adjustment,
... on the vertical axis indicates the setting position from above, and the number on the left side thereof, for example, the number on the top row, indicates that the distance between the setting position and the number is 10 mm. The uppermost setting position is, for example, a position where the upper surface 5a (FIG. 1) of the cooling block 5 almost contacts the retaining ring 1a, and the lowermost setting position is, for example, a position where the lower surface 5b is the lower surface of the bottom 2c of the molded part 2. It is located at almost the same level as the Q ₁ ，…，
_Q6 is the air flow rate and is determined by adjusting the opening degree of a flow rate solenoid valve provided between the guide hole 17 and the pressurized air source using an input signal to the controller. v ₁ , ..., v ₄ indicate the descending speed or ascending speed of the cooling block 5 (in FIG. 5, a downward arrow indicates descending and an upward arrow indicates ascending), and the rotational speed of the stepping motor 8 and the direction of rotation. t ₁ , . . . , t ₅ are the stop times of the cooling block 5 and are equal to the stop times of the stepping motor 8.

In the figure, in the section , the cooling block 5 descends at a speed of v ₁ and air is blown out from the outlet 20 at a flow rate of Q ₂ . In the section , and the section , the air blowing flow rate is equal to _Q1 , but the descending speed is different from _v2 and _v3 , respectively. At the set position,
The cooling block 5 is stopped for a time _t1 , during which air is blown out at a flow rate of _Q3 . After that, the cooling block 5 is
It rises to the position at a speed of v ₄ , while air with a flow rate of Q ₁ is blown out.

Although the explanation will be omitted hereafter, the cooling block 5 is raised, lowered, stopped, and air is blown out in accordance with the symbols Q _i , v _i , t _i shown in the figure in the same manner as described above. After the cooling block 5 reaches the lowest position and the predetermined amount _Q5 of air has finished blowing out, the parison 1 is taken out from the cooling block 5, and then the cooling block 5 stops blowing out air and returns to the top position. to return to. In the case shown, the intervals ~, ~, ~
, ~, the time during which air is blown is relatively short, and the section ~ is relatively long. If you want to cool only a specific part of the molding section 2,
It is not necessary to move the cooling block 5 up and down.

The parison 1 taken out from the cooling block 5 is
The product is immediately transferred to a stretch blow mold (not shown) and biaxially stretch blow molded by a known method to form a bottle (see 22 in FIG. 6).

(Effects of the Invention) According to the method of the present invention, since gas is simultaneously blown from the inner circumferential direction to the molded part of the parison which is at a relatively high temperature, each part of the molded part is substantially It is easy to uniformly cool to a predetermined temperature suitable for stretch blow molding above the glass transition point,
In other words, it is easy to adjust the temperature to be cooled,
Therefore, it is possible to easily and reliably adjust the wall thickness distribution of the formed bottle.

Further, according to the apparatus of the present invention, each part of the molded part of the parison, which is relatively high in temperature, can be reliably cooled substantially uniformly in the circumferential direction to a predetermined temperature.

(Experiment example) Examples will be described below.

The outer diameter of the upper part 2a that contacts the lower surface of the retaining ring 1a is 26.26 mm, the outer diameter of the smallest diameter part of the cylindrical part 2b is 23.28 mm, and the height of the molded part 2 is 115.04 mm.
A bottomed parison 1 made of polyethylene terephthalate having a wall thickness of 3.7 mm was formed by injection molding, immediately removed from the mold, and set in a cooling device 4 as shown in FIG. When the temperature of the molding part 2 was measured with a radiation thermometer immediately after setting, it was 120°C near the upper end of the upper part 2a, and the temperature decreased as it went downward, and the temperature near the lower end of the cylindrical part 2b was 90°C. It was warm at ℃.

The thickness of the cooling block 5 used in the cooling device 4 is 20 mm, the height of the opening 20a of the air outlet 20 is 12 mm,
The width w of the gap 11 was 8.6 mm. Immediately after setting the parison 1, place the cooling block 5 on its lower surface 5.
Move b so that it is located 60 mm above the bottom surface of the bottom part 2c of the parison, and while keeping it in that position,
Air is blown out from the blow-off port 20, and the molding part 2 is heated for 3 seconds.
cooling was carried out. The primary pressure of the high pressure chamber 13 and the secondary pressure of the low pressure chamber 15 were 1 Kg/cm ² and 0.3 Kg/cm ² , respectively, and the cooling air volume was 150 Nl/min.

Immediately thereafter, the parison 1 was sent to a stretch blow mold and subjected to biaxial stretch blow molding to produce a bottle 22 having the shape shown in FIG. The total height of bottle 22 is 200
mm, and a thick portion 22a ₁ was formed approximately at the center of the body portion 22a in the height direction as shown in the figure. The thickness of the thick portion _22a1 was 0.3 mm, and the thickness of the other body portions was 0.2 mm. The height of the thick wall portion _22a1 was 80 mm, and the height of its lower end from the bottom of the bottle was 50 mm.

For comparison, when a bolt was formed in the same manner as described above, except that parison 1 was not forcedly cooled, the wall thickness of the body was approximately 0.2 mm over the entire height.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a cross-sectional view taken along the line - in FIG. 1, showing a cooling block of the apparatus of the present invention. Drawings showing the embodiment, FIG. 3 is a vertical sectional view taken along the - line of FIG. 2, and FIG. 4 is a longitudinal sectional view taken along the - line of FIG.
5 is a diagram showing an example of a schedule for cooling a parison using the cooling block of FIG. 2, and FIG. 6 is an example of a bottle manufactured by the method of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Bottomed parison, 2... Molding part, 5... Cooling block, 12... Through hole, 13... Annular high pressure chamber, 15... Annular low pressure chamber, 16a, 16b...
Slit, 17... Guide hole, 18... Pressurized air (pressurized gas), 19... Annular constriction section, 20... Annular air outlet, 22... Bottle.

Claims (1)

[Scope of Claims] 1. In a method of manufacturing a bottle by stretch blow molding a molded part of a polyester bottomed parison, the molded part is heated to a relatively high temperature higher than the glass transition point of the polyester than an injection mold. The parison is taken out in this condition, and the molded part of the taken out parison is simultaneously blown with gas from the circumferential direction to cool the molded part to a predetermined temperature above the glass transition point, and then stretch blow molding is immediately performed. A method for manufacturing a bottle, characterized by: 2. An apparatus for manufacturing a bottle by stretch blow molding a molded part of a polyester bottomed parison, the apparatus comprising a through hole into which the molded part can be inserted, an annular high pressure chamber surrounding the through hole, and the annular high pressure chamber. A guide hole extending substantially tangentially to the annular high-pressure chamber to introduce pressurized gas into the annular high-pressure chamber, and a plurality of discontinuous slits located radially inside the annular high-pressure chamber and discontinuous along the circumferential direction. Gas is introduced into an annular low-pressure chamber connected to the annular low-pressure chamber and the molded part inserted into the through hole, which is connected to the annular low-pressure chamber through an annular constriction part and widens radially inward to have a trapezoidal cross section. 1. A bottle manufacturing apparatus comprising a cooling block having an annular gas outlet for cooling the molded part to a predetermined temperature by spraying.