JPS5953860B2 - Method for forming biaxially stretched blow-molded bottle pieces - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a piece as a primary molded product that is injection-molded to form a polyethylene terephthalate resin increaser that is biaxially stretched and blow-molded. The purpose of this invention is to make the neck portion that is not stretch-molded during biaxial stretch blow molding into a bale to have excellent physical properties and durability equivalent to the same portion that is stretch-molded.

Polyethylene terephthalate resin has extremely excellent physical properties and durability;
This effect is first exhibited when a polyethylene terephthalate resin molded product is stretch-molded.

For this reason, polyethylene terephthalate resin salary increases are
In order to undergo effective stretch molding, a piece, which is a primary molded product in the shape of a cylinder with a bottom, is first molded by injection molding, and then this piece is stretch-blow molded to increase the size. Molded by blow molding.

By the way, in this injection blow molding, the piece to be stretch-blow-molded into the bulge is assembled and held in the blow mold at its neck, so the body of the burlap must be stretched sufficiently. In contrast, the neck will not be stretched.

As described above, in the case of conventional polyethylene terephthalate resin pads, since the neck cannot be stretch-molded, the neck has a serious disadvantage of inferior physical properties and durability compared to the body. Ta.

For example, in the case of conventional ballast increases, when high-concentration alcohol is stored as the liquid content, this alcohol penetrates into the neck and causes the neck to become white and mechanically brittle, which also creates a large number of thin cracks. Disadvantage 5 arises in that the sealing effect is significantly deteriorated.

The present invention was devised to eliminate the serious drawbacks of the conventional examples described above, and will be described below with reference to the drawings.

The present invention heats the neck part P1 of a piece body P that is injection molded into a bottomed cylindrical shape to a temperature that produces a stretching effect, and also holds this piece body P uniformly over at least the entire outer circumferential surface of the neck part P1 using a mold H to prevent it from idling. The rotating piece 2 is inserted into the neck P1 of the piece body P held in this manner, and is inserted into the inner circumferential surface of the neck P1 tightly without slipping in the circumferential direction. The piece is formed by rotating it in a certain direction until the temperature of the neck portion P1 becomes below the temperature at which a stretching effect is produced.

The rotomolded body 1 having the rotary piece 2 as the main part holds the rotary piece 2 so that it can rotate about its central axis and align this central axis with the central axis of the piece body P.
Although the structure is not particularly limited, consideration must be given to prevent the resin material of the neck P1 portion, which is forced to flow and move due to the rotational operation of the rotary piece 2, from flowing out of the neck P1. In the case of the illustrated embodiment, this rotomolded body has its axis centered on the lower surface of the base plate 4 which can be raised and lowered along the central axis of the piece body P held in the holding mold H. The center shaft 5 is fixed in alignment with the center shaft 5, and the rotary piece 2, which fits snugly into the neck P1 and has almost the same height and length as the neck P1, is rotatably attached to the center shaft 5. It has a structure in which a short cylindrical holding tip 3 having an outer diameter equal to the inner diameter of the piece body P is fixed to the lower end of the piece body P. The base plate 4 is attached to the upper surface of the holding mold H in which the piece body P is assembled so as to prevent it from idling, with its upper surface aligned with the neck P and upper end surface of the piece body P.
The lower surface is formed to be a smooth surface so that the lower surface can be brought into close contact.

Further, the holding tip 3 has a relatively low cylindrical shape with an outer diameter equal to the inner diameter of the piece body P, and its lower end is slightly tapered so that it cannot be inserted into the piece body P. It is designed to be easy to use.

This holding tip 3 prevents a part of the resin material forming the neck P1 from being forcibly pushed out to the trunk portion of the piece body P adjacent to the neck P1 when the rotary piece 2 rotates. Therefore, the holding tip 3 is designed to bring its peripheral surface into contact with the inner surface of the piece body P at a desired height and width.

Of course, the above-mentioned action by the holding tip 3 is not achieved by the holding tip 3 alone, but works together with the holding mold H.

From this, it is clear that the holding mold H must uniformly contact and hold at least the outer surface of the portion of the piece P that faces the circumferential surface of the holding tip 3 from the neck P1 of the piece P over the entire circumference. be understood. Now, the rotating piece 2 for rotating and flowing the neck P1 is a cylindrical body having a height equal to that of the neck P1 and an outer diameter equal to the inner diameter of the neck P1, with the central axis of this cylindrical body aligned with the central axis 5. The cylindrical body assembled to the central shaft 5 has several (eight in the case of the embodiment shown in FIG. 3) locking protrusions 2a on the outer peripheral surface of the cylindrical body. It is constructed in the form of vertical stripes that run the entire length of the body.

In the case of the embodiment shown in FIGS. 1 to 3, the inner circumferential surface of the neck P1 is a completely smooth surface, so when the rotating piece 2 is inserted into the neck P1, each of the locking protrusions 2a is pushed into the inner side of the neck P1, and as a result, the resin material on the inner side of the neck P1 into which each of the locking protrusions 2a has penetrated will change because the absolute volume occupied by the neck P1 remains unchanged. ,
This brings about the inconvenience of not being able to move.

Therefore, in the case of the embodiment shown in FIGS. 1 to 3, in the sense of forming a relief part for the resin material of the inner part of the neck P1 pushed out by each of the locking protrusions 2a, A relief recess 2b having a vertical groove shape on the outer circumferential surface adjacent to the stop ridge 2a
need to be formed.

In this way, when the inner circumferential surface of the neck P1 is a simple smooth surface, in order to position the locking protrusion 2a inside the neck P1, the inner peripheral surface of the neck P1 of the locking protrusion 2a is Since the escape recess 2b must be formed to fit the volume of the intrusion, the configuration of the two rotating pieces becomes relatively complicated.

Therefore, as shown in FIGS. 4 and 5, if an engaging longitudinal groove P2 in which the locking protrusion 2a is tightly engaged is formed in the inner part of the neck P1 from the beginning, the rotating piece 2 There is no need to form the escape recess 2b, and it is sufficient to simply form the locking protrusion 2a.

In any case, when the rotating piece 2 is inserted into the neck P1, an extremely high frictional resistance is generated between the neck P and the inner portion along the circumferential direction.

Incidentally, although not shown in the drawings, as a matter of course, an appropriate rotational driving force is transmitted to the rotating piece 2.
This rotational driving force from the outside causes the rotating piece 2 to move toward the center shaft 5.
It rotates using the axis of rotation. In addition, there is a completely close contact between the rotating piece 2 and the holding tip 3 and between the rotating piece 2 and the base plate 4, and the resin material forming the piece body P enters between them. It goes without saying that consideration has been taken to ensure that nothing happens.

The embodiments of the rotomolded body 1 shown in FIGS. 6 to 9 are as follows:
This makes it easier to insert the rotary molded body 1 into the neck P1, and the locking protrusion 2a is separate from the rotating piece 2, and the locking protrusion 2a is inserted outward from the circumferential surface of the rotating piece 2. The structure is such that it can be protruded by a desired amount.

That is, a vertical hole is formed in the circumferential wall of the rotating piece 2, which has a cylindrical shape and whose outer diameter is slightly smaller than the inner diameter of the neck part P1, over almost its entire length, and a piece-shaped hole is formed in the vertical hole. The locking protrusions 2a are tightly fitted in a slidable manner in the radial direction of the rotary piece 2, and the ends of each locking protrusion 2a ( The outer peripheral surface side edge of the rotating piece 2 is held so as to be located inward from the outer peripheral surface of the rotating piece 2.

A cylindrical extruded cylindrical body 6 is assembled into the cylindrical rotating piece 2 to which several (four in the illustrated embodiment) locking protrusions 2a are assembled so as to be able to move up and down. , each locking protrusion 2
When it moves to the lower limit opposite to a, its outer circumferential surface pushes the tip of the locking protrusion 2a onto the outer circumferential surface of the rotary piece 2 by a predetermined amount against the elastic material assembled to the locking protrusion 2a. When the locking protrusions 2a are brought to the protruding position and held in this state and moved upward to a position where they no longer face each of the locking protrusions 2a, each of the locking protrusions 2a is configured to return to its original position by the action of the elastic material. There is.

In the case of the embodiment shown in FIGS. 6 to 9, the neck P1 is deformed when the rotomolded body 1 is assembled into the neck P1, as in the embodiment shown in FIGS. 1 to 3. Therefore, there is no risk of distorting the overall shape of the neck P1.
The rotomolded body 1 can be assembled safely into the neck P1, and the structure of the piece body P itself can be complicated to make the core structure special, as in the embodiments shown in FIGS. 4 and 5. The advantage is that there is no need to

Since the configuration of the rotary molded body 1 is as described above, as shown in FIG. Once the rotary molded body 1 is attached and held, the rotary molded body 1 is moved downward along the axis of the piece body P, and the rotary piece 2 and the holding tip 3 are inserted into the piece body P to a position.

The base plate 4 is in close contact with the upper surface of the holding mold H, and the rotary molded body 1
Once the assembly is completed, the rotary piece is rotated in a fixed direction by a suitable drive device.

Due to this rotational movement of the rotary piece 2, the semi-molten resin material forming the neck portion P1 is pushed by each of the locking protrusions 2a and rotated. Since the forced flow of the resin material forming the neck portion P1 is against the adhesive force between the resin materials, the neck portion P1 is subjected to flow stretching. In this way, the rotating movement of the rotating piece 2 is applied to the neck "P1" by the rotation of the rotating piece 2, and the rotating movement of the rotating piece 2 is stopped until the temperature of the neck P1 becomes below the temperature at which the stretching effect is produced. The piece body P is cooled to form a piece.

As described above, the present invention provides a stretching effect by forcing the resin material forming the neck portion P1 to flow in a certain direction without changing the shape of the neck portion P1. The shape of the neck P1 does not change, and especially when a screw is molded on the outer circumferential surface of the neck P1 as in the illustrated embodiment, there is no inconvenience such as the screw being distorted, and the shape of the neck P1 does not change. And the dimensions can be maintained exactly as they were at the time of injection molding.

In addition, the time required for the temperature of the neck JPl, which has been heated to a temperature at which a stretching effect is produced, to be cooled down to a temperature below which a stretching effect is produced, is as follows.
Since this is a molding technique that can be known with common sense, it is sufficient to control the operation of the rotary piece 2 with a timer or the like, and the molding operation can be easily controlled.

9 As is clear from the above description, the present invention allows the neck portion P1 of a biaxially stretched polyethylene terephthalate resin bottle to have the same excellent physical properties and durability as the body portion. It is possible to improve the physical properties and durability of the bottle as a whole, and the molding operation itself is simple and easy to carry out.Furthermore, since the neck P1 is not deformed, the neck P1 can be molded by injection molding. It has excellent effects such as being able to maintain high dimensional accuracy at the time of use.

[Brief explanation of drawings]

1 to 3 show an embodiment of the method of the present invention, in which FIG. 1 is a longitudinal cross-sectional view showing the positional relationship before insertion and assembly of the rotomolded body into the piece body, and FIG. 2 is a rotary molded body. FIG. 3 is a cross-sectional view taken along the line I--I in FIG. 2, showing a flow-stretching state of the neck-forming resin material by the rotating piece. 4 and 5 show the neck of a piece body shaped to facilitate the implementation of the method of the present invention, FIG. 4 being a longitudinal sectional view of the neck, and FIG. 5 being a plan view. Figures 6 to 9
The figures show other embodiments of the rotomolded body, FIG. 6 is a longitudinal sectional view showing the state before the rotomolded body is inserted into the front part, and FIG. 7 shows the rotomolded state at this time. FIG. 8 is a longitudinal sectional view showing the state of the rotomolded body inserted into the neck, and FIG. 9 is a plan sectional view showing the state of the rotomolded body at this time. Explanation of symbols, P; Piece body, P1;
Neck, P2; Engagement longitudinal groove, H; Holding mold, 1; Rotational molded body, 2; Rotating piece, 3; Holding tip, 4; Base plate, 5; Central shaft, 2a; Locking protrusion, 2b; Escape recess, 6; extruded cylindrical body.

Claims (1)

[Claims] 1 A method for molding a piece as a primary molded product that is injection molded for biaxial stretch blow molding of a polyethylene terephthalate resin bottle, in which a neck P_1 of a piece P molded into a predetermined bottomed cylindrical shape is The piece body P is heated to a temperature that produces a stretching effect, and at least the entire outer circumferential surface of the neck P_1 is held uniformly by a holding mold H so as not to be idly rotated. is inserted in such a state that a plurality of locking protrusions 2a provided in a vertical strip shape on the circumferential surface of the rotating piece 2 are tightly engaged with the inner circumferential surface portion of the neck P_1, and then,
A method for forming a piece for a biaxial stretch blow-molded bottle, in which the rotary piece 2 is rotated in a certain direction while the temperature of the neck portion P_1 is within a temperature range in which a stretching effect is produced.