JPS59184628A - Orientation blow molding method - Google Patents

Abstract

PURPOSE:To make orientation blow molding whose thickness is uniform, by changing a moving speed of an orientation rod orientating parison in the longitudinal direction at the time of making the blow molding while orientation of the premolded parison in the longitudinal direction is being done or after orientation of the premolded parison in the longitudinal direction. CONSTITUTION:An orientation rod 5 is penetrated through a neck mold 1, inserted into a parison 6 and the orientation rod 5 is moved up to a position of about a half of prientation length S of the parison 6 under a state wherein the parison 6 controlled at a temperature suitable for orientation beforehand is inserted into a blow molding metal mold 4. Then after making a movement of the orientation rod by reducing suddenly a moving speed of the orientation rod or reducing suddenly the speed for an appropriate period of time, orientation is made by accelerating to the moving speed at the initial stage again. Then compressed fluid is blown into the orientation rod 5 through a blowing hole 5 provided on the orientation rod 5, molded into a shape of a final molded article by making the blow molding, and mold releasing is done by uncovering the blow molding metal mold.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in stretch blow molding methods.

In recent years, when blow molding resins with stretching effects such as polyethylene terephthalate or vinyl chloride into containers, etc.
By stretching the parison in the longitudinal direction in addition to blowing, the mechanical strength is increased, making it possible to form containers with a thinner wall and eaves width, so the stretch blow molding method is becoming more widely adopted.

This conventionally known stretch blow molding method involves soaking or heating a parinone (preformed product) that has been formed by the hot parison method or gold parison method to a temperature suitable for stretching, and then transferring it to a blow mold. Approximately 15 to 30 times the parinon length
The material is stretched vertically to double its original size using a stretching rod, or after stretching, a pressurized fluid such as compressed air is blown into the final molded product.

However, in general, containers formed by the stretch blow molding method have a neck part for a cap.
In order to form the 71-sided surface of the parinon, it is necessary to cool the neck quickly to prevent deformation during stretching and blowing, and to prevent whitening and rain caused by gradual cooling. Since the tips of the rods are in direct contact with each other, it is necessary to cool the rods at a predetermined temperature so that they already have a certain degree of mechanical strength during stretching to prevent breakthrough during stretching.

For this reason, it is almost unavoidable that the top and bottom parts of Parinon become colder than the body of the middle part before the stretching and blowing process. As shown in the figure, only the body part, which is easy to stretch, stretches and deviates, while the outer part hardly stretches, and even if the stiffness is molded, the meat becomes uneven and unnecessary parts become thick. In extreme cases, problems such as blow-out during molding and defective molding were inevitable.

This invention has been made to solve the above-mentioned problems, and when P-prepared and molded Palino/ is stretched in the longitudinal direction, or after stretching in the longitudinal direction, it is blow-molded.
The above-mentioned problems are solved by varying the moving speed of a stretching rod that stretches Parinon in the longitudinal direction.

The following will explain the embodiment shown in FIG.

1 is a neck mold, 2 is a blowing split mold, and 3 is a blowing bottom 1 (these molds 1.2.3 form a blow molding mold soil.

Reference numeral 5 denotes a stretching rod, which is moved back and forth by a cam or L (not shown) to stretch Parinon, which will be described later.The rod 5 is usually provided with a blow hole, through which compressed air is supplied 4B of pressurized fluid for blow molding is supplied, and a hole is provided at the mouth to prevent the pressurized fluid from escaping from the mouth.

6 is a preformed parison, 61 is a parison in the middle of stretching 6
11 is a parison that has been stretched, and 7 is a molded product.

Next, the present invention will be explained step by step.

Figure 2 (,) shows a state in which a parinon (preformed product) 6 whose temperature has been controlled in advance to a temperature suitable for stretching is inserted into a blow molding mold A, and from this state a stretching rod 5 is passed through the neck mold L. As shown in FIG. 2(b), the stretching rod 5 is moved at the same moving (lowering) speed as in the conventional method at a position 1 outside the path of the stretched length S of the parinon 6.

Therefore, up to approximately y2 of this stretching amount, the trunk portion, which is most easily stretched, is mainly stretched and becomes thinner.

From the state shown in Figure 2(b) (approximately % elongated state), the moving speed of the stretching rod is suddenly reduced (less than % of the initial speed) and the stretching rod is moved, or this state (Fig. 2(b) (h)) from the outside-stretched state) for an appropriate period of time (e.g., several seconds, depending on conditions such as the former resin to be processed and the shape of the molded product) and then rapidly decelerate (speed to 1/1°F or more of the initial speed). After wetting, the speed of movement is increased again to the initial speed and stretching is performed.

During this deceleration stretching, the parts that were stretched in the previous process and became thinner are hardly stretched, making it perfect! The temperature of the thinner middle part (body part) is the same as that of the part below it (near the lobes and bottom part, which cools quickly) because it cools down more rapidly than the tip part. The tensile strength will be closer to or lower than 1 degree, and the tensile strength will also increase due to being stretched.

Therefore, in decelerated stretching from this state to the final stretching position shown in FIG. 2(c) and accelerated stretching after decelerated stretching,
The body part that had been elongated in the previous process hardly elongated due to cooling during deceleration stretching and the increase in tensile strength due to the stretching effect of being stretched in the previous process, and the neck and bottom parts that had hardly elongated in the previous process. Since the part near the end is relatively high temperature and has low tensile strength, this part is mainly stretched, so the wall thickness of the parinon after stretching is equal to the total length, as shown in Fig. 2(c). It is almost uniform throughout.

From this state, pressurized fluid is blown into the blow hole provided in the drawing rod 5 (not shown), and the blow molding is performed to form the final molded product as shown in FIG. 2(d). Open and release the mold to complete one process.

Although this example describes an example in which blow molding is performed after the completion of the drawing process, blow molding may be performed simultaneously with the drawing process, and in this case, when the moving speed of the drawing rod is reduced, the moving speed is At the same time, the amount of blowing is also reduced.

As shown in Figure 3, line a, the drawing rod is drawn at a constant speed at a reduced speed from approximately the middle of the drawing straw to the final stroker, or depending on conditions such as the length of drawing or the forming material. As shown in the line in Figure 3, an example is given in which the moving speed of the drawing rod is rapidly reduced for a certain period of time and then increased again. It goes without saying that changes can be made within the scope of the gist.

According to the present invention, by continuously changing the stretching speed of the stretching rod, the wall thickness of the burr horn after stretching can be made approximately uniform, so that the molded product also has a uniform thickness distribution. Since the stretching effect becomes uniform and uniform, there is no possibility that the mechanical strength will be locally reduced due to overstretching or insufficient stretching.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the T culm of conventional stretch blow molding, Figure 2
The figure is a schematic diagram showing the second step of stretch blow molding of the present invention, and the third
The figure is a diagram showing the relationship between the stretching stroke and time of the present invention. 5: Stretching rod 6: Parinono

Claims (1)

[Scope of Claims] ■) Stretch blow molding in which preformed paris horns are stretched in the longitudinal direction or ε or after stretched in the longitudinal direction, a pressurized fluid such as compressed air is blown into the shape of the final molded product. In the process of stretching Parinon in the longitudinal direction, the moving speed of the stretching rod is changed.I) Stretch blow molding method with TC stretching as a percentage characteristic 2) The stretching rod is stretched up to approximately y2 of the stretch meter. Stretch blow molding method according to claim 1), in which the rod is moved at a high speed and then decelerated to a speed less than % of this speed. After
1 of this speed. Move by decelerating to the speed of /10T, then increasing the speed to the initial speed of 1.'t
Stretch blow molding method according to claim 1)