JP2516596B2 - Mouth tube processing method for polyethylene terephthalate resin bottle primary molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a method for treating a mouthpiece of a bottle made of polyethylene terephthalate resin which is biaxially stretch blow molded.

[Conventional technology]

In a polyethylene terephthalate resin bottle body that is biaxially stretch-blow-molded, the part that is sufficiently stretch-molded, such as a barrel, exhibits excellent heat resistance, but the mouthpiece that is difficult to undergo sufficient stretch-molding is heat-resistant. It is a part of inferiority.

In order to increase the heat resistance of this mouthpiece, conventionally, as shown in FIG. 2, the mouthpiece 2 of the preform 1 which is a primary molded product is heated from the outside by a far infrared heater 4 or the like to be thermally crystallized. . After completion of this thermal crystallization, the cooling nozzle 5 is tightly fitted in the mouth tube 2, and the mouth tube 2 is pressed from the inside to correct the dimensions of the mouth tube 2 while quenching the mouth tube 2 from the inside. ，
Moreover, the cold air 6 was blown to the outer surface of the mouthpiece 2 to quench the mouthpiece 2 from the outside.

[Problems to be solved by the invention]

 However, the above-mentioned conventional method has a problem.

The bottle mouthpiece processed by this conventional method is vulnerable to high-temperature filling and hot water, and is
Rolling sterilization for 0 seconds is the limit that it can withstand, for example, shower sterilization with hot water at 80 ° C for 30 minutes or high temperature heat sterilization (retort) at 120 ° C for 30 minutes, etc. As a result, there were problems such as a decrease in the opening torque and liquid leakage due to contraction of the mouthpiece.

[Means for solving problems]

The present inventor considered that the above-mentioned problems were caused by the density of the bottle mouthpiece and the cooling method after heating the mouthpiece. That is, if the density of the mouthpiece is increased, the heat resistance is improved, and with the conventional method, residual stress is generated in the mouthpiece because the mouthpiece is rapidly cooled by the cooling nozzle after heating. The bottle mouth tube contracts when it is subjected to high temperature shower sterilization.

The present inventor repeated experiments in accordance with the above idea and obtained the experimental values shown in the table of FIG.

In this table, the polygonal line A is the conventional method, that is, the mouth tube is heated from the outside and then rapidly cooled, and the B is the same as the mouth tube is heated from the outside and then gradually cooled (spontaneously cooled) for 60 seconds and then rapidly cooled. And C, which are heated in the same way and then gradually cooled.

Line D is 90 in the mouth tube after heating the mouth tube from the outside.
After inserting the heating nozzle of ℃, and heating the mouthpiece from the inside,
The heating nozzle was pulled out and the mouth tube was gradually cooled (natural cooling). E was the same method as D, and the heating nozzle temperature was set to 140 ° C.

From this experimental value, the bottle mouth tube is not only on the outside,
Higher density can be obtained by heating from the inside.
As a result, it was obtained that the slow cooling of the mouthpiece gives a higher density than the rapid cooling.

Also, as a result of an experiment on shrinkage of the mouthpiece after the treatment, for example, a test of soaking in hot water of 80 ° C for 30 minutes using a bottle with an outer diameter of 38 mmφ, the conventional method was used. The treated bottle mouth tube shrank 0.16 mm, whereas the one that was gradually cooled after heating the mouth tube from the inside did not shrink at all.

Based on the above experimental results, the present inventor established the following method. This will be described with reference to FIG.

First, a mouthpiece 2 of a preform 1 which is a primary molded product of a polyethylene terephthalate resin bottle is heated to be thermally crystallized. Next, insert the heating nozzle 3 inside the mouth tube 2,
The mouth tube 2 is pressed and spread from the inside and is heated from the inside. Then, after removing the heating nozzle 3 from the mouth tube 2, the mouth tube 2 is gradually cooled.

The spread of the mouthpiece 2 by the heating nozzle 3 is
This is done in anticipation of contraction due to slow cooling, and the diameter will be a preset value when the mouth tube contracts.

[Action]

As described above, according to the present invention, since the mouthpiece 2 of the preform which is the primary molded product is heated, the heating nozzle 3 is fitted inside the mouthpiece 2, and the mouthpiece 2 is further heated from the inside,
The thermal crystallization of the mouthpiece 2 is more advanced and the density is higher.

By the way, the density of the mouth tube 2 obtained by the conventional method was 1.3737 g / ml at the upper end of the mouth tube 2, but according to the present invention when the temperature of the heating nozzle is set to 140 ° C., it is 1.3870 g / ml. rose to ml.

Further, since the mouth tube 2 is spread by the heating nozzle to correct its size and then gradually cooled, no residual stress is generated in the mouth tube 2. Therefore, shrinkage of the mouthpiece 2 after processing and molding hardly occurs, and high dimensional accuracy can be obtained.

As a result, the bottle mouth tube 2 that could not handle hot water or filling at 85 ° C or higher has been improved to handle those at 120 ° C.

〔Example〕

 FIG. 1 shows an embodiment of the present invention.

First, the mouth tube 2 is heated from the outside by the far infrared heater 4 and the like, and the mouth tube 2 is heated to 180 to 200 ° C.

Next, the heating nozzle is fitted into the mouth tube. This is preferably done 20 to 30 seconds after the above steps due to thermal crystallization of the mouthpiece.

Although the temperature of the heating nozzle is not particularly limited, for example, as shown in the table of FIG.
Higher density can be obtained by setting at ℃,
Although not shown in this table, around 190 ° C is the most suitable temperature.

The heating nozzle 3 is preferably tapered so that the upper end portion of the mouth cylinder having the largest contraction is pushed more than the other portions.

Although the final cooling is performed, the cooling method is not particularly limited. However, the method by natural cooling is generally advantageous in consideration of all points.

The heating of the mouth tube 2 can be performed simultaneously from the outside and the inside.

〔The invention's effect〕

As described above, according to the present invention, since the mouthpiece is also heated from the inside, the thermal crystallization is further advanced, and the mouthpiece density can be further increased. Further, since the mouthpiece is heated and then gradually cooled, the mouthpiece after the processing and molding hardly shrinks. As a result, the bottle mouthpiece treated according to the present invention has a contracted mouth opening and an opening torque even if it is filled with a content liquid having a higher temperature than before or sterilized with hot water having a temperature higher than before. It will not drop and will not leak.

[Brief description of drawings]

FIG. 1 is a process diagram showing an embodiment of the present invention, FIG. 2 is a process diagram showing a conventional example, and FIG. 3 is a table showing the values of the mouthpiece density. Explanation of signs 1: preform, 2: mouthpiece, 3: heating nozzle, 4: heater, 5: cooling nozzle, 6: cold air.

Claims (1)

(57) [Claims] 1. A method for treating a mouthpiece primary molded product made of a polyethylene terephthalate resin, which is biaxially stretch-blow molded, by heating the mouthpiece (2) of a preform (1) which is the primary molded product by heating. The heating nozzle (3) is crystallized and the heating nozzle (3) is tightly fitted into the mouth tube (2) to heat the mouth tube (2) from the inside to further promote thermal crystallization, and the mouth tube (2) is moved to the inside. From the mouth tube (2) by pressing and spreading from the mouth nozzle (3), and then gradually cooling the mouth tube (2) to treat the mouth tube of the polyethylene terephthalate resin bottle primary molded product. Method.