JPS6274622A - How to make polyester bottles - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a highly efficient method for obtaining a biaxially oriented bottle from ethylene prephthalate polyester resin that exhibits low heat shrinkage and has a shape that is faithful to the mold. It is something.

(Prior art) Bottles made of polyester resin, typified by polyethylene terephthalate, are widely used for various purposes due to their excellent transparency, strength, and hygienic properties.・There are some drawbacks.

In order to improve this drawback, the l')° method is known, in which blow-stretched bottles are heat-treated at high temperatures.
If the heat treatment is not carried out for a considerable period of time, the bottles will shrink and deform when taken out, resulting in extremely slow bottle manufacturing speed.

(Problems to be Solved by the Invention) According to the present invention, when trying to obtain a bottle with small heat shrinkability, the production speed is low, and when the production speed is increased, only a heat shrinkable bottle with a small size can be obtained. This solves the conventional problem of not having

(Means for Solving the Problems) In other words, the present invention heats a polyester bottomed commercial parison to 110 to 1255°C, and places the parison in a mold whose surface is maintained at 80 to 110°C. Within, 25
000% at a stretching speed of 7 minutes or more, the stretched bottle is subsequently held in the mold while being pressed, and then released from the mold.

The present invention will be specifically explained below.

1P for this invention! The polyester resin to be used is one containing 70% or more of ethylene terephthalate units, and a normal resin having an intrinsic viscosity of 0.6 or more can be used.

The method of obtaining a parison from this polyester resin is conventionally well known, such as by injection molding to obtain a parison in the form of a cylinder with a bottom, or by closing one end of a pipe produced by extrusion molding to form a cylinder with a bottom. .

When stretching and molding this parison, the parison temperature is set in the range of 110 to 125°C, and the surface is
Blow stretching can be performed in a mold maintained at 110°C at a stretching speed of 125,000%/min or more! I! It is essential.

In general, when the mold temperature is raised, the heat treatment effect when the blow stretch-molded bottle comes into contact with the mold is greater, and the bottle
Although the heat shrinkability of the bottle decreases, at high temperatures exceeding 100°C, the bottle shrinks and deforms when taken out from the mold, making it impossible to obtain a bottle with the desired shape and capacity in a short period of time.

As a result of our investigation, we found that by setting the mold temperature to a range of 80 to 100 degrees Celsius, we could significantly reduce heat shrinkage by simply avoiding contact between the bottle and the mold for a short period of time, and it was also possible to remove the bottle. However, the shrinkage and deformation of the bottle still remained, and even though it took -1 minute, it was not good.

As a result of further investigation, we found that by increasing the parison temperature to 110-125℃, which is higher than normal temperature, and stretching the bottle, the bottle would remain faithful to the shape of the mold even if the mold temperature was raised to about 110℃. They found that this could be solved by stretching at a high speed of 25,000% or more at an unstretched speed, although the strength of the bottle was slightly lower.

When the parison temperature is lower than 110"C, the temperature is 80~110
If you use the σ type maintained at 125°C, the shape of the bottle you take out will not come out accurately, which is harmful.If the temperature is higher than 125°C, spherulite whitening may occur in the parison during heating.

Polyester resin parison on inner and outer circumferences, etc. 110~1
To heat the parison to 25° C., it is preferable to heat the parison from both the inside and outside. If heating is done only from the outside surface, the inside surface of the parison where the stretching ratio is greatest will be at a low temperature.
It is difficult to get the desired ball.

Methods of heating the parison from the inside include 1) inserting a radiant heater such as an infrared heater inside the parison; 2) inserting a hot air blowing rod inside the parison and heating it with hot air; 3) inserting a black body rod inside the parison. Among the radiation from an external infrared heater, there is a method in which visible to near-infrared radiation that is not absorbed by the polyester parison is absorbed by an internal rod to absorb the radiation.

If you want to create an axial temperature distribution on the inner surface, use a radiant heater that is much longer than the length of the parison.

It is also effective to move the parison in the axial direction in a predetermined movement-stop pattern and change the heating time by the heater for each part of the parison to provide a desired temperature profile r=l.

The mold maintains its surface at 80-110°C. .

The heat shrinkability of the ball becomes noticeable at temperatures below 80℃,
If the temperature exceeds 110'C, the shrinkage deformation when taking out the shell becomes large.

The stretching speed is 25,000%/min or more, preferably 350%/min.
Set to 00%/min or higher.

If the temperature is lower than that, the parison will be at a high temperature, so the stretching orientation effect will be reduced, and the strength of the ball will be reduced. The upper limit of the stretching speed is 50000%/min tα.

The stretching speed can be adjusted by blowing al. Note that the stretching speed here refers to the stretching ES rate in one direction around the circumference (expressed in %, for example, 3x magnification is 200%)
is the +lL uniform stretching speed in the circumferential direction divided by the time from the start of stretching to contact with the mold 1.The stretching speed in the axial direction is usually such that the axial magnification is smaller than the circumferential magnification. Therefore, the irises are smaller than this.

The stretching magnification is 2 to 3 times in the axial direction and 3 to 4 times in the circumferential direction, which are the conditions for stretching in order to give the ball sufficient strength.
It is best to set the magnification as high as possible within the range of magnification.

Blow-stretched bottles can be taken out as they are, without contacting the inner surface of the mold for 2 to 15 seconds while maintaining the internal pressure (D-pressure), and then releasing the internal pressure and cooling. .

(Example) A body with an outer diameter of 27 m + 1 and a length of 1 was made by injection molding from polyethylene terephthalate resin with an ultimate viscosity of 110.85.
A parison of 25 mm and 3.6 mm+ thickness was produced. This was heated from the inner and outer surfaces with an infrared heater, then blow-stretched, brought into contact with the mold for 4 seconds while maintaining the internal pressure, and then taken out.
The bottle was n+m and had a capacity of 1 liter. The stretching ratio is 2.5 times in the axial direction and 3.5 times in the circumferential direction.

Here, the parison temperature, mold temperature, a3, and stretching speed were changed, and the following quality items were evaluated for the balls 1 to 1.

1) Heat shrinkage rate In a bottle whose full capacity was measured at room temperature, pour 72 degrees of warm water up to the bottom of the bottle, and leave it asexual for 24 hours. After being placed in f+ at room temperature, the full volume was measured, and the rate of decrease in volume was expressed as %.

2) Tensile yield strength ta Length 65 mm, width 3 m taken along the circumferential direction of the bottle
The yield point strength was determined when a test piece of m was pulled at a tensile rate of 1150111111/min based on ASI-M-D1822.

3) The shrinkage rate of the bottle immediately after being taken out from the bottle shape mold is 5% or less in capacity and 2% or less in dimension compared to the mold shape.
I chose X for something more humane than that.

The blow stretch molding conditions and bottle quality evaluation results were first evaluated.
Also shown in the table.

Table 1 From the results, the bottles (N
It can be seen that O,7> is excellent in all characteristics.

(Effects of the Invention) According to the present invention, by stretching the parison at high temperature and high speed in a mold maintained at an appropriate temperature, heat shrinkage is small and the shape is i.
r' Accurate bottles can be manufactured with high efficiency.

Claims (1)

[Claims] In a method for producing a biaxially oriented bottle by blow-stretching a parison of ethylene terephthalate polyester, a bottomed cylindrical parison is heated to 110 to 125°C, and the surface of the parison is maintained at 80 to 110°C. Production of a polyester bottle, characterized in that the bottle is stretched at a stretching speed of 25,000%/min or more in a mold, the resulting bottle is held while being pressed against the mold, and then released from the mold. Method.