JPS6040369B2 - Method for imparting thermal stability to oriented polyester blow molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for imparting thermal stability to oriented polyester blow molded articles.

Many methods for manufacturing oriented polyester blow molded products (hereinafter abbreviated as blow molded products) have been introduced in the past.

The general method is to first make a hollow preform from molten polyester, reheat the preform by various methods to a temperature at which it can be stretched, insert it into a forming mold, and then insert the preform into the preform. By blowing gas into the product and expanding it, a hollow product having a desired shape is formed. The hollow molded product obtained in this way is transparent and has excellent properties such as impact resistance and gas permeability, but is thermally unstable.
When used as a container, it cannot be filled with high-temperature substances or sterilized at high temperatures, and can only be used for specific purposes. (Polyester film retains its strength)
In order to impart thermal stability, it is common to carry out so-called heat setting, which is heating to a predetermined temperature under tension, after stretching.

Furthermore, after heat setting, it is also carried out to slowly cool the material by passing it through a temperature region lower than the heat setting temperature without rapidly cooling it under tension. In this way, in the case of a film, a satisfactory thermal stability can be obtained, but this is because the shape is simple and the orientation within the film plane is uniform throughout.
At that time, heat fixation was performed at the same temperature, and the processing temperature was 20°C.
It is a high temperature like 0-235q0. However, in the case of blow molded products, the shapes are various and non-uniform, and the degree of orientation usually differs depending on each part of the molded product. In order to provide stability, when blow molded products are simply heated to the same temperature and heat-set at a high temperature, as in the case of film, whitening occurs in the low-orientation areas, making them brittle and cracking on impact, which impairs their performance. The transparency and appearance deteriorate as well. Furthermore, when heat setting is performed at low temperatures to prevent whitening, the highly oriented portions are not sufficiently heat set, and thermal stability sufficient to maintain performance as a blow molded product cannot be obtained. Also,
Even if heat setting is performed sufficiently, sufficient thermal stability cannot be obtained because the distortion generated during molding remains within the hollow molded product. Thus, the product produced by the conventional method is 60q.
If left in an atmosphere of about
00 high-temperature filling causes a volumetric contraction of 3.5% or more and a large change in shape, making it unusable in a high-temperature atmosphere not only in high-temperature filling but also in normal use.
The present invention provides a hollow molded product which does not have the above-mentioned disadvantages, maintains transparency and strength at high temperatures, is not deformed even by high-temperature filling, and has excellent thermal stability without deformation over time. The purpose of the present invention is to provide a method for imparting thermal stability to an oriented polyester blow molded product by applying lk9/t (gauge pressure) to the molded product in a mold. ) with internal pressure above Tg
+1000 (Tg is the glass transition temperature) or higher, and in the low orientation part where the degree of plane orientation (△P) is △Pmi90×10-3, the temperature within the range with Tg+5000 as the upper limit, the plane orientation 235 in highly oriented parts where the degree is △P>90×10-3
Heat fixation is carried out at a temperature within a range with an upper limit of 0.00, and then the entire molded product is cooled to below Tg while applying internal pressure, and then the entire molded product is heated to a temperature of 40 to There exists a method for imparting thermal stability to a polyester blow molded product by oriented orientation, which is characterized by heat treatment at a temperature of 80°C for 30 minutes or more.

The present invention will be explained in detail below.

The polyester used as the material for the blow molded product in the present invention is polyethylene terephthalate, or a copolymer using other acidic components or glycols as a monomer to the extent that the properties of polyethylene terephthalate are not impaired, such as ethylene terephthalate component % by weight or more, or a blend thereof, with an intrinsic viscosity of 0.
50 or more, and may contain calcium, germanium, antimony, zinc components, or other lubricants.

Any conventionally known method may be used to produce oriented blow molded articles from these polyesters.

That is, first, a preformed product is made from polyester, this preformed product is heated to a temperature at which it can be stretched, and then gas is blown into the molded product in a mold to expand it. For example, either a hot parison method or a cold parison method may be used. In the method of the present invention, the hollow molded product obtained as described above is placed in a mold under an internal pressure of lk9' (gauge pressure) or higher, preferably 1 to 20 [9/gauge pressure], and is placed under low orientation. Heat fixation is performed under conditions that do not cause whitening of the part, followed by cooling with internal pressure applied, and then heat treatment at a temperature within the range of 40 to 80 oo for 30 minutes or more without applying internal pressure. do. The above-mentioned heat setting is generally carried out at a temperature of 10° C. or more above the glass transition temperature, that is, (Tg+10)° C. or above, and under conditions that the low-temperature-directing portion of the hollow molded product does not whiten. The upper limit of the heat fixing temperature is Tg+5000 (heating time is 15-18 silica sand) for the low orientation part where the degree of plane orientation (ΔP) is ΔPS90×10-3, and the degree of plane orientation (ΔP>90×10). In the highly oriented portion of -3, 235 points are set to 0 (heating time is 1 second or more). After the heat setting is completed, the entire hollow molded product is cooled to below Tg while the internal pressure is still applied, the hollow molded product is taken out from the mold, and then the hollow molded product is heated for 40 minutes without applying internal pressure. Heat treatment is performed at a temperature of ~80°C for 30 minutes or more. There is no upper limit to the time of this heat treatment, and it may be carried out for a long time, but since no particularly favorable effects have been obtained by carrying out the heat treatment for a long time, it may be determined as appropriate from an economical point of view. In heat setting before heat treatment,
It is essential to apply an internal pressure of lk9 (gauge pressure) or more to the hollow molded product, and if this internal pressure is not applied, the molded product will be deformed by heating. The heat setting temperature at this time must be (Tg110)°C or higher; if it is lower than this temperature, even if further heat treatment is applied after heat setting, a product with excellent thermal dimensional stability will not be obtained. . In addition, if the heat setting temperature is higher than (Tg + 50) °C in areas with a low degree of planar orientation, whitening will occur, making it impossible to provide stable heat resistance and damaging the impact strength and appearance, so be careful not to heat it to an excessively high temperature. It is necessary to pay attention to For highly oriented parts with one-sided orientation degree of ΔP>90×10-3, the heat setting temperature is preferably selected from the range of Tg+1000 or higher (preferably Tg16000 or higher) and 235o0 or lower, and is less than this lower limit. Even if further heat treatment is applied after heat setting, it is difficult to obtain desirable thermal dimensional stability, and heat setting at a temperature of 23,500 or higher causes a decrease in orientation and physical properties, resulting in loss of properties as an oriented hollow molded product. Fear arises. In addition, if the hollow molded product is cooled without applying internal pressure after heat-setting, the molded product may be deformed during the cooling process, so it should be cooled while applying the same internal pressure as during the previous heat-setting. It is essential to do so. Next, heat treatment after heat setting is performed at 40 to 8
It is carried out at a temperature of 0qo.

At this time, if the temperature is less than 4000, it is not possible to remove the distortion caused during blow molding, and sufficient thermal dimensional stability cannot be obtained. Furthermore, if this heat treatment is performed at a temperature higher than 800°, deformation will occur, especially in the low-orientation portion, and if heat treatment is further applied at this high temperature for a long period of time, whitening will occur, causing problems in the shape and appearance of the blow molded product. Furthermore, if heat treatment is applied without first heat setting, the volume will change greatly when filled with 8000 ml high temperature material, and sufficient thermal stability will not be obtained. Furthermore, if internal pressure is applied to the molded product during these heat treatments, the shape changes and the original shape of the molded product cannot be maintained. This heat treatment step after heat setting is an especially important operation when demanding thermal stability properties are required for the molded article. There are various heating methods for carrying out the heat fixing, including a method of circulating a heating medium through a mold, a method of induction heating, etc., and any method may be used.

When trying to differentiate between high and low heating temperatures for parts with a high degree of plane orientation and parts with a low degree of plane orientation, it is necessary to ) A mold that allows the heating temperature to be locally controlled may be used. The heating means in the heat treatment after heat setting may be any method such as infrared heating or hot air blowing.

In the present invention, the glass transition temperature (Tg) is a value measured by the Durato method, and in the case of polyethylene terephthalate, the value varies depending on the stretching conditions, but is usually between 65 and 750C.

Next, examples of the method of the present invention and comparative examples will be described. In these examples, the evaluation method for dimensional stability is 8
Determination was made based on the amount of deformation, shape change, and whitening when hot water at 0° C. was poured, and the degree of shape change and whitening was visually determined.

Moreover, when the amount of deformation caused a volume change of 0.4% or more, it was judged as a failure. Example 1 From polyethylene terephthalate according to the usual method,
Oriented polyethylene terephthalate blow molds (the most common type of bottle) were molded.

In this bottle-shaped molded product, the eyebrow part and the bottom part, which form a gently sloped curved surface from the entrance part to the body part, are △PS
It has a low orientation of 90×10-3, and the body part has △P>9
It was highly oriented at 0x10-3. The Tg of the low orientation part was about 6600, and the Tg of the high orientation part was about 68q0. This hollow molded product is then placed in a mold. The mold used had a jacket structure in which the heating medium (oil) could be fed and circulated independently at locations corresponding to the shoulder, bottom, and body of the bottle. Nitrogen gas at a controlled pressure was introduced into the hollow molded product inserted into the mold through its mouth, and the internal pressure was maintained at 10k9/m (gauge pressure). Then, heat fixing was carried out by heating the low orientation part with sand at about 8500°C for 6 hours, and the high orientation part at about 85q○ for 6 steps, and after that, the internal pressure of 10k9/hour was applied to the inside of the hollow molded product. A cooling medium (water) was passed through the jacket of the mold to cool the entire mold to about 50 degrees Celsius, and then the molded product was taken out and heat treated in an atmosphere of about 70 qo for about 60 minutes without applying internal pressure. The obtained molded product showed no whitening or change in shape, and had good impact resistance. Although 80 oo of hot water was injected into this molded product, the volumetric shrinkage was 0.33% and no change in shape was observed. Example 2 A bottle-shaped oriented polyethylene terephthalate blow molded product was obtained in the same manner as in Example 1.

In this product, the Tg of the low orientation portion was approximately 67° C., and the Tg of the high orientation portion was approximately 7000. In the same manner as in Example 1, heat fixing was performed by heating the low orientation area at approximately 10,000°C for approximately 3 minutes and the high orientation area at approximately 220°C for approximately 15 seconds, and then cooling the whole to approximately 50°C. The molded product was taken out from the mold and heat treated in an atmosphere of about 50° C. for 30 minutes without applying internal pressure.

The obtained molded product did not whiten or change in shape and had good impact resistance, and even though it was filled with 8,000 ml of hot water, there was no deformation and the volume change was only 0.09% shrinkage. Comparative Example 1 A bottle-shaped oriented polyethylene terephthalate blow molded article similar to Example 1 was treated.

The Tg of the low orientation part of this molded product is approximately 67C, and the Tg of the high orientation part is approximately 67C.
g was approximately 70 qo. In the same manner as in Example 1, the low orientation part was heated at about 90°C for 30 seconds and the high orientation part was heated at about 160°C for about 3 3 seconds to perform heat fixation, and after cooling the whole to about 50oC, the molded product was prepared. Remove from the mold and heat it without applying internal pressure.
Heat treatment was performed in an atmosphere of 500 °C for 15 minutes.

In this example, the heat treatment temperature was excessively high, and although the obtained molded product did not whiten, its shape changed and it was passed as a blow molded product. Comparative Example 2 The same bottle-shaped molded product as in Example 1 was used.

The Tg of the low orientation part of this molded article was about 670, and the Tg of the high orientation part was about 7000. In the same manner as in Example 1, the low orientation area was approximately 90oo and approximately 6 anchors, and the high orientation area was approximately 160mm.
00 for about 60 seconds to heat fix, and then
The whole was cooled to about 50 oo and removed from the mold without any particular heat treatment.

The obtained molded product did not whiten or change in shape and had good impact resistance, but the volume shrank by 0.54% when it was filled with 80°C hot water. Therefore, although this molded article can be used in some applications, it is not suitable for applications that require particularly severe thermal dimensional stabilization. Comparative Example 3 The same bottle-shaped molded product as in Example 1 was used.

The Tg of the low orientation part of this product is approximately 67q0, and the Tg of the high orientation part is approximately 67q0.
g was about 7000. Using the same machine as in Example 1, this molded product was heat-set by heating the low orientation part at about 9,000°C for about 6 nights and the high orientation part at about 160° C. for about 60 seconds.

Thereafter, the whole was cooled to about 500C, taken out from the mold, and heat-treated in an atmosphere of about 3000C for about 100 minutes. The obtained molded product did not cause whitening or deformation and had good impact resistance, but when filled with 8000 ml of hot water, the molded product contracted in volume by 0.50%. Comparative Example 4 A bottle-shaped oriented polyethylene terephthalate hollow molded product similar to that in Example 1 was used, but without heat setting, it was heat treated in an atmosphere of about 6,000 °C for about 60 minutes without applying internal pressure.

The obtained molded product did not whiten or deform, but when it was filled with 80q0 of hot water, a volumetric shrinkage of 6.54% occurred and a change in shape was observed. What has been explained above and shown in the examples is merely an illustration to help the understanding of the present invention, and the method of the present invention is not restricted by these examples, and the present invention does not intend to be bound by any other modifications or variations within the spirit of the present invention. An example can be taken.

Claims (1)

[Claims] 1 In order to impart thermal stability to oriented polyester blow molding, 1 kg/cm^2 (
Tg+10℃ (with internal pressure higher than gauge pressure)
Tg is the glass transition temperature) or higher, and in the low orientation part where the degree of plane orientation (△P) is △P≦90×10^-^3, the temperature and degree of plane orientation are within the range with the upper limit being Tg + 50 ° C. △
For the highly oriented part of P > 90 x 10^-^3, heat fixation is performed at a temperature within the upper limit of 235°C, and after cooling the entire molded product to below Tg while keeping the internal pressure applied, Then, the entire molded product was heated for 40 minutes without applying internal pressure.
A method for imparting thermal stability to an oriented polyester blow molded article, the method comprising heat treating at a temperature of ~80°C for 30 minutes or more.