JP4582464B2 - Preform molding method by compression molding - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a preform molding method by compression molding, and a synthetic resin container manufacturing method and a manufacturing apparatus in which stretch blow molding is combined therewith, and more specifically, a melt of a synthetic resin is compression molded by a compression molding machine to form a preform. The present invention relates to a preform molding method for removing internal distortion of a preform without using an external heating means when taking out the preform from a mold.

Plastic containers are widely used in daily life as containers for beverages and foods due to their light weight, economy, excellent physical properties, and adaptability to environmental problems. In particular, containers formed from polyethylene terephthalate (so-called PET) are in great demand as containers for soft drinks, beverages, and foods due to excellent mechanical properties and transparency. It is heavily used by consumers as containers and retort processing containers, and also as heating containers for beverages in winter.
As described above, a synthetic resin container represented by polyethylene terephthalate (PET), which is important as a container for drinking water and food in daily life, is generally formed by molding a preform (a preformed bottomed cylindrical molding material). It is efficiently manufactured by a stretch blow molding method (simply referred to as stretch molding or blow molding) in which a fluid such as air is blown into a mold.

  Conventionally, preform molding as a molding material for plastic containers and production of containers have been mainly performed by molding a preform in a multi-piece mold by an injection molding method, and then stretch blow molding into a product container. However, since the preform temperature is once cooled to near room temperature, and then the entire preform or the body is reheated and stretch blow molded, the consumption of a large amount of heat energy for reheating and the cost of reheating equipment are reduced. Issues such as burden remain. Recently, technical demands for economical production of containers with higher performance by increasing production efficiency have increased, and the cost and size of molding equipment have been reduced, production efficiency has been improved, or low-temperature molding has been transferred. Therefore, development of a better manufacturing method or manufacturing apparatus is desired.

  As one of the solutions, an injection stretch blow molding method (for example, see Patent Document 1) in which blow molding is performed immediately after injection molding without reheating the preform has been developed. High productivity cannot be obtained due to poor molding time consistency. In addition, a method has been developed in which a large number of preforms are molded at once using an injection molding machine and stretch blow molding is performed immediately thereafter. It is difficult to avoid performance deterioration due to the thermal history difference of the temperature change of the preform due to the time difference in the preform, or due to fluctuations in the stretch blow moldability due to the temperature difference between the preform surface and the interior due to the thickness of the preform There is a problem that a product container of a certain quality cannot be obtained.

On the other hand, a compression molding machine has been proposed as a molding device that can be reduced in size and low-temperature molding at a low price compared with an injection molding device, and a large number of molding dies in order to increase mass productivity and improve manufacturing efficiency. A rotary compression molding machine (rotary movable compression molding machine) in which is attached to a rotating disk has been developed and adopted (for example, see Patent Document 2).
Then, as a preform molding method using a rotary compression molding machine, a material feeding method using an extrusion method and a molding method using the rotary compression molding machine have been developed (see Patent Document 3). The adoption has dramatically improved production efficiency, and recently, the most promising method for preform production is extrusion compression molding.

As a preform molding method using a rotary compression molding machine, the material supply by extrusion method and the molding method by using this rotary compression molding machine are smaller and lower in cost than the injection molding system. Although it is a very good molding system that can be molded and has high production efficiency, the preform taken out from the compression mold is cooled by the mold, and its surface part (especially in the body part) is subjected to thermal strain, etc. Due to internal distortion caused by this, problems arise that impair the stretch blow moldability and the physical properties of the molded container product.
In general, polyester resin, etc., can remove internal strain by heat treatment after stretch molding. Therefore, in order to solve the above problems, external heat treatment is applied to the preform taken out from the compression molding die, and internal strain is removed. Has been proposed (see Patent Document 4) and put into practical use.
However, when instantaneous heat treatment is performed with a gas burner or the like according to this proposal, the burden on fire prevention management and safety management due to the use of fire in the plastic molding line increases, and the cost and maintenance of the heating equipment However, the cost increases and the economic cost decreases. Moreover, since it cools again after heat processing, energy consumption also increases and becomes a burden also in terms of economic cost or environmental measures.

JP-A-52-82967 (Claim 1 and lower right column on page 1) JP-A-60-245517 (Claim 1) Japanese Patent Laying-Open No. 2000-25729 (Claim 1 and FIG. 1) JP 2005-7648 A (Summary)

As described above in paragraph 0006 of the background art, the preform taken out from the compression mold is cooled by the mold, and an internal strain due to thermal strain or the like is generated on the surface portion (especially in the body portion). Since problems that impair blow moldability and physical properties of molded container products are derived, a method to remove internal strain by applying external heat treatment to the preform taken out from the compression mold using a gas burner, etc. However, when heat treatment is performed with a gas burner, etc., the burden on fire prevention management and safety management due to the use of fire in the plastic molding line increases, and in terms of cost and maintenance of heating equipment The cost increases and the economic cost decreases, and it is cooled again after the heat treatment, so the energy consumption increases and the economic cost and environmental measures It is also a load.
In view of this, the present invention has developed a method for removing internal distortion of a preform that has been compression-molded and taken out of a mold without performing external heat treatment using a gas burner or the like, in order to solve the problem caused by such external heat treatment. This is a problem to be solved by the invention.

  In order to find out a method for removing internal distortion of a preform that has been compression-molded and taken out from the mold without subjecting it to external heat treatment using a gas burner or the like, Various considerations have been made from various viewpoints such as molding conditions, preform material, thermodynamic properties of the preform with respect to the external temperature, and temperature dependence of the internal strain, and various experimental considerations have been made. Paying attention to the temperature dependence, if the preform taken out from the compression mold is taken out in a high temperature state and adjusted as it is, such as air cooling (hereinafter referred to as “temperature control”), thermal distortion and flow It was possible to recognize that the internal strain caused by the sexual strain and the like was efficiently removed.

  Specifically, when the preform is taken out from the mold, the preform is synthesized in a state where the outer surface temperature is high, in particular, the outer surface (outer surface) temperature of the body portion is the material of the preform. This is a novel thermal processing method for a preform to be taken out in a state of (glass transition temperature-2) ° C. or higher and (glass transition temperature + 8) ° C. or lower of the resin.

  Further, as ancillary invention, i) when the preform is taken out from the mold, the surface temperature of the preform nozzle portion is defined, and the temperature of the compression molding mold is higher than the temperature control temperature of the preform material synthetic resin. (Glass transition temperature +2) ° C. or lower, ii) Perform temperature control after taking out the preform from the mold, and iii) The outer surface of the preform body is heated by the heat inside the preform body. (Glass transition temperature + 18) ° C. or higher (Glass transition temperature + 42) ° C. or higher, iv) Furthermore, the synthetic resin of the preform material is polyethylene terephthalate (PET) having a glass transition temperature of 77 to 78 ° C. And

By the way, as described above in paragraph 0006, it is well known that a polyester resin or the like can generally remove internal strain when subjected to heat treatment after stretch molding. The preform is reheated after stretch molding to reduce internal strain. Removal is normally performed, and the preform is usually cooled and taken out from the compression molding machine. Further, as seen in the above-mentioned Patent Document 4, the preform is taken out from the compression molding die. A method for removing internal distortion by performing external heating treatment with a burner or hot air on the reform has also been put into practical use.
However, when the preform is taken out from the mold in the present invention, the preform is taken out in a state where the outer surface temperature is high, and the temperature of the preform is adjusted so that the temperature is raised by the heat inside the preform itself. The thermal treatment method is not yet known, and cannot be found even by examining the conventional patent documents.

  In the above, the basic configuration of the invention of the present application has been described in outline. However, the entire invention of the present application is composed of the following invention unit groups, and the invention of [1] is the basic invention. The inventions other than the invention embody the basic invention or form an embodiment. (The invention group as a whole is collectively referred to as “the present invention”.)

[1] It is characterized in that a drop which is a synthetic resin molten lump is compression molded by a compression molding machine to form a preform, and when the preform is taken out from the mold, the preform is taken out at a temperature higher than normal temperature. A method of forming a preform.
[2] In [1], when the temperature is higher than normal temperature, the outer surface temperature of at least the trunk portion of the preform immediately after taking out the compression-molded preform from the mold is the glass transition temperature-2 of the synthetic resin. ) The method for molding a preform according to [1], wherein the temperature is not lower than (° C) and not higher than (glass transition temperature +8) ° C.
[3] When the preform is taken out from the mold, the outer surface temperature of the preform nozzle part is taken out in a state where the temperature is not less than the temperature control temperature of the mold and not more than (glass transition temperature +2) ° C. of the synthetic resin. A method of forming the preform in [1] or [2].
[4] The method for molding a preform according to any one of [1] to [3], wherein the preform is temperature-controlled after the preform is taken out from the mold.
[5] Temperature control of the preform raises the outer surface of the preform body to (glass transition temperature + 18) ° C. or more (glass transition temperature + 42) ° C. or less of the synthetic resin by heat inside the preform body. The method for forming a preform according to [4], wherein
[6] The method for molding a preform according to any one of [1] to [5], wherein the synthetic resin is polyethylene terephthalate (PET) having a glass transition temperature of 77 to 78 ° C.

In the present invention, it becomes possible to remove the internal distortion of the preform that has been compression-molded and taken out from the mold without performing an external heating treatment with a gas burner or hot air, thereby improving the blow moldability. In addition, a product container having a certain excellent quality can be obtained.
In addition, because the preform is not subjected to normal heat treatment, there is no burden in terms of fire prevention management and safety management due to the use of fire in the plastic molding line, and there is a possibility of damage such as carbonization on the surface of the preform due to overheating. In addition, it is possible to reduce incidental equipment and heat energy for preform heating and subsequent cooling.

  The present invention has been described in accordance with the basic configuration of the present invention as means for solving the problem, but in the following, the preferred embodiments of the invention of the present invention group described above are representatively described. The present invention will be described more specifically with reference to the drawings that show various exemplary embodiments.

1. TECHNICAL FIELD The present invention relates to a compression molding and stretch blow molding method and apparatus for producing a synthetic resin container, and in particular, a preform is compression molded by a compression molding machine. In this case, the main configuration and features are a method of removing internal distortion of a preform that has been compression-molded and taken out of a mold without performing an external heat treatment with a gas burner or hot air.

(2) High-temperature removal of preform In the present invention, when the preform is compression-molded by a compression molding machine, it is compression-molded and removed from the mold without being subjected to external heat treatment with a gas burner or hot air. In order to remove the internal distortion of the reform, the preform is made of a synthetic resin (glass transition temperature -2) in which the outer surface temperature of the preform is higher than room temperature, especially the outer surface temperature of the body is the preform material. It is taken out in a state of not less than ℃ (glass transition temperature +8) ℃.

If the outer surface temperature of the preform body is lower than (glass transition temperature-2) ° C. of the synthetic resin that is the preform material, the internal strain removal action is insufficient, and if the glass transition temperature is higher than (glass transition temperature + 8) ° C. When the preform is removed from the core of the mold, the preform may be deformed. In addition, the outer surface temperature of the neck part (nozzle part) at the time of taking out high temperature is preferably not less than the temperature control temperature of the compression mold and not more than (glass transition temperature + 2) ° C. of the synthetic resin of the preform material.
The preform after compression molding is hung on the core (male mold), and the core is extracted with the outer periphery of the nozzle part (screw part) of the container held by the nozzle part molding split mold (female mold). Of course, the outer surface temperature of the nozzle portion at this time is equal to or higher than the temperature control temperature of the compression mold, but when the synthetic resin is, for example, a PET-based polyester and the glass transition temperature is 77 to 78 ° C., 80 ℃ or less (more preferably 60 ℃ or less) is preferable, and when the glass transition temperature exceeds +2 ℃, the temperature of the central portion in the thickness direction of the nozzle portion is higher than the outer surface temperature, so the resin is still insufficiently solidified Since the nozzle portion is softened, the nozzle portion is deformed, and it is difficult to maintain and manage strict dimensional and shape accuracy related to sealing. On the other hand, if the outer surface temperature of the preform body is (glass transition temperature + 8) ° C. or less, the preform body can be extracted without being deformed so as to affect the subsequent blow molding process.

(3) Internal distortion of preform In the conventional preform compression molding method, the preform taken out from the compression molding die is cooled by the die and taken out in a state of being cooled to the temperature control temperature of the die or room temperature. As a result, internal distortion due to thermal strain or the like is generated on the surface portion (particularly in the body portion), thereby deteriorating the formability of stretch blow molding and the physical properties of the molded container product.
The internal strain of the preform is mainly due to the resin flow orientation that occurs when filling the mold with the synthetic resin and the thermal strain due to the temperature difference between the surface skin layer and the internal layer when the preform is cooled. .

(4) Relieving or eliminating the internal distortion of the preform When the preform is taken out of the mold at a high temperature on the outer surface, especially at a glass transition temperature of −2 ° C. or higher of the synthetic resin of the preform material, It is possible to relax the flow orientation generated at the time of reforming.

Furthermore, if necessary, after taking out the preform from the mold, air cooling (natural leaving or natural cooling in the transfer process, or gas blowing), water cooling, or a combination of these may be performed. This is a preferred embodiment. By placing the preform extracted from the mold in a constant thermal atmosphere (by adding a partial heat treatment and / or partial cooling treatment to the preform as necessary), The outer surface is heated to (glass transition temperature +18) ° C. or higher (glass transition temperature +42) ° C. or lower of the synthetic resin by high heat inside the preform body (part near the center in the thickness direction; intermediate layer). Further, by increasing the temperature over the entire thickness direction of the preform, the flow orientation can be further relaxed for the inner and outer surface skin layers and the inner intermediate layer of the preform. The temperature difference between the skin layer and the inner layer is reduced to mitigate thermal strain, and then the body part is not whitened by excessive temperature rise, so internal strain during preform compression molding is reduced. It can be alleviated or eliminated to apply.
As a specific embodiment, the preform is taken out at a high temperature and transported at room temperature for several seconds (air cooling; natural cooling in a transported state at room temperature), and then preferably water-cooled transport (both of the body and bottom). The outer surface is water-cooled) and temperature-controlled. At that time, the inner and outer layer temperatures are raised again by using the high heat of the intermediate layer of the preform to remove compression molding strain and thermal strain, and then water-cooled before whitening by heat.

(5) Actual state of elimination of internal distortion of preform Regarding high temperature preform removal in the present invention, preform molding (i), high temperature removal from mold (ii), and air cooling (natural cooling) state (iii) 2), an example of the change in the temperature of the preform over time is illustrated in the graph of FIG. Temperature change (° C; over time) (seconds; horizontal axis) at the inner surface (0.0T; T is the thickness) and outer surface (1T) of the preform body and the center point (0.5T) of the inner layer part. The actual measurement value (vertical axis) is shown by a curve. In this example, the thickness of the preform body is 3.5 mm, the mold cooling temperature (mold temperature control temperature) is 12 ° C., and the ambient temperature is 25 ° C.
As shown in this graph, if the preform is taken out of the mold at high temperature and air-cooled, the inner surface and outer surface of the preform are once subjected to the inner surface using the high heat of the intermediate layer including the center of the thickness of the preform. About 30-45 ° C, and about 15-30 ° C on the outer surface, and over time, the inner and outer surfaces and the central part are approaching a uniform temperature (gradual temperature approach). Yes.
As a result, the flow orientation generated during the molding of the preform is alleviated, and the thermal strain due to the temperature difference between the surface skin layer and the inner layer is alleviated, so that the internal strain at the time of taking out the preform is alleviated or eliminated.

2. Ancillary Inventions in the Present Invention As described above in paragraph 0011, the following inventions can be listed as incidental inventions in the present invention.
As an additional invention, after forming a preform by compression molding, high temperature removal and air cooling are performed, and then the preform is stretch blow molded by a stretch blow molding machine to produce a synthetic resin container. It is a continuous system method.
As an apparatus for executing this system, a rotary drop supply body having a drop cutting means and a supply means, a rotary compression molding machine, a preform take-off, which is a synthetic resin molten mass extruded from the extrusion opening of the extrusion means. Each of the ejector, the rotary stretch blow molding machine, and the product container ejector is configured as a continuous system. An example of this system is illustrated as a molding process flow diagram in the schematic diagram of FIG.

As an incidental invention, a step of heating and crystallizing the mouth and neck of the container is further added, and the stretch blow molding is a biaxial stretch blow and / or a two-stage blow, It is an embodiment of the basic invention in which the synthetic resin container is a bottle or a cup.
In the present invention, preferably, a step of heating and crystallizing the mouth and neck of the container is further added as necessary. This process is normally used in stretch blow molding of synthetic resin containers typified by polyethylene terephthalate, and is used to increase the strength of the mouth and neck by heat treating and whitening and crystallizing only the mouth and neck of the preform. Is done. This crystallization step may be performed either before or after stretch blow molding.

3. Other Requirements (1) Synthetic Resin Material As a raw material resin for forming the preform of the present invention, any resin can be used as long as it is a moldable thermoplastic resin. Examples of such resins include thermoplastic polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), copolymer polyesters mainly composed of these ester units, or blends thereof, and polycarbonates. , Acrylic-butadiene-styrene copolymer (ABS resin), polyacetal resin, nylon 6, nylon 66, polyamides such as those copolymerized nylon, acrylic resin such as polymethyl methacrylate, isotactic polypropylene, polystyrene, low -, Medium- or high-density polyethylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, styrene-butadiene thermoplastic elastomer and the like.
Various additives such as a colorant, an ultraviolet absorber, a release agent, a lubricant, and a nucleating agent can be blended with these resins within a range that does not impair the quality of the product. In the case of PET, the glass transition temperature becomes approximately 77 to 78 ° C. by appropriately adding these additives so as to be suitable for products.

(2) Layer structure of preform The preform of the present invention may be composed of two or more thermoplastic resin layers in addition to the case of a single layer (one layer) of thermoplastic resin layer.
Furthermore, the preform of the present invention can be provided with an intermediate layer laminated between an inner layer and an outer layer composed of two or more thermoplastic resin layers, and the intermediate layer has a functionality such as an oxygen barrier layer or an oxygen absorption layer. It can also be a resin layer.

In the following, the present invention will be further described in Examples, which are more specific embodiments, and the rationality and significance of the constituent elements in the present invention will be demonstrated.
[Examples using graphs]
As an example of the present invention for eliminating internal distortion, an example by a graph is as described in paragraph 0023. For preform high temperature extraction, preform molding (i), and high temperature extraction from a mold (ii), In addition, a graph (FIG. 2) illustrates an example of the change over time of the temperature of the preform in the air-cooled state (iii).

[Example 1 and Comparative Example 1]
Synthetic resin (polyethylene terephthalate) heated and melted in the extruder is continuously extruded from the opening of the die head fixed to the tip of the extruder, and this molten resin is cut by a cutting tool to form a cylindrical drop (cut melted). Lump) was obtained. The drop is sandwiched between a plurality of holding mechanism fixtures and pressing tools provided on the rotary movable drop supply body, and inserted into female molds provided on a rotary compression molding machine. Furthermore, a preform was obtained by compression molding in cooperation with a female mold and a male mold.
The preform was taken out of the mold at a high temperature, and then air-cooled to relax the internal strain.

Table 1 shows the preform molding conditions and molding results. In the range where the outer surface temperature of at least the trunk portion of the preform immediately after taking out the compression-molded preform from the mold is (glass transition temperature-2) ° C. or more (glass transition temperature + 8) ° C. of the synthetic resin, That is, in the range of 75 to 86 ° C., the maximum temperature reached to the outer surface of the preform is in a suitable range of 95 to 120 ° C. (corresponding to Example 1), the preform has good moldability, and a bottle with poor appearance also occurs. There wasn't.
If the outer surface temperature of at least the body portion of the preform immediately after taking the preform that has been compression-molded out of the range of 75 to 86 ° C, the highest temperature of the outer surface of the preform is less than 95 ° C or 120 ° C. (Corresponding to Comparative Example 1), a preform with poor moldability or a bottle appearance defect was produced.

An example of the graph diagram previously described in paragraph 0028 in the example in Table 1 where the molding time is 6 seconds is illustrated in FIG. 2 for preform high temperature removal, preform molding, high temperature removal from the mold, and A time-dependent change in the temperature of the preform in the air-cooled state is shown. The measured values of temperature change (° C .; vertical axis) with respect to time (seconds; horizontal axis) at the center points of the inner and outer surfaces of the preform body and the inner layer are shown by curves. In this example, the thickness of the preform body is 3.5 mm, the mold cooling temperature is 12 ° C., and the ambient temperature is 25 ° C.
Looking at this graph, if the preform is taken out from the mold at a high temperature of about 80 ° C. and air-cooled, the temperatures of the inner surface, outer surface, and center of the preform will be equalized over time. Approaching (gradual temperature approach) has been demonstrated and good results have been obtained in preform moldability and bottle appearance.

In the comparative example in which the molding time in Table 1 is 10 seconds, a graph similar to that of the example is illustrated in FIG.
In this case, since the preform is taken out from the mold at a low temperature of about 70 ° C., it is assumed that the temperatures of the inner surface, the outer surface, and the inner layer center of the preform are approaching a uniform temperature over time. However, good results are not obtained in the appearance of the bottle.

[Example 2 and Comparative Example 2]
Using a preform similar to the preform used in Example 1, the strain distribution state of the preform, which is an index of the moldability of the preform, was examined.
The strain distribution state of the preform after compression molding was observed with a strain distribution photograph using a polarizing filter. As the strain inspection device, a strain inspection device LSM-2001 manufactured by Luceo Co., Ltd., which is a crossed Nicol type inspection device using a polarizing plate, was used.
In the photograph of the strain distribution of the preform shown in FIG. 4, immediately after taking out at a high temperature (the maximum temperature reached on the outer surface: 95 to 100 ° C.) corresponding to Example 2, as shown in (A) -1, compression molding is performed. Since the preform formed is very slight but in a softened state, the distortion is alleviated by removing it from the mold, and no interference pattern indicating distortion appears.
When air-cooled cooling (40 ° C. or lower) outside the mold as it is after taking out at a high temperature, as shown in (A) -2, a slight interference pattern due to cooling and solidification appears.
On the other hand, when sufficiently cooled in the mold (corresponding to Comparative Example 2) (maximum temperature reached on the outer surface: less than 90 ° C.), as shown in (B), distortion due to compression molding in the mold was observed. Since the preform is cooled and solidified while being held, an interference pattern appears clearly, and it appears quite noticeably above the trunk.
Therefore, it has been clarified that the high temperature take-out of the preform from the mold is less likely to cause distortion in the preform after molding and is a better technique than the low-temperature take-out.

[Results of Examples and Comparative Examples]
In each of the examples, the preform had almost no distortion, was molded normally as desired, and a molded product having a constant quality and excellent quality and appearance was obtained. On the other hand, in each of the comparative examples, a considerable distortion occurred in the preform, a molded product having poor moldability and an inferior appearance as compared with the examples was obtained.
Therefore, the rationality and significance of the requirements of the composition in the present invention are clarified.

1 is a schematic plan view specifically illustrating a preferred embodiment of a molding system constructed in accordance with the present invention. It is a graph which illustrates the example of the time-dependent change of the temperature of a preform by the high temperature extraction in this invention. It is a graph which illustrates the comparative example of the time-dependent change of the temperature of a preform by low temperature taking-out. It is a distortion distribution photograph figure by a polarizing filter which shows the distortion distribution state of a preform.

Claims (5)

Compression molding machine of a synthetic resin melt agglomerated in a drop compression molded to a preform and without, from the mold when removing the preform, after eject the preform in a state at a high temperature than ambient temperature, the preform The temperature is adjusted without heating, and the temperature adjustment is performed on the outer surface of the preform body by the heat inside the preform body (glass transition temperature + 18) ° C. or more (glass transition temperature + 42) ° C. A method for molding a preform for blow molding , characterized in that the temperature is increased as follows . Compression molding machine of a synthetic resin melt agglomerated in a drop compression molded to a preform and without, from the mold when removing the preform, after eject the preform in a state at a high temperature than ambient temperature, the preform When the temperature is adjusted without heating and the temperature is higher than room temperature, the outer surface temperature of at least the body portion of the preform immediately after taking out the compression-molded preform from the mold is the glass transition temperature of the synthetic resin. -2) A method for molding a preform for blow molding , characterized by being at least ° C (glass transition temperature +8) ° C. When the preform is taken out from the mold, the outer surface temperature of the preform nozzle is taken out in a state where the temperature is equal to or higher than the temperature control temperature of the mold and (glass transition temperature +2) ° C. or lower of the synthetic resin. A method for molding a blow-molding preform according to claim 1 or 2. The method for molding a preform for blow molding according to any one of claims 1 to 3, wherein the synthetic resin is polyethylene terephthalate (PET) having a glass transition temperature of 77 to 78 ° C. A synthetic resin container, wherein the preform is stretch blow molded continuously after being molded using the method for molding a preform according to claims 1 to 4. Production method.

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