JP2008036956A - Manufacturing process of thermoplastic resin container by two-stage blow molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem, wherein, in a conventional biaxial orientation two-stage blow molding for a polyester container, the intermediates prepared at the first stage of the biaxial orientation two-stage blow molding are thermally shrunk longitudinally and latitudinally for stress relaxation and the prediction of the amount of the shrinkage is difficult, and thus, a large amount of man hour is required in designing blow molding molds for the first stage and the shapes of the preforms, which results in the economical and temporal burden on the commercialization of the molding process. <P>SOLUTION: The primary intermediate of a preform is subjected to the primary blow molding using a primary mold, to prepare a secondary intermediate. The secondary intermediate is thermally shrunk, to prepare a tertiary intermediate. The tertiary intermediate is subjected to a secondary orientation blow molding using a secondary mold, to manufacture the container. In the primary orientation blow molding, the container is manufactured by using a conical preform as the primary intermediate and stretch-orientating the primary intermediate mainly in the direction of the height of the preform and shrinking it almost only in the circumferential direction in a thermal shrinkage process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a thermoplastic resin container by a two-stage blow molding method, and more specifically, a mold and / or a preform shape is designed in advance based on data for controlling the orientation of a preform to cause heat shrinkage. Therefore, the present invention relates to a method for manufacturing a thermoplastic resin container, which simplifies the man-hour of the two-stage blow molding method.

Polyester resin containers in thermoplastic resin containers have recently been made of conventional metals and glass due to their light weight, economy, ease of molding, various physical properties, adaptability to environmental problems, and resource reusability. It is widely used in daily life and various industrial fields, and in particular, is widely used as a container for beverages, foods, cosmetics, cleaning agents and pharmaceuticals.
Among polyester resin containers, so-called PET bottles (polyethylene terephthalate containers) have been in great demand since being approved as containers for foods and drinks, but until recently PET bottles had heat resistance and pressure resistance. However, it cannot be used for high-temperature drinks and drinks that require high-temperature sterilization, and is limited to summer drinks in daily life.
Later, in response to consumers' strong demand for portable high-temperature beverages and retort-sterilized foods for winter in PET bottles, the polyethylene terephthalate preform was sufficiently stretched and crystallized by developing a two-stage blow molding method. The heat resistance and pressure resistance of PET bottles have been remarkably improved (see Patent Documents 1 and 2), and the transparency of the PET bottles combined with the sense of security and cleanliness that allow the internal beverage to be seen directly. From this point of view, the importance of PET bottles is even more remarkable. In particular, recently, PET bottles have been heavily used by consumers as portable small containers for beverages, and demand in such fields and other uses is expected to increase in the future.

Such a two-stage blow molding method is combined with a biaxial stretch blow to remarkably improve the heat resistance and pressure resistance of a polyester resin container, and a retort sterilizable container excellent in heat resistance has been put into practical use.
Thus, the two-stage biaxial stretch blow molding method in a polyester resin container is a very important molding method. Therefore, in order to further improve the blow molding method, each process and molding conditions, the heat shrinking process, or the mold design And materials for preforms are being studied.

One aspect of the problem to be improved is that the first stage biaxially stretched blow-molded intermediate is heat-shrinked in the vertical and horizontal directions (height and circumferential direction of the container intermediate) to reduce the residual stress of the intermediate. When mitigating, it is difficult to predict the shrinkage rate, so it takes a lot of man-hours to design the shape of the first-stage blow mold and preform, and the cost and time burden of industrialization of this molding method. The problem is derived.
An improved technique in the biaxially stretched two-stage blow molding method from such a viewpoint cannot be found yet in patent documents and the like.

Japanese Examined Patent Publication No. 4-56734 (Claims and upper left column of page 2) Japanese Patent Laid-Open No. 5-200839 (Claims and paragraph 0006)

  As described above in paragraph 0004, in the biaxially stretched two-stage blow molding method for a polyester resin container, the first stage biaxially stretched blow molded intermediate is thermally shrunk in the vertical and horizontal directions to relieve the residual stress of the intermediate. of, it is difficult to shrinkage prediction sets the first stage of the blow molding mold design for deciding make advance how large the biaxial stretch blow molding intermediates first stage for its, and the draw ratio how much Since the process of designing the shape of the preform to determine whether to adjust the heat shrinkage takes a lot of man-hours, the problem that is the cost and time load of the industrialization of this molding method is derived. In the present invention, it is an object of the present invention to solve the problem by facilitating and simplifying the shrinkage rate prediction.

In order to solve the above-mentioned problems, the present inventors set the first-stage biaxially stretched blow molded intermediate in the biaxially stretched two-stage blow molding method for a polyester resin container in the vertical and horizontal directions (the height of the intermediate body serving as the container). And shrinking in the circumferential direction), and experimenting with various ways of thinking regarding the heat shrinking method, various shrinkage conditions, preform material and shape, and the structure of the primary blow mold. Search and consideration.
In that process, in order to predict shrinkage economically by easy and simple means, we can adopt a specific stretching orientation and heat shrinkage method, and also know a new means of using a unique preform shape The cost and time burden in the industrialization of the biaxially stretched two-stage blow molding method due to the fact that it takes a lot of man-hours to design the shape of the first-stage blow mold and preform by recognizing the knowledge. It was possible to create the present invention that can eliminate the problem.

  In the present invention, the specific stretch orientation and heat shrinkage method is basically the primary stretch blow molding in which the primary intermediate is stretched and oriented mainly in the height direction of the preform, and substantially in the circumferential direction during the heat shrink process. This method is the first feature of the present invention, and the primary intermediate is mainly stretched and oriented in the height direction of the preform in the primary stretch blow molding, In order to contract only in the circumferential direction, the second feature of the present invention is to use a conical preform, which is a preform having a unique shape, as a primary intermediate of the preform, Such requirements constitute the basic elements in the configuration of the present invention.

In the primary stretch blow molding, the primary intermediate is stretched and oriented mainly in the height direction of the preform, and based on the data of heat shrinkage obtained by shrinking only in the circumferential direction in the heat shrinkage process. The next mold and / or preform shape can be designed easily, simply and economically.
Furthermore, in order to obtain such heat shrinkage data, the difference between the height of the molding intermediate after the primary blow and the amount of heat shrinkage in the circumferential direction was evaluated by the difference in the amount of unloaded deformation by thermomechanical analysis (TMA) measurement. Means to do this can also be employed.

In the present invention, as described above in paragraph 0008, in the primary stretch blow molding, the primary intermediate is stretched and oriented mainly in the height direction of the preform, and is contracted only in the circumferential direction in the heat shrinking process. In addition, the primary intermediate of the preform is mainly stretched and oriented in the height direction of the preform in the primary stretch blow molding, and contracted only in the circumferential direction in the heat shrink process. A conical-shaped preform, which is a unique-shaped preform, is used as an intermediate, and this novel two element is a feature of the invention, and the invention combines these two elements, and thereby It should be noted that the problems of the present invention are solved.
In addition, the present invention aims at facilitating the design of the shape of the first-stage blow molding die and preform, so that the shrinkage rate can be predicted easily and simply by means of the above two. It is a more specific finding that the elements are the requirements of the configuration of the invention and that the requirements of this configuration are adopted for this purpose.

By the way, when the first stage biaxially stretched blow-molded intermediate is thermally shrunk in the vertical and horizontal directions to relieve the residual stress of the intermediate, it is difficult to predict the shrinkage rate. As described above in paragraph 0004, an improved technique in the biaxially stretched two-stage blow molding method has not yet been disclosed in view of the problem that it takes a lot of man-hours to design the shape of the reform.
When reviewing the prior literature, Japanese Patent Application Laid-Open No. 9-314650 discloses that in the biaxially stretched two-stage blow molding method of a polyester resin container, “the degree of shrinkage of a secondary intermediate molded product that is heat shrink molded from a primary intermediate molded product” In order to obtain a casing with less internal residual stress, high dimensional system and appropriate thickness distribution, the mold temperature of the primary blow mold can be controlled. It should be set to 110 ° C. to 230 ° C. so that the amount of heat shrinkage can be controlled ”(paragraph 0018), and there is a method for controlling the amount of heat shrinkage, but in the summary (page 1), it is intermediate. There is also a drawing in which the molded product is contracted only in the lateral direction, but there is no further explanation, and none of them has a specific relationship with the purpose described above in paragraph 0010 in the present invention and the requirements of the specific configuration. Some Not.
The use of a conical preform is slightly scattered in the prior art as seen in Japanese Patent Application Laid-Open No. 11-157524 (summary drawing on the first page). There is no description of stretching and heat shrinkage in the vertical and horizontal directions related to the shape of the preform, and the purpose described above in paragraph 0010 of the present invention and the requirements for the unique configuration are as follows. It is not related.

  In the above, since the present invention has been described in overview with respect to the background of the creation of the present invention and the basic features and components of the present invention, the present invention can be summarized as follows. The invention of [1] to [3] is a basic invention, and the inventions below that embody the basic invention or form an embodiment. . (The invention group as a whole is collectively referred to as “the present invention”.)

[1] A primary intermediate of a preform formed in advance with a thermoplastic resin is formed into a secondary intermediate by primary stretch blow molding using a primary mold, and the secondary intermediate is thermally contracted to form a tertiary intermediate. When producing a thermoplastic resin container by performing secondary stretch blow molding of the tertiary intermediate with a secondary mold, the primary intermediate is mainly used in the height direction of the preform in the primary stretch blow molding. A method for producing a thermoplastic resin container by a two-stage blow molding method, characterized in that the film is stretched and oriented and contracted only in the circumferential direction in the process of thermal contraction.
[2] In order to cause the primary intermediate to be stretched and oriented mainly in the height direction of the preform in the primary stretch blow molding and to shrink only in the circumferential direction in the heat shrinking process, as the primary intermediate of the preform, A method for producing a thermoplastic resin container by a two-stage blow molding method according to [1], wherein a conical preform is used.
[3] Based on heat shrinkage data obtained by primarily stretching and orienting the primary intermediate in the height direction of the preform in the primary stretch blow molding and shrinking only in the circumferential direction in the heat shrinking process, A method for producing a thermoplastic resin container by a two-stage blow molding method according to [1] or [2], wherein a primary mold and / or a preform shape is designed.
[4] The method for producing a thermoplastic resin container according to any one of [1] to [3], wherein the secondary stretch blow molding is biaxial stretch blow.
[5] The method for producing a thermoplastic resin container by a two-stage blow molding method according to any one of [1] to [4], wherein the thermoplastic resin is a polyester resin.
[6] In any one of [1] to [5], the height of the secondary intermediate and the degree of orientation in the circumferential direction are higher than the degree of orientation in the circumferential direction. A method for producing a thermoplastic resin container by a two-stage blow molding method.
[7] The heat by the two-stage blow molding method according to [6], wherein the orientation degree in the height and the circumferential direction of the thermoplastic resin container is higher than the orientation degree in the circumferential direction. A method for producing a plastic resin container.

  In the present invention, in the biaxially stretched two-stage blow molding method for a polyester resin container, when the first-stage biaxially stretched blow-molded intermediate is thermally shrunk in the vertical and horizontal directions, the shrinkage is economically achieved by an easy and simple means. Prediction can be made, which eliminates the need for man-hours for designing the shape of the first-stage blow molding mold and preform, and the cost and cost in industrialization of the biaxially stretched two-stage blow molding method. Can solve the problem of time load.

  The invention of the present application has been described in accordance with the basic configuration of the present invention as means for solving the problems. However, in the following, the embodiment of the invention of the present invention group described above will be described with reference to the drawings. However, it will be specifically described in detail.

1. Basic Configuration of the Present Invention (1) Two-stage Blow Molding Method The present invention relates to a method for manufacturing a thermoplastic resin container by a two-stage blow molding method, which is performed in advance on the basis of data for controlling the stretching orientation of the preform and causing heat shrinkage. The present invention relates to a method for manufacturing a thermoplastic resin container, which is designed for a mold and / or a preform shape to simplify the number of steps of the two-stage blow molding method.
The biaxially stretched two-stage blow molding method of the present invention is schematically shown in FIG. 1 as a molding process, and is viewed from the left side of the drawing in order, and is a conical preform preformed from a thermoplastic resin. The primary intermediate is subjected to primary blow molding in a primary mold, and stretched and oriented mainly in the height direction (longitudinal direction) of the intermediate to form a secondary intermediate, and then thermally contracted. Shrinkage is made almost only in the circumferential direction to form a tertiary intermediate. Finally, the tertiary intermediate is subjected to secondary blow molding in a secondary mold, biaxially stretched, and a jar (wide mouth container) is formed. This is a finished product.

(2) Peculiar stretching orientation and heat shrinkage As one of the main structural requirements in the present invention, when the primary intermediate of the preform is subjected to primary blow molding in the primary mold, the intermediate The film is stretched and oriented in the longitudinal direction (longitudinal direction) to form a secondary intermediate, and is contracted only in the circumferential direction in a thermal contraction process that relieves residual strain in the intermediate.
In the conventional biaxially stretched two-stage blow molding method for polyester resin containers, since it is stretched and oriented in both the height and circumferential directions, it usually shrinks approximately equally in both the height and circumferential directions. Has been.

In the present invention, the orientation in stretching occurs mainly in the height direction, the orientation does not occur much in the circumferential direction, and as a result, the heat shrinkage hardly occurs in the height direction, and occurs only in the circumferential direction. Become.
The thermal shrinkage hardly occurs in the height direction, but only in the circumferential direction. Therefore, it is not necessary to consider the shrinkage in the height direction when designing a mold for primary blow molding.
Therefore, the shrinkage rate can be predicted economically by an easy and simple means, and the shape of the first-stage blow molding die or preform is further taken into consideration by taking into account the data of thermal shrinkage by TMA measurement described later. It is possible to simplify the design of both or both, eliminating the time required for designing the shape of the first-stage blow mold and preform, and biaxially stretched two-stage blow molding The cost and time burden in the industrialization of the law can be solved.

(3) Cone-shaped preform As one of the main structural requirements in the present invention, a cone-shaped (conical) preform having a unique shape as exemplified in the embodiment in FIG. Thereby, in the primary stretch blow molding, the primary intermediate can be stretched and oriented mainly in the height direction of the preform, and can be easily contracted only in the circumferential direction in the heat shrinking process.
When a conical preform is used, it has been found that stretch orientation occurs only in the height direction, and this phenomenon has been found by experiments by the inventors, and is described in Table 1 in the examples described later. Proven.

2. Other Configurations in the Two-stage Blow Molding Method (1) Preform In the normal biaxially stretched two-stage blow molding method, a cylindrical (cylindrical) preform is exclusively used, but the preform (so-called parison; The bottomed cylindrical preform is preferably a conical preform and is preformed by conventional means such as an injection molding machine, an extrusion molding machine, or a compression molding machine, particularly a rotary continuous compression molding machine. The
Thermoplastic polyethylene terephthalate (PET) is preferably used as a raw material, but other polyester resins or any resin such as polyethylene, polypropylene, and polycarbonate can also be used. In addition, a laminated preform can be used as appropriate. For example, when laminated with polyamide or Eval, oxygen shielding properties are improved. Furthermore, an oxygen absorption layer may be provided in the intermediate layer to improve oxygen absorption. The oxidizable organic component used in the oxygen absorbing layer is preferably a polymer derived from polyene.

(2) Primary blow molding
The longitudinal draw ratio in the height direction of the primary blow is about 2.0 to 3.5 times, resulting in high crystal orientation and uniform drawing. Moreover, there is little extending | stretching of the circumferential direction compared with a height direction.
The mold temperature condition of the primary blow is about 20 to 160 ° C. in PET, and normal conditions are appropriately adopted in other resins.

(3) Thermal contraction process The secondary intermediate is shrunk exclusively in the circumferential direction by appropriately heating with a hot air oven or an infrared heater, but the surface temperature is 150-220 ° C, preferably 200 ° C. Thus, it is preferably contracted by about 30 to 60% in the circumferential direction to form a tertiary intermediate having a shape smaller than the final product container.

(4) Secondary blow molding In the state where the temperature of the blow molded portion of the heat-shrinked tertiary intermediate is 120 to 220 ° C, the tertiary intermediate is heated to 150 to 230 ° C on the inner surface of the secondary mold. The biaxially stretched blow molding is about 1.05 to 1.2 times in length and 1.05 to 1.2 times in width, and then the outer surface of the blow molded product is maintained in the secondary mold while maintaining the blow air pressure. Is kept in contact with the inner surface of the secondary mold, preferably for about 2 seconds, for heat setting.

3. Thermomechanical analysis (TMA) measurement In the present invention, in order to obtain the data of the secondary intermediate height and the heat shrinkage in the circumferential direction, the height of the secondary intermediate after the primary blow and the amount of heat shrinkage in the circumferential direction are measured. It is also adopted that the difference is evaluated by the difference in the no-load deformation amount by thermomechanical analysis (TMA) measurement.
The measurement method will be described later in the examples, and the measurement results are illustrated in the graph of FIG. 3 in the examples described later. The horizontal axis is the temperature rise (° C.), and the vertical axis is the length deformation amount (μm) ).

  In the following, the present invention will be described in more detail with reference to the drawings by comparison with comparative examples, but these show preferred embodiments of the present invention and make the present invention clearer. Therefore, the rationality and significance of the requirements of the configuration in the present invention will be clarified, and the adaptability of the range will be revealed more widely.

[Various measurement methods]
1. ) Evaluation of degree of orientation by Raman spectroscopy The Raman spectrum is measured from the cross-sectional direction (vertical and horizontal two directions) of the section of the container (center portion of the trunk) by laser Raman spectroscopy. The peak due to the benzene skeleton vibration in the molecular structure appears at about 1616 cm ⁻¹ , and this intensity is measured.
The higher the degree of orientation of the benzene ring, the higher the intensity when the incident laser polarization is in the 0 ° direction. By utilizing this fact, a number of orientation parameters defined as OP (= 1616cm ^-1 peak intensity of 1616cm ^-1 peak intensity / incident laser 90 ° Henhikariji the incident laser 0 ° Henhikariji), was measured.
(Raman measurement conditions)
Spectroscopic instrument: JASCO Laser Raman Spectrophotometer NRS-1000 Laser used: 532 nm Measurement wavelength range: 1800-600 cm ^-1 Measurement seconds: 5 seconds Integration count: 2 times

2. ) Measurement of TMA no-load deformation amount In order to obtain the data of the height of the secondary intermediate and the heat shrinkage in the circumferential direction, the difference between the height of the secondary intermediate after the primary blow and the amount of heat shrinkage in the circumferential direction Evaluation is based on the difference in no-load deformation by mechanical analysis (TMA) measurement.
A strip-shaped test piece cut out in the longitudinal (height) direction and lateral (circumferential) direction from the center of the body of the container is measured by TMA (thermomechanical analysis). The amount of deformation in the two directions is represented by a graph in which the horizontal axis represents the temperature rise (° C.) and the vertical axis represents the length deformation (μm) of the sample piece.
(TMA measurement conditions)
Measuring instrument: DMS6100 manufactured by SII Nanotechnology, Inc. Temperature program: 5 ° C / min temperature increase from 30 to 250 ° C Test piece: 40 x 5 mm
In addition, the graph figure showing the measurement result of the difference of TMA no-load change amount in the Example and comparative example which are mentioned later in FIG. 3 is illustrated.

3. ) Measurement of crystallinity A test piece is cut out from the body of the container, and the density ρ (g / cm ³ ) of the test piece is obtained by a density gradient tube method prepared with an aqueous calcium nitrate solution. As a result, the crystallinity is calculated by the following equation.
Crystallinity (%) = {ρc (ρ−ρa) / ρ (ρc−ρa)} × 100
ρc: Crystal density (1.455 g / cm ³ )
ρa: amorphous density (1.335 g / cm ³ )

[Example]
In the method for producing a thermoplastic resin container by the two-stage blow molding method of the present invention, (a) a conical (conical) preform shown in FIG. 1 is (b) primary blown, (c) Each step of heat shrinking and (d) secondary blowing was performed.
(A) Cone-shaped preform Blow molding is performed using commercially available polyethylene terephthalate (PET). The outermost diameter of the body is 47.6 mm, the wall thickness is 3.0 mm, the height is 25 mm, and the taper angle is 30 degrees. A substantially conical preform having a taper ratio of 1: 0.866 was preformed by injection molding to obtain a primary intermediate.
(B) Primary blow The air was blown and primary blown by a primary mold at 120 ° C., and the film was mainly expanded and expanded to a height of 80 mm, and the outer diameter was a secondary intermediate having a diameter of 105 mm.
(C) Thermal contraction The secondary intermediate was contracted and fixed at 200 ° C. for 10 seconds to obtain a tertiary intermediate contracted to an outer diameter of 55 mm substantially only in the circumferential direction.
(D) Secondary blow molding Air was blown into a tertiary intermediate whose temperature was lowered to 180 ° C, and secondary blow molding was performed with a secondary mold at 210 ° C, resulting in a length of 1.1 times and a width of 1.1 times. The biaxially stretched blow molding was carried out, and then the blow molded product was heat-set in the above-described mold having a surface temperature of 210 ° C. in the secondary mold to form a finished jar.

[Comparative example]
Instead of the preform of the example, a preform having a substantially columnar shape (cylindrical type; taper angle of 0.5 degrees) was used, and blow molding was performed in the same manner as in the example.
In addition, the shape of the preform used in the Example and the Comparative Example is posted in FIG. Further, various measurement results in Examples and Comparative Examples are shown in Table 1, and a graph of TMA measurement results is shown in FIG.

[Consideration of results of Examples and Comparative Examples]
In contrast to the examples and comparative examples, in the examples of the present invention, a conical preform is used, and the primary intermediate is stretched and oriented mainly in the height direction of the preform, and is substantially circumferential in the heat shrinking process. The degree of orientation of the secondary intermediate by the laser Raman method is considerably higher in the height direction than in the circumferential direction, and conversely, the amount of shrinkage by TMA is much lower in the height direction than in the circumferential direction. As a result, in the height direction, a desired result is obtained in which the film does not substantially shrink in the heat shrinking process after the primary blow, and contracts only in the circumferential direction.
On the other hand, in the comparative example, since a cylindrical preform is used, the degree of orientation by the secondary intermediate laser Raman method is considerably lower in the height direction than in the circumferential direction, and conversely, the shrinkage amount by TMA is in the height direction. Is considerably higher than in the circumferential direction, and as a result, in the height direction, an undesired result of shrinking in the heat shrinking process after the primary blow and shrinking in the circumferential direction is obtained.
In addition, the jar finished product in which the secondary intermediate is subjected to heat shrinkage and secondary blow also maintains the tendency of the magnitude relationship between the height direction of the orientation degree and the circumferential direction.

It is a rough molding process figure in the biaxial stretching two-stage blow molding method of the present invention. It is the schematic which shows the shape of the preform used in the Example and the comparative example. It is a graph which shows the measurement result of the TMA no-load change amount in an Example and a comparative example.

Claims (7)

A primary intermediate of a preform formed in advance by a thermoplastic resin is formed into a secondary intermediate by primary stretch blow molding using a primary mold, and a secondary intermediate is heat-shrinked to form a tertiary intermediate. When producing a thermoplastic resin container by secondary stretch blow molding of a tertiary intermediate with a secondary mold, the primary intermediate is mainly stretched and oriented in the height direction of the preform in primary stretch blow molding. A method for producing a thermoplastic resin container by a two-stage blow molding method, wherein the shrinkage is performed only in a substantially circumferential direction during the heat shrinkage process. In primary stretch blow molding, the primary intermediate is stretched and oriented mainly in the height direction of the preform, and is contracted only in the circumferential direction in the heat shrinking process. The method for producing a thermoplastic resin container by a two-stage blow molding method according to claim 1, wherein a preform is used. In the primary stretch blow molding, the primary intermediate is stretched and oriented mainly in the height direction of the preform, and based on heat shrinkage data obtained by shrinking only in the circumferential direction in the heat shrinkage process, the primary gold The method for producing a thermoplastic resin container according to the two-stage blow molding method according to claim 1 or 2, wherein the mold and / or preform shape is designed. The method for producing a thermoplastic resin container by a two-stage blow molding method according to any one of claims 1 to 3, wherein the secondary stretch blow molding is a biaxial stretch blow. The method for producing a thermoplastic resin container by a two-stage blow molding method according to claim 1, wherein the thermoplastic resin is a polyester resin. The height of the secondary intermediate and the degree of orientation in the circumferential direction are described in any one of claims 1 to 5, wherein the degree of orientation in the height direction exceeds the degree of orientation in the circumferential direction. A method for producing a thermoplastic resin container by a two-stage blow molding method. The heat of the two-stage blow molding method according to claim 6, wherein the height of the thermoplastic resin container and the degree of orientation in the circumferential direction are higher than the degree of orientation in the circumferential direction. A method for producing a plastic resin container.

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