JPS628291B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for making stretch-blow-molded containers made of thermoplastic resins such as vinyl chloride resins, and more particularly to a method for producing stretch-blow-molded containers having novel orientation properties and significantly improved impact resistance. Regarding the manufacturing method. Vinyl chloride resin is a resin with excellent oxygen barrier properties and transparency, and its blow molded containers are
It is widely used as a container for containing cosmetics, detergents, liquid foods, or other liquid contents. It is already known to produce stretch blow molded containers from vinyl chloride resin, and according to a known method, vinyl chloride resin is injection molded or melt blow molded to produce a parison with a bottom, and this plastic is then molded into a parison. The bottom parison is longitudinally stretched in the axial direction in a mold using a stretching rod in a temperature range capable of stretching, and simultaneously or sequentially blow-stretched in the circumferential direction to form a stretch-blow-molded container. However, according to the known method, only a relatively low stretching ratio can be applied to the vinyl chloride resin container. It is difficult to give orientation. However, in bottle-shaped containers, including stretch-blow molded containers, the weakest part of the structure is not the center of the body, but rather the ends of the body, which are close to the shoulders and bottom of the bottle. Reinforcing both ends of the body is very important to prevent impact damage caused by dropping the bottle. The present inventors have proposed that when stretch-blow molding a bottomed parison made of a thermoplastic resin such as a vinyl chloride resin, the bottomed parison is subjected to multi-stage axial stretching and one-stage blow stretching as detailed below. The inventors have discovered that when this is done, new orientation characteristics are imparted to the container body, and the drop impact strength, heat resistance, etc. of the container are significantly improved. That is, an object of the present invention is to provide a method for producing a thermoplastic resin stretch-blow molded container with significantly improved impact resistance and heat resistance. Another object of the present invention is to provide a method for producing a thermoplastic resin stretch-blow molded container whose container body has novel orientation characteristics. Still another object of the present invention is to provide a method for manufacturing a stretch-blow-molded container with a low incidence of defects such as uneven thickness and overfill, and with less uneven stretching. According to the present invention, a bottomed parison made of a thermoplastic resin is subjected to at least one stage of preliminary stretching in the axial direction by 5 to 70% of the total axial stretching ratio at a stretching temperature, and after the stretching operation is temporarily stopped. Next, this pre-stretched parison is stretched in the axial direction by the remaining stretching ratio and expanded in the circumferential direction by blowing fluid into the body, bottom, shoulders and neck integrally formed of an amorphous thermoplastic resin. a stretch blow-molded container in which at least the body has biaxial molecular orientation; the body generally has an axial orientation coefficient from a shoulder end to a bottom end; gradually decreases, and the circumferential orientation coefficient gradually decreases from the bottom end to the shoulder end, and at least the central portion of the body has an orientation coefficient in the thickness direction of less than 0.25. Provided is a method for producing a stretch-blow-molded container with impact resistance that is characterized by a molded container whose impact resistance is suppressed to a low value. The invention will be explained in detail below. As shown in FIG. 1, the stretch blow-molded container manufactured by the method of the present invention has a body 1, a bottom 2, a shoulder 3, and a body 1, a bottom 2, a shoulder 3, and It consists of a neck part 4, and at least this body part 1 is molecularly oriented in two axial directions, that is, in the axial direction and in the circumferential direction, by stretch blowing. In the container manufactured by the method of the present invention, the body 1 made of the amorphous thermoplastic resin has an axial orientation coefficient that gradually decreases from the shoulder end 1A to the bottom end 1B. , and the bottom end 1B
The circumferential orientation coefficient gradually decreases from the to the shoulder end 1A, and at least the central portion 1C of the body has a thickness orientation coefficient.
It is characterized by suppressing it to a value lower than 0.25. In this specification, the orientation coefficient refers to the degree of orientation of the resin constituting the container wall in a certain specific direction, which is determined by birefringence measurement, and the orientation coefficient in the axial direction of the container is compared to the orientation coefficient in the circumferential direction of the container. The orientation coefficient of
When the orientation coefficient in the thickness direction of the container is expressed as: ++=1...(1) This is the value determined so that the orientation coefficient in the thickness direction of the container is expressed as: Thus, the fact that the orientation coefficient in a certain direction is large means that
This shows the fact that molecular orientation in this specific direction occurs preferentially compared to other directions. Details of the method for calculating the orientation coefficient are as follows. It is well known that polymers generally have different refractive indexes in the long axis direction and the short axis direction of the molecule. Therefore, when a polymer film, sheet, parison, etc. is stretched, the molecular chains are oriented in the direction of stretching, and the refractive index is different in the direction of orientation and in the direction perpendicular to it, and the difference in these refractive index values is called birefringence. , △. In the orthogonal three-dimensional coordinates (x, y, z), the x direction is the thickness direction of the container, the y direction is the circumferential direction, and the z direction is the axial direction, and the refractive index in each direction is n. Assuming _x , _ny , _nz ,
The following formula n _i = (n〓−n⊥)+n⊥ (i=x, y,
z) ...(2) In the formula, n _N is the refractive index in the axial direction when the sample is completely uniaxially oriented, and n _I is the refractive index in the direction perpendicular to the axial direction when the sample is also completely uniaxially oriented. ,
(i = x, y, z) was determined by R. SS _TEIN et al. (J.
Applied Physics, 37 , 3990 (1966)). n〓 and n⊥ each have a unique value depending on the thermoplastic resin. For example, for polyvinyl chloride, Kiyoichi Matsumoto et al.
(1970)) and others. Therefore, birefringence, △ _x = _nz − _ny , △ _y = _nz −
If any two values of n _x , △ _z = n _x - n _y are measured, R・SS _TEIN report (J. Polymer
Sci., 24 , 383 (1957)),
, , is required. In addition, in this specification, the overall orientation tendency of the container body refers to slight irregularities or irregularities at the measurement position when the relationship between the distance from one end of the container body and the orientation coefficient is plotted. Even if there are variations, it means that there is a certain tendency as a whole, for example, an increasing tendency or a decreasing tendency. To explain this orientation tendency by giving specific numerical values for a preferred example, the axial orientation coefficient of the shoulder end 1A of the trunk wall is _A , the circumferential orientation coefficient is _A , and the axial orientation of the bottom end 1B is If the coefficient is _B and the circumferential orientation coefficient is _B , then 0.350≧ _A − _B ≧0.005, especially 0.300≧ _A − _B ≧0.007, 0.400≧ _B − _A ≧0.005, especially 0.350≧ _B − _A ≧0.007, It's summery. In addition, the thickness direction orientation coefficient _C of the central portion 1C of the trunk wall is smaller than 0.25, especially 0.20.
In other words, the in-plane orientation coefficient ( _C + _C ) at the center is larger than 0.75, especially 0.80.
It's getting bigger than that. Furthermore, the relationships are ( _C + _C ) - _A + _A )≧0.005 and ( _C + _C ) - ( _B + _B )≧0.005. As described above, in the container of the present invention, an axial molecular orientation effect is preferentially imparted to the bottom end of the container body, and a circumferential molecular orientation effect is preferentially imparted to the shoulder end. It is a remarkable feature that the in-plane orientation is maximum at the center of the body. Due to this feature, in the container of the present invention, the center part of the body not only has a structure that is resistant to heat and shock, but also the connection between the bottom and the body and the connection between the shoulder and the body due to drop impact. This effectively prevents parts from breaking or shrinking due to thermal deformation of these connecting parts during hot filling with contents. In the present invention, manufacturing a stretch-blow-molded container from an amorphous thermoplastic resin has a wide range of rubber-like elasticity and exhibits significant advantages in terms of stretch-molding workability. For example, in the case of crystalline thermoplastic resins, the range of rubber-like elasticity suitable for stretch molding is as high as just below the melting point, which poses problems in terms of stretch molding workability. There is also the inconvenience that rapid cooling is required to prevent whitening due to crystallization. On the other hand, according to the present invention, by using an amorphous thermoplastic resin, stretch blow molding is possible without such restrictions. In the present invention, amorphous means that the thermoplastic resin does not exhibit a clear endothermic peak due to melting of crystals in terms of differential thermal analysis.
Suitable amorphous thermoplastic resins include vinyl chloride resins such as vinyl chloride homopolymers or large amounts of vinyl chloride, vinylidene chloride, vinyl acetate, acrylic monomers, vinyl ether, butadiene, etc. in terms of gas barrier properties and moldability. It is a copolymer consisting of a small amount of In addition to vinyl chloride resins, thermoformable nitrile polymers, polystyrene, polycarbonate, amorphous polyesters, acrylic (methacrylic) resins, and the like can also be used. As a thermoformable nitrile polymer, 60 to 95% by weight of acrylonitrile or methacrylonitrile
and 5 to 40% by weight of at least one of styrene, butadiene, vinyl ether, acrylic ester, methacrylic ester, etc. Such a copolymer is called a high nitrile resin and is used as a gas barrier resin. It is known for its excellent sex. In the manufacturing method of the present invention, first, a bottomed parison made of thermoplastic resin is manufactured. This bottomed parison is
It can be manufactured by resin injection molding or melt blow molding. Next, this bottomed parison is stretched at a stretching temperature of 5 to 70% of the total stretching ratio in the axial direction.
In particular, it is subjected to at least one pre-stretching in the axial direction by 20 to 50%. Finally, this pre-stretched parison is stretched in the axial direction by the remaining stretching ratio, and expanded and stretched in the circumferential direction by blowing fluid into the parison to form the final container. In the present invention, the stretchable temperature of the amorphous thermoplastic resin varies depending on the type of resin, but generally it is a temperature higher than the glass transition temperature and lower than the plastic temperature of the resin. be. 80 to 40℃ for vinyl chloride resin, 8 to 130℃ for high nitrile resin, 90 to 145℃ for styrene resin, 120 to 200℃ for polycarbonate, polymethyl A temperature range of 120 to 180°C is suitable for methacrylates. Heating the bottomed parison to this temperature is easily accomplished by passing the bottomed parison through a heating furnace such as a hot air oven or an infrared heating furnace. Stretch blow molding is suitably performed using a combination of a stretch rod and a split mold. A second example showing this aspect
-A, 2-B, and 2-C, first, the opening 11 of the bottomed parison 10 heated to a temperature that allows stretching is held between a pair of split molds 12a and 12b,
The drawing rod 1 is passed through the opening 11 of this parison 10.
3 (Figure 2-A). Next, the stretching rod 1
The tip 14 of the parison 3 is brought into contact with the parison bottom 15 and pressed downward to pre-stretch it in the axial direction by the aforementioned pre-stretching ratio, and in this state the stretching rod 13 is stopped (FIG. 2-B). Due to this axial pre-stretching, the parison body wall 16 undergoes molecular orientation in the axial direction, but since this stretching operation is stopped, all but the bottom end 16A of the parison body wall, which is restrained by engagement with the stretching rod, It is thought that the axial molecular orientation in the parison shell wall is relaxed in response to the stopping time. In the present invention, this stopping time is 0.1 to 2
seconds, especially in the range from 0.2 to 1 second, is advantageous for the above-mentioned purpose. Finally, as shown in FIG. 2-C, the parison is stretched in the axial direction by the entire stretching ratio by moving the stretching rod 13 downward, and the parison is drawn inside the parison through the fluid inlet 17 provided on the stretching rod 13. A final stretch-blow-molded container 18 is obtained by blowing fluid into the parison and blow-stretching the parison. According to the present invention, by combining such multi-stage stretching and subsequent blow stretching, the vinyl chloride resin parison is axially stretched 1.2 to 3 times, particularly 1.5 to 2.8 times, and 1.2 to 8 times, especially It becomes possible to carry out blow stretching of 1.2 to 6 times, and furthermore, it becomes possible to impart the above-mentioned unique molecular orientation to the container body. In the present invention, the amount of parison varies depending on the use, but generally speaking, it is 25 to 50g/
A range of 1000ml is recommended. The invention is illustrated by the following example. A Nikon polarizing microscope POH model manufactured by Nippon Kogaku Kogyo Co., Ltd. was used to measure birefringence. I used the included Babinet type compensator for the letterer. Also,
If the sample was significantly oriented in one direction, resulting in a large difference in refractive index, and if the sample was thick, a quartz crystal retarder was also used for correction. Example 1 A polyvinyl chloride resin with an average degree of polymerization of = 780 was molded into a wall thickness of 3.05 m/m using an 8 oz injection molding.
A preform with an effective length of 119.5 m/m excluding the neck is molded, and in the next step, the temperature of this preform is adjusted to be uniform (approximately 115°C), and then this preform is sent into a blow mold. 1.3 times the vertical axis with a stretching rod (wall thickness 2.58m/m effective length 156.1m/m)
Immediately after stretching and stopping, the preform stretched 1.3 times was further stretched vertically to 1.4 times (effective length 218.6 m/m) (two-stage longitudinal stretching),
It was blown at a blowing pressure of 10 kg/cm ² to obtain a stretched blow container with a basis weight of 39 g and 600 c.c. For comparison, I tried to vertically stretch the preform obtained in the same manner as above by 1.8 times to obtain a stretch-blown container with a weight of 39 g and 600 c.c. having the same shape as in the example, but there was no need for a stretching rod. The bottom of the bottom parison (preform) was pierced, making it impossible to form a container. For the polyvinyl chloride bottle obtained by the two-stage longitudinal stretch blow method obtained in this way, the axial orientation coefficient ( _A ) of the shoulder end and the circumferential orientation coefficient (
_A ), the axial orientation coefficient of the bottom end ( _B ), the same circumferential orientation coefficient ( _B ), and the axial orientation coefficient of the central part ( _C ), the same circumferential orientation coefficient ( _C ) and the thickness direction The coefficient ( _C ) was measured according to the method described in the text. The results are _B = 0.345, _B = 0.429, _A = 0.404,
_A = 0.359, _C = 0.420, _C = 0.385, _C =
0.195, so _A − _B = 0.059, _B −
The values _A = 0.070 and _C + _C = 0.805 were obtained. Next, 20 polyvinyl chloride bottles produced by the two-stage longitudinal stretch blowing method of the present invention were filled with 10% by weight saline solution, left in an atmosphere (refrigerator) at 5°C for one day and night, and then heated to a height of 1.2 m at room temperature. A drop test was conducted by dropping each bottle from the side so that the bottom touched the concrete surface. The number of falls was repeated up to 10 times. Not a single bottle was found to be damaged. Further, three bottles of the present invention were fully filled with hot water at 70°C, and after being left at room temperature for 10 minutes, the hot water was removed and the degree of thermal deformation of each bottle was visually observed. No deformation was observed in the polyvinyl chloride bottle molded by the two-stage longitudinal stretch blow method of the present invention. Example 2 Polyvinyl chloride resin with an average degree of polymerization of = 780 was molded into a wall thickness of 2.91 m/m using an 8 oz in-die extension.
m, a preform with an effective length of 136.6 m/m excluding the neck is molded, the temperature of this preform is adjusted uniformly (approximately 115°C) in the next process, and then this preform is sent into a blow mold. 1.15 times (wall thickness 2.58m/m effective length 156.1m/
m), and after stopping, immediately
The preform stretched 1.15 times is further stretched vertically to 1.4 times (effective length 218.6 m/m) and blowing pressure 10
It was blown at Kg/cm ² to obtain a stretch-blown container with a basis weight of 39 g and 600 c.c. For comparison, a preform obtained in the same manner as above was vertically stretched to 1.6 times, and Example 1
A stretch-blown container of the same shape and weight of 39 g and 600 c.c. was obtained. For the polyvinyl chloride bottle obtained by the two-stage longitudinal stretch blow method obtained in this way, the axial orientation coefficient ( _A ) of the shoulder end and the circumferential orientation coefficient (
_A ), the axial orientation coefficient of the bottom end ( _B ), the same circumferential orientation coefficient ( _B ), and the axial orientation coefficient of the central part ( _C ), the same circumferential orientation coefficient ( _C ) and the thickness direction The coefficient ( _C ) was measured according to the method described in the text. The results are _B = 0.365, _B = 0.457, _A = 0.515,
_A = 0.367, _C = 0.490, _C = 0.366, _C =
0.144, so _A − _B = 0.150, _B − _A
= 0.090, and _C + _C = 0.856. On the other hand, the results of each orientation coefficient from the bottle obtained by longitudinal stretching 1.6 times (single-stage longitudinal stretching) are
_B = 0.392, _B = 0.390, _A = 0.394, _A =
0.387, _C = 0.365, _C = 0.351, _C = 0.284, so _A − _B = 0.002, _B − _A = 0.003,
_C + _C = 0.716. Next, 20 polyvinyl chloride bottles molded by the two-stage longitudinal stretch blow method of the present invention and a polyvinyl chloride bottle molded by the ordinary single-stage longitudinal stretch blow method for comparison were filled with 10% by weight saline solution. death,
After being left in a 5°C atmosphere (refrigerator) for one day and night, a drop test was performed by dropping each bottle from a height of 1.2 m at room temperature so that the bottom of each bottle touched the concrete surface. The number of falls was repeated up to 10 times. Table 1 shows the number of bottles that were damaged the first time.
Table 1 shows the number of bottles that were broken up to 5 times and up to 10 times, and the number of bottles that remained undamaged even after being dropped 10 times. From Table 1, it is known that the impact resistance of the bottle produced by the two-stage longitudinal stretch-blowing method of the present invention is clearly superior to that of the bottle produced by the conventional single-stage longitudinal stretch-blowing method. In addition, for bottles molded using the conventional one-step method, breakage occurred from the bottom corners or the lower part of the mouth. Furthermore, three bottles each of the present invention and three bottles for comparison were filled with hot water at 70°C, and
After standing for a minute, the hot water was removed and the degree of thermal deformation of each bottle was visually observed. In all of the polyvinyl chloride bottles produced by the conventional one-stage longitudinal stretch blow molding method, clear deformation was observed in the lower part of the mouth and the bottom. On the other hand, no deformation was observed in the polyvinyl chloride bottle molded by the two-stage longitudinal stretch blow method of the present invention.

[Table] On the other hand, for the polyvinyl chloride bottle molded by the two-stage longitudinal stretch blowing method of the present invention and the polyvinyl chloride bottle molded by the ordinary single-stage longitudinal stretch blowing method molded for comparison, from the shoulder end to the bottom end. Table 2 shows the results of measuring the wall thickness of each bottle at 11 corresponding locations. It can be seen from this table that the bottles of the present invention have clearly less variation in wall thickness values and less uneven thickness.

[Table] Example 3 Polyvinyl chloride resin with an average degree of polymerization of = 780 was molded into a wall thickness of 3.01 m/m using an 8 oz injection molding.
A preform with an effective length of 125.0 m/m excluding the neck is molded, and in the next step, the temperature of this preform is adjusted to be uniform (approximately 117°C), and then this preform is sent into a blow mold. 1.28 times the vertical axis with a stretching rod (wall thickness 2.80m/m effective length 160.7m/m)
Immediately after stopping, the preform stretched 1.28 times was further vertically stretched 1.4 times (effective length 225 m/m), and the blowing pressure was 10 kg/cm ^2.
A stretched blow container with a basis weight of 40 g and a capacity of 1000 c.c. was obtained. For comparison, I tried to vertically stretch the preform obtained in the same manner as above by 1.8 times to obtain a stretch-blown container with a fabric weight of 40 g and 1000 cc. The bottom of the parison (preform) was pierced, making it impossible to form a container. For the polyvinyl chloride bottle obtained by the two-stage longitudinal stretch blow method obtained in this way, the axial orientation coefficient ( _A ) of the shoulder end and the circumferential orientation coefficient (
_A ), the axial orientation coefficient of the bottom end ( _B ), the same circumferential orientation coefficient ( _B ), and the axial orientation coefficient of the central part ( _C ), the same circumferential orientation coefficient ( _C ) and the thickness direction The coefficient ( _C ) was measured according to the method described in the text. The results are _B = 0.350, _B = 0.446, _A = 0.371,
_A = 0.438, _C = 0.403, _C = 0.370, _C =
0.227, so _A − _B = 0.021, _B − _A
= 0.006, _C + _C = 0.775 were obtained. Next, 20 polyvinyl chloride bottles produced by the two-stage longitudinal stretch blowing method of the present invention were filled with 10% by weight saline solution, left in an atmosphere (refrigerator) at 5°C for one day and night, and then heated to a height of 1.2 m at room temperature. A drop test was conducted by dropping each bottle from the side so that the bottom touched the concrete surface. The number of falls was repeated up to 10 times. One bottle was found to be damaged on the seventh occasion. Further, three bottles of the present invention were fully filled with hot water at 70°C, and after being left at room temperature for 10 minutes, the hot water was removed and the degree of thermal deformation of each bottle was visually observed. No deformation was observed in the polyvinyl chloride bottle molded by the two-stage longitudinal stretch blow method of the present invention. Example 4 An acrylonitrile styrene copolymer resin containing 72% by weight of acrylonitrile was formed into a preform with a wall thickness of 3.35 m/m and an effective stretching length of 120.0 m/m excluding the neck using an 8-ounce in-die extrusion, and then subjected to the next process. to keep the temperature of this preform uniform (approximately
Adjust the temperature to 110℃), feed it into a blow mold, and use a stretching rod to stretch it by 1.12 times (effective length 134m/
m) and immediately after stopping the stretching.
A second stage of vertical stretching is performed to 1.15 times (effective length 154.2 m/m), and this stretched preform is
The third stage of vertical stretching was performed to 1.4 times (effective length 216.0 m/m) and blowing was performed at a blowing pressure of 10 Kg/cm ² to 1000 c.c.
(Weight: 41 g) A stretched blow container was obtained. For comparison, an attempt was made to vertically stretch the same preform as above by 1.8 times to obtain a 1000 c.c. stretch-blown container, the same as in the example, but the stretching rod broke through the bottom of the preform, causing the container to collapse. It was impossible to mold it. Regarding the acrylonitrile-styrene copolymer bottle obtained by the two-stage longitudinal stretch blowing method, the axial orientation coefficient ( _{A) at the shoulder end, the circumferential orientation coefficient (A} ), and the axial orientation coefficient ( _A ) at the bottom end. directional orientation coefficient ( _B ), also circumferential orientation coefficient ( _B ) and central axial orientation coefficient ( _C ), also circumferential orientation coefficient ( _C ) and thickness direction orientation coefficient ( _C )
was measured according to the method described in the text. The results are _B = 0.404, _B = 0.391, _A = 0.411,
_A = 0.357, _C = 0.465, _C = 0.365, _C =
0.170, so _A − _B = 0.007, _B − _A
= 0.034, and _C + _C = 0.830. Next, 20 polyvinyl chloride bottles produced by the two-stage longitudinal stretch blowing method of the present invention were filled with 10% by weight saline solution, left in an atmosphere (refrigerator) at 5°C for one day and night, and then heated to a height of 1.2 m at room temperature. A drop test was conducted by dropping each bottle from the side so that the bottom touched the concrete surface. The number of falls was repeated up to 10 times. Not a single bottle was found to be damaged. Further, three bottles of the present invention were fully filled with hot water at 70°C, and after being left at room temperature for 10 minutes, the hot water was removed and the degree of thermal deformation of each bottle was visually observed. No deformation was observed in the polyvinyl chloride bottle molded by the two-stage longitudinal stretch blow method of the present invention.

[Brief explanation of the drawing]

The first is a diagram showing the entire stretch blow molded container of the present invention, and Figure 2-A, Figure 2-B, and Figure 2-C are explanatory diagrams showing the process of stretch blow molding. Number 1 is the torso (1A is the shoulder end, 1B is the bottom end, 1C is the center), 2 is the bottom, 3 is the shoulder,
4 is a neck, 10 is a bottomed parison, 11 is a mouth of the bottomed parison 10, 12a and 12b are paired split molds, 13 is a stretching rod, 14 is a tip of the stretching rod 13, 15 is a bottom of the parison, 16 is the parison body wall;
16A represents the bottom end of the parison body wall, 17 represents the fluid inlet, and 18 represents the final stretch blow molded container.

Claims (1)

[Scope of Claims] 1. A bottomed parison made of a thermoplastic resin is subjected to at least one stage of preliminary stretching in the axial direction by 5 to 70% of the total axial stretching ratio at a stretching temperature, and the stretching operation is temporarily stopped. Then, this pre-stretched parison is stretched in the axial direction by the remaining stretching ratio, and expanded in the circumferential direction by blowing fluid into the body, which is integrally formed of an amorphous thermoplastic resin.
A stretch blow molded container comprising a bottom, a shoulder and a neck, at least the body having biaxial molecular orientation, the body generally extending from the shoulder end to the bottom end. The body has an orientation tendency in which the axial orientation coefficient gradually decreases toward the shoulder end, and the circumferential orientation coefficient gradually decreases from the bottom single part toward the shoulder end, and at least the central part of the body part has an orientation in the thickness direction. A method for producing an impact-resistant stretch-blow-molded container, characterized by forming a molded container whose orientation coefficient is suppressed to a value lower than 0.25. 2. The manufacturing method according to claim 1, wherein the thermoplastic resin is a vinyl chloride resin. 3. The method of claim 1, wherein the parison as a whole is stretched at an axial stretch ratio of 1.2 to 3 and blow stretched at a circumferential stretch ratio of 1.2 to 8. 4. The method according to claim 1, wherein the stretching operation is stopped for 0.1 to 2 seconds between the preliminary stretching and the subsequent stretching.