JP5779322B2 - Multilayer blow bottle and method for producing the same - Google Patents

Description

  The present invention relates to a method for producing a multilayer bottle mainly composed of polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or a PEN / PET mixture.

  The applicant first provides a low-cost cosmetic small bottle for cosmetics having pearl luster by direct blow molding using raw materials mixed in a weight ratio of PEN: PET = 40: 60 to 60:40. A technique was proposed (Patent Document 1).

  The technique of Patent Document 1 is excellent as a container for cosmetics such as mascara, but there is a point that should be improved in terms of water vapor barrier properties when used in skin lotions. Further, since lotion requires a bottle having a larger capacity than mascara, it is also necessary to improve impact resistance.

  Therefore, the applicant decided to study a multilayer blow bottle in which the PEN / PET mixture is the outer layer and the inner layer is polypropylene.

  With regard to this type of technology, an object of the present invention is to provide a polypropylene multilayer blow bottle having excellent surface gloss, transparency, etc. and improved drop strength, and a polypropylene copolymer having specific flow characteristics. There is a patent document that discloses a technique for producing an amorphous or low-crystalline polyethylene terephthalate copolymer (PET-G) as a main layer and a direct blow molding machine as an outer layer (Patent Document 2).

JP 2010-89319 A Japanese Patent No. 3899787

  However, since the high design bottle proposed by the applicant in Patent Document 1 is a technique using PEN and PET having a high melting point, the method using PET-G proposed in Patent Document 2 is applied as it is. However, there is a problem that the inner layer and the outer layer of the bottle do not join well.

  Moreover, since the multilayer bottle which uses PET-G as an outer layer and PP as an inner layer is easily scratched on the surface, there is also a problem that it is not suitable for a bottle that requires design properties.

  Therefore, the present invention has developed a new technology for producing a multilayer bottle having PEN, PET, or a PEN / PET mixture as an outer layer and PP as an inner layer by direct blow molding, has a high designability, and has a water vapor content. The purpose was to provide a multilayer blow bottle with high barrier properties and high impact resistance at low cost.

The present application is manufactured by a direct blow molding method as a problem solving means, and any one of PEN, PET, and a PEN / PET mixture is used as an outer layer material, polypropylene resin is used as an inner layer material, and the outer layer material and the inner layer material are adhesive layers. The inner layer material is a polypropylene resin layer containing at least 40% by weight of high melt tension polypropylene (trade name “SH9000” manufactured by Nippon Polypro Co., Ltd. or equivalent). A multi-layer blow bottle comprising the outer layer material as a main layer is proposed as a first invention.

Further, it is manufactured by a direct blow molding method, and any one of PEN, PET, and PEN / PET mixture is used as an outer layer material, polypropylene resin is used as an inner layer material, and the outer layer material and the inner layer material are bonded via an adhesive layer. A multilayer blow bottle, wherein the inner layer material is composed of a polypropylene resin layer adjusted so that the melt flow rate at a temperature of 250 ° C. and a pressure of 5 kgf is 0.5 to 3.0 g / min, and the outer layer material A multi-layer blow bottle characterized in that is used as a main layer is also proposed as a second invention as a problem solving means.

  When these multilayer blow bottles of the present invention are manufactured by direct blow molding, the inner layer material does not peel off, and even if the vicinity of the bottle bottom is pressed from both ends of the pinch offline, the inner layer material is not easily broken, and the contents It will have sufficient crushing strength and impact resistance that will not cause fatal damage even if dropped with the And since the water vapor barrier property is sufficiently exhibited, it can be applied to bottles containing water-soluble contents such as lotion, and the outer layer is hard to be damaged, and is a highly designable bottle. is there.

  In the multilayer blow bottle of the first invention, the strength is further increased when the inner layer material is formed of a polypropylene resin layer containing 50% or more by weight of high melt tension polypropylene. In the multilayer blow bottle of the second invention, When the inner layer material is formed of a polypropylene resin layer adjusted so that the melt flow rate at a temperature of 250 ° C. and a pressure of 5 kgf is 0.5 to 2.5 g / min, the strength is further increased.

  In the multilayer blow bottles of the first and second inventions, the outer layer material is formed by a PEN / PET mixture in which PEN and PET are mixed at a weight ratio of 40:60 to 60:40, and the outer layer material is The multilayer blow bottle of the third invention as the main layer is proposed as a problem solving means. According to the multilayer blow bottle of the third aspect of the invention, it is possible to provide a highly designable bottle having excellent water vapor barrier properties, excellent crushing strength and impact strength strength, and being hard to be scratched on the surface and having a pearly luster. Can do.

Also, as a problem solving means, PEN or PET pellets are put into an outer layer screw type extruder, polypropylene resin pellets are put into an inner layer screw type extruder, and resin pellets used as an adhesive are intermediate layers. The screw-type extruder is used, and the pellets are heated, melted and kneaded in each extruder, then the three-layered tube parison is discharged, and the lower end of the three-layer tube-like parison is pinched off. In this way, the blow molding mold is closed, the parison is cut, the blow pin is inserted, and air is blown in to produce a multilayer blow bottle by direct blow molding. A method for producing a multilayer blow bottle according to the fourth invention is also proposed.
(A1) Polypropylene resin pellets containing at least 40% by weight of high melt tension polypropylene (trade name “SH9000” manufactured by Nippon Polypro Co., Ltd. or equivalent) as the polypropylene resin pellets.
(A2) In the screw extruder for the outer layer, a temperature gradient is provided so that the temperature in the molding machine decreases toward the discharge port.
(A3) In the inner layer screw extruder and the intermediate layer screw extruder, a temperature gradient is provided so that the temperature in the molding machine rises toward the discharge port.

Similarly, as a problem solving means, PEN or PET pellets are put into an outer layer screw type extruder, polypropylene resin pellets are put into an inner layer screw type extruder, and resin pellets used as an adhesive are intermediate layers. The screw-type extruder is used, and the pellets are heated, melted and kneaded in each extruder, then the three-layered tube parison is discharged, and the lower end of the three-layer tube-like parison is pinched off. In this way, the blow molding mold is closed, the parison is cut, the blow pin is inserted, and air is blown in to produce a multilayer blow bottle by direct blow molding. The manufacturing method of the multilayer blow bottle of 5th invention characterized by these is also proposed.
(B1) Polypropylene resin pellets adjusted to have a melt flow rate of 0.5 to 3.0 g / min at a temperature of 250 ° C. and a pressure of 5 kgf are used as the polypropylene resin pellets.
(B2) In the screw extruder for the outer layer, a temperature gradient is provided so that the temperature in the molding machine decreases toward the discharge port.
(B3) In the inner layer screw extruder and the intermediate layer screw extruder, a temperature gradient is provided so that the temperature in the molding machine rises toward the discharge port.

  According to these 4th and 5th invention, the multilayer blow bottle mentioned above as the 1st and 2nd invention can be manufactured exactly.

In addition, in the present application, PEN / PET mixture pellets are put into an outer layer screw extruder, polypropylene resin pellets are put into an inner layer screw extruder, and resin pellets used as an adhesive are used for an intermediate layer After throwing into a screw-type extruder and heating, melting, and kneading the pellets in each extruder, the tube-shaped parison with a three-layer structure is discharged,
The blow molding mold is closed so as to pinch off the lower end of the three-layer tubular parison, the parison is cut, the blow pin is inserted, and air is blown to produce a multilayer blow bottle by direct blow molding. A method for producing a multilayer blow bottle according to the sixth aspect of the present invention is also proposed, characterized in that the following conditions are adopted.
(C1) As pellets of the PEN / PET mixture, pellets of approximately the same size are mixed at a weight ratio of PEN: PET = 40: 60 to 60:40 and used in a dry state.
(C2) Polypropylene resin pellets containing at least 40% by weight of high melt tension polypropylene (trade name “SH9000” manufactured by Nippon Polypro Co., Ltd. or an equivalent product) are used as the polypropylene resin pellets.
(C3) In the screw extruder for the outer layer, a temperature gradient is provided so that the temperature in the molding machine decreases toward the discharge port.
(C4) In the inner-layer screw extruder and the intermediate-layer screw extruder, a temperature gradient is provided so that the temperature in the molding machine rises toward the discharge port.

Similarly, in the present application, PEN / PET mixture pellets are put into an outer layer screw extruder, polypropylene resin pellets are put into an inner layer screw extruder, and resin pellets used as an adhesive are used for an intermediate layer. It is put into a screw type extruder and heated, melted and kneaded in each extruder, then a three-layer tube parison is discharged, and the lower end of the three-layer tube parison is pinched off. The blow mold is closed, the parison is cut, the blow pin is inserted, and air is blown into it to produce a multilayer blow bottle by direct blow molding. The manufacturing method of the multilayer blow bottle of 7th invention characterized by the above is also proposed.
(D1) As pellets of the PEN / PET mixture, pellets of approximately the same size are mixed at a weight ratio of PEN: PET = 40: 60 to 60:40 and used in a dry state.
(D2) Polypropylene resin pellets adjusted to have a melt flow rate of 0.5 to 3.0 g / min at a temperature of 250 ° C. and a pressure of 5 kgf are used as the polypropylene resin pellets.
(D3) In the screw extruder for the outer layer, a temperature gradient is provided so that the temperature in the molding machine decreases toward the discharge port.
(D4) In the inner-layer screw extruder and the intermediate-layer screw extruder, a temperature gradient is provided so that the temperature in the molding machine rises toward the discharge port.

  According to these sixth and seventh inventions, the multilayer blow bottle described above as the third invention can be accurately manufactured.

Furthermore, the present application also proposes a method for producing a multilayer blow bottle according to the eighth invention, wherein the following conditions are further adopted in the method for producing a multilayer blow bottle according to the sixth and seventh inventions.
(E) The tube-shaped parison having the three-layer structure has an outer layer: intermediate layer: inner layer = 6: 2: 2 to 7: 1: 1 in the thickness ratio.

  According to the 8th invention, the multilayer blow bottle which has the pearl luster mentioned above as the 4th invention can be manufactured exactly.

  According to the present invention, it is possible to provide a low-cost multilayer blow bottle with PEN, PET, or a PEN / PET mixture as an outer layer, PP as an inner layer, high design properties, and high water vapor barrier properties and impact resistance. .

It is a mimetic diagram explaining composition and operation of a multilayer blow bottle molding device of an embodiment. It is a schematic diagram which shows the temperature setting example in the multilayer blow bottle molding apparatus of embodiment. It is a schematic diagram which shows the method of a crushing strength test.

  Hereinafter, modes for carrying out the present invention will be described.

  First, an apparatus for producing a multilayer blow bottle will be described. As shown in FIG. 1, the multilayer blow molding apparatus 1 of the embodiment includes an outer layer screw type extruder 11, an inner layer screw type extruder 12, an intermediate layer screw type extruder 13, and a blow molding machine. A mold 30, an air blow device 40, and a product recovery device 50 are provided.

  In molding, pellets are put in from the hoppers 11a, 12a, 13a of the extrusion molding machines 11, 12, 13 and heated, melted and kneaded in each molding machine, and then extruded, head H, adapter AD, heads H1, H2. The tubular parisons 21 and 21 having a three-layer structure are discharged through the dies D1 and D2 and the lips L1 and L2. Next, the blow molding die 30 is closed so as to pinch off the lower ends of the three-layered tube-shaped parisons 21 and 21, and the upper ends of the parisons 21 and 21 are cut by a heating wire cutter 31. When the parisons 21 and 21 are taken into the molding die 30 in this way, the molding die 30 is moved directly below the air blow device 40, and the blow pins 41 and 41 are inserted to blow air. Thereby, the multilayer blow bottles 2 and 2 are molded.

  Next, the molding die 30 is opened and moved to take in the next parison, and the holder 51 of the product recovery device 50 is moved directly below the air blowing device 40 to close the die, and the multilayer blow bottles 2 and 2 are closed. Hold in holder 51. At this time, the molding die 30 also performs a mold closing operation. Then, after the parisons 21 and 21 are separated by the heating wire cutter 31, the molding die 30 and the holder 51 are moved in the right direction in the figure. At this time, the shooter 52 protrudes directly below the movement destination of the holder 51. Next, the blow pins 41 and 41 are protruded in the air blow device 40, and the parisons 21 and 21 in the molding die 30 are stretched by direct blow to form the next products 2 and 2. Then, the molding die 30 and the holder 51 are opened simultaneously, the product molded in the previous operation is dropped onto the shooter 52, and after receiving the products 2 and 2, the shooter 52 is retracted to the collection position.

  In addition, when the holder 51 is closed at the time of collection, a leak test is also performed in which air blow is performed again from the air blow device 40 to check for leaks.

  According to the multilayer blow molding apparatus 1 of this embodiment, the multilayer blow bottles 2 and 2 can be continuously manufactured by repeatedly performing the above operation.

  In the present embodiment, the inside of the cylinder of the outer layer screw type extruder 11 is divided into three chambers C1 to C3 so that the temperature can be controlled. The cylinders of the inner layer and intermediate layer screw extruders 12 and 13 are divided into two chambers C1 and C2 so that the temperature can be controlled. Further, the head H, the adapter AD, the heads H1 and H2, the dies 1 and D2, and the lips L1 and L2 are also temperature-controlled.

  In the present embodiment, as shown in FIG. 2, in the outer layer screw extruder 11, a temperature gradient is set so that the temperature in the molding machine gradually decreases, and the inner layer screw extruder is used. In the screw extruder 13 for the intermediate layer 12 and the intermediate layer, the temperature is controlled under conditions set so as to provide a temperature gradient so that the temperature in the molding machine gradually increases. Finally, the temperatures of the parisons 21 and 21 are saturated by the lips L1 and L2.

  Next, the specific Example which shape | molds the multilayer blow bottle 2 using the multilayer blow molding apparatus 1 which performs the structure, operation | movement, and control demonstrated by embodiment is demonstrated.

[material]
As an outer layer material, PEN pellets and PET pellets of approximately the same size are mixed well in a weight ratio within the range of PEN: PET = 40: 60 to 60:40 and sufficiently dried. PET mixture pellets were prepared. The trade name “TN8065S” manufactured by Teijin Chemicals Ltd. was used as PEN, and the trade name “P115” manufactured by Nanya Plastics (Taiwan) was used as PEN.

  As an inner layer material, pellets of general grade polypropylene (hereinafter referred to as “general PP”) having approximately the same size and pellets of high melt tension polypropylene (hereinafter referred to as “high melt tension PP”) are weight ratios. In this case, general PP: high melt tension PP = well mixed within the range of 60:40 to 0: 100. As a general PP, a trade name “EG7FT” manufactured by Nippon Polypro Co., Ltd. was used, and as a high melt tension PP, a trade name “SH9000” manufactured by Nippon Polypro Co., Ltd. was used.

  As the adhesive, an olefin-based special grade adhesive (trade name “F534A” manufactured by Mitsubishi Chemical Corporation) was used.

[Temperature control conditions]
The temperature of each of the extruders 11, 12, 13 and the adapter AD and the head H was controlled under the conditions shown in Table 1 until the outer layer, the inner layer, and the intermediate layer had a three-layer structure.

  The temperature control for the resin after the three-layer structure has the conditions shown in Table 2 for the heads H1 and H2, the dies D1 and D2, and the lips L1 and L2.

[Thickness ratio of three-layer parison]
Moreover, the tube-shaped parisons 21 and 21 having a three-layer structure were adjusted so that the thickness ratio was outer layer: intermediate layer: inner layer = 6: 2: 2 to 7: 1: 1.

  When a multilayer blow bottle having a capacity of 10 ml was molded under the above conditions, the joining condition of each layer was good, the result of the crushing strength test described later was also good, and a multilayer blow bottle having pearl luster could be molded.

  Molding was performed under conditions where the lip temperature was changed within the range of 230 ° C to 260 ° C. Conditions other than the lip temperature are the same as in Example 1. The multilayer blow bottle formed according to Example 2 also had good bonding conditions and crushing strength of each layer, had pearly luster, and had no particular problem.

  Molding was performed under conditions where the die temperature was changed within the range of 235 ° C to 270 ° C. Conditions other than the die temperature are the same as in Example 1. The multilayer blow bottle molded according to Example 3 was also good in both the joining state and crushing strength of each layer, had a pearly luster, and had no particular problem.

  Molding was performed under conditions where the head temperature was changed within the range of 235 ° C to 295 ° C. Conditions other than the head temperature are the same as in the first embodiment. The multilayer blow bottle molded according to Example 4 also had good bonding conditions and crushing strength of each layer, had pearly luster, and had no particular problem.

  A multilayer blow bottle was molded in the same manner as in Example 1 except that the outer layer material was 100% PET. The multilayer blow bottle molded according to Example 5 also had good bonding conditions and crushing strength of each layer. In addition, although the external appearance did not exhibit pearl luster, it exhibited luster not found in PP bottles.

  A multilayer blow bottle was molded in the same manner as in Example 1 except that the outer layer material was 100% PEN. The multilayer blow bottle molded according to Example 6 also had good bonding conditions and crushing strength of each layer. In addition, although the external appearance did not exhibit pearl luster, it exhibited luster not found in PP bottles.

Comparative Example 1

  When the inner layer material was general PP: high melt tension PP = 100: 0 to 70:30 and the other conditions were the same as in Example 1, an insufficient crushing strength was observed.

[Crushing strength test]
As shown in FIG. 3, the crushing strength was examined by a method of observing the breakage state by sandwiching the vicinity of the bottom of the multilayer blow bottle with pliers and pressing from both ends of the pinch offline.

  Table 3 shows the test object and the result together with the observation result of the bonding state between the layers.

  For general PP: high melt tension PP = 100: 0, the state of bonding between the layers was NG, so the crushing strength test was not performed.

  The crushing strength ▲ means that both the inner and outer layers are damaged in a pinch off-line state with a little force applied, causing air leakage, and it is difficult to provide as a product.

  The crushing strength ○ indicates that the pinch off-line was not broken in both the inner and outer layers unless the adult male fully grasped the pliers.

  The crushing strength ◎ is that the inner layer did not break even when an adult male grasped the pliers with his full power.

  From the above test results, general PP: high melt tension PP = 0: 100 to 60:40, that is, when PP containing high melt tension PP in a weight ratio of 40% or more is used as an inner layer material, it is shipped as a product. A conclusion is drawn that possible multilayer blow bottles can be formed. In particular, when general PP: high melt tension PP = 0: 100 to 50:50, that is, PP containing high melt tension PP in a weight ratio of 50% or more is used as an inner layer material, regarding crushing strength and delamination, It has been found that a multilayer blow bottle can be formed without any problems.

[Measurement of melt flow rate (MFR)]
The results of measuring the melt flow rate at a temperature of 250 ° C. and a pressure of 5 kgf for the inner layer material are shown in Table 4 along with the crushing strength.

  From the measurement result of the melt flow rate, when a polypropylene resin adjusted so that the melt flow rate at a temperature of 250 ° C. and a pressure of 5 kgf is 0.5 to 3.0 g / min is used as an inner layer material, it can be shipped as a product. The conclusion is drawn that a simple multilayer blow bottle can be formed. In particular, when a polypropylene resin adjusted to have a melt flow rate of 0.5 to 2.5 g / min at a temperature of 250 ° C. and a pressure of 5 kgf is used as an interior material, there is no problem with respect to crushing strength and delamination. It has been found that no multilayer blow bottle can be molded.

  Table 5 shows the results of measuring the melt flow rate of the outer layer material at a temperature of 280 ° C. and a pressure of 2.16 kgf.

  It can be seen that the mixing ratio of PEN and PET does not affect the melt flow rate of the outer layer material.

[Drop test]
Water is poured into a 200 ml multi-layer blow bottle manufactured in the same manner as in Example 1, and the cap is put in three postures: upright (cap is up), sideways, and inverted (cap is down). The drop strength was measured by a method of dropping onto the P tile from a height of 70 cm from the surface. As a result, the bottle did not break in any posture, and no water leakage occurred. Although there were some cases where scratches were observed on the bottle surface in a sideways posture, neither scratches nor dents were observed in upright or inverted positions. Therefore, it turned out that the multilayer blow bottle of an Example fully satisfies fall strength.

[Pearl luster]
When the appearance of pearly luster when the outer layer material is a PEN / PET mixture was observed, the ratios of PEN: PET = 40: 60, 50:50, 60:40 were applied for single layer bottles. Similar to the results reported in 2008-259917 (Patent Document 1), good pearl luster was observed.

[Discussion]
From the examination results of Examples and Comparative Examples, the following is considered.

  Any one of PEN, PET, and a PEN / PET mixture is used as an outer layer material, a polypropylene resin is used as an inner layer material, and the outer layer material and the inner layer material are joined via an adhesive layer. A multilayer blow bottle characterized by being a polypropylene resin layer containing 40% or more of high melt tension polypropylene by weight ratio has no peeling of the inner layer material, sufficient crushing strength and drop strength, and has a water vapor barrier property. Since it has, it can be applied to bottles containing water-soluble contents such as skin lotion, and the outer layer is hardly damaged, resulting in a highly designable bottle.

  From a different viewpoint, this bottle is made of any one of PEN, PET, and a PEN / PET mixture as an outer layer material, a polypropylene resin as an inner layer material, and a multilayer in which the outer layer material and the inner layer material are bonded via an adhesive layer. A multilayer bottle characterized in that the inner layer material is a polypropylene resin layer adjusted so that the melt flow rate at a temperature of 250 ° C. and a pressure of 5 kgf is 0.5 to 3.0 g / min. It is a bottle.

  Further, the inner layer material is formed of a polypropylene resin layer containing 50% or more by weight of high melt tension polypropylene (if the viewpoint is changed, the inner layer material has a melt flow rate of 0.5 at a temperature of 250 ° C. and a pressure of 5 kgf. By forming a polypropylene resin layer adjusted to be ~ 2.5 g / min), the strength is further increased.

  Further, the outer layer material is formed by a PEN / PET mixture in which the weight ratio of PEN: PET = 40: 60 to 60:40 is mixed, and by using the outer layer material as a main layer, the design property having pearly luster is high. Bottles can be provided.

  It can be used for cosmetic bottles.

DESCRIPTION OF SYMBOLS 1 ... Multi-layer blow molding apparatus 11 ... Screw type extruder for outer layer 12 ... Screw type extruder for inner layer 13 ... Screw type extruder for intermediate layer 21 ... Parison 30 ... -Blow molding die 31 ... Heating wire cutter 40 ... Air blow device 41 ... Blow pin 50 ... Product recovery device 51 ... Holder 52 ... Shooter

Claims (6)

Multi-layer blow manufactured by direct blow molding method, with PEN, PET, and PEN / PET mixture as outer layer material, polypropylene resin as inner layer material, and outer layer material and inner layer material joined via adhesive layer The bottle is composed of a polypropylene resin layer adjusted so that a melt flow rate at a temperature of 250 ° C. and a pressure of 5 kgf is 0.5 to 3.0 g / min, and the outer layer material is mainly used. Multi-layer blow bottle characterized by having a layer. 2. The multilayer blow bottle according to claim 1 , wherein the inner layer material is a polypropylene resin layer adjusted so that a melt flow rate at a temperature of 250 ° C. and a pressure of 5 kgf is 0.5 to 2.5 g / min. Multi-layer bottle. The multilayer blow bottle according to claim 1 or 2 , wherein the outer layer material as the main layer is formed of a PEN / PET mixture in which PEN and PET are mixed at a weight ratio of 40:60 to 60:40. Multi-layer blow bottle characterized by PEN or PET pellets are put into an outer layer screw extruder, polypropylene resin pellets are put into an inner layer screw extruder, and resin pellets used as an adhesive are put into an intermediate layer screw extruder. After the pellets are heated, melted and kneaded in each extruder, the tubular parison with a three-layer structure is discharged,
The blow molding mold is closed so as to pinch off the lower end of the three-layer tubular parison, the parison is cut, the blow pin is inserted, and air is blown to produce a multilayer blow bottle by direct blow molding. A method for manufacturing a multilayer blow bottle, characterized in that the following conditions are adopted.
(B1) Polypropylene resin pellets adjusted to have a melt flow rate of 0.5 to 3.0 g / min at a temperature of 250 ° C. and a pressure of 5 kgf are used as the polypropylene resin pellets.
(B2) In the screw extruder for the outer layer, a temperature gradient is provided so that the temperature in the molding machine decreases toward the discharge port.
(B3) In the inner layer screw extruder and the intermediate layer screw extruder, a temperature gradient is provided so that the temperature in the molding machine rises toward the discharge port. PEN / PET mixture pellets are put into an outer layer screw extruder, polypropylene resin pellets are put into an inner layer screw extruder, and resin pellets used as an adhesive are intermediate layer screw extruder , And after heating, melting, and kneading the pellets in each extruder, the tube-shaped parison with a three-layer structure is discharged,
The blow molding mold is closed so as to pinch off the lower end of the three-layer tubular parison, the parison is cut, the blow pin is inserted, and air is blown to produce a multilayer blow bottle by direct blow molding. A method for manufacturing a multilayer blow bottle, characterized in that the following conditions are adopted.
(D1) As pellets of the PEN / PET mixture, pellets of approximately the same size are mixed at a weight ratio of PEN: PET = 40: 60 to 60:40 and used in a dry state.
(D2) Polypropylene resin pellets adjusted to have a melt flow rate of 0.5 to 3.0 g / min at a temperature of 250 ° C. and a pressure of 5 kgf are used as the polypropylene resin pellets.
(D3) In the screw extruder for the outer layer, a temperature gradient is provided so that the temperature in the molding machine decreases toward the discharge port.
(D4) In the inner-layer screw extruder and the intermediate-layer screw extruder, a temperature gradient is provided so that the temperature in the molding machine rises toward the discharge port. 6. The method for producing a multilayer blow bottle according to claim 5, wherein the following conditions are further adopted.
(E) The tube-shaped parison having the three-layer structure has an outer layer: intermediate layer: inner layer = 6: 2: 2 to 7: 1: 1 in the thickness ratio.