JP2000043126A - Preform of two-layered constitution for stretch blow molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the cooling shift and the lowering of the welding strength of a preform of two-layered constitution due to the generation of stress in a cylindrical sleeve and the return of the stress during cooling operation caused by such a phenomenon that the cylindrical insert sleeve of an outside preform is shifted and moved within a mold when a molten resin for molding an inside preform is injected into the mold at a predetermined speed under predetermined injection pressure. SOLUTION: A preform of two-layered constitution is constituted of a resin outside preform A having a cylindrical body part 1 and a bottom part 2 and molded so that a hole providing part 2a is provided to the bottom part 2 and the resin inside preform B closely bonded to the inner surface of the outside preform and molded so as to have a cylindrical body part 11 and a bottom part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch blow molding preform used for molding a resin container such as a plastic bottle by a stretch blow molding method.
In particular, the present invention relates to a two-layer preform for stretch blow molding in which the preform is composed of two resin layers.

[0002]

2. Description of the Related Art A conventional two-layer preform for stretch blow molding is provided with an insert sleeve (cylindrical body) made of resin as an outer preform, and is in close contact with the inner surface of the outer preform to form a cylindrical body. An inner preform made of a resin comprising a part, a bottom part, and a mouth part is formed.

In order to mold this conventional two-layered preform, an insert sleeve (cylindrical body) as an outer preform is inserted into a mold for preform molding, and then the inner preform is molded. By injecting a molten resin for molding into a mold for preform molding at a predetermined injection pressure and speed, an outer preform of a cylindrical body and an inner preform composed of a cylindrical body, a bottom and a mouth are provided. And a preform having a two-layer structure consisting of

[0004]

However, when the molten resin for molding the inner preform is injected into the mold at a predetermined injection pressure and speed, a small but cylindrical insert sleeve is formed in the mold. The molding position may not be constant due to the displacement.

[0005] Further, stress is applied to the insert sleeve which is displaced and moved in the mold during the injection, thereby causing a cooling displacement due to the return of the stress during the cooling operation after the injection, and thus the molded two-layered mold. The welding strength between the outer preform and the outer preform of the reform tends to decrease, and therefore, when the two-layer preform is stretch blow-molded, a displacement at the two-layer interface is likely to occur.

Further, the bottom of the conventional two-layered preform formed in this manner has an insufficient gas barrier property because of the single-layered structure of the inner preform.

The present invention provides a two-layered preform for solving the above-mentioned problems.

[0008]

According to a first aspect of the present invention, there is provided a resin outer preform having a cylindrical body and a bottom and having a hole formed in the bottom, A two-layer preform for stretch blow molding, comprising a resin inner preform molded with a cylindrical body portion and a bottom portion in close contact with the inner surface of the outer preform. .

A second aspect of the present invention relates to a resin outer preform having a cylindrical body and a bottom, and having a hole formed in the bottom, and a resin outer preform. It is composed of a resin inner preform formed with a cylindrical body and a bottom that are in close contact with the inner surface, and the resin at the bottom of the inner preform that faces the hole of the outer preform is formed in the hole. It is a two-layered preform for stretch blow molding characterized by being filled in a part.

Next, the invention according to a third aspect of the present invention is the two-layer preform for stretch blow molding according to the second aspect of the present invention, wherein the hole portion extends from the inside to the outside. is there.

Next, according to a fourth aspect of the present invention, in the second or third aspect, the resin at the bottom of the inner preform filled in the hole is
It is a two-layer stretch blow molding preform that is filled out of the hole and filled so as to cover the periphery of the hole.

[0012]

1 (a) to 1 (c) show an embodiment of a two-layer preform for stretch blow molding according to the present invention.
This will be described in detail below with reference to the side sectional view of the two-layer preform of the present invention shown in FIG.

The two-layered preform of the present invention shown in FIG. 1 (a) has an elongated cylindrical body 1 and a bottom 2 and is formed of a resin formed by providing a hole 2a in the bottom 2. It has a two-layer structure of an outer preform A and a resin inner preform B formed with a cylindrical body 11 and a bottom 12 that are in close contact with the inner surface of the outer preform A. If necessary, on the side opposite to the bottom 12 of the cylindrical body 11, a mouth C, a screw 14, and a flange 15 of a container formed by stretch blow molding using this two-layer preform later. Are integrally formed.

Further, as shown in FIG. 1 (b), the flange portion 15 may be provided with a coating flange portion 1a in which the resin of the outer preform A is partially inserted. Coating flange part 1a which is a reference for
Thereby, both resins of the outer preform A and the inner preform B are held, and the mutual displacement of the preforms A and B is suppressed.

The two-layered preform of the present invention shown in FIG. 1 (c) has a cylindrical body 1 and a bottom 2 and the bottom 2
An outer preform A made of resin molded with a hole 2a formed therein, and a cylindrical inner body 11 and a bottom part 12 that are in close contact with the inner surface of the outer preform A, and an inner preform made of resin B and the hole 2
a, a filling protrusion 12a is provided extending from the bottom 12 of the inner preform B in a protruding manner so as to cover the hole 2a, and the filling protrusion 12a is filled with the hole. 2
The outer surface of the bottom portion 2 of the outer preform A protrudes from the outer surface of the bottom portion 2 of the outer preform A.

Further, as shown in FIG. 1 (d), the flange portion 15 may be provided with a coating flange portion 1a in which the resin of the outer preform A is partially inserted. Coating flange part 1a which is a reference for
Thereby, both resins of the outer preform A and the inner preform B are held, and the mutual displacement of the preforms A and B is suppressed.

The two-layered preform of the present invention shown in FIG. 1 (e) has a cylindrical body 1 and a bottom 2
An outer preform A made of resin molded with a hole 2a formed therein, and a cylindrical inner body 11 and a bottom part 12 that are in close contact with the inner surface of the outer preform A, and an inner preform made of resin B, and the inside preform B is provided in the hole 2a so as to close the hole 2a.
A filling protruding portion 12a is provided extending from the bottom portion 12 in a protruding manner, and the filling protruding portion 12a protrudes outside the hole 2a and is filled, and is exposed to the outside of the filling protruding portion 12a. The exposed surface 12b is crushed by pressing and compressing or hitting the exposed surface 12b protruding from the outer surface of the bottom portion 2 from the outside in the direction of the arrow so that the exposed surface 12b is substantially flush with the outer surface of the bottom portion 2 of the outer preform A. Shape
The hole 2a is formed so as to cover the periphery of the hole 2a.

Further, as shown in FIG. 1 (f), the flange portion 15 may be provided with a coating flange portion 1a in which the resin of the outer preform A is partially inserted. Coating flange part 1a which is a reference for
Thereby, both resins of the outer preform A and the inner preform B are held, and the mutual displacement of the preforms A and B is suppressed.

The hole portion 2a may have the same diameter from the inner surface to the outer surface of the bottom portion 2 of the outer preform A, or may have a tapered shape having a gradually increasing or decreasing diameter. In the present invention, it is appropriate that the diameter gradually increases as shown.

Next, a method for forming and processing the two-layered preform of the present invention will be described below with reference to FIGS.

[Outer Preform Forming Process] First, among the forming processes of the two-layered preform of the present invention, a forming die used for forming the outer preform A will be described below.

FIG. 2A shows an embodiment of a molding die for molding the outer preform A of the two-layer preform.

This molding die is composed of a cavity 20 and a core 30.
It is constituted by a pair of cavity blocks 21, 21 that move opposite to each other in the direction of the arrow and couple from the separated state. 1 (b), FIG. 1 (d), and FIG.
As shown in (f), when forming the outer preform A in which the coating flange portion 1a in which the resin of the outer preform A partially enters the flange portion 15 is formed, the cavity for forming the coating flange portion 1a. Cavity block 2 in which space 22a (indicated by a dotted line) is formed at one end
1, 21 are used.

The pair of cavity blocks 21,
21 is provided with a semi-cylindrical cavity 22 and a curved bottom cavity 23 on opposing sides, and is moved in the direction of the arrow and overlapped by a coupling line 25 to form a cylindrical hollow inside the cavity blocks 21 and 21. A portion and a closed curve bottom are formed.

At the bottom of the closed curve, a cavity block 2 is provided.
1 is provided with a protruding part 24 for forming a hole provided part protruding toward the cylindrical hollow part side.

The protrusions 24 may be provided integrally with the cavity block 21, respectively, or may be respectively connected to the cavity blocks 21 and 21 for fitting and connecting a resin injection gate to be used later as required. May be provided at the tip of a fitting block 27 that is separate from the cavity block 21 that is fitted (attached and fixed with a screw or set screw 28) to a gate hole 26 provided as necessary.

The core portion 30 is loaded into a hollow cavity formed by a cylindrical hollow portion formed inside the cavity blocks 21 and 21 of the cavity portion 20 and a closed curved bottom portion,
When it is loaded, it is loaded so that a predetermined distance a corresponding to the thickness of the outer preform A is maintained between the inner surface of the cavity blocks 21 and the outer surface of the core portion 30.

The core section 30 is composed of a core body 31 and a base 32. The core body 31 has the base 32 attached to and held by a ring-shaped core support block 33.

The tip of the core body 31 is
0 when loaded into the hollow cavity of
The protrusions 24 are in close contact with the protrusions 24 of the zero.

The core support block 33 has a resin injection gate 34 penetrating therethrough. The injection gate 34 is directed toward a gap a formed by the inner surfaces of the cavity blocks 21, 21 and the outer surface of the core portion 30. The resin melted by heating for molding the outer preform A is injected and filled from the injection gate 34 into the space a.

FIG. 2B shows a molding die according to another embodiment for molding the outer preform A.
The cavity portion 20 of the molding die is constituted by a pair of cavity blocks 21 and 21 which move in a direction opposite to each other in the direction of the arrow and couple from the separated state.

The pair of cavity blocks 21,
21 is provided with a semi-cylindrical cavity 22 and a curved bottom cavity 23 on opposing sides, and is moved in the direction of the arrow and overlapped by a coupling line 25 to form a cylindrical hollow inside the cavity blocks 21 and 21. A portion and a closed curve bottom are formed.

A tapered gate hole 26 into which the resin injection gate 40 is fitted is provided at the bottom of the closed curve of the cavity blocks 21, 21.
Can be fitted and connected in the gate hole 26.

The core portion 30 is loaded into a hollow cavity formed by a cylindrical hollow portion formed inside the cavity blocks 21 and 21 of the cavity portion 20 and a closed curved bottom portion,
When it is loaded, it is loaded so that a predetermined distance a corresponding to the thickness of the outer preform A is maintained between the inner surface of the cavity blocks 21 and the outer surface of the core portion 30.

The core portion 30 is composed of a core body 31 and a base 32. The core body 31 is held by attaching the base 32 to a ring-shaped core support block 33.

The tip of the core body 31 is
0 when loaded into the hollow cavity of
0, which does not come into close contact with the tip 41 of the resin injection gate 40 fitted and connected in the gate hole 26, and maintains a certain interval to secure a path for the injection resin from the injection gate 40 to the interval a of the cavity 20. It is formed so that.

As shown in FIG. 2A, first, a pair of cavity blocks 21 and
1 in the direction of the arrow to couple the core body 3
The molding die is closed by moving 1 in the direction of the arrow and loading it into the cavity of the cavity 20.

Subsequently, as shown in FIG. 3A, after the heated molten resin R is injected and filled into the space a from the resin injection gate 34, the molding die is cooled to solidify the resin R in the space a. I do.

Alternatively, as shown in FIG.
The pair of cavity blocks 21, 21 facing each other in the cavity portion 20 are moved in the direction of the arrow to be coupled, and the core body 31 is moved in the direction of the arrow to be loaded into the cavity hollow portion of the cavity portion 20, thereby forming a molding die. Closed, gate hole 26 of cavity block 21, 21
The tip portion 41 of the resin injection gate 40 is fitted and connected therein.

Subsequently, as shown in FIG. 3B, after the heated molten resin R is injected and filled into the space a from the resin injection gate 40, the molding die is cooled to solidify the resin R in the space a. By doing so, the outer preform A is formed within the interval a.

Subsequently, the cavity blocks 21, 21 of the molding die shown in FIG. 3 (a) or FIG. After removing the reform A, as shown in FIG. 4, a cylindrical body 1, a bottom 2, and a hole 2 formed in the bottom 2.
The outer preform A consisting of a is obtained.

In the case of the molding die shown in FIG. 3 (b), a part of the resin injected from the tip 41 of the resin injection gate 40 is part of the molded outer preform A shown in FIG. Since the residual resin adheres to the hole portion 2a via the thin film resin (connecting portion), the residual resin is cut off by pressing or by a cutter. As a result, FIG.
An outer preform A in which a hole 2a is formed as shown in FIG. Further, as shown in FIG. 4B, an outer preform A having a coating flange portion 1a formed by coating on one surface of the flange portion 15 is formed.

[Two-Layer Preform Molding Process 1]
Next, as shown in FIG. 5, an inner preform is injection-molded on the inner surface of the formed outer preform A to produce a two-layer preform for injection molding.

As shown in FIG. 5, a molding die used for molding the outer preform A (FIG. 2A) is used for molding a two-layer preform for injection molding. 2 (b)), and a cavity forming cavity 60 mounted on the end of the cavity block 21, 21 opposite to the curved bottom cavity 23, 23 of the cavity 20. It consists of.

The cavity 20 for forming the two-layered preform is as described above with reference to FIGS. 2A and 2B. The cavity 20 having the structure provided (FIG. 3A)
In the case where the cavity portion 20 is used, the cavity portion 20 in which the gate hole 26 is provided on the side of the closed curved bottom portion 23 of the cavity block 21 (see FIG. 2A or FIG. 2B or FIG. 5)
Is used to form a two-layer preform.

As shown in FIG. 5, the tip 51 of the resin injection gate 50 for injecting the molding resin of the inner preform B is provided in the gate hole 26 of the cavity 20 for molding and processing the two-layered preform. The leading end of the tip 51 is fitted into the hole 2a of the outer preform A loaded in the cavity 20 so as to form the same surface as the inner surface thereof.

The cavity 60 for forming the mouth is formed as shown in FIG.
As shown in the figure, move and approach each other in the direction of the arrow,
It is constituted by a pair of cavity blocks 61, 61 which are coupled from the separated state.

The pair of cavity blocks 61,
Although the internal shape of the cavity 61 is not particularly limited in the present invention, for example, a flange-like cavity 62 and a ring-like cavity 63 are provided on opposite sides of each other.
A threaded cavity 64 is provided, which is moved and approached in the direction of the arrow and overlapped by the coupling line 65 so that a flange-shaped hollow portion, a ring-shaped hollow portion, and a screw-shaped hollow portion are formed inside the cavity blocks 21, 21. It is formed.

The outer preform A formed by the outer preform forming process has a pair of opposing cavity blocks 21 and 21 of the cavity 20 shown in FIG.
The cavity blocks 21 and 21 are moved and approached to each other in the direction of the arrow and coupled to each other, and are loaded into the cavity 20.

As shown in FIG. 5, a core part 35 for forming a two-layer preform is formed by a core body 36, a base 37 thereof, and a support block 38 for supporting the core body 36 at the base 37. The core body 36 of the core portion 35 is configured to be loaded in the outer preform A loaded in the cavity portion 20 while maintaining a predetermined interval b.

After the core body 36 of the core 35 is loaded into the cavity 20, the mouth forming cavity 60 is
As shown in FIG. 5, the pair of cavity blocks 61, 61 facing each other are moved closer to each other in the direction of the arrow and coupled by a coupling line 65, thereby closing the mold for molding a two-layer preform. I do.

Subsequently, as shown in FIG. 6, after the heated molten resin R is injected and filled from the resin injection gate 50 into the space b between the cavities 20 and into the mouth forming cavity 60, the molding die is removed. By cooling and solidifying the resin R in the gap b, the inner preform B and the mouth C are formed in the gap b along the inner surface of the outer preform A in the gap b. And the outer preform A
And a two-layered preform composed of the inner preform B and the inner preform B.

Subsequently, the cavity blocks 21, 21 and the cavity blocks 61, 6 of the molding die shown in FIG.
Then, the mold is opened by moving the preform 1 in a direction away from the preform 1, and the molded two-layer preform is removed from the core body 36. As a result, as shown in FIG. 7A, an outer preform A comprising a cylindrical body 1, a bottom 2, and a hole 2a formed in the bottom 2, and a cylindrical body fused to the inside thereof. 1
Thus, a two-layered preform including an inner preform B composed of the inner preform 1 and the bottom portion 12 and a mouth portion C extending from the inner preform B is obtained. Further, as shown in FIG. 7B, an outer preform A in which a coating flange portion 1a in which the resin of the outer preform A partially enters one side of the flange portion 15 of the inner preform B is formed. An inner preform B comprising a cylindrical body 11 and a bottom 12 fused to the inside, and a mouth C extending to the inner preform B
And a two-layered preform consisting of

[Two-Layer Preform Molding Process 2]
The two-layered preform of the present invention can be produced as follows in addition to the above method.

FIG. 8 shows a molding die for the two-layered preform. The cavity of the molding die (see FIGS. 2A and 2B) used for molding the outer preform A is shown in FIG. Part 20, and a cavity block 21, 21 on the opposite side of the curved bottom cavity 23, 23 of the cavity part 20.
For forming a mouth part to be attached to the end of the cavity 60
(See FIG. 6) and a core section 35 (see FIG. 6).

A tip 56 of a resin injection gate 55 for injecting the molding resin of the inner preform B is fitted and mounted in the gate hole 26 of the cavity 20 for forming a two-layered preform. The foremost portion of the portion 56 is set so as not to protrude from the inner surfaces of the curved bottom cavities 23 and 23 of the cavity portion 20, and the outer edge of the hole 2 a of the outer preform A loaded in the cavity portion 20 from the outer surface. Fitted to cover.

As shown in FIG. 8, after the molten resin R is injected and filled from the resin injection gate 55 into the space b between the cavities 20 and into the mouth forming cavity 60,
By cooling the molding die and solidifying the resin R in the space b, the inner preform B is formed along the inner surface of the outer preform A in the space b, and the opening C is formed in the opening forming cavity 60. Is molded to form a two-layered preform including the outer preform A and the inner preform B.

Subsequently, the cavity blocks 21, 21 and the cavity blocks 61, 6 of the molding die shown in FIG.
1 is moved away from the mold, the mold is opened, and the molded two-layer preform is removed from the core body 36, and the cylindrical body 1, the bottom 2, and the bottom 2 are removed as shown in FIG. Preform A comprising a hole 2a formed in the outer preform A
And a cylindrical body 11 and a bottom 12 fused to the inside thereof, and a hole 2a filled from the bottom 12 and filled in the hole 2a.
A two-layered preform including an inner preform B having a protruding portion 12a protruding outward and a mouth portion C extending from the inner preform B is obtained.

As shown in FIG. 10, the inner preform B is provided with a coating flange portion 1a formed on one side of the flange portion 15 and is provided with holes in the cylindrical body portion 1, the bottom portion 2, and the bottom portion 2. Outer preform A comprising a hole 2a
And a cylindrical body 11 and a bottom 12 fused to the inside thereof, and a hole 2a filled from the bottom 12 and filled in the hole 2a.
A two-layered preform including an inner preform B having a protruding portion 12a protruding outward and a mouth portion C extending from the inner preform B is obtained.

The two-layered preform shown in FIG. 9 has a projection 12a projecting from the bottom 12 of the inner preform B to the outside of the hole 2a of the bottom 2 of the outer preform A.
As shown in FIG. 1 (c), the outer preform A can be made substantially flush with the outer surface of the bottom 2 of the outer preform A by melting or pressing in the direction of the arrow from the outside.

[0061]

The two-layer preform for stretch blow molding of the present invention comprises two inner and outer resin layers used for blow molding a resin container such as a plastic bottle by a stretch blow molding method. The preform for stretch blow molding is constituted, in particular, both the inner preform and the outer preform are provided with a cylindrical body and a bottom, and the molten resin for forming the inner preform is formed into an outer preform (insert When the inner surface of the sleeve is injected into the mold at a predetermined injection pressure and speed, the bottom of the outer preform suppresses the phenomenon that the insert sleeve of the outer preform shifts in the mold and moves the molding position. It has the effect of stabilizing, so that preform molding can be performed stably, and there is an effect that stable and high-quality preforms can be obtained.

The two-layered preform for stretch blow molding of the present invention can suppress the phenomenon that the insert sleeve of the outer preform is displaced and moved in the mold. The stress applied to the insert sleeve can be reduced, and there is no cooling displacement due to the return of stress during the cooling operation after the injection of the inner preform, so that the welding strength between the formed inner preform and the outer preform is not easily reduced. When the two-layered preform is used for stretch blow molding, there is an effect that the two-layer interface is less likely to be displaced or peeled off at the two-layer interface.

In the two-layer preform for stretch blow molding of the present invention, the inner surface of the inserted outer preform is pressed against the inner surface of the cavity of the cavity block by the flow pressure of the molten resin from the resin injection gate. It is possible to assist the fusion force at the two-layer interface, improving the fusion property by heat, especially when heating with a cold parison. Because it is molded in close contact,
A two-layer preform having no distortion on the outer surface is obtained.

Also, since the injection resin temperature of the injection gate near the curved bottom cavity of the cavity is highest near the inner surface of the outer preform, the fusion strength between the bottom of the outer preform and the bottom of the inner preform is the highest. Therefore, when the formed two-layered preform of the present invention is subjected to stretch blow molding, the most stress is applied to the bottom of the two-layered preform, which is advantageous for stretch blow molding.

Further, since the preform of the present invention having a two-layer structure for stretch blow molding has not only a body portion but also a bottom portion having a two-layer structure, the gas barrier property of a container such as a plastic bottle formed by stretch blow molding is obtained. Has the effect of being sufficiently obtained.

[Brief description of the drawings]

FIG. 1A is a side sectional view showing one embodiment of a two-layer preform for stretch blow molding of the present invention, and FIGS.
(F) is a sectional side view showing another embodiment.

FIG. 2 (a) is a side sectional view showing an example of a mold for forming an outer preform of a two-layer preform for stretch blow molding of the present invention, and FIG. 2 (b) is a side sectional view showing another example.

FIG. 3 (a) is a side sectional view showing a state where an outer preform is injection-molded using an outer preform molding die according to the present invention, and FIG. 3 (b) is a side sectional view showing another example.

4A is a side sectional view showing an example of an outer preform injection-molded in the present invention, and FIG. 4B is a side sectional view showing another example of the outer preform injection-molded in the present invention.

FIG. 5 is a side sectional view showing an example of a two-layer preform molding die according to the present invention.

FIG. 6 is a side sectional view showing an example of a two-layered preform injection-molded using a two-layered preform molding die according to the present invention.

7A is a side sectional view showing an example of a two-layered preform injection-molded in the present invention, and FIG. 7B is a side sectional view showing another example of a two-layered preform injection-molded in the present invention. FIG.

FIG. 8 is a side sectional view showing another example of a two-layer preform molding die according to the present invention.

FIG. 9 is a side sectional view showing an example of a two-layer preform injection-molded in the present invention.

FIG. 10 is a side sectional view showing another example of a two-layer preform injection-molded in the present invention.

[Explanation of symbols]

A: Outer preform B: Inner preform C: Mouth R: Injection resin 1 ... Body 1a ... Coating flange 2 ... Bottom 2a ... Drilled part 11 ... Body 12 ... Bottom 12a ... Projection filling part 12b
... Exposed surface 14 ... Screw part 15 ... Flange part 20 ... Cavity part 21 ... Cavity block 22
... trunk cavity 23 ... curved bottom cavity 24 ... protruding part 25 ... coupling line 26 ... gate hole 27 ... fitting block 28 ... set screw 30 ... core part for outside preform molding 31 ... core body 32 ... core body base 33 ... Supporting block 34 ... Resin injection gate 35 ... Core part for forming a two-layer preform 36 ... Core body 37 ... Core body base 38 ... Support part 40 ... Resin injection gate 41 ... Gate tip 50 ... Resin injection gate 51 ... Gate Tip 60: Cavity for forming the mouth 61: Cavity block

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B29L 22:00 F term (Reference) 4F201 AD05 AD12 AD18 AG03 AG07 AG23 AG24 AG28 AH55 BA03 BC02 BC13 BC21 BC29 BD06 BM05 BM12 BQ09 BQ38 4F208 AD05 AD12 AD18 AG03 AG07 AG23 AG24 AG28 AH55 LA05 LA08 LB01 LB22 LG03 LG06 LG15 LG19 LG28

Claims (4)

[Claims] 1. An outer preform made of a resin having a cylindrical body and a bottom, and formed with a hole in the bottom,
A two-layer stretch blow molding preform, comprising: a resin inner preform having a cylindrical body portion and a bottom portion that are in close contact with the inner surface of the outer preform. 2. An outer preform made of a resin, comprising a cylindrical body and a bottom, and formed with a hole in the bottom.
A resin inner preform formed with a cylindrical body portion and a bottom portion that are in close contact with the inner surface of the outer preform, and a resin at a bottom portion of the inner preform opposed to the hole portion of the outer preform. Is filled in the hole, and a two-layered preform for stretch blow molding. 3. A two-layer preform for stretch blow molding according to claim 2, wherein said hole portion extends from the inside to the outside. 4. The resin at the bottom of the inner preform filled in the hole is formed so as to protrude outside the hole and is filled and covers the periphery of the hole. The two-layer preform for stretch blow molding according to claim 2 or 3.