JP2002326221A - Method for manufacturing two-layer preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a two-layer preform having good moldability and characteristics of inserting an outer layer shell with a bottom which does not need postprocessing and which has a wide selecting range of a molding resin to be used. SOLUTION: The method for manufacturing the two-layer preform comprises the steps of previously adhering fixedly the outer layer shell to the cavity surface of a female mold for an injection molding the preform, an integrating the inner layer shell with the inside of the outer layer shell. The method further comprises the steps of forming a protrusion 110 having a hollow part 111 projected down at a gate corresponding position of a mold for injection molding the preform of the bottom with the outer layer shell 100, cutting the protrusion by a gate cutter 20, and forming a through hole 120 for the gate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a two-layer preform by biaxially stretch-blowing a PET bottle.

[0002]

2. Description of the Related Art Conventionally, PET bottles widely used as non-food containers such as foods such as soft drinks and kitchen detergents generally include a single-layer injection-molded preform (a test tube preform). ) Is biaxially stretch blow-molded, but recently, in order to impart properties according to the intended use of the container to the PET bottle, a multilayer PET bottle formed by biaxially stretch-blow-molding a multilayer preform has been developed. It became so. And, as a method of manufacturing the multilayer preform, development has been advanced by a multilayer injection molding method, an insert injection molding method, or the like.

[0003]

However, as a method of manufacturing a two-layer preform, an inner shell is closely adhered to a male cavity surface of an injection molding die for a preform, and is fixed from a female gate. Inject the molten resin into the cavity and injection mold the outer shell outside the inner shell, and at the same time, integrate it with the inner shell to produce a two-layer preform, or use a cylindrical outer shell without a bottom. The two-layer preform was fabricated by closely adhering and fixing to the cavity surface of the female mold of the injection molding die for preform, and simultaneously injection-molding the inner shell inside the outer shell and integrating it with the outer shell. .

In the former method of inserting the inner shell, since the inner shell comes into contact with the contents, it is necessary to consider the contents of the molding resin of the inner shell, and the selection range of the molding resin which can be used naturally is narrowed. . For example,
It has been difficult to use recycled resins having low freshness and barrier resins having problems of hygiene and elution. In addition, the method of inserting the latter outer layer shell is as follows:
When manufacturing the outer shell, it is necessary to post-process the lower end, and when using an outer shell made of a barrier resin for the purpose of imparting barrier properties to the container, there is no barrier resin layer at the bottom of the container, In some cases, the barrier properties of the container became insufficient. In addition, when biaxially stretched blow molding was performed, there was a case where a displacement occurred at an adhesive interface between the inner shell and the outer shell.

The present invention solves the above-mentioned problem in the method for producing a two-layer preform by insert injection molding, and does not require any post-processing and has a wide selection range of molding resin to be used. It is intended to provide a method for producing a two-layer preform having good moldability and characteristics for inserting a preform.

[0006]

That is, the first aspect of the present invention is as follows.
The present invention relates to a method for manufacturing a two-layer preform in which an outer shell is brought into close contact with a cavity surface of a female mold of an injection molding die for a preform, and the inner shell is integrally molded inside the outer shell. In the above, the outer shell forms a hollow projection projecting downward at a position corresponding to the gate of the injection mold for preform at the bottom, and cuts this projection with a gate cutter to form a gate through-hole. A method for producing a two-layer preform characterized by being formed.

A second aspect of the present invention is characterized in that the hollow shape of the protruding portion is continuous in a truncated right conical shape with a lower end having a right conical shape and an upward inclination angle larger than the lower end. The method for producing a two-layer preform according to the first aspect of the present invention.

Next, a third aspect of the present invention is the first aspect, wherein the hollow shape of the projecting portion is continuous in an upwardly truncated right conical shape with a lower end having a spherical shape. Is a method for producing a two-layer preform.

Next, a fourth invention of the present invention provides
The method for manufacturing a two-layer preform, wherein the outer shell is closely adhered to and fixed to the cavity surface of the female mold of the injection mold for preform, and the inner shell is integrally molded inside the outer shell, wherein the outer shell is A concave portion is formed from a lower surface and a thin portion is formed on an upper surface at a position corresponding to a gate of a preform injection molding die at a bottom portion by a projection provided at a tip of a valve gate pin. This is a method of manufacturing a reform.

A fifth aspect of the present invention is the second aspect of the present invention, wherein the shape of the projection provided at the tip of the valve gate pin is a truncated right circular cone. It is a manufacturing method of a layer preform.

In a sixth aspect of the present invention, the projection provided at the tip of the valve gate pin has a right circular cone shape. This is a method of manufacturing a reform.

According to a seventh aspect of the present invention, there is provided a method for manufacturing a two-layer preform according to the fourth aspect, wherein the projection provided at the tip of the valve gate pin has a hemispherical shape. is there.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 3, a two-layer preform (10) according to the manufacturing method of the present invention comprises an outer shell (100) having a through hole at the bottom and an inner layer having a gate (11) at the bottom. And a shell (200). The manufacturing method is that the outer layer shell manufactured by the manufacturing method of the present invention is separately brought into close contact with the cavity surface of the female mold of the injection mold for preform in advance. Then, the inner shell is integrally injection-molded inside the outer shell. The two-layer preform is preheated, and a predetermined container is manufactured by biaxial stretch blow molding. In addition, the molding resin used for the outer shell and the inner shell is selected and used in accordance with the purpose of the container, but conventionally, the molding resin which may be affected to the contents, for example, freshness, It is possible to use a low-recycled resin, a barrier resin having a problem of hygiene or elution, etc. for the outer shell, and a wide selection range of usable resin molding resin is possible. Further, in the manufacturing method of the present invention, since the outer shell has a bottom,
Adhesion with the inner shell is improved, and no displacement occurs at the adhesive interface between the inner shell and the outer shell during biaxial stretch blow molding. Incidentally, as the resin used for the inner shell, for example, polyethylene terephthalate,
There is a polyester resin such as polyethylene naphthalate.

Next, as shown in FIG. 1A, the manufacturing method of the embodiment of the outer shell (100) of the present invention is as follows. A protruding portion (110) of a protruding hollow (111) is formed, and this protruding portion is cut by a gate cutter (20) provided in a mold as shown in FIG. A gate through-hole (120) is formed, and the mold is released. In addition, even if cutting burrs remain on the inner periphery of the gate through-hole, when the preform is molded, it is melted by the heat of the molten resin injected from the inner shell, and the moldability is reduced. There is no loss.

The hollow (111) of the above-mentioned projection (110)
As shown in FIG. 1 (a), the shape of the lower end is generally a straight cone, and the shape of the lower end is generally a truncated right conical shape with an inclination angle larger than that of the lower end. It has a spherical shape and a shape that is continuous upward in a truncated right conical shape. The hollow shape of the protrusion is the tip shape of the male mold of the injection mold when molding, and the tip shape of the male mold that forms the two hollow protrusions described above is injected from the gate. The flow state of the melt-molded resin is good, and the whitening phenomenon does not occur at the bottom of the outer shell.

Next, in a method of manufacturing the outer shell (100) of another embodiment of the present invention, a mold with a valve gate is used, and a projection is provided at the tip of the valve gate pin. As shown in FIG. 2, a concave portion (1) is formed at the bottom of the preform injection mold at a position corresponding to the gate, as shown in FIG.
30) to form a thin portion (140) on the upper surface. The thin portion is usually formed with a clearance of 0.3 mm or less between the lower end surface of the male die and the tip end surface of the protruding portion of the valve gate pin, and is extremely thin. The resin is melted and pierced by the heat and pressure of the molten resin injected into the inner shell.

The shape of the projection provided at the tip of the above-mentioned valve gate pin is usually a truncated right circular cone (the shape of the concave portion (130) in FIG. 3), a right circular cone, or a hemisphere. With such a shape, when the outer shell is formed, the flow of the injected molten resin is good, and the moldability is improved.

[0018]

When the two-layer preform is manufactured by the manufacturing method of the present invention, it is not necessary to post-process the through hole for the gate at the bottom of the outer shell, so that the selection range of the molding resin to be used is wide, and the moldability and characteristics are improved. Can be produced with good productivity.

[Brief description of the drawings]

FIG. 1 shows a method for producing an outer shell in a production method of the present invention. FIG. FIG. 4 is an explanatory view showing a state in which a gate through-hole is formed at the bottom.

FIG. 2 is a cross-sectional view of a main part of an outer layer shell that forms a thin portion on a bottom portion manufactured by another manufacturing method in the manufacturing method of the present invention.

FIG. 3 is a cross-sectional view of one embodiment of a two-layer preform manufactured by the manufacturing method of the present invention.

[Explanation of symbols]

 10 Double-layer preform 11 Gate 20 Gate cutter 100 Outer shell 110 Projection 111 Hollow 120 Through hole 130 Depression 140 Thin section 200 Inner shell

Continued on the front page F-term (reference) 4F201 AA24 AD05 AD18 AD24 AD27 AG03 AG07 AH55 BA03 BC01 BC12 BC21 BD06 BM05 BM09 BM12 BM13 4F202 AA24 AD05 AD18 AD24 AD27 AG03 AG07 AH55 CA11 CB01 CB12 CK06 CK07 4F206 AA24 AD05 AD05 AD05 JA06 JB12 JF05 4F208 AA24 AD05 AD18 AD24 AD27 AG03 AG07 AH55 LA02 LA04 LG06 LG28

Claims (7)

[Claims] 1. The method according to claim 1, wherein the outer layer shell is brought into close contact with the cavity surface of the female mold of the injection mold for the preform, and is fixed.
In the method for manufacturing a two-layer preform in which an inner shell is integrally injection-molded inside the outer shell, the outer shell is projected downward at a position corresponding to a gate of a bottom preform injection mold. A method for manufacturing a two-layer preform, comprising forming a portion, and cutting the protrusion with a gate cutter to form a through hole for a gate. 2. The two-layered projection according to claim 1, wherein the hollow shape of the projection is continuous with a truncated right conical shape having a lower end with a right conical shape and an upward inclination angle larger than the lower end. How to make a renovation. 3. The method for producing a two-layer preform according to claim 1, wherein the hollow shape of the projection is continuous with a lower end having a spherical shape and an upwardly truncated right conical shape. 4. The method according to claim 1, wherein the outer shell is brought into close contact with the cavity surface of the female mold of the injection mold for the preform, and is fixed.
In the method for manufacturing a two-layer preform in which the inner shell is integrally injection-molded inside the outer shell, the outer shell is formed by a projection provided at the tip of a valve gate pin.
A method for manufacturing a two-layer preform, wherein a concave portion is formed from a lower surface at a position corresponding to a gate of an injection molding die for a preform at a bottom portion and a thin portion is formed at an upper surface. 5. The method for manufacturing a two-layer preform according to claim 4, wherein the shape of the projection provided at the tip of the valve gate pin is a truncated right conical shape. 6. The method for manufacturing a two-layer preform according to claim 4, wherein the shape of the projection provided at the tip of the valve gate pin is a right circular cone. 7. The method for manufacturing a two-layer preform according to claim 4, wherein the projection provided at the tip of said valve gate pin has a hemispherical shape.