JP2002326220A - Method for manufacturing two-layer preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a two-layer preform capable of obtaining a two-layer bottle having a high strength against an external load without bringing about an interface deviation at the time of biaxially stretching blow molding with a high fusion bonding strength of interface fusion bonding the inner surface of an outer layer shell to the outer surface of an inner layer shell. 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, and integrating the inner layer shell with the inside of the outer layer shell. The method further comprises the steps of molding the outer layer shell 100 by the mold for injection molding the outer layer shell with the cavity surface of a male mold as a rough surface, and integrally injection molding the inner layer shell 200 with the inner surface of the rough surface of the outer layer shell with is inner surface being the rough surface.

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. As a method of manufacturing the multilayer preform, there are a multilayer injection molding method, an insert injection molding method, and the like, and the development has mainly been advanced by the latter insert injection molding method.

[0003]

However, the outer shell is inserted into an injection mold in advance, and the inner shell is injection-molded and simultaneously manufactured by the insert injection molding method in which the outer shell is integrated with the outer shell (FIG. 1A). When the two-layer preform (10) shown in (1) is biaxially stretch blow-molded to produce a two-layer bottle, a fusion interface (12) between the inner surface of the outer shell (100) and the outer surface of the inner shell (200) is obtained. In this case, when an interface shift occurs and a drop impact is applied, whitening occurs,
As shown in (a), the mouth and neck (2) of the two-layer bottle (20)
When a load (P) is applied to 1), for example, as shown in FIG.
As shown in (1), interface separation (23) occurred on the shoulder (22). When interfacial peeling occurs, the commercial value of the product is reduced, and the buckling strength is 12 to 24.
% Was confirmed to decrease.

The present invention solves the above-mentioned problem in the method for producing a two-layer preform by the insert injection molding method, and has a high fusion strength at the fusion interface between the inner surface of the outer shell and the outer surface of the inner shell. Another object of the present invention is to provide a method for producing a two-layer preform capable of obtaining a two-layer bottle resistant to an external load without causing interface displacement during biaxial stretch blow molding.

[0005]

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. 3. The method for producing a two-layer preform according to claim 1, wherein the outer shell is formed by an injection molding die for an outer shell having a rough cavity surface of a male mold, and the inner surface is rough.

Next, a second invention of the present invention is the first invention, wherein the cavity surface of the male mold of the injection mold for the outer layer shell is roughened by shot peening. This is a method for manufacturing a two-layer preform.

Next, a third invention of the present invention is the method according to the first invention, wherein the cavity surface of the male mold of the injection mold for the outer shell is roughened by sandblasting. It is a manufacturing method of a layer preform.

Next, a fourth invention of the present invention is the method according to the first invention, wherein a cavity surface of the male mold of the injection mold for the outer layer shell is roughened by etching. It is a manufacturing method of a layer preform.

In a fifth aspect of the present invention, the cavity surface of the male mold of the injection mold for the outer layer shell is roughened by electric discharge machining. It is a manufacturing method of a layer preform.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A method of manufacturing a two-layer preform (10) according to the present invention comprises, for example, forming an outer shell having a through hole for a gate at the lower end bottom on a cavity surface of a female mold of an injection molding die for a preform. Fig. 1 (a)
As shown in the figure, an inner shell (200) is integrally injection-molded inside an outer shell (100). The outer shell used in the present manufacturing method is an outer shell having a rough cavity surface of a male mold. It is molded by an injection molding die for roughening the inner surface. 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 production method of the present invention, since the outer shell is provided with the bottom, the adhesion to the inner shell is improved, and the displacement at the adhesive interface between the inner shell and the outer shell during biaxial stretch blow molding. Never wake up. Incidentally, examples of the resin used for the inner shell include polyester resins such as polyethylene terephthalate and polyethylene naphthalate.

When a two-layer preform is manufactured by insert injection molding using an outer shell having an inner surface roughened,
As shown in FIG. 1 (b), the rough surface of the inner surface of the outer shell (1001) exerts an anchoring effect on the inner shell (200) to be injection-molded, and a fusion interface between the outer shell and the inner shell. (12) The adhesion is improved. Also, at the time of preheating during biaxial stretch blow molding, the area of the fusion interface between the inner surface of the outer shell and the outer surface of the inner shell is large, radiant heat is concentrated at the fusion interface, fusion is promoted, and biaxial stretching is performed. When blow molding, it is difficult to generate an interface deviation of a fusion interface between the inner surface of the outer shell and the outer surface of the inner shell.

One embodiment of the method for roughening the cavity surface of the male mold of the injection mold for the outer shell described above is shot peening (shot) in which angular steel grains are shot at high speed by compressed air or other methods. peeening).

In another embodiment of the present invention, a method of roughening the cavity surface of a male mold of an injection mold for an outer shell is by sand blast in which sand particles are blown at high speed by compressed air or another method. It is.

In another embodiment, the method of roughening the cavity surface of the male mold of the injection molding die for the outer shell is by etching which is corroded by a corrosive liquid.

[0015] In another embodiment of the present invention, the male mold surface of the injection molding die for the outer shell is roughened by intermittent discharge between the machining electrode and electric discharge machining.
Rospark machining).

Next, the inventors of the present invention made the surface roughness of the male mold cavity surface of the injection mold for the outer layer shell by the above-mentioned four types of surface treatment methods of shot peening, sand blasting, etching and electric discharge machining. Is 25S and 10
Each of the two types of OSS is roughened, and eight types of inner layer shells are roughened to produce outer layer shells. Using these outer layer shells, eight types of two-layer preforms are manufactured by insert injection molding. A bottle was produced from the two-layer preform by biaxial stretch blow molding. For comparison, a conventional inner shell having a flat inner layer was used for insert injection molding.
A layer preform was prepared, and a bottle was prepared from this two-layer preform by biaxial stretch blow molding. The case where the inner surface of the outer shell was roughened and the case where the inner surface of the outer shell was flat were evaluated comparatively. Table 1 shows the results.

[0017]

[Table 1]

According to the evaluation results shown in Table 1, the shearing shear stress of the preform is four times or more in any case where the inner surface of the outer shell is roughened than when the inner surface of the outer shell is flat. Was roughened. The shear shear stress of the stretch blow-molded product (bottle) is 4 times or more in any case where the inner surface of the outer shell is roughened, compared to the case where the inner surface of the outer shell is flat. there were. The transparency of stretch blow molded products (bottles)
In any case where the surface roughness of the male mold cavity surface was 25S and the inner surface of the outer shell was roughened, there was no inferiority to the case where the inner surface of the outer shell was flat. In each case where the surface roughness of the cavity surface of the male mold is 100S and the inner surface of the outer shell is roughened, the haze is 10% or less,
The transparency was practically acceptable. The shape of the rough surface of the inner surface of the outer shell was different depending on the method of treating the male cavity surface.

[0019]

As described above, the two-layer preform produced by the production method of the present invention has a high fusion strength at the fusion interface between the inner surface of the outer shell and the outer surface of the inner shell. Without producing, the produced two-layer bottle is strong against external loads such as drop impact and load.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view illustrating a structure of an example of a two-layer preform, and FIG. 1B is a fusion interface between an outer shell and an inner shell of the two-layer preform according to the manufacturing method of the present invention. It is an expanded sectional view of A part showing the state of.

FIG. 2A is an explanatory view showing a state where a load is applied to the mouth and neck of a bottle formed by biaxial stretching blow molding from a conventional two-layer preform, and FIG. It is an expanded sectional view of B part which shows the state of the interface peeling of the fusion | melting interface of the outer shell and the inner shell which occurred.

[Explanation of symbols]

 10 Double-layer preform 11 Gate 12 Fusion interface 20 Bottle 21 Mouth and neck 22 Shoulder 23 Interfacial peeling 100 Outer shell 200 Inner shell P load

Continued on the front page F term (reference) 4F201 AA24 AD05 AD18 AD24 AD27 AG03 AG07 AH55 AJ08 BA03 BC01 BC12 BC21 BD06 BM05 BM09 BM13 4F202 AA24 AD05 AD08 AD18 AD24 AD27 AG03 AG07 AH55 AJ08 CA11 CB01 CB12 CD23 AD24 AD18 AD08 AD05 AD24 AD08 AD05 AD206 AD27 AG03 AG07 AH55 AJ08 JA06 JB12 JF05 JQ81

Claims (5)

[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 producing a two-layer preform, wherein an inner shell is integrally formed by injection molding the inner shell inside the outer shell, the outer shell is molded by an injection molding die for an outer shell having a roughened cavity surface of a male mold, Is a rough surface, the method for producing a two-layer preform. 2. The method for producing a two-layer preform according to claim 1, wherein the cavity surface of the male mold of the injection mold for the outer layer shell is roughened by shot peening. 3. The method for producing a two-layer preform according to claim 1, wherein the cavity surface of the male mold of the injection mold for the outer layer shell is roughened by sandblasting. 4. The method for producing a two-layer preform according to claim 1, wherein the cavity surface of the male mold of the injection mold for the outer layer shell is roughened by etching. 5. The method for manufacturing a two-layer preform according to claim 1, wherein the cavity surface of the male mold of the injection mold for the outer layer shell is roughened by electric discharge machining.