JPS5845030A - Manufacture of biaxially oriented blow molded container and stretching rod device - Google Patents

Abstract

PURPOSE:To mold readily a container with an elongated neck section, by stretching a preform, which will be molded into a hollow container, at a section thereof which will constitute the neck section of the hollow container by a stretching rod, and blow molding it while stretching a section where the barrel section will be formed. CONSTITUTION:First an outer stretching rod 2 is projected down to stretch the section of a preform 1 by a predetermined ratio where the neck section of a hollow container will be formed. When the stretching of the neck section of the hollow container is completed, an inner stretching rod 3 is extended to form the barrel section of the hollow container while a pressurized gas is introduced, so that the aimed hollow container 5 is finally molded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a biaxially stretched blow container and a stretch rond apparatus.

In recent years, biaxially stretched blow containers made of polyethylene terephthalate have become commonly used as containers for soybean oil, edible oil, cosmetics, etc. due to their safety to the human body, shelf life of contents, and transparency. Became.

All of these containers have a body that spreads out laterally from just below the spout, and there are no containers that have an elongated neck like that seen in conventional glass bottles.

This is because it is difficult to produce a hollow container with an elongated neck using the biaxial stretch blow molding method.

That is, in the biaxial stretch blow molding method, a preformed body that has been prepared in advance is usually heated to a molding temperature, placed in a mold, and one end of which is clamped, and a rod called a stretch rod is used to stretch the bottom of the preformed body. Molding is carried out by blowing while ejecting and longitudinally stretching.

However, the heated preform, which can be molded, stops expanding when it comes into contact with the stretching rod, so generally, the preform is blown out little by little so that it does not come into contact with the stretching rod. Molding is performed by stretching and then final blowing to bring the molded article into close contact with a mold.

When manufacturing a conventional container with a shape that spreads laterally from just below the spout, there is no particular problem with this method because the preform comes into contact with the mold after being sufficiently stretched. .

However, when producing a hollow container with an elongated neck as targeted by the method of the present invention.

The mold corresponding to the neck of the preform and the final molded product, and the part of the preform corresponding to the neck of the hollow container expands with pressurized gas and contacts the mold before being sufficiently stretched. Put it away. Therefore, with the conventional method, it has been difficult to manufacture a hollow container having an elongated neck in which the neck is also uniformly stretched.

In view of these circumstances, the inventors of the present invention have conducted extensive studies in order to provide a method for producing a hollow container having a sufficiently stretched elongated neck by biaxial stretch blow molding, and a stretching rod device suitable for the method. As a result, when performing biaxial stretch blow molding, by performing a special stretching operation and using a special stretching rod device, it is possible to achieve sufficient stretching, which was extremely difficult with conventional biaxial stretch blow molding. It has been discovered that a hollow container with an elongated neck can be manufactured, and the present invention has been arrived at.

That is, the gist of the present invention is to biaxially stretch blow mold a preform to produce a hollow container having an elongated neck.
A method for producing a biaxially stretched blown container, which comprises first stretching a neck-corresponding part of a preformed body with a stretching rod, and then blowing the body-corresponding part while stretching it with a stretching rod.

The present invention also provides an outer stretching rod having an annular engagement part with the inner surface of the preform at its lower end, and an inner stretching rod that is located inside the outer stretching rod and can be operated separately from the outer stretching rod. The gist of this invention is also a stretching rod device for biaxial stretching blowing having rods and a mechanism for operating these stretching rods.

The present invention will be explained in more detail below.

In the present invention, a hollow container is manufactured by biaxial stretch blow molding, and a preform is first manufactured as a preliminary step.

Here, the material of the preform is not particularly limited as long as it is a synthetic resin applicable to biaxial stretch blow molding, such as polyethylene terephthalate resin, acrylonitrile resin, polypropylene resin, vinyl chloride resin, etc. Polyethylene terephthalate resin is preferably used in terms of safety, storage stability, and transparency of the contents.

The polyethylene terephthalate referred to in the present invention means a polyester having ethylene terephthalate as the main repeating position, and within the scope of the present invention, phthalic acid, isophthalic acid, hexahydrophthalic acid, hexahydrophthalic acid, Dicarboxylic acids such as naphthalene dicarboxylic acid, adipic acid, and sepacic acid, polycarboxylic acids such as trimellitic acid and pyromellitic acid, and oxybenzoic acids such as p-oxybenzoic acid can be used as the acid component. There is also an alcohol component, /, 2prono(undiol, '+ 3) * Handiol, /,
Dialcohols such as Hirobutanediol, A hexanediol, neopentyl glycol, diethyl glycol, triethylene glyconyl, cyclohexane dimetatool, polyhydric alcohols such as trimethylolpropane, trimethylolpropane, and pentaerythritol. It is also possible to use it.

The above-mentioned polyethylene terephthalate may be produced by a two-step method in which a transesterification reaction is performed to obtain a polyester oligomer, followed by a polycondensation reaction, or by a direct esterification reaction, using a conventional known method.
Known catalyst systems can be used. Additionally, additives such as stabilizers, color tone improvers, and colorants that are commonly used in the production thereof may also be included as necessary.

The polymerization degree of polyethylene terephthalate is phenol and
/, /, 2.2 It is desirable that the intrinsic viscosity is 005 or more when measured at 30° C. with a mixed solvent of tetrachloroethane in a weight ratio of 1:1.

The preform used in the method of the present invention may be one manufactured by injection molding, for example, or a pipe-shaped intermediate material obtained by extrusion molding, the tip of which is welded to form the bottom, and the rear end is transformed into the desired shape Any type of material such as a mouth part may be used.

The preform is conventionally heated to a moldable temperature and then inserted into a mold and clamped. The preform is then formed into a hollow container of a predetermined shape by stretching in the longitudinal direction using a stretch rond and stretching in the lateral direction using pressurized gas. Of these, the portion corresponding to the elongated neck of the product is first subjected to the process, followed by the portion corresponding to the body of the product. That is, the stretching by the stretching rod is carried out in two stages, and in the first stage, a portion of the preform corresponding to the elongated neck of the hollow container that is the product is stretched to a predetermined magnification.

During this time, the lower part of the product corresponding to the neck, that is, the part corresponding to the trunk of the product, is not stretched in principle, but if desired, it may be stretched at a smaller magnification than the part corresponding to the neck. After the first stage of stretching is completed, a second stage of stretching is subsequently performed. In the second stage of stretching, a portion corresponding to the body of the product is stretched to a predetermined magnification. The introduction of pressurized gas into the preform does not take place in principle during the first stage, but takes place in the usual way during the λ-th stage.

The present invention will be explained in more detail based on the accompanying drawings.
FIG. 1 is a schematic vertical cross-sectional view schematically showing the relationship between the stretching iron, the preform, and the obtained hollow container in the method of the present invention, and FIG. 2 shows the state after the seventh stage of stretching in the method of the present invention has been completed. FIG. 3 is a schematic vertical cross-sectional view showing a state where the λ-th stage of stretching has been completed.

In these figures, the stretch rond is the outer stretch rond (2
) and an inner stretching rond (3), both of which are capable of operating independently. The outer stretching rod (2) has a cylindrical shape, and its lower end forms an engaging portion (4) that engages with the inner surface of the preform (1). Note that the outer extending rond does not necessarily have to be cylindrical, and may be composed of several rods arranged in an annular shape, for example, but it is preferable that the engaging portion (4) is annular as shown in the figure. By doing this, when the outer stretching rod (2)' is actuated while being engaged with the inner surface of the preform (1), the preform (1) is uniformly spread out without creating any unevenness on the inner wall surface. Stretched.

The inner stretching rod (3) is inside the outer stretching rod (2) and has a similar shape to a normal stretching rod. The inner stretching rond (3) and the outer stretching rond (2) are usually
The preform (1) is arranged concentrically and its moving direction is
Align the axis direction of the

To explain the stretching operation in the method of the present invention in more detail with reference to FIGS. 1 to 3, a preform (1) is heated to the full molding temperature, inserted into a mold, and held at one end. The outer stretch rond (2) is brought into engagement with the inner surface of the entire preform (1) (FIG. 7). The position at which the outer stretched rond (2) and the preform (1) are engaged depends on the shape of the hollow container to be obtained, but generally corresponds to the lower end of the elongated neck. Next, when the outer stretching rod (2) is fully projected downward, the portion of the preform (1) corresponding to the neck is stretched to a predetermined magnification (FIG. 2). During this period, the preform (1) is not expanded by introducing pressurized gas in principle. This is because if stretching is performed while introducing pressurized gas as usual, the gap between the neck of the molding die and the preform (1) is narrow, so the neck corresponding part of the preform (1) is insufficient. This is because the film contacts the mold before it is fully stretched, resulting in poor stretching. Therefore, there is no problem in introducing pressurized gas to such an extent that the preform (1) does not come into contact with the mold.

During the stretching by the outer stretching rod (2), the inner stretching rod (3) does not, in principle, stretch the preform, but if desired, it can stretch the preform at a lower magnification than by the outer stretching rod (2). You may do so.

Note that the stretched neck corresponding part is cold outside the stretching rod (
It is preferable to heat the outer stretching rod (2) because if it is cooled by contact with the outer stretching rod (2), the expansion by the pressurized gas will not be performed well.

Once the neck-corresponding part of the hollow container has been stretched, pressurized gas is introduced using the inner stretching rod (3) in a conventional manner, while the body-corresponding part is stretched, and finally the preform is formed. (1
) is formed into the shape of a hollow container (5) (Fig. 3).

According to the present invention, it is possible to easily manufacture a hollow container having an elongated neck, which has been difficult to produce using the conventional biaxial stretch blow molding method.

[Brief explanation of drawings]

Fig. 1 is a schematic vertical cross-sectional view showing the relationship between the drawn rod, the preform, and the resulting hollow container in the method of the present invention; Fig. 2 is a schematic longitudinal cross-sectional view showing the first step of the method of the present invention;
The figure is also a schematic vertical cross-sectional view showing the final stage. l...Preformed body 2...Outer stretching rod 3...Inner stretching rod ≠...
・Engaging part j...Hollow container Applicant Mitsubishi Chemical Industries, Ltd.

Claims (4)

[Claims] (1) When manufacturing a hollow container having an elongated neck by biaxial stretch blow molding of a preform, the part of the preform corresponding to the neck of the hollow container is first stretched using a stretching iron, and then the part corresponding to the body is stretched. 1. A method for producing a biaxially stretched blow container, which comprises blowing while stretching the portion using a stretching rod. (2) The manufacturing method according to claim 1, characterized in that the portion of the preformed body corresponding to the neck of the hollow container is stretched, and at the same time, the portion corresponding to the body is stretched at a smaller magnification than the portion corresponding to the neck. (3) The manufacturing method according to claim 1 or 2, wherein the seven-sided molded body is made of polyethylene terephthalate. (4) an outer stretching rond having an annular engagement portion with the inner surface of the preform at its lower end; and an inner stretching rond located inside the outer stretching rod and capable of operating separately from the outer stretching rod; A stretching rond device for biaxial stretching blowing having a mechanism for operating these stretching rods.