JPH0485007A - Mold core for high temperature releasing of preform - Google Patents

Abstract

PURPOSE:To prevent a perform from deforming when a mold core is released from the preform by forming a number of fine recesses into which flowing of molten resin is difficult to be done and which allow the air to remain at the time of forming the preform on a surface layer on the side lower than a mouth section of the mold core. CONSTITUTION:A number of fine recesses 14 of 0.03mm or smaller into which the flowing of molten resin is difficult to be done and allow the air to remain at the time of forming a preform are formed all over a surface layer on the side lower than a mouth section forming section 11a of mold core 11. Such a mold core 11 runs through a lip mold 13 form above and is inserted into a cavity mold 10, and when molten resin is injection filled from a gate of a cavity mold bottom section into the cavity after mold clamping to form a preform 12, the air remains intermittently in the surface layer by means of respective recesses 14. Releasing is carried out while said preform is of high temperature and in the softened state. First the mold core 11 is moved upward together with the lip mold 13, and the preform 12 is released from the cavity mold 10, and further the mold core 11 is moved upward to release the preform 12 retained by the lip mold 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a method of releasing a preform while it is in a softened state at a high temperature.

[Prior Art] As one of injection stretch blow molding methods, there is a method in which an injection molded preform is immediately stretch blow molded. Since this method omits the temperature control that was performed before stretch blow molding, the preform is released from the mold while it is still in a softened state at a high temperature.

[Problems to be Solved by the Invention] In normal injection molding, a molded product solidified by cooling is released from a mold. In addition, due to shrinkage due to assimilation, the inner surface of the molded product clings to the core mold and is difficult to remove, so the surface of the core mold is given a mirror finish or hard chrome plating to minimize frictional resistance and facilitate removal. That's what I do.

Even in conventional high-temperature mold release of preforms, the surface of the core mold has been treated to have low frictional resistance, as in the case of normal injection molding. The problem here is that the area around the bottom of the preform deforms when the core mold is removed.

This deformation is rare in preforms for wide-mouthed containers, where the core mold can have a large drawing taper, but it is more likely to occur in preforms for bottle-shaped containers, which are limited by the drawing taper due to their small diameter and are long, and are used there. This is even more noticeable when the resin used is polypropylene.

The cause of this deformation is that because the preform is flexible, it is difficult to cut the edges between the two due to relative movement, and as shown in Figure 4, the edges of the core mold 1 and the inner surface of the preform 2 are cut. However, since the surface of the core mold 1 is smooth and the inner surface of the preform 2 is soft, they immediately adhere to each other. The inside of the bottom of the preform 2 that is about to come off from the tip becomes negative pressure and is crushed. Therefore, if the phenomenon of negative pressure is prevented by some means, the phenomenon of deformation of the preform can be solved.

An object of the present invention is to provide a new core mold for high-temperature mold release that can prevent deformation of the preform by extremely simple means.

[Means for Solving the Problems] The feature of the present invention according to the above-mentioned object is that, while the injection-molded preform is in a softened state at a high temperature, the portion below the mouth molding part of the core mold is removed from the injection-molded preform while the preform is in a softened state at a high temperature. The surface layer is formed with a large number of fine depressions that make it difficult for molten resin to flow in and allow air to remain during preform molding.

[Function] In the core mold described above, when a preform is formed by injecting and filling the cavity with molten resin, air intermittently stays in the surface layer due to the depressions. Also, the contact between the soft inner surface of the preform and the surface of the core mold becomes partial due to the dent.
The adhesion force is smaller than when there is full contact.

When the relative movement between the core mold and the preform causes a misalignment and the edges of the two are cut, the surface layer of air is interposed between the two, allowing air to circulate and creating a negative pressure inside the preform. prevent it from becoming

[Examples] The present invention will be described in more detail below with reference to Examples shown in FIGS. 1 to 3.

10 is a cavity type, 11 is a core type, 12 is a preform, and 13 is a lip type that also serves as a holding member for the preform 12.

As shown in FIG. 2, the surface layer below the mouth molding part 11a of the core mold 11 has a large number of 0.0.
Fine depressions 14 of mm or less are formed over the entire surface.

The recesses 14 may be in the form of long grooves, connected to each other, or independent, and their formation state is selected depending on the design of the preform 12 and the resin.

Such a core mold 11 is inserted into the cavity mold 10 through the lip mold 13 from above, and after mold clamping, molten resin is injected and filled into the cavity from the gate at the bottom of the cavity mold to form the preform 12. Each dent 14...
Air stays in the surface layer intermittently due to...

In addition, the preform 12 immediately after injection is at an extremely high temperature, and the internal resin has fluidity, but the inside and outside ([1
The shape is maintained by the skin layer 15 of 11,
The softer skin layer 15 comes into close contact with the surface of the core mold 11 by shrinking as it cools.

The mold release is performed while the preform 12 is in a softened state at a high temperature. First, the lip mold 13 and the core mold 11
is moved upward to extract the preform 12 from the cavity mold 10, and further the core mold 11 is moved upward and extracted from the preform 12 held by the lip mold 13.

The adhesion of the preform 12 during this high-temperature release is due to the small contact area with the core mold surface due to the large number of depressions 14, and the fact that air remains in the surface layer. Therefore, it is weaker than when the entire surface is in close contact,
The solidified mouth portion 12a of the preform 12 is molded into a lip mold 13.
The frictional resistance when the core mold 11 is pulled out is extremely small.

For this reason, even if the preform 12 is in a soft state, the edges of the core mold 11 and the preform 12 can be easily cut by relative movement of the core mold 11 and the preform 12 without damaging the shape of the preform 12.

Furthermore, when the edges of the two are cut and a shift occurs there, air in the surface layer becomes interposed between the two. Then, a gap 16 is formed between the two, although the air is small, so that the air can circulate. Therefore, there is no negative pressure inside the preform, and there is no deformation due to the negative pressure at the bottom of the preform, which is separated from the tip of the core mold and is no longer supported.

[Effects of the Invention] As described above, this invention has a number of minute dents in the surface layer below the mouth molding part of the core mold that make it difficult for molten resin to flow in and allow air to stay during preform molding. form,
This prevents deformation of the preform when the core mold is removed from the softened preform, thereby reducing preform loss due to deformation. In addition, preforms made of resin such as polypropylene can be released from the mold earlier than before, and the molding cycle is correspondingly faster. Furthermore, stretch molding of bottle-shaped containers, which are limited by the drawing taper, becomes easier, and the core mold itself requires only surface treatment, so there is no need for high costs.

[Brief explanation of drawings]

1 to 3 show one embodiment of a core mold for high-temperature release of preforms according to the present invention, and FIG. 1 is a vertical cross-sectional view of the injection mold, and FIG. FIG. 3 is a partial cross-sectional view of the reform, FIG. 3 is an explanatory view of the edge cutting state, and FIG. 4 is a vertical cross-sectional view showing deformation of the preform using a conventional core mold. 10... Capitey type 11...
... Core mold 12 ... Preform 13 ... Lip mold 14 ...
...Concave patent applicant Aoki Hard Research Institute 1a

Claims (1)

[Claims] A core mold that is extracted from an injection-molded preform while the preform is in a softened state at a high temperature,
A preform characterized in that a surface layer below the mouth molding part of the core mold is formed with a large number of fine depressions that make it difficult for molten resin to flow in and allow air to stay during preform molding. Core mold for high temperature mold release.