JPS5833430A - Metal mold for blow molding - Google Patents

Abstract

PURPOSE:To provide the title metal mold capable of rapidly cooling a cavity metal mold and preventing prolongation of a molding cycle consisting of the cavity metal mold having a heating element and a rear metal mold having a cooling element closely contacted with the metal mold during mold clamping. CONSTITUTION:A cavity metal mold 1 having a heating element provided to the part or the entire part thereof and a rear metal mold 2 having a cooling element between metal mold attaching plates 3 are provided are connected by a guide rod 30 so as to be closely contacted during mold clamping and parted during mold opening and a stopper 31 is fixed to the top surface thereof and a spring 33 is arranged around the guide rod 30. In this structure, the cavity surface of the metal mold is heated by passing a heating oil through a heat pipe 20 through the heating oil passage 11 of said metal mold during mold opening and the metal mold 2 is cooled during mold clamping as well as the cavity surface is rapidly cooled by passing a cooling oil through a heat pipe 20 from a cooling oil passage 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blow molding mold suitable for reflecting the gloss and fine patterns of a cavity surface on the surface of a molded product in blow molding of a crystalline thermoplastic resin.

Blow molded products are molded using thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, and polycarbonate, and are used in many fields such as detergent bottles, makeup skins, milk containers, and kerosene cans. Among these, polyethylene has excellent moldability and impact resistance, and is in the greatest demand. However, the surface of polyethylene blow-molded products usually exhibits a faded surface lacking luster, making them unsuitable for applications requiring a high gloss and splendid appearance.

This phenomenon is also seen in polypropylene No. C, although there are some differences, and it cannot be compared to non-quality thermoplastic resins such as polyvinyl chloride, and polyethylene/polypropylene is a crystalline thermoplastic resin. This has been considered a major problem due to this.

The present invention was arrived at as a result of various studies regarding such phenomena and their solutions. A blow molding mold characterized in that it comprises a rear mold having a mosquito system.

The present invention will be explained below using the drawings.

1 and 2 are perspective views respectively showing the mold closing state and the mold opening state of the present invention. Reference numeral 1 represents a capitivity mold in which halinon injected with compressed air swells and comes into close contact with the capitivity mold L and the rear pot. As shown in the cross-sectional view of FIG. 3, a guide rod 30 connects both molds so that the mold 2 can be brought into close contact with each other during mold clamping and separated during mold opening, and a stopper 31 is fixed to the top surface of the mold with a screw, and a guide rod A spring 33 is arranged around 30.

The reason why crystalline thermoplastic resins such as polyethylene cannot reflect minute patterns such as mirror surfaces or embossments on the cavity surface on the surface of the blow molded product is because in conventional blow molding, the cavity mold is set at a low temperature and the molten state is This is thought to be because when the parison touches the cavity surface, it is rapidly cooled and the solidification rate is extremely high due to its crystallinity. This can be solved by raising the mold temperature and making the cavity surface hot near the melting point, but in conventional blow molding molds, the cavity mold is directly fixed to the mold mounting plate, and the cavity mold cannot be elevated. It is difficult to rapidly cool the mold, and the molding cycle becomes extremely long, resulting in high costs.

In the present invention, a rear mold ψ having a cooling element is provided between the cavity mold 1 and the mold number plate 3 to prevent the temperature rise of the cavity mold 1 during mold opening before sandwiching Balinon. The two molds are separated to prevent this from happening, and during mold clamping which requires cooling, both molds come into close contact and the cavity mold 1 is cooled by the cooling action based on the cooling water flow path 13 of the rear mold 2. Ru. The cavity mold has a cooling element. Furthermore, it is preferable for the cavity mold to have a cooling element in addition to the heating element, since the cooling time can be shortened.

FIG. 4 is a perspective view of the cavity mold 1, FIG. 5 is a sectional view taken along the line V-V in FIG. 4, and FIG. 6 is a sectional view taken along the line V--VR in FIG. There is. 11 is a heating oil flow path, 12 is a cooling oil flow path, and 20 is a heat pipe whose upper and lower ends protrude into both flow paths. Thus, when heated oil is passed through the heated oil flow path 11 during mold opening, the temperature of the cavity surface is raised due to the good heat conduction of the heat pipe, and during mold clamping, the temperature of the cavity surface is increased through the cooling oil flow path 12.
The cavity surface is cooled by passing cooling oil through it. In order to shorten the heating and cooling time, it is preferable that the heat capacity of the cavity mold 1 is small, and the cavity mold 1 is preferably made thin along the cavity surface.

The above description is an example of the present invention, and the present invention is not limited thereto. For example, the contact surface between the cavity mold and the rear mold may be not only a flat surface but also a curved surface, and the connecting guide rod may be fixed to the cavity side and slide within the rear mold. Furthermore, not all of the plurality of cavity molds have heating elements, and some parts may have heating elements depending on the purpose, and the same can be said of a single cavity mold, but such heating elements may not be included. A mold having a cavity or a rear mold having a cooling element for cooling that area is required. On the other hand, there is also a mode in which the mold mounting plate has a cooling element and is used as a rear mold.

As described above, the blow molding mold of the present invention can give gloss to a blow molded product made of crystalline thermoplastic resin, and also prevents the molding cycle from becoming longer.

The present invention will be described in more detail with reference to Examples and Comparative Examples. In addition, the surface roughness in each example is Toyo Seiki ■NT a
Measured by b' e r, gloss is JIS Z874
Measured based on 1.

Example 1 The blow molding molds shown in FIGS. 1 to 6 were installed in a blow molding machine with a screw diameter of 90 mm, and the fabric go, q49t/CC, and melt index 0.3? Using 710min high density polyethylene, internal volume 200CG, average wall thickness 2m
A bottle of m was molded.

Both the cavity mold and the rear mold were made of iron, and the cavity surface was chrome plated to have a mirror finish with a surface roughness of 005/I. 250℃ heated oil and 10℃ cooling oil are alternately poured into the cavity mold, 5℃ cooling water is poured into the rear mold, and the waiting time during mold opening, that is, the heating time of the cavity mold, is set to 1 min. , mold clamping time, that is, cooling time, is 1.5
It was set to min. The cavity surface temperature at the mold clamping size ^1j was 120°C, and the bottle surface temperature at the time of removal was 50°C.

The surface roughness of the flat part of the obtained bottle was 0.15μ, and the gloss was 9.
It was 0chi.

Comparative Example 1 The same procedure as in Example 1 was carried out except that only cooling water at 20° C. was constantly flowed into the cavity mold. The surface temperature of the cavity just before the mold was closed was 20°C, and the surface temperature of the bottle at the time of removal was 21°C.

The surface roughness of the flat part of the obtained bottle was 1.9μ, and the gloss was 30
%Met.

Comparative Example 2 Imitating a conventional mold, removing the spring around the guide rod of Example 1 and keeping the cavity mold and rear mold in close contact with each other at all times, and heating the cavity mold at 250°C without cooling the rear mold. 5 ml of heating oil was poured into the mold, and when the cavity surface reached 121° C., the mold was clamped, and 8 ml of cooling oil at 10° C. was poured into the mold. The surface temperature of the bottle at the time of removal was 60°C.

The surface roughness of the flat part of the obtained bottle was 02μ, and the gloss was 80%.
Met.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the blow molding mold of the present invention in a closed state, Fig. 2 is a perspective view showing the same mold in an open state, and Fig. 3 is a connection between the cavity mold and the rear mold of the same mold. Cross-sectional view showing the state 1 Figure 4 is a perspective view of the cavity mold of the same mold, Figure 5 is Figure 4
FIG. 6 is a cross-sectional view taken along vr-vr of FIG. 1... Cavity mold 2... Rear mold 3... Mold mounting plate 11... Heating oil flow path 12... Cooling oil flow path 13... Cooling water flow path 20... Heat pipe 30... Guide rod 31... ... Stopper 32 ... Screw 33 ... Hane Patent Applicant Showa Poe Co., Ltd. Agent Patent Attorney Kozue Kikuchi - Figure 5 Rod Figure 6

Claims (1)

[Claims] A blow molding mold comprising a cavity mold having a heating element in part or all of the mold, and a rear mold which can be brought into close contact with the cavity mold during mold clamping and has a cooling element.