JP3061241B2 - Mold for blow molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for blow molding, and more particularly to a mold for improving the surface properties of a molded product.

[0002]

2. Description of the Related Art In a conventional blow molding method, a parison is extruded from a die, a parison formed into a bag by a parison pinch is pre-blown, slightly inflated, and the left and right dies are closed by a mold clamping device. ing. Simultaneously with or immediately before the mold is closed, the gas in the cavity is evacuated, and a high pressure is blown into the parison so that the parison is brought into close contact with the cavity, and the mold is cooled and molded. After molding, open the mold, take out the product, and mold 1
The cycle is completed.

[0003] The parison has a predetermined shape in close contact with the mold cavity.
During the cycle, the mold is set at a sufficiently low temperature that the parison is sufficiently cooled and can be removed as a molded article, usually keeping this temperature constant.

[0004]

However, blow molded articles have the disadvantage that the surface properties of the molded articles are poor because molding is not performed by applying high pressure as in injection molding. In order to improve the surface properties, the mold surface temperature may be heated to above the softening point (glass transition point or crystallization temperature) of the resin, but as a result, there is a contradictory problem that the molding cycle becomes longer. Would.

An object of the present invention is to provide a blow molding die capable of efficiently producing a blow molded product having good surface properties in a short cycle by focusing on the above-mentioned conventional problems.

[0006]

In order to achieve the above object, a blow molding die according to the present invention is a blow molding die made of thermoplastic resin, wherein a base material of the die is made of a material having a low heat capacity. And forming a temperature control medium passage inside the mold base material, and vertically and horizontally on the cavity surface of the mold.
A continuous girder-shaped groove was provided, and a heat-resistant resin film having pores with an open pore diameter of 1 mm or less and an open pore density of 1 / cm ² or more was attached to the cavity surface.

[0007]

In a normal standby state of the mold, a medium for temperature control is circulated to raise the temperature to a desired temperature, and then a parison is extruded from a die, clamped between the molds, and clamped. After that, it moves to high-pressure blowing, but by pressing the parison against the heat-insulating resin film with high heat insulation while forcibly discharging residual air between the parison and the heat-resistant resin film attached to the cavity surface. Obtain molded products with high surface properties.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the blow molding die according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a configuration diagram of a blow molding die 10 according to an embodiment. The mold 10 includes a pair of left and right molds 10.
R, 10L, and a cavity 12 (12R, 12L) is formed on the mold-matching surface, a parison ejected from a die (not shown) is sandwiched, and air is blown into the parison to form the mold. A hollow container corresponding to the closed cavity is formed.

The mold body 14 in such a mold 10
(14R, 14L) are formed as castings of aluminum material, but in this embodiment, each mold body 14R,
On the surfaces of the cavities 12R and 12L of the 14L, the girder-shaped grooves 16 (16R and 16L) are provided as shown in FIGS.

The depth and width of the girder-shaped groove 16 are about 1
For example, the distance between the grooves 16 is about 50 mm, and the grooves 16 communicate vertically and horizontally.

In this embodiment, as shown in FIG. 2, a heat-resistant resin film 18 (18
R, 18L). As the heat-resistant resin film 18, for example, a polyimide resin, a polyetherimide resin, a polyamideimide resin, a polysulfone resin, a fluororesin, or the like is preferable, and the parison is sandwiched between the mold bodies 14R and 14L. When the heat-resistant resin film 18 is in close contact with the mold cavity 12, the heat of the parison is hardly transferred to the mold bodies 14R and 14L due to the low thermal conductivity, so that the parison serves as a heat insulating material that does not easily lower the temperature of the parison. To have.

The heat-resistant resin film 18 has a thickness of 10 μm or less.
A thickness in the range of 500 μm is a rough guide. The heat-resistant resin film 18 has, for example, an open hole diameter of 1 mm or less,
Preferably, the opening is formed such that the open hole diameter of about 0.05 to 0.3 mm has an open hole density of 1 / cm ² or more.

The open holes 15 of the heat-resistant resin film 18 can be punched, punched, or opened with a YAG laser, an excimer laser, or the like. The heat-resistant resin film 18 may be attached to the mold body 14 by an appropriate method such as attachment by a baking method or an adhesive.

In the vicinity of the cavity 12 in the mold body 14, a temperature control medium passage 19 formed by drilling a plurality of drilled holes or casting a copper pipe along the surface of the cavity 12 is provided. . The temperature control medium passage 19 is supplied with a temperature control medium such as oil, water, and steam from a supply source.

The temperature control medium passage 19 is provided in the cavity 12.
The mold body 14 is heated by introducing the temperature control medium from one end thereof, discharging the temperature control medium from the other end side, and supplying the temperature control medium.

As shown in FIG. 1, the temperature control medium passage 19
Each mold body 14R, 1
A temperature control medium supply port 20 and a temperature control medium discharge port 22 are formed in the 4L bottom plate section and the top plate section, and a pipe 26 is connected to a medium temperature control apparatus 30 installed outside the mold body 14. I have.

The blow molding operation using the blow mold thus constructed is performed as follows.

The temperature of the mold body 14 is set at a sufficiently low temperature at which a molded product can be removed and at a sufficiently high temperature range at which surface properties can be obtained (for example, 85 to 14 depending on the type of resin).
(5 ° C.), and the parison is extruded from a die (not shown) to perform pre-pinch, pre-blow, and mold clamping.

The parison is pressed against the heat-resistant resin film 18 adhered to the surface of the cavity 12 by high-pressure blowing following mold clamping. At this time, as shown in FIG. The residual air remaining in the mold 16 is sucked and discharged by a vacuum pump (not shown), or the parison presses the heat-resistant resin film 18 to form the residual air between the parison and the mold as shown in FIG. The air is released to the atmosphere from the end of the groove 16 which is opened in all directions through the space 16.

[0021]

When the parison is sandwiched between the two mold bodies 14R and 14L and the parison is pressed against the surface of the cavity 12 by high-pressure blowing, the heat held by the parison is transferred to the two mold bodies 14; Since the heat-resistant resin film 18 having a low thermal conductivity is adhered to the surface of the cavity 12, heat transfer from the parison to the mold body 14 can be delayed.

In the meantime, the parison and the heat-resistant resin film 1
The residual air between 8 is opened from the opening hole 15 → the groove 16 to the mold body 1
4 of the vacuum pump to external pressing the parison can be sucked and discharged in a (shown teeth) or the like on the heat-resistant resin film 18,
Close contact ensures high surface transferability. Since the mold body 14 is cooled below the softening point of the resin, the mold body 14
The parison sandwiched between R and 14L solidifies, and the molded product can be taken out of the mold without deformation.

Table 1 shows the results of a comparative experiment conducted between the blow molding die body 14 of this embodiment and a conventional aluminum blow molding die.

[0025]

[Table 1]

As shown in Table 1, in the present embodiment, the temperature of the mold body 14 is lower than that of the conventional mold by attaching the heat-resistant resin film 18 having a low thermal conductivity to the surface of the mold body 14. Therefore, the molding cycle can be shortened. Further, since the residual air between the parison and the heat-resistant resin film 18 can be forcibly discharged, a high surface transfer property having a glossiness of 90 or more can be obtained.

[0027]

From what has been above description, according to the present invention as is apparent, in the hollow mold of the thermoplastic resin, the base material of the die is formed of a material of a low heat capacity, the interior of the mold base material In addition to forming a temperature control medium passage in the cavity, a girder-shaped groove communicating vertically and horizontally is provided on the cavity surface of the mold, and the cavity surface has a pore diameter of 1 mm or less and a pore density of 1 hole / cm ² or more. By attaching a heat-resistant resin film with holes, the parison surface is kept at a temperature above which it does not solidify until the air between the parison and the mold is removed from the pores. Is obtained.

In addition, since the heat diffusion of the parison into the mold can be delayed by the heat-resistant resin film, the mold temperature can be kept at a temperature sufficient to solidify the resin, and the molding cycle can be shortened. Thus, a molded product without deformation can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a blow molding die according to an embodiment.

FIG. 2 is an enlarged cross-sectional view of a main part of the mold.

FIG. 3 is a perspective view of a mold showing a groove on a cavity surface of the mold according to the embodiment of the present invention.

FIG. 4 is a perspective view of a mold showing another embodiment of the present invention, showing a groove on the surface of a cavity.

[Explanation of symbols]

 Reference Signs List 10 (10R, 10L) Mold 12 (12R, 12L) Cavity 14 (14R, 14L) Mold body 15 Open hole 16 (16R, 16L) Groove 18 (18R, 18L) Heat-resistant resin film 19 Temperature control medium passage Reference Signs List 20 Temperature control medium supply port 22 Temperature control medium discharge port 26 Piping 30 Medium temperature control device

Claims (1)

(57) [Claims] 1. A mold for hollow molding of a thermoplastic resin, wherein a base material of the mold is formed of a material having a low heat capacity, a medium control medium passage is formed inside the mold base material, and the mold is formed. A girder-shaped groove portion communicating vertically and horizontally was provided on the cavity surface of the mold, and a heat-resistant resin film having pore diameters of 1 mm or less and pore density of 1 hole / cm ² or more was attached to the cavity surface. A blow molding die, characterized in that: