JP3029831B1 - Mold - Google Patents

Abstract

An object of the present invention is to excel in heat dissipation, to rapidly cool and cure a resin in a cavity without arranging a refrigerant circulation pipe, and to excel in lightness compared to a conventional steel mold. In addition, the present invention provides a mold capable of shortening a mold manufacturing period and capable of molding a plastic molded product with higher dimensional accuracy than a conventional resin mold. SOLUTION: In a molding die 10 comprising a core die 21 having a molding die surface 22, 12 for a plastic molded product and a cavity die 11, at least a die surface portion of the surface of the graphite base material portions 23, 13. The surface resin layer 2
6, 16 were formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for plastic molded articles.

[0002]

2. Description of the Related Art In general, the manufacture of plastic molded products is as follows.
It is often performed by injection molding using a molding die or the like. The molding die includes a core die having a protruding die surface, and a cavity die having a depressed die surface, wherein a cavity is formed between the die surface of the core die and the die surface of the cavity die by closing the die. Used. The cavity of the molding die is filled with a high-temperature molten resin or a reaction resin raw material during the production of a plastic molded product, cooled and solidified in the mold to a predetermined temperature, and then the molding die is opened and a desired one is opened. The plastic molding is removed.

[0003] The core type is sometimes called a male type.
On the other hand, the cavity mold is sometimes called a female mold. When the core mold and the cavity mold are arranged to open and close in the up-down direction, one may be called an upper mold and the other may be called a lower mold. Also, when one of the core mold and the cavity mold is fixed and the other is moved to open and close,
One may be called a fixed type and the other may be called a movable type.

[0004]

However, the conventional molds for plastic molded articles, which are made of steel, are heavy and difficult to handle, and require a long period of time to manufacture the molds, which increases the cost. There is. In particular, a steel mold for a large plastic molded product weighs several tons and cannot be easily transported and installed.

[0005] In addition, although the resin mold has the advantages of being lighter in weight and having a shorter production time than the steel mold, the dimensional accuracy of the plastic molded product obtained from the steel mold is improved. Is inferior. Further, regardless of the mold made of steel or resin, the mold itself does not have sufficient heat radiation, and it takes a long time to cool and solidify the resin filled in the cavity. Therefore, in order to accelerate the cooling and solidification of the resin and shorten the molding time of the plastic molded product, it was necessary to forcibly cool the molding die. Therefore,
2. Description of the Related Art A refrigerant circulation pipe is buried in the vicinity of a mold surface of a molding die, and the refrigerant flows through the refrigerant circulation pipe. But,
There is a disadvantage that the work of burying the refrigerant circulation pipe in the mold is extra, and the production period of the molding die is prolonged.In addition, since the refrigerant circulation device must be provided at the installation location of the molding die,
There are also problems such as an increase in equipment costs and a tendency for refrigerant to leak.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and has excellent heat radiation properties, and can rapidly cool and cure the resin in the cavity without embedding a refrigerant circulation pipe. In addition, it provides a mold that is superior in lightness compared to conventional steel molds, can shorten the mold manufacturing period, and can mold plastic molded products with higher dimensional accuracy than conventional resin molds. is there.

[0007]

In order to achieve the above object, the present invention relates to a mold comprising a core mold and a cavity mold having a molding surface for a plastic molded product. Is formed by forming at least the mold surface portion of the surface of the graphite base material portion with a surface resin layer, and the resin material of the surface resin layer is a metal powder.
And an epoxy resin .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view schematically showing an entire molding die according to one embodiment of the present invention, and FIGS. 2 to 7 are schematic process diagrams in manufacturing the molding die of the present invention. The present invention is not limited to an injection mold, but is applied to a mold used for molding a plastic molded product into a mold surface shape, such as a foam mold and a blow mold. Is done.

A molding die 10 shown in FIG. 1 is for injection molding and comprises a cavity mold 11 and a core mold 21. A concave mold surface 12 for forming a product-shaped cavity 31 when the mold is closed and a convex mold surface. Is mounted on an injection molding apparatus (not shown) via mounting plates 41 and 42 provided on the opposite back side. The cavity mold 11 in this example is also called a fixed mold,
The sprue 32 is formed through the sprue 32 and the molten resin is supplied from the screw of the injection device through the sprue 32 to the cavity 3.
1. On the other hand, the core mold 21 of this example is also called a movable mold, and is slidable in the direction of the cavity mold 11 by a plunger of an injection molding apparatus.

The cavity mold 11 and the core mold 21
Is composed of base materials 13 and 23 and surface resin layers 16 and 26. The base materials 13 and 23 constitute the main body of the cavity mold 11 and the core mold 21 and impart required strength, rigidity, and the like to the mold 10. The base material parts 13, 23
Is made by processing a graphite block into a required shape. Graphite is also referred to as graphite and has excellent lightness and thermal conductivity. Therefore, the base material portion 13,
This mold 10 having graphite 23 is lighter in weight than the conventional mold made of steel, and is excellent in natural cooling property, so that the molten resin injected into the cavity 31 can be rapidly cooled and solidified. In addition, the refrigerant circulation pipe required in the conventional molding die can be omitted.
As the graphite constituting the base materials 13 and 23, a known material used for a forging die, a die casting die, an electrode material or the like can be used. As an example, graphite EX series (trade name: EX-5) of Ibiden Co., Ltd.
0, EX-70, etc.) and ED series (product name: ED-
2, ED-3, ED-4, etc.).

The surface resin layers 16 and 26 are formed on the base material 1.
The precision mold surfaces 12 and 22 are formed at least at the mold surface positions on the surfaces of the base materials 3 and 23 and the base material portions 13 and 2 are formed.
3 is provided at a required portion of the surface, and has an effect of protecting the base material portions 13 and 23 and the like. It is preferable that the surface resin layers 16 and 26 are directly cured on the surfaces of the base materials 13 and 23 because the bonding with the graphite base materials 13 and 23 is strong.

As the surface resin layers 16 and 26, a resin material for a resin mold in which a metal powder and an epoxy resin are mixed is used because of its excellent moldability and good thermal conductivity.
Can be In particular, a mixture of alumina or aluminum powder and an epoxy-based resin is preferable because of its excellent lightness. The content of the metal powder is appropriately determined according to the type of the metal powder, but is generally 65% by weight to 85% by weight. As such a resin material, a known resin material can be used. For example, a quinate CTR series manufactured by Zeon Rise Co., Ltd. as a mixture of alumina powder and epoxy resin, and a quinate MEZ series manufactured by ZEON RISE Co., Ltd. as a mixture of aluminum powder and epoxy resin ( For example, if the aluminum powder content is 7
5% by weight of Quinnate MEZ200), and other products such as Vistax NX-11 manufactured by Nippon Pernox Co., Ltd.
01 and the like. Further, the resin material may be mixed with a required amount of graphite powder, usually 3 to 7% by weight. Then, a better mold surface can be formed.

The surface resin layers 16 and 26 have an appropriate thickness depending on the shape of the mold surface, the size of the mold, and the like, but generally have a thickness of about 3 to 5 mm.
Further, the surface resin layers 16 and 26 are
May be provided so as to cover the entire surface, but in this example, the mold surface 1
2, 22 are provided except for the surface on the mounting side opposite to the side.

Next, an embodiment of manufacturing the molding die 10 will be briefly described with reference to FIGS. The manufacturing of the molding die 10 includes a model die processing step, a cavity die base material roughing step, a cavity die surface resin layer forming step, a model die surface shaving step, a core die surface resin layer forming step, and heating. It consists of a curing step and a finishing step.

In the processing step of the model die, as shown in FIG. 2, a model die 51 is formed from a graphite block 50 having required dimensions by precision processing using an NC machine tool or the like. This model mold 51 has a convex surface 52 obtained by inverting the mold surface 12 of the cavity mold 11,
It is formed larger than the base material portion 23 of the core mold 21 by the thickness of the surface resin layer 26 and the cavity 31.

In the rough machining step of the cavity-type base material portion, as shown in FIG.
The base material portion 13 of the cavity mold 11 is roughly processed by an NC machine tool or the like. The base material portion 13 is formed smaller than the final shape of the cavity mold 11 by the thickness of the surface resin layer 16, and a portion corresponding to the concave mold surface 12 is larger than the concave shape of the mold surface 12. It has a concave surface 14. Either the rough machining step of the cavity mold base material portion or the machining step of the model mold may be performed first or simultaneously.

Next, a cavity type surface resin layer forming step is performed. In this step, first, as shown in FIG. 4, the convex surface 52 of the model mold 51 is turned upward, and the periphery of the side surface of the model mold 51 is surrounded by a frame material 71 that is taller than the thickness of the model mold 51. After applying a release agent to the upper surface of the model die 51 surrounded by the material 71 and the inner surface of the frame material 71, a required amount of the resin material P is disposed on the upper surface of the model die 51. Then, the cavity-shaped base material portion 13 is replaced with the concave surface 14.
Is lowered from above the model die 51 so that the resin material P is pressed downward between the model die 51 and the base material portion 13 of the cavity die. At this time, the distance S1 between the side surface of the cavity mold base material portion 13 and the frame material 71 and the space S2 between the cavity mold base material portion 13 and the model mold 51 at the lowest time are determined by the thickness of the surface resin layer 16 of the cavity mold 13. Is equal to The resin material P is formed between the model mold 51 and the cavity base material 13 and between the cavity mold base material 13 and the frame material 71 by the press, and reacts by covering the surface of the cavity mold base material 13. The curing is started, and a cavity type semi-finished product 11A is formed integrally with the base material portion 13.
Reference numeral 16A denotes a resin layer in the middle of curing made of the resin material P.

As the resin material P, a metal powder, preferably an aluminum powder or a mixture of an alumina powder and an epoxy resin is used. Further, a graphite powder may be mixed with the resin material P in a required amount, usually 3 to 7% by weight. In this case, air bubbles that are easily entrained when the resin material P is injected are absorbed by the graphite, and fine voids can be hardly generated in the formed surface resin layer 16. The graphite powder is preferably passed through a 30-80 mesh sieve (filter). Also,
As the graphite powder, a powder in the above-described range except for lumps by sifting graphite powder or granules generated when grinding a graphite block in the rough machining process of the model mold processing step or the cavity mold base material portion is used. It is economical to use.

Next, a model type surface cutting step is performed.
In this step, the frame member 71 is removed, the model die 51 is taken out, and a required amount of the surface of the model die 51 is cut off as shown in FIG. The cut amount at this time is made equal to the thickness of the surface resin layer 26 of the core mold 21.

In the core mold surface resin layer forming step, as shown in FIG. 6, the cavity mold semi-finished product 11A is set so that the concave surface 14 side faces upward, and curing is performed on the surface of the cavity mold semi-finished product 11A. A spacer sheet 70 having a thickness equal to the thickness of the cavity 31 of the molding die 10 is laminated on the upper surface of the resin layer 16A of
A frame member 81 disposed around the side surface of 1A surrounds the upper part of the cavity-type semi-finished product 11A. The spacer sheet 70 is made of a material to which the resin material P does not adhere (for example, fluororesin).
Exposed resin layer 16 of cavity type semi-finished product 11A
A release agent is applied to the surface A, the inner surface of the frame member 81 and, if necessary, the surface of the spacer sheet 70. Then, a required amount of the same resin material P as described above is disposed on the upper surface of the cavity mold semi-finished product 11, and the core mold base material portion 23 is set so that its convex surface 23a faces downward. The resin material P on the cavity-type semifinished product 11 is pressed down from above, and pressed. At this time, the interval S3 between the core mold base member 23 and the frame material 81 and the interval S4 between the core mold base material portion 23 and the cavity mold semi-finished product 11A at the lowest time are determined by the core surface resin layer 26. Thickness.
By the pressing, the resin material P is transferred between the cavity-type semifinished product 11 and the core-type base material 23 and between the core-type base material 2
The resin layer 26A is formed by spreading between the frame material 81 and the frame material 81, and starts the reaction hardening to become the resin layer 26A in the middle of the hardening.

In the heat curing step, the frame material 81 is removed from the cavity-type semi-finished product and the core-type semi-finished product, and the cavity-type semi-finished product 11A and the core-type semi-finished product 21A are placed in a heating furnace 75 as shown in FIG. And the base material portion 1
The resin layers 16A and 26A during the curing of the surfaces of the surfaces 3 and 23 are heated to accelerate the curing and are completely cured, and are firmly bonded to the base materials 13 and 23, respectively. Reference numeral 76 denotes a heating device such as an electric heater.

After the completion of the heat curing step, the spacer sheet 70 is removed, and a part necessary for an injection molding die such as formation of a sprue is formed in a finishing step, so that a desired molding die 10 as shown in FIG. Is obtained. According to this molding method, since the model die 51 finally becomes the core base material portion 23, no extra material is required, which is economical. Since it is a part of the manufacturing operation of the material portion 23, the operation is not wasted, and the molding die can be manufactured efficiently. When injection molding was performed using the molding die 10 thus manufactured, without providing a refrigerant circulation pipe, only by natural cooling,
Plastic moldings could be molded in a short molding cycle.

[0023]

As shown and described above, according to the molding die of the present invention, it is composed of a combination of a graphite base material and a surface resin layer, and the resin material of the surface resin layer is made of gold.
Since it is made of a mixture of a metal powder and an epoxy resin , the weight can be reduced to about one third to one fifth as compared with a conventional steel mold, and handling is easy . In addition, since the mold surface can be formed by injecting and hardening the resin material in the production of the molding die, the construction period required for the production of the mold can be shortened, which is economical. In addition, since there is less shrinkage due to heat as compared with a conventional resin mold, there is an effect that a plastic molded product can be molded with high precision. Furthermore, since it is not necessary to provide a circulation pipe for the refrigerant, etc., it is also possible to shorten the manufacturing period of the molding die and reduce the cost of the molding die. Is unnecessary, so that the total equipment cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an entire molding die according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a processing step of a model die when manufacturing a molding die of the present invention.

FIG. 3 is a schematic view showing a rough processing step of a cavity mold base material portion.

FIG. 4 is a schematic view showing a step of forming a cavity type surface resin layer.

FIG. 5 is a schematic view showing a model-type surface cutting step.

FIG. 6 is a schematic view illustrating a step of forming a core-type surface resin layer.

FIG. 7 is a schematic view showing a heat curing step.

[Explanation of symbols]

 10 Mold of one embodiment of the present invention 11 Cavity mold 12 Cavity mold surface 13 Cavity mold base material 16 Cavity mold surface resin layer 21 Core mold 22 Core mold mold surface 23 Core mold base material 26 Core type surface resin layer 31 Cavity 32 Sprue 41, 42 Mounting plate

Claims (4)

(57) [Claims] 1. A molding die comprising a core die having a molding die surface for a plastic molded product and a cavity die, wherein the cavity die and the core die have at least a die surface portion of a surface of a graphite base material portion. made from those formed in the surface resin layer, the resin material of the surface resin layer, the metal powder and epoxy resin
A molding die comprising a mixture . 2. The mold according to claim 1, wherein the surface resin layer is formed by directly curing the resin material on the surface of the graphite base material. 3. The method according to claim 1, wherein the metal powder of the resin material is alumina powder or
Is aluminum powder.
Or the mold according to 2. 4. A graphite powder is mixed with a resin material.
4. The method according to claim 1, wherein
The mold described.