JP7236028B2 - Resin mold - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin mold that is used in place of a metal mold when molding a resin material, and more particularly to a novel resin mold that is excellent in cooling efficiency and durability.

Molds made of metal materials such as aluminum are widely used in the molding of resin molded articles such as blow molding. However, since metal molds are expensive, resin molds (so-called resin molds) are also being considered, for example, as prototype molds. Since the resin mold is mainly made of a resin material, it is less expensive than a mold made of a metal material, and when used as a prototype mold, the cost can be greatly reduced.

However, resin molds are insufficient in terms of thermal conductivity, durability, etc., compared to metal molds, and their use is limited to a small number of prototypes of about 50 shots at most. In mass production, there are many concerns about durability and the like.

Under these circumstances, attempts have been made to improve thermal conductivity and durability by adding metal powder to the resin mold. For example, Patent Document 1 discloses a method for manufacturing a resin mold in which a molten resin is poured and then cured to form a resin mold. It is disclosed that the density of the metal powder around the cavity is increased by increasing the density.

As described above, the resin mold manufactured by the technique described in Patent Document 1 has a high concentration of metal powder around the cavity. It is possible to improve the manufacturing efficiency when the product is injection molded, and to increase the rigidity of the cavity peripheral portion.

JP 2009-255361 A

However, with the technique described in Patent Document 1, a special manufacturing method is required for manufacturing the resin mold, and it is difficult to properly control the distribution of the metal powder. Furthermore, since it is necessary to control the viscosity of the molten resin, usable resin materials may also be restricted.

The present invention has been proposed in view of the above-mentioned conventional circumstances. The object is to provide a resin mold.

In order to achieve the above-mentioned object, the resin mold of the present invention is a resin mold having a multilayer structure consisting of at least three layers, wherein the inner layer in contact with the innermost resin molded product has a metal powder content of A%. , where B% is the ratio of the metal powder contained in the intermediate layer and C% is the ratio of the metal powder contained in the outer layer, A>B>C, and in the composition of each layer, only the content of the metal powder is characterized by being different .

In the resin mold of the present invention, a multi-layer structure is adopted, and an inorganic powder having excellent heat conductivity is added to the inner layer in which the cavity is formed and which is in contact with the resin material to be molded. Addition of inorganic powder is also effective in improving durability. However, for example, if a two-layer structure of an inner layer to which inorganic powder is added and an outer layer to which inorganic powder is not added is repeated, the difference in physical properties (thermal conductivity, etc.) of these two layers may occur. As a result, it has been found that the resin mold may crack or break. For example, in the case of a relatively large resin mold for blow molding, the inner layer is formed by dividing it into a plurality of pieces, which are then integrated with an adhesive to form a resin mold. In some cases, cracks may form between the divided inner layers.

Therefore, in the resin mold of the present invention, an intermediate layer containing an inorganic powder at a ratio intermediate between the inner layer containing the inorganic powder and the outer layer containing no inorganic powder (or containing less inorganic powder) is provided. is intervening. By interposing the intermediate layer, the difference in physical properties between the layers is reduced, and the occurrence of cracks and breakage is suppressed.

Further, the resin mold of the present invention has a multi-layer structure, and by adjusting the ratio of the inorganic powder contained in each layer, necessary thermal conductivity and durability are ensured. Each layer can be formed simply by changing the blending ratio of the inorganic powder, and no special process is required to properly distribute the inorganic powder. Therefore, the resin material to be used is not restricted at all.

ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide a resin mold that can be easily manufactured, does not impose restrictions on the resin material to be used, and is excellent in heat conduction and durability.

It is a schematic sectional drawing which shows an example of the layer structure of the resin type|mold to which this invention is applied. It is a schematic front view when a resin mold is seen from the inner layer side.

EMBODIMENT OF THE INVENTION Hereafter, embodiment of the resin type|mold to which this invention is applied is described in detail, referring drawings.

FIG. 1 shows a resin mold 1 of this embodiment. As shown in FIG. 1, the resin mold 1 of this embodiment has a three-layer structure, in which an inner layer 11, an intermediate layer 12, and an outer layer 13 are formed in order from the inside. A cavity is formed in the inner layer 11, and the molten resin (parison in blow molding) is shaped following the shape of this cavity.

The resin mold 1 of this embodiment is a resin mold for blow molding, and as shown in FIG. The inner layer 11 is constructed by combining and adhering these after processing.

Although the intermediate layer 12 and the outer layer 13 are not divided in this embodiment, it is also possible to form the intermediate layer 12 in the same manner as the inner layer 11, for example.

In the resin mold 1 of this embodiment, all of the inner layer 11, the intermediate layer 12, and the outer layer 13 are mainly made of inexpensive resin materials. Any resin material can be used as the resin material, but chemical wood (so-called chemiwood) or the like is preferable in terms of mechanical properties and the like.

Chemical wood is a resin plate excellent in cutting workability and dimensional accuracy, which is used, for example, when producing prototype design models for automobiles and home appliance parts, and is also called artificial wood. Chemical wood is usually formed by blending hollow beads, inorganic fillers, colorants, etc. with a liquid resin that serves as a binder, and curing the mixture in a mold into a plate shape. For example, urethane-based chemical wood has an apparent specific gravity of about 0.3 to 0.8 and contains considerable fine voids. Urethane-based chemical wood contains hollow beads and inorganic fillers that do not adversely affect machinability. be.

In addition to the urethane-based chemical wood described above, the chemical wood includes epoxy-based chemical wood and the like, and any of these may be used. Various chemical woods are commercially available, and representative examples thereof include Sanyo Kasei Co., Ltd., trade name Sun Module, Lamp Co., Ltd. trade name, Rakutool, and the like.

However, if the inner layer 11 constituting the resin mold 1 is made only of a resin material (chemical wood), the thermal conductivity and durability may be insufficient. An inorganic powder having excellent heat conductivity is added to the layer 11 . By adding an inorganic powder to the inner layer 11 that is in direct contact with the molten resin, the cooling efficiency during molding can be enhanced, and molding efficiency can be improved. Further, by adding an inorganic powder to the inner layer 11, the durability can be improved as compared with the case where the chemical wood is used alone.

Any inorganic powder may be added as long as it has excellent thermal conductivity, and metal powder, titanium oxide, alumina, aluminum nitride, boron nitride and the like can be exemplified. Among these, metal powder is most suitable from the viewpoint of various physical properties such as thermal conductivity. As the metal powder, powders of various metals can be used, but aluminum powder is most suitable from the viewpoints of performance, cost, and the like.

The amount of the inorganic powder added to the inner layer 11 may be appropriately set according to the required performance and the type of inorganic powder to be added. It is preferable to make it about 10% by mass to 30% by mass. If the amount of the metal powder added is less than 10% by mass, performance such as thermal conductivity and durability may become insufficient. Conversely, even if the addition amount exceeds 30% by mass, the performance will be saturated, resulting in an increase in cost, so 30% by mass is made the upper limit.

On the other hand, the outer layer 13, which is opposite to the inner layer 11, has less influence on molding, and does not require performance such as thermal conductivity and durability as much as the inner layer 11 does. Therefore, for the outer layer 13 , inexpensive chemical wood is used, and inorganic powder such as metal powder is not added or added in a smaller amount than the inner layer 11 .

However, if the inner layer 11 containing a predetermined amount of inorganic powder such as metal powder and the outer layer 13 that does not contain inorganic powder such as metal powder (or the content is extremely small) are in contact with each other (the inner layer 11 and the outer layer 13 If a two-layer structure is used, cracks or the like may occur in the resin mold 1 due to differences in these physical properties (thermal conductivity, etc.). Therefore, in the resin mold 1 of this embodiment, the intermediate layer 12 is interposed between the inner layer 11 and the outer layer 13 to form a three-layer structure.

Here, the intermediate layer 12 has a role of connecting the inner layer 11 and the outer layer 13, and has an intermediate content between the inorganic powder content of the inner layer 11 and the inorganic powder content of the outer layer 13. Containing the inorganic powder serves to reduce the difference in physical properties between the inner layer 11 and the outer layer 13 .

That is, when the ratio of the inorganic powder contained in the inner layer is A%, the ratio of the inorganic powder contained in the intermediate layer is B%, and the ratio of the inorganic powder contained in the outer layer is C%, then A>B>C. do. For example, when the content of the metal powder (aluminum powder) in the inner layer 11 is 20% by mass and the content of the metal powder (aluminum powder) in the outer layer 13 is 0% by mass, the metal powder (aluminum powder) in the intermediate layer 12 ) is 10% by mass. Considering the setting range of the content of the metal powder (aluminum powder) in the inner layer 11, the content of the metal powder (aluminum powder) in the intermediate layer 12 is about 5% by mass to 15% by mass.

As a result, it is possible to prevent cracks and breakage occurring in the resin mold 1 containing the inorganic powder. If the intermediate layer 12 is not formed, cracks, peeling, and the like are likely to occur due to differences in thermal conductivity and the like.

The layer structure of the resin mold 1 is not limited to the above-described three-layer structure. For example, it is possible to set four or more layers so that the content of the inorganic powder gradually decreases from the inside to the outside. be. However, since an increase in the number of layers causes an increase in cost, a three-layer structure is most practical.

Although the resin mold for blow molding has been described in the present embodiment, it may be used as other molds (for example, molds for injection molding). However, the resin mold of the present embodiment is expected to have a great effect when, for example, the resin mold is selected with priority given to cost and the number of production needs to be large, so it is preferable to use it for blow molding. Among them, it can be preferably applied to foam blow molding. This is because the molding temperature of foamed resin is lower than the molding temperature of unfoamed resin (for example, in the case of polypropylene, the molding temperature of unfoamed resin is about 200°C, whereas the molding temperature of foamed resin is 160 to 170°C. °C). Resin molds have low thermal conductivity and are less capable of cooling resin than molds, but in the case of foamed resin, the molding temperature is low from the beginning, so the molding cycle is not so long compared to unfoamed resin.

In the resin mold 1 of the present embodiment, adding an inorganic powder such as a metal powder to the resin mold 1 is effective for improving durability during trial production, but the inorganic powder is added only to the inner layer 11 that is in contact with the molded product. By doing so, the material cost can also be reduced. Furthermore, as mentioned above, by making the resin mold 1 a multi-layered structure, it is possible to aim for the effect of preventing cracks, breakage, etc. due to differences in thermal conductivity. , is very effective in such cases.

In addition, the resin mold 1 of the present embodiment employs a multi-layered structure, making it easy to manufacture. do not have.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments, and that various modifications are possible without departing from the gist of the present invention.

Examples of the present invention will be described below based on specific experimental results.

Example 1
A three-layered resin mold was produced using urethane-based chemical wood. 20% by mass of aluminum powder was added as an inorganic powder to the inner layer. No inorganic powder was added to the outer layer. 10% by mass of aluminum powder was added as an inorganic powder to the intermediate layer. In this embodiment, the inner layer is divided into six.

Comparative example 1
A resin mold having a two-layer structure was produced using urethane-based chemical wood. 20% by mass of aluminum powder was added as an inorganic powder to the inner layer. No inorganic powder was added to the outer layer. The inner layer is divided into six.

Comparative example 2
Using urethane-based chemical wood, a resin mold having a single-layer 6-partition configuration was produced. No inorganic powder was added.

Comparative example 3
Using urethane-based chemical wood, a resin mold having a single-layer 6-partition configuration was produced. 20% by mass of aluminum powder was added as inorganic powder.

Evaluation These examples and comparative examples were examined for thermal conductivity, durability, occurrence of cracks and breakage, and production cost. Table 1 shows the results.

As is clear from Table 1, in Example 1, which has a three-layer structure and an appropriate amount of aluminum powder added to each layer, excellent thermal conductivity and durability are obtained. It can be seen that a resin mold that is advantageous in terms of manufacturing cost can be realized without cracks occurring in the mold. On the other hand, in Comparative Example 1 in which the inner layer containing aluminum powder and the outer layer not containing aluminum powder were in direct contact, there was no problem in terms of thermal conductivity and durability, but cracks and breakage occurred. occurred. In Comparative Examples 2 and 3 of single layers, it is difficult to ensure all performances.

1 resin mold 11 inner layers 11a to 11f split piece 12 intermediate layer 13 outer layer

Claims (7)

A multi-layered resin mold comprising at least three layers,
When the percentage of metal powder contained in the inner layer in contact with the innermost resin molded product is A%, the percentage of metal powder contained in the intermediate layer is B%, and the percentage of metal powder contained in the outer layer is C%, A>B>C,
A resin mold characterized in that only the content of metal powder is different in the formulation of each layer . 2. The resin mold according to claim 1, wherein said metal powder is aluminum powder. 1 or 2, wherein the ratio of the metal powder contained in the inner layer is 10% by mass to 30% by mass, and the ratio of the metal powder contained in the intermediate layer is 5% by mass to 15% by mass. 2. The resin mold according to 2 above. 4. The resin mold according to claim 1, wherein each layer is made of chemical wood. The resin mold according to any one of claims 1 to 4, which is for blow molding. 6. The resin mold according to claim 5, which is for foam blow molding. 7. The resin mold according to any one of claims 1 to 6, wherein the inner layer is divided into a plurality of pieces.

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