JP2020104445A - Resin mold - Google Patents

Abstract

To provide a resin mold which can be produced easily, is free from restriction of resin materials to use, and has excellent heat conduction and durability.SOLUTION: Disclosed herein is a resin mold having a multilayer constitution of at least 3 layers. When a rate of an inorganic powder involved in an inner layer being in contact with the innermost resin molding is shown as A%, a rate of an inorganic powder involved in an intermediate layer is shown as B% and a rate of an inorganic powder involved in the outer layer is shown as C%, these rates satisfy A>B>C. The inorganic powder is e.g., a metal powder, and the metal powder is, e.g., aluminum powder. Each layer is composed of, e.g., a chemical wood.SELECTED DRAWING: Figure 1

Description

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

A mold made of a metal material such as aluminum is widely used for molding a resin molded product such as blow molding. However, since metal molds are expensive, for example, as a prototype mold, a resin mold (so-called resin mold) is also being studied. Since the resin mold is formed mainly of a resin material, it is cheaper than a mold made of a metal material, and the cost can be significantly reduced when it is used as a prototype mold.

However, the resin mold is insufficient in thermal conductivity, durability and the like as compared with a metal mold, and its application is limited to a small number of prototypes of about 50 shots at most. When producing a large number of products, there are many concerns about durability.

Under such circumstances, attempts have been made to improve the thermal conductivity and durability by adding metal powder to the resin mold. For example, in Patent Document 1, in a method of manufacturing a resin mold in which a molten resin is poured and then cured to form a resin mold, a metal powder is added to the molten resin, and the viscosity of the molten resin is reduced and then cured. It is disclosed that by doing so, the concentration of the metal powder around the cavity is increased.

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

JP, 2009-255361, A

However, in the technique described in Patent Document 1, a special manufacturing method is required to manufacture the resin mold, and it is difficult to appropriately control the distribution of the metal powder. Further, since it is necessary to control the viscosity of the molten resin, the resin material that can be used may be limited.

The present invention was proposed in view of the above-mentioned conventional circumstances, can be easily manufactured, does not impose restrictions on the resin material used, and is excellent in heat conduction and durability. The purpose 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 multi-layered structure composed of at least three layers, and the proportion of the inorganic powder contained in the inner layer in contact with the innermost resin molded product is A%. When the proportion of the inorganic powder contained in the intermediate layer is B% and the proportion of the inorganic powder contained in the outer layer is C%, A>B>C.

In the resin mold of the present invention, a multilayer structure is adopted, and an inorganic powder having excellent thermal conductivity is added to the inner layer in contact with the resin material in which the cavity is formed and molded. The addition of inorganic powder is also effective in improving durability. However, for example, if a two-layer structure of an inner layer to which an inorganic powder is added and an outer layer to which an inorganic powder is not added is used, it is caused by a difference in physical properties (heat conductivity etc.) of these two layers when trial production is repeated. It has become clear that the resin mold may be cracked or damaged. For example, in the case of a relatively large resin mold for blow molding, the inner layer is divided into a plurality of parts, which are then assembled with an adhesive to form a resin mold. In some cases, cracks may occur between the divided inner layers.

Therefore, in the resin mold of the present invention, an intermediate layer containing an inorganic powder in an intermediate ratio between the inner layer containing the inorganic powder and the outer layer not containing the inorganic powder (or having a small content of the inorganic powder). Is intervening. By interposing the intermediate layer, the difference in the physical properties between the layers is relaxed, and the occurrence of cracks and damages is suppressed.

Further, the resin mold of the present invention has a multi-layered structure and adjusts the ratio of the inorganic powder contained in each layer to ensure the required thermal conductivity and durability. Each layer can be easily formed simply by changing the blending ratio of the inorganic powder, and no special process is required to make the distribution of the inorganic powder proper. Therefore, the resin material used is not limited at all.

According to the present invention, it is possible to provide a resin mold which can be easily manufactured, does not impose restrictions on the resin material used, and is excellent in heat conduction and durability.

It is an outline sectional view showing an example of the layer composition of the resin type to which the present invention is applied. It is a schematic front view when the resin mold is seen from the inner layer side.

Hereinafter, embodiments of a resin mold to which the present invention is applied will be described in detail with reference to the drawings.

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

The resin mold 1 of the present embodiment is a resin mold for blow molding, and as shown in FIG. 2, the inner layer 11 is divided into a plurality of pieces (here, six pieces), and the divided pieces 11a to 11f are formed respectively. After processing, the inner layer 11 is formed by combining and bonding these.

The intermediate layer 12 and the outer layer 13 are not divided in this embodiment, but the intermediate layer 12 may be divided and formed similarly to 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 formed mainly of an inexpensive resin material. Although any resin material can be used as the resin material, chemical wood (so-called chemi wood) or the like is preferable in terms of mechanical properties and the like.

The chemical wood is a plate made of resin having excellent machinability and dimensional accuracy, which is used when, for example, producing a prototype design model for automobiles and home electric appliances, and is also called artificial wood. The chemical wood is usually formed by mixing a liquid resin as a binder with hollow beads, an inorganic filler, a coloring agent and the like and curing the mixture into a plate in a mold. And, for example, urethane-based chemical wood has an apparent specific gravity of about 0.3 to 0.8 and has a fairly fine void therein. Urethane-based chemical wood contains hollow beads and an inorganic filler that does not adversely affect the machinability. It is very easy to cut, and the resin-based wood has a low hygroscopic property, so the dimensional accuracy is relatively good. is there.

As the chemical wood, there are epoxy chemical wood and the like in addition to the urethane chemical wood, and any of these may be used. Various chemical woods are commercially available, and typical examples are Sanyo Chemical Co., Ltd., trade name Sun Module, Lamp Co., trade name Lactool, and the like.

However, if the inner layer 11 forming the resin mold 1 is made of only a resin material (chemical wood), the thermal conductivity and durability may be insufficient. Therefore, in the resin mold 1 of the present embodiment, Inorganic powder having excellent heat conductivity is added to the layer 11. By adding the inorganic powder to the inner layer 11 that is in direct contact with the molten resin, the cooling efficiency during molding can be increased and the molding efficiency can be improved. Further, by adding the inorganic powder to the inner layer 11, it is possible to improve the durability as compared with the case of forming the chemical wood alone.

The inorganic powder to be added may be any one as long as it has excellent thermal conductivity, and examples thereof include metal powder, titanium oxide, alumina, aluminum nitride, and boron nitride. 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 mentioned, but aluminum powder is most suitable in terms of performance, cost and the like.

The addition amount of the inorganic powder in the inner layer 11 may be appropriately set depending on the required performance and the type of the inorganic powder to be added. For example, when the metal powder (aluminum powder) is added as the inorganic powder, the addition amount is It is preferably about 10% by mass to 30% by mass. If the addition amount of the metal powder is less than 10% by mass, the performance such as thermal conductivity and durability may be insufficient. On the contrary, if the addition amount exceeds 30% by mass, the performance will be saturated and the cost will increase, so the upper limit is 30% by mass.

On the other hand, the outer layer 13, which is the opposite of the inner layer 11, has little influence on molding, and performance such as thermal conductivity and durability is not required as much as the inner layer 11. Therefore, with respect to the outer layer 13, inexpensive chemical wood is used, and the inorganic powder such as metal powder is not added, or the amount thereof is smaller than that of the inner layer 11.

However, when the inner layer 11 containing a predetermined amount of inorganic powder such as a metal powder and the outer layer 13 containing no inorganic powder such as a metal powder (or having a very small content) are in contact with each other (of the inner layer 11 and the outer layer 13). In the case of a two-layer structure), the resin mold 1 may be cracked due to the difference in these physical property values (heat conductivity, etc.). Therefore, the resin mold 1 of the present embodiment has a three-layer structure in which the intermediate layer 12 is interposed between the inner layer 11 and the outer layer 13.

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 content of the inorganic powder of the inner layer 11 and the content of the inorganic powder of the outer layer 13. By containing the inorganic powder, it plays a role of relaxing the physical property difference 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%, A>B>C. To do. For example, when the content of the metal powder (aluminum powder) of the inner layer 11 is 20 mass% and the content of the metal powder (aluminum powder) of the outer layer 13 is 0 mass %, the metal powder (aluminum powder) of the intermediate layer 12 is ) Content is 10 mass %. Considering the setting range of the content of the metal powder (aluminum powder) of the inner layer 11, the content of the metal powder (aluminum powder) of the intermediate layer 12 is about 5% by mass to 15% by mass.

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

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

Although the resin mold for blow molding has been described in the present embodiment, it may be used as another molding mold (for example, a molding mold for injection molding). However, the resin mold of the present embodiment is preferably used for blow molding because a large effect can be expected when it is necessary to select the resin mold in consideration of cost and to increase the number of products to be produced. Above all, it can be preferably applied to foam blow molding. This is because the molding temperature of the foamed resin is lower than the molding temperature of the unfoamed resin (for example, in the case of polypropylene, the molding temperature of unfoamed is about 200° C., while the molding temperature of foamed is 160 to 170). C is about). The resin mold has a low thermal conductivity and a lower ability to cool the resin than the mold, but in the case of the foamed resin, the molding temperature is low from the beginning, so that the molding cycle is not so long as compared with the unfoamed resin.

In the resin mold 1 of the present embodiment, addition of an inorganic powder such as a metal powder to the resin mold 1 is effective in improving the durability during trial manufacture, but the inorganic powder is added only to the inner layer 11 that is in contact with the molded product. Therefore, the material cost can be reduced. Furthermore, as described above, the resin mold 1 having a multi-layered structure can also be aimed at the effect of preventing cracks, breakage, etc. due to the difference in thermal conductivity, but this phenomenon tends to occur with larger products and longer trial production periods. In such a case, the effect is great.

In addition, the resin mold 1 of the present embodiment can be easily manufactured by adopting a multi-layer structure, and it is not necessary to employ a special construction method, and the material to be used may be restricted. Absent.

Although the embodiment of the present invention has been described above, it is needless to say that the present invention is not limited to this embodiment and various modifications can be made without departing from the gist of the present invention.

Hereinafter, examples of the present invention will be described based on specific experimental results.

Example 1
A resin mold having a three-layer structure was prepared using urethane chemical wood. 20 mass% of aluminum powder was added as an inorganic powder to the inner layer. No inorganic powder was added to the outer layer. Aluminum powder was added to the intermediate layer as an inorganic powder in an amount of 10% by mass. In this embodiment, the inner layer is divided into six parts.

Comparative Example 1
A resin mold having a two-layer structure was produced using urethane chemical wood. 20 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
A resin mold having a single-layer 6-division structure was prepared using urethane chemical wood. No inorganic powder was added.

Comparative Example 3
A resin mold having a single-layer 6-division structure was prepared using urethane chemical wood. 20 mass% of aluminum powder was added as an inorganic powder.

Evaluation These examples and comparative examples were examined for thermal conductivity, durability, occurrence of cracks and breakage, and production cost. The results are shown in Table 1.

As is apparent from Table 1, in Example 1 in which the amount of aluminum powder added to each layer is three layers and the amount of aluminum powder is appropriate, the thermal conductivity and durability are excellent. It can be seen that a resin mold, which is advantageous in terms of manufacturing cost, can be realized without causing cracks in the above. On the other hand, in Comparative Example 1 in which the inner layer containing the aluminum powder and the outer layer not containing the aluminum powder were brought into direct contact with each other, there was no problem in terms of thermal conductivity and durability, but cracks and breakage occurred. Was observed. In the single-layer comparative examples 2 and 3, it is difficult to secure all performances.

1 Resin Mold 11 Inner Layers 11a to 11f Divided Piece 12 Intermediate Layer 13 Outer Layer

Claims (7)

A resin type having a multi-layered structure including at least three layers,
When the proportion of the inorganic powder contained in the inner layer in contact with the innermost resin molded product is A%, the proportion of the inorganic powder contained in the intermediate layer is B%, and the proportion of the inorganic powder contained in the outer layer is C%, A resin mold characterized in that A>B>C. The resin mold according to claim 1, wherein the inorganic powder is a metal powder. The resin mold according to claim 2, wherein the metal powder is aluminum powder. The resin mold according to any one of claims 1 to 3, wherein each of the layers is made of chemical wood. The resin mold according to any one of claims 1 to 4, which is for blow molding. The resin mold according to claim 5, which is for foam blow molding. 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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