JP2013166314A - Mold for high heat efficiency injection molding, and injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a molded article with excellent quality and productivity by enabling heat exchange of a product transfer surface with high efficiency.SOLUTION: Highly-efficient heat exchange is made possible by including assist blocks which abut on a cavity block and a core block directly relating to heat conduction of filled resin, and increase a heat conduction area of mold temperature control. More preferably, a heat shield layer formed of a low-heat conductivity member and an air insulation layer are included in a fitting and abutting part between the cavity block and a mold base for supporting and fixing the core block.

Description

  The present invention relates to a mold for injection molding a resin product and an injection molding method.

  A resin product made by injection molding is shaped by injection-filling and solidifying a molten resin in a product forming space provided in a molding die. Therefore, it can be said that the injection mold is a heat exchanger that takes the heat of the molten resin by the mold and solidifies it.

  From the viewpoint of the heat exchange rate at which the molten resin is solidified by the molding die, if the die temperature is low, the solidification time is shortened and the molding cycle can be shortened. However, the high-temperature resin injected and filled in the low-temperature mold is instantly deprived of heat by the mold, and only the surface layer is solidified to form a skin layer. At that time, a weld line is formed in the surface layer portion at a portion where the resin flow is merged, which causes a decrease in designability and decoration. In addition, the difference in the cooling rate between the surface layer and the inner layer causes distortion in the molded product and causes various quality defects such as deformation and sink marks. Therefore, in the conventional injection molding method, in order to satisfy both requirements of quality and productivity, a molding method in which the mold temperature is controlled in an intermediate temperature range is general.

  On the other hand, in recent years, various efforts have been made to improve the design and decorating properties of resin products without causing a decrease in productivity, and the following patent documents represented by the representatives disclose such means.

  Patent Document 1 states that “a thermoplastic resin injection mold according to the present invention is formed between a cavity mold, a core mold fitted to a core plate, and the cavity mold and the core mold. A cavity part filled with a molten resin, a heat insulating layer is provided on the surface of the cavity mold, a heating means is provided on the core mold, and both are provided between the core mold and the core plate. A gas supply means capable of supplying a gas to the bottom surface of the core mold through the inside of the core mold, wherein the core mold is formed entirely of a porous metal member, and a heat insulating wall is provided. Thereby achieving the above object. Is described.

  Patent Document 2 states that “a first mold, a second mold that can be moved forward and backward with respect to the first mold, and a transfer surface made up of concavity and convexity patterns in a cavity space. A transfer plate attached to one of the first and second molds toward C1 and C2, and a heat insulating material disposed between the one mold and the transfer plate and made of metal glass And having a layer. Since a heat insulating material layer made of metal glass is disposed between one mold and the transfer plate, the temperature of the mold apparatus can be set low. Since the time required for cooling and solidifying the molding material after transfer can be shortened, the molding cycle can be shortened. Is described.

  Patent Document 3 states that “a mold for a resin product in which a cavity formed between a cavity block supported by a fixed-side die base and a core block supported by a movable-side die base is filled with molten resin and injection-molded. In the mold, a heat insulating layer is provided between the cavity block and the fixed-side die base, a first temperature control unit for holding the cavity block at 110 ° C. or higher is provided, and an ambient temperature other than the cavity block such as the core block is set to 90 ° C. A fixed-side temperature control unit and a movable-side temperature control unit for maintaining the temperature at or below ° C. are provided. Is described.

Japanese Patent No. 336639 JP 2010-149421 A JP 2008-105229 A

  By means of forming a heat insulating layer made of a low thermal conductivity member on the product transfer surface that comes into contact with the molten resin, a rapid temperature drop of the resin filled in the molding die is suppressed, transferability is improved, and low pressure is achieved. Can be filled with resin. However, various members having low thermal conductivity used for the heat insulating layer have fragile properties, and there is a concern about rapid temperature change and long-term durability of the transfer surface exposed to a high pressure environment.

  Improving transferability by instantly preventing the growth of the skin layer of the molten resin in contact with the transfer plate by means of a composite structure with a transfer plate and a heat insulating layer made of metal glass on the transfer surface that contacts the molten resin It becomes possible to make it. However, it is considered difficult to apply to a mold having a complicated product shape because of the structure of the transfer surface heat insulating layer which is a composite structure.

  A heat insulating layer is provided between the cavity block that contacts the molten resin and the fixed die base that supports and fixes the molten resin, and the temperature of the cavity block is controlled by the means that suppresses the escape of heat from the cavity block to the fixed die base. It becomes possible to control the temperature higher than that of the mold and delay the temperature drop of the resin flowing through the cavity. However, since the transfer surface held at high temperature is limited to the cavity block side, the transferability and design properties on the core block side, which is relatively low temperature, and the temperature difference provided between the cavity block and the core block are the molded products. Therefore, there is a concern that a difference in cooling rate is caused to cause distortion in the molded product.

  In view of such problems, the object of the present invention is to suppress a rapid temperature drop of the filled resin, and without impairing the characteristics of the mold as a heat exchanger, and having high thermal efficiency and excellent long-term durability. It is to provide a method for producing a molded article excellent in quality and productivity.

  Injection molds are roughly divided into a cavity block, a core block, and a mold base that supports and fixes them, and a molten resin is injected and filled into a product forming space formed by the cavity block and the core block and solidified.

  The temperature of the molten resin to be injected and filled is generally higher than 250 ° C., and how quickly and efficiently this heat is taken away by the mold greatly affects the productivity.

  On the other hand, as the behavior of the resin during injection filling, the rapid temperature drop of the resin due to contact with the product transfer surface of the mold is a cause of various quality defects, and avoid sudden temperature drop during the filling process. Is desirable. Therefore, as a means to satisfy these contradictory requirements, an injection mold having high thermal efficiency has been developed.

  In the present invention, the cavity block and the core block that take away the heat of the filling resin are provided with an assist block that abuts against these to increase the heat conduction area of the mold temperature control, thereby enabling highly efficient heat exchange. It is characterized by that. More preferably, a heat shield layer and an air heat insulating layer made of a low thermal conductivity member are provided at the fitting contact portion between the cavity block, the core block, and the mold base that supports and fixes the assist block, thereby improving the heat exchange efficiency. It is characterized by that.

  By using the injection mold according to the present invention, heating and cooling the mold according to the molding process for the cavity block, the core block, and the assist block, the product transfer surface that the molten resin contacts is intended. It becomes possible to control the temperature efficiently.

  By using the high thermal efficiency injection mold according to the present invention, by heating and cooling the mold according to the molding process, the product transfer surface with which the molten resin contacts can be efficiently controlled to the intended temperature, and the filling process It is possible to suppress a rapid temperature drop of the resin. Therefore, it is possible to fill the resin with low viscosity, low pressure, and low strain, and it is possible to produce molded products with excellent quality and productivity such as reduced burr generation, improved appearance quality, and reduced deformation due to uniform distribution of holding pressure. It is possible to manufacture.

It is a half-cut sectional view of the high thermal efficiency injection mold of the first embodiment. It is a half-cut sectional view of a molding die as a reference example. It is a schematic plan view of the molding die shown in FIG. It is a fragmentary sectional view which shows the example of an installation mode of a heat shield layer. It is a half section view of the molding die of the 2nd example.

  An embodiment of a high thermal efficiency injection mold according to the present invention will be described with reference to the drawings.

  FIG. 1 is a half sectional view of a high thermal efficiency injection mold according to an embodiment of the present invention.

  The cavity block 1 and the core block 2 form a product forming space 3 for modeling a resin product, and the injection-filled molten resin is a resin-filling space in a molding die including a sprue, a runner, and a gate (not shown). The product forming space 3 is filled and solidified.

  The cavity block 1 and the core block 2 are respectively provided with a cavity side temperature adjusting hole 4 and a core side temperature adjusting hole 5 for controlling the respective temperatures, and the temperature is controlled by passing a heating medium such as water or oil inside. The

  The transfer surface that forms the product formation space 3 is ideally controlled to have a uniform temperature distribution as a whole, but depending on the placement balance of the temperature control holes, the heat of the molten resin cannot be removed efficiently. Heat accumulation may occur. Therefore, in designing the arrangement of the temperature control holes in the cavity block 1 and the core block 2, careful attention is paid to realizing a uniform temperature distribution.

  However, in an injection mold having a product forming space 3 as shown in FIG. 2 (reference example), a core pin 6 provided in the core block 2 and an ejector pin for taking out a product (not shown) are provided. In some cases, it is difficult to arrange the core-side temperature adjusting holes 5 intended to achieve a uniform temperature distribution due to structural restrictions due to the above.

  In the present invention, the mold-side assist block 7 and the core-side assist block 8 that can efficiently remove the heat of the molten resin are also provided for an injection mold in which structural restrictions are imposed on the arrangement of the temperature control holes. It is characterized by comprising.

  As shown in FIG. 1, the cab-side assist block 7 and the core-side assist block 8 are each provided with a cab-side assist temperature adjustment hole 9 and a core-side assist temperature adjustment hole 10, and a heating medium such as water or oil inside. The temperature is controlled through.

  The cavity side assist block 7 and the core side assist block 8 have a structure in which the cavity block 1 and the core block 2 are in surface contact with each other, and the cavity block 1 and the core side through the cavity side heat conduction surface 11 and the core side heat conduction surface 12. Assist block 2 temperature control. Therefore, since each assist block is required to have a performance for controlling its own temperature in a short time, it is necessary to use a member having high thermal conductivity and high temperature conductivity.

  Plastic mold steel used for the cavity block 1 and the core block 2 is a steel material that emphasizes corrosion resistance and wear resistance, and its thermal conductivity is approximately 40 (W / m · k) or less. As a member used for the assist block that does not directly contact the molten resin, it is desirable to use a member (for example, a copper alloy material) having a high thermal conductivity of three times or more and a relatively high strength. The cavity side heat conduction surface 11 and the core side heat conduction surface 12 formed by the cavity side assist block 7 and the core side assist block 8 in surface contact with the cavity block 1 and the core block 2 respectively increase the contact area. Thus, the heat exchange efficiency can be increased, and a plurality of assist blocks can be arranged in a form surrounding the cavity block 1 and the core block 2.

  In order to efficiently control the product transfer surface forming the product formation space 3 to the intended temperature, the region 100 in which the cavity block 1 is accommodated in the mold side mold base 13 and the core block 2 are in the core side mold base 14. In the region 200 that fits in the area, the cavity side heat conduction surface 11 and the core side heat conduction surface 12 occupy 35% or more of the heat conduction area with respect to the surface area of the cavity block 1 and the core block 2. It is desirable to arrange.

  With the above high heat efficiency injection mold, it is possible to increase the heat exchange efficiency between the cavity block 1 and the core block 2 that form the product forming space 3, but in order to further improve the heat exchange efficiency, the mold It is desirable to reduce the escape of heat to the cavity block 1 and the core block 2 and the cab side assist block 7 and the core side assist block 8 to the outside by temperature control. As a means for this, the fitting contact portions of the cavity side mold base 13 and the core side mold base 14 that support and fix the cavity block 1 and the core block 2 and the cavity side assist block 7 and the core side assist block 8 are blocked. It is desirable to heat.

  FIG. 3 shows a schematic plan view of the injection mold of the half-cut cross section shown in FIG. 1 when the core block 2 side is viewed from the cavity block 1 side.

  A gap space 19 formed between the outer contour surface 17 of the core block 2 and the support contact surface 18 formed by pocket holes provided in the core-side mold base 14 is shielded by a member having low thermal conductivity (for example, metal glass). The heat layer 15 is fitted and abutted to support and fix the core block 2. Furthermore, the air insulation layer 16 is formed in the space where the heat shield layer 15 does not contact.

  In order to reduce the heat given to the core block 2 and the core side assist block 8 by the mold temperature control from escaping to the core side mold base 14, it is desirable to reduce the contact area with which the heat shield layer 15 contacts. In order to ensure the positional accuracy of the core block 2 and the core-side assist block 8 to which a high resin pressure is applied, 70% or more of the surface area of the outer contour surface 17 of the core block 2 and the core-side assist block 8 It is desirable that the heat shield layer 15 is fitted and brought into contact with the contact area, and the positions in the X and Y directions are supported and fixed. Further, in FIG. 1, the heat shield layer 15 a disposed at the bottom of the core-side assist block 8 and the contact surface 300 of the core-side mold base 14 need to receive the applied resin pressure dispersed over a wide area. It is desirable to secure the widest possible contact area and to support and fix the position in the Z direction.

  Although only the core block 2 side has been described above, the same effect can be obtained by using the same structure on the cavity block 1 side.

  Using the above-described high thermal efficiency injection mold according to the present invention, the cavity side temperature adjusting hole 4, the core side temperature adjusting hole 5, the cavity side assist temperature adjusting hole 9, and the core side assist temperature adjusting hole 10 are set in advance. The molten resin is injected and filled by heating the transfer surface temperature of the product forming space 3 formed by the cavity block 1 and the core block 2 to near the heat deformation temperature of the resin material to be used. In addition, the resin can be filled in a state excellent in transferability and designability.

  Next, at a predetermined timing before resin filling is completed, the cavity side temperature adjusting hole 4, the core side temperature adjusting hole 5, the cavity side assist temperature adjusting hole 9, and the core side assist temperature adjusting hole 10 are set in advance. By cooling the cavity block 1 and the core block 2 through a low-temperature heating medium, the heat on the product transfer surface can be efficiently removed and the molded product can be taken out in a short time. Therefore, by repeating heating and cooling of the mold in accordance with the above molding process, the rapid temperature drop of the resin during the filling process is suppressed, the generation of burrs is reduced, the appearance quality is improved, and the deformation is caused by the uniform distribution of the holding pressure. It is possible to manufacture a molded product that achieves reduction and the like without causing a decrease in productivity.

  Although metal glass was mentioned as an example of the member used for the heat shielding layer 15, it is not limited to this as long as it is a member that shields heat and can secure the positional accuracy of the cavity block 1 and the core block 2. It is desirable to have toughness, hardness and thermal expansion coefficient comparable to steel for plastic molds, and the thermal conductivity is 5.5 (W / m · k) or less.

  The heat shielding layer 15 is not limited to a single member, and a heat shielding effect can be obtained by a composite member coated with a low thermal conductivity member made of ceramics, glass, or a polymer material. Therefore, as shown in FIG. 4, it may be a composite form in which the low thermal conductivity member 21 is coated on both surfaces in the direction of heat insulation with respect to the base material 20 or on one side end surface, and the heat shielding effect is obtained by using this in a superimposed manner. May be raised.

  FIG. 5 shows an embodiment of a molding die having a core block 2 having a shape that easily causes heat accumulation.

  The high heat conductivity member 23 that is fitted and fixed inside the core block 2, extends toward the heat accumulation shape 22, and contacts the core side assist block 8 is disposed, so that the heat of the heat accumulation shape 22 can be efficiently absorbed into the core. It is possible to conduct the cooling to the side assist block 8 and cool it. The high thermal conductivity member 23 desirably has a thermal conductivity equivalent to that of the core-side assist block 8, and the heat exchange effect is further improved by providing the temperature control path 24 therein.

DESCRIPTION OF SYMBOLS 1 Cavity block 2 Core block 3 Product formation space 4 Cavity side temperature control hole 5 Core side temperature control hole 6 Core pin 7 Cavity side assist block 8 Core side assist block 9 Cavity side assist temperature control hole 10 Core side assist temperature control hole DESCRIPTION OF SYMBOLS 11 Cavity side heat conduction surface 12 Core side heat conduction surface 13 Cavity side mold base 14 Core side mold base 15, 15a Heat insulation layer 16 Air heat insulation layer 17 External outline surface 18 Support contact surface 19 Crevice space 20 Base material 21 Low heat conduction The rate member 22 The heat accumulation shape 23 The high thermal conductivity member 24 The temperature control path 100 The region 200 where the cavity block fits in the mold side mold base 200 The region where the core block fits inside the core side mold base 300 Contact surface

Claims (8)

In an injection mold for injecting and filling a molten resin into a product forming space formed by a cavity block and a core block and solidifying it,
An injection mold having an assist block that abuts either or both of the cavity block and the core block and increases the heat conduction area of the mold temperature control. In the mold for injection molding in which molten resin is injected and filled into the product forming space formed by the cavity block and the core block and solidified,
Provide a mold base that supports and fixes both the cavity block and the core block or any one of them,
An injection mold comprising a heat shielding layer made of a low thermal conductivity member and an air heat insulating layer at a fitting contact portion between the cavity block and / or the core block and the mold base. In the injection mold according to claim 1,
An injection mold in which the thermal conductivity of the mold steel used for the assist block is three times or more the thermal conductivity of the plastic mold steel used for the cavity block or core block. The injection mold according to any one of claims 1 and 3,
For each surface area of the area where the cavity block and core block fit within the mold base,
The heat conduction area formed by the cavity block and the core block being in surface contact with the assist block,
Injection molds that occupy over 35% of each. In the injection mold according to claim 2,
For the surface area of the outer contour surface of the cavity block, the core block, and the assist block,
An injection molding die in which the heat shielding layer abuts on the mold base and supports and fixes with a contact area of 70% or more. In the injection mold according to claim 2 or 5,
The thermal conductivity of the member used for the heat shield layer is 5.5 (W / m · k) or less,
The member used for the heat shield layer is an injection mold formed of a single member or a composite member coated with a low thermal conductivity member. Using the injection mold according to any one of claims 1, 3, and 4,
An injection molding method for controlling heating and cooling of a mold for the cavity block, the core block, and the assist block to control the temperature of the product transfer surface that is in contact with the molten resin. Using the injection mold according to any one of claims 2, 5 and 6,
An injection molding method for controlling heating and cooling of a mold for the cavity block, the core block, and the assist block to control the temperature of the product transfer surface that is in contact with the molten resin.