JP2000052390A - Molding method for plastic parts and its mold - Google Patents

Abstract

(57) [Problem] To provide a thick part on the outer periphery of a molded article, perform injection molding while actively cooling the outer periphery, prevent deformation of the peripheral thick part, and reduce the removal time. Provided is a plastic part molding method and a mold for improving workability at an early stage. SOLUTION: In molding a plastic molded product,
The outer peripheral portion of the molded product is set at a temperature lower than the temperature required for molding the surface of the cavity 4, and the outer peripheral portion 4a is solidified before the other portions. In order to do so, the mold blocks 2 and 3 forming the molded product cavity and the mold blocks (cooling blocks) 5 and 6 forming the outer peripheral portion of the molded product have a structure capable of independently controlling the temperature. I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a plastic part which shortens the molding cycle by actively cooling the peripheral part of the molded article during plastic molding and also improves the finished state of the product. It concerns the mold.

[0002]

2. Description of the Related Art Conventionally, in plastic injection molding or compression injection molding, measures have been taken to increase the fluidity of injected resin and to instantaneously fill the cavity at a low pressure. For this purpose, a flow path for circulating a heat medium (a fluid such as water or oil) is provided in the mold to maintain the mold temperature at a moderate temperature in consideration of the resin flow and cooling and solidification. on the other hand,
When performing high cycle molding, it is advantageous to give a mold a cycle of heating and cooling.When injection and injection of the resin into the cavity, it is heated to increase the fluidity of the resin, and after molding, the mold is cooled. Attempts have been made to adjust the temperature so that the resin molded in the cavity can be cooled and quickly taken out.

[0003] The cycle of heating and cooling of such a molding die varies depending on the shape and volume of the product to be molded. When the resin is injected and filled into the cavity, the cavity surface temperature is set to a temperature at which the fluidity of the resin can be increased. It is heated so as to be cooled, and after the filling is completed, it is cooled in order to speed up the time for solidification, and is kept at a temperature at which it can be taken out.

[0004] In lamination molding, the molding resin temperature is set low in order not to damage the adherend. However, when thin-wall molding requires fluidity, the mold temperature is raised slightly. Must be set to

[0005]

However, in molding plastics, raising the temperature of the mold to improve the flowability of the injected resin is contrary to increasing the molding cycle. Generally, the mold temperature is raised to the limit with emphasis on quality, but as a result, there is a problem that the molding cycle time becomes longer and the productivity is reduced.

In the thermal cycle molding in which heating and cooling are repeated, the thermal expansion and contraction of the mold can be switched.
Adoption is being considered only in limited fields where the clearance between the dies is likely to be out of order.

[0007] In addition, when the peripheral portion of the molded product becomes thick, there is a problem that the molding cycle time is prolonged, especially since it takes time to solidify the molded product. In short, when the same handling as the removal of general molded products is performed, the resin is deformed when the resin is removed from the mold in a state where solidification has not progressed because the thick portion is the peripheral edge, and who is generated Product defects will occur. By the way,
One example is shown in FIGS. 3 (a), 3 (b) and 3 (c).
This example relates to so-called lamination molding,
As shown in FIG. 3A, a transparent plate member (for example, a polycarbonate 101 and a glass plate 102) is integrally formed by a thermoplastic resin layer 103 melted by injection compression molding. In the obtained product, a peripheral edge portion 104 that becomes thicker of the thermoplastic resin is formed on the peripheral edge of the molding process. However, since the thermoplastic resin layer 103 is thin in the laminated portion of the transparent plate members 101 and 102 to be bonded during molding, the thermoplastic resin layer 103 is solidified in a short time. Is slowed down, so when removing the molded product,
As shown in FIG.
5 (who) occurs and becomes a defective product. In addition, such a lamination is generally performed by a mold 106 having a heat medium flow path 108 for temperature control as shown in FIG.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and a method of filling a cavity of a mold by cooling a thick edge portion of a molded product separately from a mold main body. Plastic that actively cools the thick edges of the resin to be used to promote shape preservation of molded products so that deformation of the thick edges does not occur, and at the same time, shortens removal time and improves workability. It is an object of the present invention to provide a molding method of a part and a mold therefor.

[0009]

Means for Solving the Problems and Functions / Effects In order to achieve the above-mentioned object, a method for molding a plastic part according to the first invention is a method for molding a plastic molded article, which has a thick edge portion. Is actively cooled to solidify the thick edge portion earlier than other portions.

According to such a method, the plastic molded article to be molded is actively cooled at the thick edge regardless of its shape, thereby promoting the shape preservation. When the molded product is formed to be thick, the molded product is not deformed due to solidification of the outer peripheral portion when the molded product is taken out of the mold, and the take-out time is shortened by that amount, and as a result, the molding is performed. The effect is that the cycle time can be reduced. Of course, the molded article
Since the thick edge portion is cooled and solidified first, it is possible to obtain an effect of preventing the occurrence of defective products without deformation.

In the method of molding a plastic part according to the first aspect of the present invention, it is preferable that the thick edge of the molded product to be molded is set at a temperature lower than a temperature required for molding the surface of the cavity. By doing so, even if a thick part is provided in the window-shaped opening at the outer peripheral part or in the middle of the molded product, the thick part is quickly solidified from the skin portion of the filled resin. A speed of solidifying faster than other portions or equivalent to that of other uniform thickness portions can be obtained, and the time for removing the molded article from the mold can be reduced.

In the method for molding a plastic part according to the first aspect of the present invention, when laminating a rigid dissimilar material member by lamination, the molten resin protruding from the molded product cavity to the thick-walled portion is placed in a mold. It is preferable that the mold be opened immediately after cooling and solidifying to reach a temperature at which the molded article can be handled, and the molded article is taken out. In this way, in the injection compression molding of the laminated material, the resin that is injection-injected and compression-molded is protruded to the outer peripheral portion of the laminated material, and the thicker portion is positively solidified, and the adhesive layer in the laminated portion is formed. When the resin is not solidified in the part where it is solidified, in other words, even if the solidification of the molding resin is not completed, the resin is solidified at the outer peripheral part or the intermediate opening, and if the adherend has rigidity, treat it as an individual Therefore, the molded article can be taken out from the mold at an early stage, and the molding cycle time can be easily shortened. Of course, no deformation such as "who" occurs around the product.

Next, a mold configured to carry out the molding method according to the second invention is a mold block for forming a molded product cavity and a mold block for forming a thick edge of the molded product. Is characterized by having a structure capable of independently adjusting the temperature.

By thus dividing the mold at a required position and adjusting the temperature, the mold temperature becomes more constant than in the thermal cycle molding, and the molding is stabilized. In addition, there is an effect that the cycle time can be improved as compared with the thermal cycle molding.

It is preferable that the mold block forming the molded article cavity and the mold block forming the thick edge portion of the molded article are combined via a heat insulating material. In this way, even if the temperature conditions of the two are different, the temperature can be adjusted independently without affecting each other, and it is possible to obtain a thermo-economically effective mold without causing any trouble. This has the effect.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a concrete embodiment of the method for molding a plastic part according to the first invention will be described with reference to an embodiment of a mold according to the second invention used in the method. This will be described with reference to FIG.

FIG. 1 is a sectional view showing a main part of a mold for carrying out the molding method of the present invention. It should be noted that the state of the initial operation of bonding the dissimilar material members is also shown.

A specific example of the molding method shown in FIG. 1 is to form a so-called plastic laminate in which different kinds of material members are bonded. In this specific example, a polycarbonate plate 11 and a glass plate 12 are made of a thermoplastic material. The case of bonding and lamination with a resin will be described.

First, the mold 1 used is, as a whole,
A fixed mold block 2 and a movable mold block 3 are mounted on an injection molding machine (not shown) by a known means.
The cooling blocks 5 and 6 formed into an in-row structure so as to surround the periphery of the forming portion of the cavity 4 for receiving the stacked body are formed such that one is concave on the inside and the other is convex, and It is integrally fixed via a heat insulating material 7 having a thickness.

In the thus-formed mold 1, both the fixed-side mold block 2 and the movable-side mold block 3 circulate the heat medium at appropriate locations corresponding to the cavities 4 as in the conventional mold. Paths 8, 8 'are provided, respectively, and these flow paths 8, 8' are connected to heat sources (heating source and cooling source) by a control circuit (not shown). In each of the cooling blocks 5, 6, a refrigerant flow passage 9, 9 'is formed, and a cooling fluid is circulated and supplied from a cooling device (not shown) to the refrigerant flow passage 9, 9' via a control valve. It has become so.

FIG. 2 is an explanatory view showing an embodiment of the molding method according to the present embodiment. In order to mold the laminate 10 by injection compression molding using the mold 1 configured as described above, the laminate 10 is mounted on a well-known injection compression molding machine (not shown), and the fixed mold block 2 and the movable mold are mounted. A control circuit (not shown) is connected to heat sources (heating source and cooling source) in the flow paths 8 and 8 'of the respective heat mediums in the block 3 as in the prior art. Is operated such that a cooling fluid (hereinafter referred to as a cooling liquid) from a cooling device (not shown) is circulated and supplied.

First, as illustrated in FIG. 1, the glass plate 12 is placed on the cavity 4 of the movable mold block 3 with the mold 1 open, for example, facing the cavity 4 of the fixed mold block 2. , The polycarbonate plates 11 are respectively mounted. In this state, the mold is closed, and a molten thermoplastic resin (hereinafter, referred to as a molten resin) 15 is injected and injected into the cavity 4 from an injection nozzle (not shown) (see FIG. 2A).

As shown in FIG. 2A, the molten resin 15 injected into the cavity 4 is compressed by the advancement of the movable mold block 3 to move outwardly (in the direction of the arrow).
Flows to Then, the outer peripheral portion 4a of the cavity 4 becomes a space portion which is slightly wider than the end portions of the mounted polycarbonate plate 11 and glass plate 12, and is made thicker by the thickness of both. ing. Cooling blocks 5 and 6 are located around the outer peripheral portion 4 a of the cavity 4, and the refrigerant flow passages 9 and
Since the coolant is circulated through 9 ', the temperature of the cooling blocks 5 and 6 is lower than that of the cavity 4 in contact with the fixed mold block 2 and the movable mold block 3.

Therefore, the molten resin 15 flowing and filling the outer peripheral portion 4a of the cavity 4 is exactly as shown in FIG.
As shown in (b), the movable mold block 3 is cooled to a predetermined position until the movable mold block 3 advances and is compression-molded,
It is molded and solidified into a predetermined shape. Generally, the temperature of the molten resin at the time of injection and injection is about 200 ° C., and the temperature of the cooling liquid supplied to the cooling blocks 5 and 6 in this embodiment is 10 ° C.
In this case, the temperature at which the molded product is taken out from the mold in the molded state is 60 ° C., and the outer peripheral portion of the laminated molded body of the molten resin 15 molded by the outer peripheral portion 4 a of the cavity 4 is solidified to a temperature close to the temperature. .

The outer peripheral portion which becomes thicker while the molding operation proceeds in this way is surrounded by the cooling blocks 5 and 6 which are cooled separately from the fixed mold block 2 and the movable mold block 3 and injected. As soon as the cooling is started from the surface layer portion, the molding solidification speed of the outer peripheral portion is accelerated, and even if the layer of the molten resin 15 in the portion to be laminated and formed is not yet solidified, if the temperature approaches the molded product removal temperature, this In the case of a molded body, since the outer surface is solid and the adherend is solid, even if the mold is opened and the removal operation is performed, the treatment can be performed without any trouble.

Further, as in this embodiment, in the mold 1, the cooling blocks 5, 6 are attached to the main body (fixed and movable mold blocks 2, 3) around the outer periphery 4 a of the cavity 4. By separately providing a structure in which heat transfer is blocked by the heat insulating material 7, the flow of the molten resin is caused to overblow to the outer peripheral portion when performing the lamination molding (lamination molding) as described above, and this overflow is caused. By actively cooling the formed part to accelerate the solidification, it is possible to reduce the speed of taking out the molded product. FIG. 4 shows a graph of this case in comparison with the conventional method. As shown in FIG. 4, when the outer peripheral portion is cooled, the molding cycle time can be reduced by 120 seconds as compared with the conventional case where cooling is not performed. In addition, by cooling the thick portion of the outer peripheral portion, the thick portion is suppressed from becoming a flow leader (runner), and there is also an effect of preventing unexpected flow. The sample used in this test example was 600 × 400 × 2t (unit: mm, the same applies hereinafter).
When a polycarbonate plate is laminated and formed, a thick portion of 6 t is formed on the outer peripheral edge, and there is no cooling block: mold adjustment temperature of 60 ° C. With cooling block: mold adjustment temperature of 60 ° C. The test was performed at a block temperature of 30 ° C.

Further, according to the method of molding a plastic part of the first invention, in addition to performing the lamination molding as in the above-described embodiment, a molded article having a thick outer peripheral portion is molded. Even in this case, if the mold is injection-molded by incorporating a cooling block in the above-described manner in a portion corresponding to the outer peripheral portion of the cavity according to the shape of the molded product so as to be locally cooled, a molding cycle Time can be reduced.

Further, in the above description of the embodiment, it has been described that only the outer peripheral portion of the molded article to be molded is cooled.
In addition, a similar effect can be obtained by cooling a portion where the injected resin is directly in contact with the mold, such as an opening window or a cutout portion in lamination molding.

In addition, if the mold has an in-blow structure and the clearance of the in-blow portion is the same, the cooling of the in-blow member immediately reduces the fluidity of the resin in contact with the member. The effect of preventing the generation of burrs can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main part of a mold for performing a molding method of the present invention.

FIGS. 2A and 2B are explanatory views of an embodiment of a molding method according to the present embodiment. FIG. 2A shows an embodiment in which a molten resin is injected into a cavity of a mold and flows, and FIG. FIG. 3 is a diagram showing an aspect in which is formed by compression molding, respectively.

3A and 3B are diagrams showing a problem of a conventional molded article of a laminated body, wherein FIG. 3A is a cross-sectional view of a main part of the laminated molded article, and FIG. FIG. 3C is a cross-sectional view illustrating an aspect of a portion where a droop occurs, and FIG. 3C is a cross-sectional view of a main part of a conventional laminated body forming die.

FIG. 4 is a graph showing a comparative example between a case where the outer peripheral portion is cooled and a case where the outer peripheral portion is not cooled in lamination molding.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mold 2 fixed-side mold block 3 movable-side mold block 4 cavity 4a outer peripheral portion of molded product formation 5,6 cooling block 7 heat insulating material 8,8 'heat medium flow path 9,9' refrigerant flow path 11 polycarbonate Plate 12 Glass plate 15 Molten resin

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) // B29L 9:00 F term (reference) 4F202 AG23 AM32 CA11 CB01 CM01 CN05 CN12 CN22 4F206 AG23 AM32 JA07 JB11 JF05 JQ81

Claims (5)

[Claims] 1. When molding a plastic molded product,
A method for molding a plastic part, wherein a thick edge of the molded product is actively cooled to solidify the thick edge before other portions. 2. The method of molding a plastic part according to claim 1, wherein the thick edge of the molded article to be molded is set at a temperature lower than a temperature required for molding the surface of the cavity. 3. When laminating dissimilar material members together,
2. The mold according to claim 1, wherein the molten resin protruding from the molded product cavity to the outer peripheral portion is cooled and solidified in a mold, and the mold is opened immediately after reaching a temperature at which the molded product can be handled, and the molded product is taken out. Plastic parts molding method. 4. A mold characterized in that a mold block forming a molded product cavity and a mold block forming a thick edge portion of the molded product have a structure capable of independently controlling the temperature. . 5. A mold block forming the molded product cavity and a mold block forming a molded product thick edge portion,
The mold according to claim 4, wherein the mold is configured to be combined via a heat insulating material.