JPS6117257B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plastic injection mold device with improved responsiveness to heating and cooling, and an injection molding method using the same.

Plastic injection molding has advantages such as a relatively wide degree of freedom in the shape of molded products, high speed molding using the same mold, and low production costs. Therefore, in recent years, they have been widely used in so-called engineering plastics such as cameras, watches, electrical products, and automobile parts. For the above-mentioned use as engineering plastics, the dimensional accuracy, density, optical properties,
Residual stress, uniform dispersion of fillers such as pigments, and uniformity of various physical properties such as strength and hardness are strongly required, and from the viewpoint of productivity, shortening of molding cycles is also required. In order to meet these demands, it is necessary to equalize the injection conditions for each shot during injection molding, especially the injection pressure and time, resin temperature, mold temperature, etc., to equalize the flow of resin, and to make injection molding It is important to make the subsequent cooling process of each part of the molded product uniform.

Furthermore, in the field of food containers such as dessert food cups, pharmaceutical containers, etc., molded products of the same type are often produced in large quantities, and there is a demand for thinner containers from the viewpoint of resource conservation. However, when molding thin-walled containers by injection molding, the flow orientation of the resin during injection becomes a problem, and this orientation causes the strength to decrease in the flow direction, making it more likely that cracks will occur in this direction. . Furthermore, in order to make the resin thinner, it is necessary to increase the injection pressure, which further promotes flow orientation. Therefore, there is a strong demand for an injection molding method in which flow orientation is less likely to occur even during thin wall molding.

On the other hand, in order to control the temperature of the injection mold equipment currently in use, a flow path for circulating a gas such as fluorocarbon gas, carbon dioxide gas, or nitrogen gas or a cooling medium such as cold water is required in the mold. Alternatively, a channel for circulating a heating medium such as hot water, steam, or high-temperature oil may be provided in the mold, or a band heater, casting heater, etc. may be installed inside the mold or on the outside surface of the mold. Mainly, either one of the following methods has been used:
Alternatively, performing heating and cooling simultaneously or alternately within the same mold requires temperature increases and decreases in considerable parts, including the target mold part and the mold part that comes into contact with the flow path of the heat medium. However, it has extremely poor thermal response and consumes a lot of energy, making it impractical. Therefore, as mentioned above, in order to improve the dimensional accuracy of molded products, prevent flow orientation, eliminate non-uniformity of residual stress, improve formability, etc., it is necessary to improve the molding surface of the mold. Despite the need for rapid heating and cooling as well as precise temperature control, the reality is that no injection molding mold apparatus or injection molding method has been developed to achieve this.

The present invention relates to an injection mold that has extremely good thermal responsiveness both temporally and spatially and to an injection molding method using the same, in order to solve the above-mentioned problems in injection molding. Here, "good thermal response in terms of time" means that the temperature of the molding surface of the mold increases or decreases rapidly in a short time, and "good thermal response in space" means that the temperature of the molding surface of the mold increases or decreases rapidly in a short time. This means that a sharp temperature gradient can be created on the heating side or cooling side with respect to positional changes on the molding surface or positional changes in the thickness direction of the mold.

More specifically, the injection mold device according to the first invention of the present application has a layered heating and cooling element provided along the molding surface on at least a part of the surface layer of the molding surface, and a separate layer inside the mold. A semiconductor comprising a system heating and/or cooling device, the heating and cooling element comprising a large number of n-type semiconductors and p-type semiconductors arranged alternately in a plane and connected in series with conductors on the front and back surfaces thereof. It is characterized by having a structure in which a bonded body is sandwiched between integral insulating layers.

Further, the injection molding method according to the second invention of the present application relates to one method of using the above-mentioned mold device, and uses the above-mentioned mold device, and before injection of the resin in the mold cavity, the above-mentioned layered heating and cooling is performed. A direct current is applied so that the element heats the molding surface, and then
Before and after injection of the resin into the cavity, the molding surface is cooled by stopping the energization to the layered heating/cooling element or reversing the direct current, and the molded body is released from the mold after cooling. It is.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the drawings. In addition, in all the figures below, similar parts are represented by similar symbols. Furthermore, in all the figures except for FIG. 2, illustrations of conductive wires leading from the layered heating/cooling element to the power source, knock pins for mold release, protruding pins, etc. are omitted.

FIG. 1 is an enlarged sectional view of the vicinity of the molding surface of an embodiment of the injection mold device of the present invention, in which a pair of base molds 1a and 1b includes a heating and/or cooling device 2a, 2b is provided. These devices 2a and 2b consist of temperature regulating fluid passages or heaters, etc., and keep the foundation molds 1a and 1b at a predetermined temperature, and serve as a heat source when heating the molded product or as a heat sink when cooling it. It is something. These heating and/or cooling devices 2
a and 2b are similar to those used in conventional injection molding mold apparatuses, and no particular explanation is required. When a heating device and a cooling device are used together, they are of course provided separately to some extent. Layered heating and cooling elements 3a and 3b are provided on the foundation molds 1a and 1b, respectively, and surface mold layers 4a and 4b are provided on top of the layered heating and cooling elements 3a and 3b.
Form aa, 4bb and cavity 5.

The layered heating and cooling elements 3a and 3b have essentially the same structure, and the detailed cross-sectional structure thereof is as shown in FIG. That is, generally, the layered heating/cooling element 3 is obtained by alternately arranging a plurality of n-type semiconductors 31 and p-type semiconductors 32 in a plane and joining them in series with conductors 33 alternately on the front and back surfaces. It has a structure in which a semiconductor assembly is sandwiched between a pair of insulating layers 34. The semiconductor assembly of this layered heating/cooling element is connected to a DC power source 36 via a conducting wire 35, as schematically shown in FIG. 2, when necessary. When connected in this way, the well-known Peltier effect occurs, and heat generation occurs on the surface 37 where electrons flow from the n-type semiconductor 31 to the p-type semiconductor 32 at the contact point, and on the surface 37 where electrons flow in the opposite direction.
At 8, cooling occurs. This heating surface 37 and cooling surface 38
The relationship becomes reversed if the direction of current supply to the layered heating/cooling element 3 is reversed. At this time, the space 39 between each semiconductor
An air layer is formed between the semiconductors and serves as an electrical and thermal insulation layer between the semiconductors, and a temperature sensor (not shown) is provided if necessary.
The thickness of the individual semiconductors 31 and 32 is 1 mm or less, and the thickness of the element 3 as a whole is suppressed to 2 to 5 mm.
It is possible to give a temperature difference of about 70℃ between
Moreover, this temperature difference can be further increased by stacking the layered heating and cooling elements 3. In addition, since the heat capacity of the element 3 itself is very small, the first
When arranged as shown in the figure, surface mold layers 4a, 4b
By keeping the thickness relatively thin, for example, 10 mm or less, the temperature of the molding surface including the surface mold layers 4a and 4b can be rapidly raised and lowered. That is, it is possible to provide a molding surface with good temporal thermal response.

Examples of semiconductor materials include PbTe,
Bi ₂ Te ₃ , PbSe, InAs, InP, Ge, Si, Sb ₂ Te _{3 ,} etc. are used, and among them, the quaternary alloy of Bi-Te-Se-Sb takes into account electrical resistance, thermal conductivity, and Peltier effect. Most preferred. For example, when Bi ₂ Te ₃ is used as a base, CuI, AgI, etc. can be added to obtain an n-type semiconductor 31, and Bi can be added to obtain a p-type semiconductor.

The material of the conductor 33 that connects the n-type and p-type semiconductors may be any material as long as it has good conductivity, and general metals such as Cu, Ag, Sn, Zn, etc. may be used, and if necessary, it may be used for bonding. Bonding materials such as high-temperature solder and low-temperature solder are used for this purpose. Further, connection to the semiconductor may be performed by any method such as soldering, silver brazing, welding, or welding.

As the insulating layer 34, a material that is excellent in electrical insulation and preferably also has good thermal conductivity is used. For example, plastics, rubber, ceramics, and composites thereof can be used, and ceramics, especially beryllia ceramics, are most preferred because of their smooth surface finish, strength, and thermal conductivity.

In order to obtain a mold device with better temporal thermal response than that shown in FIG. 1, a layered heating and cooling element 3 can be provided in the very surface layer of the mold, as shown in FIG. At this time, it is preferable to provide surface treatment layers 6a, 6b on the surfaces of the layered heating/cooling elements 3a, 3b in order to improve the smoothness of the molding surface and the releasability of the molded product. Examples of such surface treatment layers 6a and 6b include metal vapor deposition, sputtering, ion blating, plating, etc. when a ceramic layer is provided as the insulating layer 34 in FIG. 2. Therefore, in this specification, "along the molding surface" refers to the case where the molding surface is formed almost entirely by the layered heating/cooling element 3 itself as shown in FIG. This includes both cases in which the layered heating/cooling element 3 is arranged approximately parallel to the molding surface at a relatively shallow distance of 10 mm or less from the molding surface.

In the mold apparatus of the present invention, the layered heating and cooling element 3 can be provided along only a part of the molding surface of the mold. For example, FIG. 4 is a cross-sectional view of another embodiment of the mold apparatus of the present invention for molding a pot with legs. 5a and the thinner parts 5b at the top and bottom. However, in the leg portion 5a, the high temperature resin flows in the largest amount and for the longest time, and is the portion where cooling is slowest. For this reason, in the conventional mold apparatus, molding is performed in accordance with the cooling time of the thick portion 5a, and the molding cycle has to be lengthened. but,
As shown in FIG. 4, according to the present invention, the heating/cooling element 3 is arranged along the thick portion 5a so that its cooling surface 38 faces the thick portion 5a, and by applying direct current to this portion, Since cooling can be accelerated, the overall molding cycle can be shortened accordingly.

In the mold apparatus of the present invention, the heating/cooling element 3 can be subdivided and wired for each unit to heat and cool them individually, or to change their heating/cooling capacity. For example, FIG. 5 is a sectional view of another embodiment of the mold apparatus of the present invention for obtaining disc-shaped resin molded bodies with different wall thicknesses, and the resin entering the cavity 5 through the sprue 8 passes through the cooling passage. Fund types 1a and 1b cooled by passing cooling water
However, because the thickness of the resin inside the cavity 5 differs, a uniform cooling rate cannot be obtained. For this purpose, concentrically divided layered heating/cooling elements 3a _{1 to 5} and 3b _{1 to} 5 are provided along the molding surface, and additional, and different Cool the load (or partially heat it if necessary). That is, the elements 3a _{1 to 6} and 3b _{1 to 5} are
In order to compensate for the differences in the cooling process caused by the differences in wall thickness of each part of the molded object and the difference in the flow position of the resin, the current is controlled independently for each part, allowing uniform and rapid cooling while controlling the cooling capacity. That is. This makes it possible to reduce the residual stress distortion caused by non-uniformity in the cooling process in each part of the molded product, to obtain a high-quality molded product, and to shorten the molding cycle.

The injection molding method of the present invention utilizes the property of the above-mentioned layered heating/cooling element 3 that the heating surface and cooling surface can be easily and quickly reversed by changing the direction of energization. For example, FIG. 6 is a cross section of another embodiment of the mold apparatus of the present invention for molding thin-walled containers, and the resin injected from the hot runner 7 flows through the flow channels 2 ₁ to 2 ₄ for temperature adjustment. Fund type 1a, 1b _1-4 whose temperature is controlled by fluid
In addition to this temperature, it is introduced into the cavity 5 which has been heated in advance by the layered heating/cooling element 3 with sufficient fluidity despite its thin wall. Next, at the same time as the molten resin is injected and starts filling into the cavity 5, or in some cases earlier in consideration of the heat capacity of the mold, the direction of energization to the heating and cooling element 3 is reversed and the cavity is filled. Activate the cooling function to 5. This makes it possible to start cooling almost at the same time as the filling of the resin into the cavity 5 is completed, and to perform rapid cooling. The resin then cools below its softening point and solidifies before being released from the mold.

According to the injection molding method of the present invention described above, when molding a thin-walled container with a wall thickness of 0.2 to 1 mm, for example, the injection mold is at a sufficiently high temperature, so the injection molding pressure can be extremely low. . Also, along with this, (a) high pressure hydraulic pressure is not required, (b) there is no need for the mold strength to withstand high pressure, and (c) there is less orientation due to good fluidity within the mold. (d) It has high formability and does not cause short molding, and (e) It also avoids lengthening of the overall molding cycle. Benefits such as:

[Brief explanation of the drawing]

1 and 3 are sectional views of essential parts of an embodiment of the mold apparatus of the present invention, FIG. 2 is an enlarged schematic sectional view for explaining the detailed structure and operation of the layered heating/cooling element, and FIG. 6 to 6 respectively show cross-sectional views of other embodiments of the mold apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Fund type, 2... Heating and/or cooling device, 2 ₁ , 2 ₂ , 2 ₃ , 2 ₄ ... Temperature adjustment fluid passage, 3... Layered heating and cooling element, 4... Surface mold, 4aa, 4bb... Mold molding surface, 5... Cavity (filling resin), 6... Surface treatment layer, 7... Hot runner, 8... Sprue, 31... N-type semiconductor, 32... P-type semiconductor , 33... conductor, 3
4...Insulating layer, 35...Conducting wire, 36...DC power supply, 37...Heating surface, 38...Cooling surface, 39...
space. The subscripts a and b in 1a, 1b, 2a, 2b, etc. indicate individual members of a pair of molds. 1c,
The subscripts c and d in 1d etc. indicate additional mold parts depending on the molded product. 1b ₁ , 1b ₂ ...
..., 3a ₁ , 3a ₂ , 3b ₁ , 3b ₂ , etc., the subscripts ₁ , ₂ , . . . indicate divided parts of each member.

Claims (1)

[Claims] 1. A layered heating and cooling element is provided along the molding surface on at least a part of the surface layer of the molding surface, and a separate heating and/or cooling device is provided inside the mold. , the heating/cooling element has a structure in which a semiconductor assembly is sandwiched between a pair of insulating layers, in which a plurality of n-type semiconductors and p-type semiconductors are alternately arranged in a plane and connected in series with conductors on the front and back surfaces thereof. An injection mold device comprising: 2. The layered heating/cooling element is provided at a portion of the molding surface where cooling is delayed due to differences in the wall thickness of the molded object or due to differences in the flow position of the resin, thereby eliminating the partial cooling delay of the molded object and improving the molding cycle. The mold device according to item 1 above, which improves. 3. The mold according to item 1 above, in which the layered heating and cooling elements are provided in pieces along the molding surface and can be independently controlled, thereby enabling uniform cooling at each position along the molding surface. Device. 4 A layered heating and cooling element is provided along the molding surface on at least a part of the surface layer of the molding surface, and a separate heating and/or cooling device is provided inside the mold, and the heating and cooling element is A mold device is used which has a structure in which a semiconductor assembly is formed by arranging a large number of n-type semiconductors and p-type semiconductors alternately in a plane and joining them in series with conductors alternately on the front and back surfaces, which is sandwiched between a pair of insulating layers. , before the resin is injected into the mold cavity, direct current is applied to the layered heating and cooling element to heat the molding surface, and after that, before and after the resin is injected into the mold cavity, the layered heating and cooling element is An injection molding method characterized by cooling the molding surface by stopping the current supply or reversing the direct current, and releasing the molded product after cooling.