JP2000202865A - Molding die and manufacture of thermoplastic resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent clogging at a downstream end of a molten resin passage by providing a tapered port penetrating a nozzle disposed to expose with a molding space and enlarging toward a downstream side and a heat insulation passage at a molten resin passage, and providing heaters for heating and heat insulating them. SOLUTION: A molten resin passage 4 opened with a die cavity surface 7 exposed with a molding space and connected to communicate with a molten resin supply source is provided at a female mold 2. A downstream side passage 41 intersected with the surface is formed in a predetermined range of the downstream side, and a nozzle 5 is provided at its downstream side. A tapered port 51 enlarged in its diameter toward the molding space is penetrated through a center of the nozzle 5. Further, a supply tube 42 is continuously provided at an upstream side of the nozzle 5, and an upstream side in the passage 4 is connected to communicate with its upstream side. The tube 42 is heat insulated by a first heater 44 wound at a plurality of places of the tube 42 at a heat insulation passage 43. An annular second heater 52 is contained in the nozzle 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die used for molding with a thermoplastic resin,
In particular, it relates to a mold suitable for molding with a thermoplastic resin of a type having a small moldable temperature range.

[0002]

2. Description of the Related Art A thermoplastic resin is molded into a product by a method such as injection molding or injection compression molding. In each case, a molding space is formed in a pair of male and female molds. The molten resin filled in the molding space is formed into a product shape only by injection into the inside or by compression after the injection.

[0003] The downstream end of a molten resin passage in this type of conventional molding die is open to a molding space. Of the molten resin passage, a passage in a certain range including the open portion is usually formed in a straight line, and the upstream portion of the straight passage is kept warm by a heater. On the other hand, the opening of the open portion at the downstream end is often formed to penetrate a separately formed nozzle in order to prevent heat from being transmitted by the heater. Usually, since the opening communicates with the molding space, after the molding is completed, the molded body and the resin remaining in the opening are integrally joined together and removed together with the molded body. Therefore, in order to facilitate removal of the surplus molded product remaining in the mouth, the mouth is a tapered mouth expanding toward the molding space. Further, in order to prevent the adverse effect of the temperature of the molten resin on the molded product, the upstream end of the tapered opening is closed by the tip of the passage opening / closing pin after the molten resin is injected into the molding space. .

[0004] However, if the finish of the mouth surface is insufficient, the excess molded product may bite into the mouth and become clogged. There was a problem of sink marks.
Further, although excessive heat transfer from the molten resin passage to the molding space is prevented by the passage opening / closing pin, in some cases, the heat capacity of the passage opening / closing pin lowers the temperature of the nozzle. And the above-mentioned clogging phenomenon is likely to occur.

[0005] In particular, in the case of a resin having a small difference between the no-flow temperature and the decomposition temperature, that is, a resin having a narrow molding temperature range, the above-described resin clogging is likely to occur.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in view of the above-mentioned problem. "A molding space formed in a molding die comprising a pair of male and female molds is filled with a thermoplastic resin from a molten resin passage. The molten resin is supplied, and after the supply is completed, the molten resin passage is closed by a passage opening / closing pin. It is an object of the present invention to prevent the flow of the molten resin in the molten resin passage portion at the downstream end portion of the inside from flowing smoothly and to prevent clogging at the downstream end of the molten resin passage. * 1

[0007]

Means for Solving the Problems The technical means of the present invention taken to solve the above-mentioned problem is as follows.
A tapered mouth penetrating through a nozzle arranged to be exposed to the molding space and expanding toward the downstream side, and a heat retaining passage formed following the upstream side of the tapered mouth portion; A first heater that abuts against and separates from the upstream end peripheral edge of the tapered mouth to open and close the molten resin passage by opening and closing so as to open and close the molten resin passage; And a second heater that heats and maintains the tapered mouth portion forming portion of the nozzle.
It was that.

The above technical means operates as follows. Since both the tapered mouth portion and the heat retaining passage provided immediately before the molding space are heated to a predetermined temperature by the heater, the molten resin passage in the fixed range immediately before the molding space is kept warm. Further, since the constituent walls of the heat retaining passage and the nozzles are individually kept warm, it is easy to set the heat retaining temperature distribution to a predetermined distribution.

Thus, even if the mold is cooled by the cooling device during the molding cycle, it is possible to prevent the temperature of the tapered mouth portion forming portion of the nozzle from becoming excessively low. In addition, the portion communicating with the molding space expands toward the downstream side, that is, since it has a tapered mouth portion that expands toward the molding space, the clogging described above does not occur even after the molding is completed. .

[0010] In particular, it is more effective if the temperature of the nozzle is detected by incorporating a temperature sensor in the nozzle and the nozzle temperature is maintained at the set temperature based on the detected temperature.
If the temperature of the heat retaining passage heated by the second heater is detected and the temperature is controlled so as to be maintained at the set temperature, a further effect is obtained.

[0011]

According to the present invention having the above configuration, the following specific effects are obtained. Since the excess molded product does not occur, sink is unlikely to occur on the surface of the product opposite to the tapered opening. In addition, since the tapered mouth portion, which is a so-called sprue portion, has a tapered shape expanding toward the molding space, clogging of the resin in the sprue portion can be prevented.

Since the molten resin passage in the predetermined range immediately before the molding space reaching the molding space can be kept at a predetermined temperature, the phenomenon of resin clogging due to a decrease in the temperature of the nozzle is eliminated. Further, since the nozzle and the constituent wall of the heat retaining passage are separately heated and kept warm, it is easy to control the temperature distribution in these passage portions. * 2. In the above item 1, in which the inner surface of the tapered opening is covered with a smooth plating layer, the inner peripheral surface of the tapered opening is smooth in addition to the effect of item 1. As a result, the adhesion of the thermoplastic resin at the tapered opening can be reduced. Therefore, the clogging is less likely to occur. * 3 Clause 1 or 2 above, wherein the surface of the passage opening / closing pin is covered with a smooth plating layer.
Adhesion of the thermoplastic resin to the flow path wall surface or the passage opening / closing pin in the heat retaining passage can be reduced. Therefore, the resin replacement operation is easy and can be shortened. * 4. In the molding die described in the above item 2 or 3, in the case where "the plating layer is a plating layer of a ternary alloy of nickel, phosphorus and boron", the plating layer is subjected to an electroless plating treatment. Therefore, the plating layer can be reliably formed on the inner surface of the tapered opening, and particularly, the plating layer has high heat resistance and excellent abrasion resistance. The durability of the wall is improved. * 5. The method according to any one of items 1 to 4, wherein "the first cooling means for partially cooling a predetermined annular area of the mold wall surface located in the outer peripheral area of the mouth of the nozzle and exposed to the molding space." The heat generated by the first heater provided in the nozzle can be prevented from adversely affecting the molded product. * 6 In the above-mentioned items 1 to 5, in the case where "the second cooling means for partially cooling a predetermined range of the mold wall surface portion facing the mouth portion of the nozzle is incorporated", as in item 5, The adverse effect of the heat generated by the first heater provided on the nozzle on the molded product can be prevented. * 7. A thermoplastic resin form can be produced by the following process using the molding die described in section 1. (1) A step of maintaining the passage opening / closing pin at a position separated from the peripheral edge of the upstream end of the tapered mouth, and supplying the molten resin passage to the molding space in the molding die including a pair of male and female dies. (2) a step of bringing the passage opening / closing pin into contact with the peripheral edge of the upstream end of the tapered opening after the completion of the supply of the thermoplastic molten resin to block the molten resin passage; and (3) completing the supply of the thermoplastic molten resin. After or during the supply, the pair of male and female molds is clamped, and after the mold is clamped, the mold is cooled and after the solidification of the thermoplastic molten resin is completed, the male and female molds are molded (4). And removing the cooled and solidified product from the mold.

According to this method, the characteristics of the molding die described in item 1 are most effectively used. Here, it is desirable that "the closing pressure of the tapered mouth by the passage opening / closing pin is set to be higher than the mold clamping pressure".

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described together with the illustrated example. Overview of the molding die of the present invention,
As shown in FIGS. 1 and 2, the female mold (1) and the male mold (2) are opposed to each other, and these are fitted together to form a molding space (100).
In this embodiment, the present invention is applied to injection compression molding.

The male mold (2) has a molten resin passage (4) which is open to a so-called mold cavity surface (7) exposed to the molding space (100) and is connected to a molten resin supply source. A predetermined range on the downstream side of the molten resin passage (4) is a linear downstream passage (41) intersecting with the mold cavity surface (7). A nozzle (5) is provided at the downstream end of the downstream passage portion (41), and an end surface of the nozzle (5) is exposed to the molding space (100) and is flush with the mold cavity surface (7). Has become. In the center of the nozzle (5), a tapered mouth (51) whose diameter increases toward the molding space (100) penetrates.

A linear supply pipe (42) is connected to the upstream side of the nozzle (5), and the upstream end of the molten resin passage (4) is connected to the upstream end of the supply pipe (42). Communication is established.
The passage formed by the supply pipe (42) is a heat retaining passage (43), and the heat is kept by a first heater (44) wound around a plurality of locations of the supply pipe (42). The nozzle (5) has a built-in annular second heater (52) and a sensor (53) for detecting the temperature of the nozzle (5).

The lower part of the nozzle (5) and the outer peripheral area of the supply pipe (42) form an adiabatic space (11). Therefore, the heat of the first heater (44) and the second heater (52) is not directly conducted to the outer peripheral portion of the male die (2), that is, the outer peripheral region of the mounting portion of the nozzle (5). Absent. The heat of the heater is insulated by air. In this example, the tapered mouth portion (51) is a circular tapered through-hole portion, and the taper angle θ is generally about θ = 0.1 ° to 2 °, preferably θ = about 2 °. 0.5 ° to 1 °. The diameter of the inlet (50) at the upstream end of the tapered mouth (51) is 1 mm to 15 mm.
mm, preferably, diameter: 1.5 mm to 5 m
m.

A cylindrical passage opening / closing pin provided coaxially with the tapered opening (51) and upstream of the molten resin supply path.
(3) is provided coaxially with respect to the downstream passage portion (41), and penetrates downwardly through a constituent wall of the molten resin passage (4). The lower part of the passage opening / closing pin (3) is
The linear drive means (12), such as a hydraulic cylinder or an air cylinder, is connected to the output shaft of the linear drive means (12), and moves forward and backward in accordance with the operation of the linear drive means (12). The diameter of the passage opening / closing pin (3) is set to be larger than the diameter of the inflow port (50) at the upstream end of the tapered mouth (51), and the tip of the pin is tapered toward the upstream side. head
(31).

Therefore, as shown in FIGS. 2 to 4, when the passage opening / closing pin (3) is retracted downward from the tapered opening (51), the molding space (5) is formed through the tapered opening (51). 100) and the molten resin passage (4) communicate with each other, and as shown in FIG. 6, the tapered head (31) at the upper end of the passage opening / closing pin (3) has the tapered mouth portion.
When it comes into contact with the periphery of the inflow port (50) at the upstream end of (51), the tapered port (51) is closed, and the molten resin passage (4) is blocked. In this example, the tapered head portion and the inflow port portion (50) come in contact with each other, but may have a so-called surface contact where the tapered surfaces are fitted to each other.

As described above, by controlling the linear drive means (12), the passage opening / closing pin (3) advances and retreats to move the molten resin passage.
The resin supply circuit from (4) to the molding space (100) is opened and closed. When a product is molded using this molding die, as shown in FIGS. 3 and 4, with the female mold (1) opened to a predetermined degree with respect to the male mold (2), With the operation of (12), the passage opening / closing pin (3) is retracted downward (upstream side) from the tapered opening (51) to open the passage, and in this state,
Molding space from molten resin supply via molten resin passage (4)
Supply molten resin (M) to (100). At this time, by adjusting the distance between the tip of the passage opening / closing pin (3) and the nozzle (5), the opening of the passage opening / closing pin (3) can be adjusted, and the supply amount of the molten resin (M) can be adjusted.

When the supply amount reaches a predetermined amount, the linear drive means (12) is operated to move the passage opening / closing pin (3) to the closed position (FIGS. 5 and 6). ) Is closed at the specified pressure. As a result, the molten resin (M) supplied into the molding space (100) fills the molding space (100) which has been compressed and reduced to the final shape. Thereafter, when cooled to a predetermined degree, the molding is completed, and as shown in FIGS. 7 and 8, the female mold (1) is released from the male mold (2) again, and the product (40) is taken out.

In the above-mentioned series of molding steps, the heat insulating passage (4
3) is provided by the first heater (44), and the nozzle (5) is provided by the second heater (44).
The heater (52) maintains the temperature at a predetermined temperature suitable for the flow of the molten resin, so that the molten resin (M) supplied through the molten resin passage (4) is smoothly supplied into the molding space (100). You. Although it is not preferable for the heat of the first heater (44) to excessively move with respect to the molten resin (M) supplied into the molding space (100), in this embodiment, the nozzle (5) An annular water cooling passage (10) is formed in the outer peripheral area of the mold cavity surface (7) to prevent overheating of the outer peripheral area of the tapered mouth (51) in a predetermined range in the mold cavity surface (7).

The tapered mouth of the female mold (1)
A water cooling circuit (8) is provided in a portion facing (51),
Cold water is supplied from a cold water supply unit, and this portion is cooled to a predetermined temperature according to the type of resin. Thereby, the cooling rate of the molded product can be increased. Molding failure due to overheating of this portion can be prevented. The heat retention temperature of the first heater (44) and the heat retention temperature of the second heater (52) are set to predetermined temperatures depending on the type of resin and the like.

In particular, the temperature at which the second heater (52) keeps the temperature of the nozzle (5) as long as the temperature can be kept at 30 ° C. to 300 ° C. depends on the resin used and the diameter of the tapered opening (51). However, it is often controlled to about 50 ° C. For this temperature control, the second heater (52) may be turned on and off by feedback control based on the output from the sensor (53). In this example, when the temperature becomes 50 ° C. or more, the second heater (52) is used. Heating is stopped. The first and second heaters can prevent the inconvenience of excessive cooling, and can also prevent the inconvenience caused by the cooling.

Further, the inflow port (5) of the tapered port (51)
The diameter of 0) is about 1.5 mm to 15 mm, preferably 5 to 10 mm. Further, in this example, plating is performed on the surface of the tapered opening (51) and the surface of the passage opening / closing pin (3).
It is configured to slide with a predetermined fitting tolerance enough to seal the molten resin. With this plating layer, adhesion of the molten resin can be suppressed. Incidentally, the plating layer,
It may be formed on one of the surface of the tapered opening (51) and the surface of the passage opening / closing pin (3). Furthermore, the plating treatment may be applied to the entire area of the portion that comes into contact with the molten resin.

For example, the plating treatment may be a commonly used chromium electrolytic plating, electroless nickel plating or the like as long as the plating film has a predetermined heat resistance. To reliably plate the tapered mouth (51), electroless plating is preferable. In the case of electrolytic plating, it is difficult to form a plating layer on the hole, but in the case of electroless plating, such inconvenience does not occur. As a plating layer, a plating layer of a ternary alloy of nickel, phosphorus and boron is effective. This is because the heat resistance is high and the wear resistance is excellent.

The cross section of the passage opening / closing pin (3) may be an ellipse or a polygon other than the above-mentioned circle. In the case of a circle other than the circle, the tapered head (31) is moved by the axial direction. The shape is set to be hermetically sealed by contacting the upstream end of the mouth (51). Further, beryllium-copper alloy can be used for the nozzle (5), and ceramic can be used for the passage opening / closing pin (3) when the plating layer is not formed.

The driving force for pushing up the passage opening / closing pin (3) by the linear driving means (12) is converted into a pressure, which is larger than the clamping pressure of the female type (1) and the male type (2). It is desirable to set. Furthermore, the upper end surface of the passage opening / closing pin (3) does not necessarily have to be a tapered surface,
It may be flat or spherical as long as (50) can be closed.

In the above embodiment, the present invention is applied to the injection compression molding, but it goes without saying that the molding die of the present invention can be used for ordinary injection molding. As the thermoplastic resin applied to the present invention described above, in general injection molding, extrusion molding, stamping molding and the like, commonly used resins are applied, for example, polyethylene, polyolefin resin such as polypropylene, polystyrene, polycarbonate, Acrylic nitrile / styrene / butadiene block copolymer, general thermoplastic resin such as nylon,
Thermoplastic elastomers such as ethylene-propylene block copolymer, styrene-butadiene block copolymer,
Alternatively, these polymer alloys and the like can be mentioned.

In the present invention, among these resins, a resin having a small difference between the no-flow temperature and the decomposition temperature, that is, a resin having a narrow molding temperature range, for example, PPE /
Particularly suitable for molding using PA, ABS / PC, ABC / PA and the like.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory sectional view of a mold structure according to an embodiment of the present invention.

FIG. 2 is a detailed view of a nozzle (5) and a downstream passage portion (41).

FIG. 3 is an explanatory view at the time of supplying a molten resin in injection compression molding.

FIG. 4 is a detailed view of the nozzle (5) and its vicinity in the case of FIG.

FIG. 5 is an explanatory view of a state where the female mold (1) and the male mold (2) are closed.

FIG. 6 is a detailed view of the nozzle (5) and its vicinity in that case.

FIG. 7 is an explanatory view showing a state in which the female mold (1) and the male mold (2) are opened and the product is taken out.

FIG. 8 is a detailed view of the nozzle (5) and its vicinity at that time.

[Explanation of symbols]

(1): female mold, (2): female mold, (100): molding space, (7): mold cavity surface (4): molten resin passage, (41): downstream passage, (5): Nozzle, (50): Inlet, (51): Tapered mouth, (52): Second
Heater, (53): sensor, (42): supply pipe, (43): heat retaining passage, (44): first heater, (12): linear drive means, (3): passage opening / closing pin (31): taper Head, (11): Insulated hollow trunk, (40): Product (The same reference numerals in each figure indicate the same or corresponding parts.)

Claims (8)

[Claims] 1. A thermoplastic molten resin is supplied from a molten resin passage to a molding space formed in a molding die composed of a pair of male and female molds, and after the supply is completed, the molten resin passage is closed by a passage opening / closing pin. In a molding die for molding a thermoplastic resin molded product in a shut-off state, the molten resin passage penetrates a nozzle arranged so as to be exposed to the molding space and has a tapered shape expanding toward the downstream side. A mouth portion, comprising a heat retaining passage formed following the upstream side of the tapered mouth portion, abutting against and separating from the upstream end portion periphery of the tapered mouth portion, thereby forming the molten resin passageway. Forming a first opening / closing passage opening / closing pin that heats and heats the constituent walls of the heat insulation passage; and a second heater that heats and heats the tapered opening forming portion of the nozzle. Mold. 2. The molding die according to claim 1, wherein an inner surface of said tapered mouth is covered with a smooth plating layer. 3. The molding die according to claim 1, wherein a surface of the passage opening / closing pin is covered with a smooth plating layer. 4. The molding die according to claim 2, wherein the plating layer is made of nickel, phosphorus, or boron.
A molding die that is a plating layer of the original alloy. 5. A molding die according to claim 1, 2, 3 or 4, wherein a predetermined annular area of a wall surface of the molding die which is located in an outer peripheral area of a mouth of the nozzle and is exposed to the molding space. A molding die incorporating first cooling means for partially cooling the mold. 6. The molding die according to claim 1, wherein the second cooling part partially cools a predetermined area of the die wall surface facing the mouth of the nozzle. Molding mold with built-in means. 7. The molding die according to claim 1, wherein (1) the passage opening / closing pin is maintained at a position separated from the peripheral edge of the upstream end of the tapered mouth portion, and the pair of male and female molds is used. Supplying the molten resin passage to the molding space in the molding die (2) After the completion of the supply of the thermoplastic molten resin, the passage opening / closing pin is brought into contact with the peripheral edge of the upstream end of the tapered opening. Step of shutting off the molten resin passage (3) After the supply of the thermoplastic molten resin is completed or during the supply, the pair of male and female molds is clamped, and after the mold is clamped, the mold is cooled and then the thermoplastic molten resin is cooled. (4) removing the cooled and solidified product from the mold after the solidification of the mold is completed. 8. The manufacturing method according to claim 7, wherein a closing pressure of the tapered opening by the passage opening / closing pin is set to be larger than the mold clamping pressure.