JP2008006788A - Surface-modification injection mold for thermoplastic resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-modification injection mold for a thermoplastic resin, which dispenses with the remodeling of a molding machine and the like and enables a material for modification, such as a relatively expensive metal complex, to be efficiently deposited in high concentration on the surface of a molded article without a loss by means of a standard molding machine. <P>SOLUTION: The surface-modification injection mold 10 for the thermoplastic resin is provided with a molten resin holding portion 30. In the holding portion 30 which can hold a molten resin inside, a modification material 3, consists of a metal complex melted into a high-pressure gas or a supercritical fluid, a metal alkoxide, or its modified material, and can be injected into and held in the proper portion of the held molten resin 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface-modified injection mold that realizes surface modification of a thermoplastic resin.

In recent years, techniques using a supercritical fluid such as supercritical carbon dioxide or a high-pressure gas such as carbon dioxide as a medium have been studied. Related art documents related to this include, for example, those shown in Patent Document 1 and Patent Document 2.
JP 2004-218062 A JP 2005-205898 A

  However, the conventional surface modification injection molding of a thermoplastic resin has the following problems.

  That is, the conventional surface modification injection molding of a thermoplastic resin has a structure in which a reforming material such as a metal complex dissolved in a supercritical fluid is introduced and held in a nozzle tip portion of a molding machine. Therefore, it is necessary to modify the screw / cylinder of the molding machine body, around the nozzle, and the nozzle sealing mechanism. In addition to these modifications, a special modification is required in terms of software for operating the molding machine.

  In addition, when molding by introducing a modifying material such as a metal complex dissolved in a supercritical fluid at the tip of the nozzle of an injection molding machine, if the mold is a cold runner, the sprue runner can be used together with the resin material. Loss of modifying materials such as complexes. Since metal complexes and the like are relatively expensive with respect to the resin material, in this case, it is inevitable that the molding cost increases.

  When the mold is a hot runner, there is a required volume and flow distance from the metal complex introduction position to the gate before the cavity. Therefore, when the molten resin moves from the introduction position to the gate, the modifying material such as the metal complex is dispersed in the pressure loss portion of the flow path, and the amount of the metal complex or the like deposited on the surface of the molded product tends to decrease. is there.

  There are sprue runners and dead spaces for both cold and hot runners. Therefore, if supercritical carbon dioxide in which a modifying material such as a metal complex is dissolved is injected in the vicinity of the molding machine nozzle, the metal complex is injected at a position where the metal complex is most precipitated on the surface of the molded article with little loss of the metal complex. Is extremely difficult.

  The present invention has been made in order to solve the above-described problems, and does not require modification of a molding machine. A standard molding machine is used to lose a relatively expensive metal complex or other modifying material. An object of the present invention is to provide a thermoplastic resin surface-modified injection mold that can be efficiently deposited on the surface of a molded product at a high concentration.

  The thermoplastic resin surface-modifying injection mold according to claim 1 of the present invention is capable of holding a molten resin therein, and a high-pressure gas or a supercritical fluid is provided in an appropriate portion of the held molten resin. And a molten resin holding part capable of injecting and holding a modifying material made of a metal complex, a metal alkoxide, or a modified product thereof dissolved in the resin.

  The thermoplastic resin surface-modified injection mold according to claim 2 of the present invention is the thermoplastic resin surface-modified injection mold according to claim 1, wherein the molten resin holding portion includes a gate. It is possible to communicate with a mold cavity via a hot runner and communicate with a sprue bush.

  The thermoplastic resin surface-modified injection mold according to claim 3 of the present invention is the thermoplastic resin surface-modified injection mold according to claim 2, wherein the molten resin holding portion is the hot resin mold. The reforming portion between the gate pin that opens and closes the gate and the periphery of the gate pin through the gate pin in a space having the connection portion with the runner as a substantially rear end and the gate as a tip. A cylindrical valve member that forms a passage for the material, and the tip opening of the passage can be opened and closed by contacting and separating the tip portion of the valve member and the tip back portion of the gate pin. It is what.

  The thermoplastic resin surface-modified injection mold according to claim 4 of the present invention is the thermoplastic resin surface-modified injection mold according to claim 3, wherein the gate pin is located behind the void. The gate opening and closing of the gate can be switched by operating the gate piston in the cylinder provided in the cylinder with the pressure fluid.

  The thermoplastic resin surface-modified injection mold according to claim 5 of the present invention is the thermoplastic resin surface-modified injection mold according to claim 3, wherein the valve member is provided in the space. The opening and closing of the front end opening of the passage can be switched by operating a valve piston in a cylinder provided on the rear side with a pressure fluid.

  A thermoplastic resin surface-modified injection mold according to claim 6 of the present invention is the thermoplastic resin surface-modified injection mold according to claim 3, wherein the valve member is arranged around an axis. The valve member can be rotated in a state in which the reformer is injected from the passage into the runner portion by opening the tip opening of the passage by separating the tip portion and the tip back portion of the gate pin. By rotating around the axis, the molten resin and the injected modifying material are agitated.

  The thermoplastic resin surface-modified injection mold according to claim 7 of the present invention is the thermoplastic resin surface-modified injection mold according to claim 6, wherein the valve member has the stirring efficiency. In order to ascend, a spiral uneven shape is provided on the outer periphery.

  The thermoplastic resin surface-modified injection mold according to claim 8 of the present invention is the thermoplastic resin surface-modified injection mold according to claim 6, wherein the molten resin holding portion is an injection mold. In order to promote uniform diffusion of the molten resin and the injected modifier by the flow of the resin, a spiral uneven shape is provided on the inner periphery of the runner portion.

  A thermoplastic resin surface-modified injection mold according to a ninth aspect of the present invention is the thermoplastic resin surface-modified injection mold according to the third aspect, wherein the molten resin holding portion is the empty mold. Equipped with a pressure-holding piston that bears the rear end surface of the plant, and in order to maintain the pressure of the molten resin injected with the modifier in a state where the back pressure of the molding machine is effective, the holding force of the molten resin by the pressure-holding piston is adjusted. It is characterized by being made possible.

  As described above, the present invention is capable of holding a resin in a molten state, and comprises a metal complex, a metal alkoxide, or a modified product thereof dissolved in a high-pressure gas or a supercritical fluid in an appropriate portion of the held molten resin. Because it has a structure with a molten resin holding part that can inject and hold the reforming material, it is possible to introduce the modifying material into the molten resin inside the mold, so a standard molding machine that does not require remodeling etc. Can be used to efficiently deposit a relatively expensive modifier such as a metal complex on the surface of a molded article at a high concentration without loss.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of a main part showing an embodiment of a thermoplastic resin surface-modified injection mold according to the present invention. The fixed-side mold 20 and the movable-side mold 60 are provided, and a cavity 70 is formed in the movable-side mold 60.

  The fixed-side mold 20 includes a sprue bush 21 to which the nozzle 1 of a molding machine (not shown) is in close contact, a hot runner 22 connected to the sprue bush 21, and a gate 23 leading to the cavity 70.

  The fixed-side mold 20 can hold a molten resin therein, and a metal complex, a metal alkoxide, or a modified product thereof dissolved in a high-pressure gas or a supercritical fluid in an appropriate portion of the held molten resin 2. The molten resin holding | maintenance part 30 which can inject | pour and hold | maintain the modifier 3 which consists of is provided.

  The molten resin holding unit 30 can communicate with the cavity (mold cavity) 70 through the gate 23, and can communicate with the sprue bush 21 through the hot runner 22. That is, the molten resin holding part 30 is disposed in a space 31 having a connection part with the hot runner 22 as a substantial rear end and a gate 23 as a substantial front end.

  FIG. 2 is an enlarged cross-sectional view of the main part of the fixed-side mold 20, and the molten resin holding unit 30 is inserted into the space 31 through the gate pin 40 that opens and closes the gate 23 and the gate pin 40. A cylindrical valve member 50 that forms a passage 45 of the reforming material 3 between itself and the periphery is provided. And the front-end | tip opening of the channel | path 45 can be opened and closed because the front-end | tip part 51 of the valve member 50 and the front-end | tip back part 41 of the gate pin 40 contact / separate.

  The rear end of the passage 45 is connected to the reformer inlet 24 at the rear of the space 31.

  The gate pin 40 can switch the opening and closing of the gate 23 by operating a gate piston 43 in a gate cylinder 42 provided behind the space 31 with a pressure fluid (gas or liquid). That is, the gate pin 40 closes the gate 23 by applying the pressure gas to the gate pin advance port 44a. Moreover, the gate pin 40 opens the gate 23 by applying pressure gas to the gate pin receding port 44b.

  The valve member 50 can switch opening and closing of the front end opening of the passage 45 by operating a valve piston 53 in a valve cylinder 52 provided behind the space 31 with a pressure fluid (gas or liquid). That is, the valve member 50 closes the front end opening of the passage 45 by applying the pressure gas to the valve member advancement port 54a. Moreover, the valve member 50 opens the front end opening of the passage 45 by applying the pressure gas to the valve member receding port 54 b.

  Further, the valve member 50 can be rotated around the axis by the action of a drive source (not shown). Therefore, as will be described later, the distal end portion 51 of the valve member 50 and the distal end facing portion 41 of the gate pin 40 are spaced apart to open the distal end opening of the passage 45, and the runner portion 35 holding the molten resin 2 is modified from the passage 45. In a state where the material 3 is injected, the valve member 50 is rotated around the axis, whereby the valve member 50 agitates the molten resin 2 and the injected modifying material 3.

  The valve member 50 includes a spiral concavo-convex shape, specifically, a concavo-convex spiral groove 56 on the outer periphery located in the runner portion 35 in order to increase the efficiency of stirring.

  The molten resin holding part 30 has a spiral concavo-convex shape on the inner periphery of the runner part 35 in order to promote uniform diffusion of the molten resin 2 and the injected modifier 3 by the flow of the resin during injection. Specifically, an uneven spiral groove 36 is provided.

  The molten resin holding unit 30 includes a pressure-holding piston 33 that bears the rear end surface of the cavity 31, and maintains the pressure of the molten resin 2 into which the modifying material 3 has been injected in a state where the back pressure of the molding machine is effective. The holding force of the molten resin 2 by the pressure piston 33 can be adjusted. That is, the holding force of the molten resin 2 can be adjusted by adjusting the pressure of the pressure fluid (gas or liquid) applied to the pressure holding piston holding port 34.

  As shown in FIG. 1, the movable mold 60 includes a counter pressure port 61 for applying a counter pressure to the cavity 70.

  Next, the operation of the above embodiment will be described with reference to FIGS.

  First, as shown in FIG. At this time, the pressure gas is applied to the pressure holding piston holding port 34 to hold the pressure holding piston at a predetermined pressure. Further, the pressure gas is applied to the gate pin advance port 44 a and the gate 23 is closed by the gate pin 40. Further, pressure gas is applied to the valve member advancement port 54 a, and the valve member 50 closes the front end opening of the passage 45. Then, the counter pressure is applied from the counter pressure port 61 to the cavity 70.

  In this clamped state, the molten resin 2 is introduced into the hot runner 22 and the molten resin holding part 30 from the nozzle 1 of the molding machine through the sprue bush 21. Further, the modifier 3 made of a metal complex, metal alkoxide or a modified product thereof dissolved in the supercritical fluid is introduced into the passage 45 from the modifier introduction port 24. At this time, since the front end opening of the passage 45 is closed, the modifying material 3 does not leak to the runner portion 35.

  Next, as shown in FIG. 4, the modifying material 3 is injected. That is, by applying pressure gas to the valve member retreating port 54b instead of the valve member advancement port 54a, the valve member 50 is retreated, and the tip part 51 and the tip back part 41 of the gate pin 40 are separated, The tip opening of the passage 45 is opened. Thereby, as shown by many small points in FIG. 4, the modifying material 3 is injected into the molten resin 2 held by the runner portion 35 from the front portion of the runner portion 35. The injected modifying material 3 spreads toward the back of the runner portion 35.

  Next, as shown in FIG. 5, the modifier 3 is kneaded. That is, first, instead of the valve member retreating port 54b, the pressure gas is applied again to the valve member advancement port 54a, the valve member 50 is advanced, and the front end opening of the passage 45 is closed. Thereby, injection | pouring of the modifier 3 is complete | finished. Thereafter, the valve member 50 is rotated around the axis by the action of a drive source (not shown), so that the valve member 50 agitates the molten resin 2 held by the runner portion 35 and the injected modifier 3. .

  At this time, since the valve member 50 includes the concave and convex spiral grooves 56 on the outer periphery located in the runner portion 35, high stirring efficiency is obtained. Therefore, the modifier 3 injected into the molten resin 2 held by the runner portion 35 is stirred together with the molten resin 2 and sufficiently kneaded.

  Next, as shown in FIG. 6, the resin holding pressure before injection is adjusted. That is, if the pressure of the molten resin 2 into which the modifying material 3 is injected in the molten resin holding part 30 increases by a certain level or more due to the injection / kneading of the modifying material 3, the back pressure of the molding machine may not be effective. In order to avoid this, the holding force of the molten resin 2 by the holding pressure piston 33 is adjusted in the pressure reducing direction by adjusting the pressure of the pressure gas applied to the pressure holding piston holding port 34 in the pressure reducing direction. Thereby, the pressure of the molten resin 2 into which the modifying material 3 is injected in the molten resin holding unit 30 is maintained in a state where the back pressure of the molding machine is effective.

  Next, injection is started as shown in FIG. That is, instead of the gate pin advance port 44a, the pressure gas is applied to the gate pin retract port 44b to open the gate 23. At the same time, pressure gas is applied to the valve member retreating port 54b instead of the valve member advancement port 54a, and the valve member 50 is retreated while the front end opening of the passage 45 is closed. As a result, the gate pin 40 moves backward together with the valve member 50, thereby injecting the molten resin 2 injected with the modifier 3 held in the runner portion 35 of the molten resin holding portion 30 into the cavity 70.

  At this time, since the molten resin holding part 30 includes the concave and convex spiral grooves 36 on the inner periphery of the runner part 35, the molten resin 2 and the injected modifying material 3 are caused by the flow of the resin at the time of injection. It spreads uniformly, and the uniform diffusion is promoted.

  Next, as shown in FIG. That is, the pressure of the resin 2 in the cavity 70 is maintained until the molten resin 2 into which the modifying material 3 has been injected sufficiently reaches all the corners of the cavity 70 or the skin layer in contact with the wall surface of the cavity 70 is cooled and solidified. Press.

  At this time, the modifying material 3 injected into the molten resin 2 gathers in the skin layer in contact with the wall surface of the cavity 70 and covers the surface of the molded product.

  Next, the gate 23 is closed as shown in FIG. That is, pressure gas is applied to the gate pin advance port 44a instead of the gate pin retract port 44b, and the gate 23 is closed by the gate pin 40. At the same time, pressure gas is applied to the valve member advance port 54a instead of the valve member retract port 54b, and the valve member 50 is moved forward with the front end opening of the passage 45 closed. When the gate 23 is closed, the application of the counter pressure from the counter pressure port 61 to the cavity 70 is released. Then cool it down.

  After the cooling is completed, the molded product taken out by opening the mold is deposited with metal fine particles formed by reducing the metal complex on the surface, and electroless nickel plating becomes possible.

  As an example of the molded product, a polycarbonate was used as the thermoplastic resin, and a disk shape having a gate of φ65 mm and a thickness of 1.2 mm was selected.

  In order to control the formation of the surface layer (skin layer) simultaneously with the injection molding of the disk shape, the surface-modified injection molding die 10 is configured to control the temperature of each part. That is, the temperature of the in-mold molten resin holding unit 30 is controlled to 325 ° C. The temperature of the fixed side mold 20 and the movable side mold 60 is controlled by 120 ° C. cooling water flowing through a temperature control circuit (not shown). The temperature of the plasticizing cylinder of the injection molding machine is 325 ° C.

  The gate 23 and the supercritical fluid inlet 24 in which the metal complex is dissolved can be sealed inside the mold. Moreover, it has a structure that stirs the supercritical fluid 3 in which the molten resin 2 and the metal complex are dissolved, and a spiral groove 36 that promotes diffusion during resin flow is cut in the outer wall of the runner portion 35. The molten resin holding unit 30 has a pressure adjusting mechanism (pressure holding piston 33). The driving source in the mold uses air or high-pressure gas, respectively. Further, portions of the mold that require airtightness are sealed by an O-ring (not shown).

  A thermoplastic resin (polycarbonate) rapidly plasticized and melted by a plasticizing cylinder (not shown) of an injection molding machine is measured from the nozzle 1 tip to the molten resin holding part 30 in the mold over a back pressure of about 5 to 6 MPa and filled. Suck back about 4mm later.

  With the seal of the gate 23 kept closed, the supercritical fluid inlet (the opening at the end of the passage 45) installed near the flow front part is opened, and hexafluoroacetylacetonate, which is a metal complex as a surface modifying material, is opened. Is introduced, 0.5 cc of supercritical carbon dioxide adjusted to 15 MPa and 45 ° C. is introduced, and the inlet (the opening of the end of the passage 45) is closed.

  After the introduction, the screw is advanced by the back pressure of the molding machine to increase the resin density, and the dissolution of supercritical carbon dioxide into the resin is promoted. At the same time, the stirring unit installed in the molten resin portion in the mold is operated (the valve member is rotated), so that the supercritical carbon dioxide is uniformly dissolved in the resin.

  Depending on the setting of the pressure and amount of supercritical carbon dioxide to be introduced, the back pressure of the molding machine may not work, so the pressure adjusting mechanism (holding piston 33) of the molten resin holding unit 30 is operated. . The pressure of the molten resin holding part 30 is reduced to a state where it can be held by back pressure, and held at a predetermined pressure, thereby suppressing foaming due to a pressure loss difference at the time of injection.

  There is also a method in which a seal is applied around the mold cavity 70 and a counter pressure using high-pressure carbon dioxide is used.

  Next, the mold cavity 70 is clamped by injection filling. During filling, diffusion of the metal complex is promoted by the spiral groove 36 cut in the outer wall of the runner portion 35. Since carbon dioxide is released from the flow front during filling with air in the cavity 70, an air vent is always provided in the mold when the counter pressure is not used.

  After completion of filling, the skin layer is held until cooling and solidification in the pressure holding step. Since the glass transition point of the skin layer portion is lowered by supercritical carbon dioxide, and the surface easily foams, the pressure is kept long enough not to foam, the gate 23 is sealed, and the process proceeds to the cooling step. When the process moves to the cooling process, the weighing process is started as the next shot process.

  After cooling is completed, the mold is opened and the molded product is taken out. Metal fine particles formed by reduction of the metal complex are deposited on the surface of the molded article, and electroless nickel plating becomes possible.

  According to the present invention, the modifying material can be introduced inside the mold, and since there is no need to modify the molding machine, surface reforming molding can be performed with a standard molding machine. Further, in the conventional apparatus, the loss of the metal material (modifying material) occurs due to the sprue / runner, dead space, etc., leading to an increase in molding cost. According to the present invention, the metal material is in a runner-less state. (Modified material) can be introduced into the part where it is efficiently deposited at a high concentration on the surface of the molded product, so that the molding cost can be reduced and the quality of adhesion strength when plating can be improved. it can.

  In the above-described embodiment, the supercritical fluid is used as a medium for a modifier formed of a metal complex, a metal alkoxide, or a modified product thereof, but the present invention is not limited to this, and if uniform mixing is possible, For example, a high-pressure gas such as carbon dioxide can be used as a medium for the modifier.

  Further, in the above embodiment, the adjustment of the holding pressure piston 33, the switching of the gate pin 40, and the switching of the valve member 50 are all performed with the pressure gas. However, the present invention is not limited to this. It is also possible to use.

It is a schematic sectional drawing of the principal part which shows one Embodiment of the surface modification injection mold of the thermoplastic resin by this invention. It is an expanded sectional view of the principal part of a stationary side metal mold | die. It is a schematic sectional drawing which shows a mold clamping process. It is a schematic sectional drawing which shows a modifier injection process. It is a schematic sectional drawing which shows a modifying material kneading | mixing process. It is a schematic sectional drawing which shows the resin holding pressure adjustment process before injection. It is a schematic sectional drawing which shows an injection start process. It is a schematic sectional drawing which shows a pressure holding process. It is a schematic sectional drawing which shows a gate closing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nozzle of molding machine 2 Molten resin 3 Reformer 10 Thermoplastic resin surface modification injection mold 20 Fixed mold 21 Sprue bush 22 Hot runner 23 Gate 24 Reformer inlet 30 Molten resin holder 31 Cavity 33 Holding pressure piston 34 Holding pressure piston holding port 35 Runner portion 36 Spiral groove 40 Gate pin 41 Front end facing portion 42 Gate cylinder 43 Gate piston 44a Gate pin advance port 44b Gate pin retreat port 45 Passage 50 Valve member 51 Tip portion 52 Valve cylinder 53 Valve Piston 54a Valve Member Advancement Port 54b Valve Member Retraction Port 56 Spiral Groove 60 Movable Side Mold 61 Counter Pressure Port 70 Cavity

Claims (9)

  A molten resin can be held inside, and a modifier made of a metal complex, metal alkoxide, or a modified product thereof dissolved in a high-pressure gas or supercritical fluid can be injected and held in an appropriate part of the held molten resin. A mold for surface modification injection molding of a thermoplastic resin, characterized by comprising a molten resin holding part.   2. The surface-modified injection molding of a thermoplastic resin according to claim 1, wherein the molten resin holding portion can communicate with a mold cavity via a gate and communicate with a sprue bush via a hot runner. Mold.   The molten resin holding part has a gate pin that opens and closes the gate, and a gate pin that opens and closes the gate pin in a space having a connection part with the hot runner as a substantially rear end and the gate as a tip. A tubular valve member that forms a passage for the reforming material between the tip of the passage and the tip of the valve member and the tip-back portion of the gate pin contacting and separating the tip of the passage The mold for surface-modified injection molding of a thermoplastic resin according to claim 2, wherein the opening can be opened and closed.   The surface of the thermoplastic resin according to claim 3, wherein the gate pin can be switched between opening and closing by operating a gate piston in a cylinder provided behind the void with a pressure fluid. Modified injection mold.   4. The heat according to claim 3, wherein the valve member is capable of switching opening and closing of a front end opening of the passage by operating a valve piston in a cylinder provided behind the space with a pressure fluid. Mold for surface modification injection molding of plastic resin.   The valve member is rotatable about an axis, and the reformer is supplied from the passage to the runner portion by separating the tip portion from the tip-back portion of the gate pin and opening the tip opening of the passage. 4. The surface-modified injection of a thermoplastic resin according to claim 3, wherein the molten resin and the injected reformer are agitated by rotating the valve member around an axis in the injected state. Mold for molding.   7. The mold for surface modification injection molding of a thermoplastic resin according to claim 6, wherein the valve member has a spiral irregular shape on the outer periphery in order to increase the efficiency of the stirring.   The molten resin holding portion is provided with a spiral uneven shape on the inner periphery of the runner portion in order to promote uniform diffusion of the molten resin and the injected modifier by injection of resin during injection. A mold for surface modification injection molding of a thermoplastic resin according to claim 6.   The molten resin holding unit includes a pressure holding piston that bears the rear end surface of the void, and maintains the pressure of the molten resin into which the modifying material is injected in a state in which a back pressure of a molding machine is effective. 4. The mold for surface-modified injection molding of a thermoplastic resin according to claim 3, wherein the holding force of the molten resin by the piston can be adjusted.

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