JP2005324483A - Injection molding nozzle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding nozzle which can improve moldability despite the fact that a hard workable material with increased viscosity as a molding material such as a rubber or a heat-curable resin. <P>SOLUTION: In this injection molding nozzle, the molding material supplied from a screw 13 of a cylinder part 11 is temporarily stored in a heating chamber 12b of a nozzle part 12, then the molding material which is temporarily stored inside the heating chamber 12b is heated up to a melting temperature complying with the material characteristics of the molding material and this heating-up state is kept as it is until the completion of injection by an induction heating coil 15 positioned outside the nozzle part 12. Further, simultaneously with the completion of injecting the molding material temporarily stored inside the heating chamber 12b, the interior of the heating chamber 12b is cooled by a refrigerant supplied to a cooling channel 12a, and at the same time, the supply of the refrigerant is suspended during heating by the induction heating coil 15 and the current temperature of the nozzle part 12 is monitored by a temperature sensor 16. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an injection molding nozzle, and more particularly to an injection molding nozzle using a vulcanized rubber or a thermosetting resin as a molding material.

  In recent years, products made of rubber or thermosetting resin as molding materials are filled with inorganic materials such as carbon black and magnetic powder fillers and carbon fibers and graphite fibers according to the properties required for the products. Achieves high performance such as performance and strength.

  However, in recent years, there has been a demand for further improvements in performance such as high strength and high elasticity and functions such as wear resistance, high conductivity, and high magnetic force, and in order to improve these performances, With the increase in the types of fillers such as the inorganic materials described above, the filling amount tends to increase.

  On the other hand, when the filling amount of these fillers is increased, the viscosity of the whole material is increased. In addition, the viscosity of the molding material increases, in other words, the fluidity of the material decreases. As a result, when these molding materials are used in an injection molding machine and injection molding is performed, the degree of workability with respect to a molding die and an injection nozzle is significantly deteriorated.

  In order to improve such a decrease in fluidity, a method of blending a compounding agent such as a plasticizer or a softening agent is used. However, a new problem that the physical properties of the material are lowered as the blending amount is increased. Will occur.

  As described above, with regard to the characteristics of the molding material, the improvement in performance and the improvement in moldability are in a trade-off relationship.

  In order to improve the fluidity by reducing the viscosity of the polymer material, techniques such as increasing the size of the molding machine, changing the molding material, using carbon dioxide gas, and controlling the temperature of the molding material are used.

  In these cases, for example, when the molding machine is enlarged, it is possible to surely mold at a high injection pressure, but it is necessary to secure a wide machine installation space. In addition, since the strength and durability of machine component parts are limited, it is not realistic to introduce a molding machine that exceeds the performance of current molding machines.

  In addition, when the molding material is changed, it is possible to add processing aids and plasticizers such as low molecular weight substances and higher fatty acid esters, or widen the molecular weight distribution of the polymer and introduce low molecular weight materials. The melt viscosity is reduced. However, when such a method is used, not only mechanical properties such as tensile strength and physical properties such as chemical resistance are deteriorated, but also it is a factor that adheres to the mold and causes mold contamination.

  Further, when a method of dissolving carbon dioxide gas in the polymer is used, it is possible to expect an effect that the glass transition temperature is lowered and the viscosity is lowered due to this. However, when such a method is used, not only the equipment (for example, a seal of a molding machine) necessary for dissolving carbon dioxide gas in the material becomes a complicated structure, but also in the molded product. Since the gas that has entered may cause appearance defects such as foaming, it is not yet recognized as a general molding method.

  In addition, when the melt temperature is lowered by increasing the material temperature and the molding processability is improved, inorganic materials are used to improve the quality of rubber and thermosetting resins, particularly molded products such as the performance and functions described above. Molding materials with an increased filling amount of fillers such as materials (hereinafter such molding materials are referred to as “difficult-to-process molding materials”) are molded by reaction solidification by three-dimensional crosslinking. The occurrence of scorch) becomes a problem. That is, this scorched material not only becomes a defective product when it enters the product, but also tends to stay in the molding machine cylinder and the molding nozzle, causing a molding defect and reducing productivity. There is a problem of becoming.

  FIG. 7 shows an example of an injection molding machine that raises the temperature of such a material (see Patent Document 1 below), and is a cross-sectional view of a nozzle peripheral portion in a metal injection molding machine.

  In FIG. 7, 1 is a cylinder that serves as a passage for molten metal as a molding material, 2 is a nozzle disposed on the tip side of the cylinder, that is, on the downstream side of the cylinder 1 in the injection direction of the molding material, and 3 is disposed in the cylinder 1. It is a screw that extrudes molten metal.

  A nozzle heater 4 is mounted on the outer peripheral base side of the nozzle 2. The nozzle heater 4 is temperature-controlled by a thermocouple 5. An induction heating coil 6 is mounted on the outer peripheral tip side of the nozzle 2. The temperature of the heating coil 6 is controlled by a thermocouple 7.

  The temperature of the nozzle 2 is rapidly controlled by the induction heating coil 6 so that a solid plug (not shown) that seals the tip end of the nozzle 2 is jetted immediately before entering the injection holding pressure process. The heating of the nozzle 2 is completed simultaneously with the end of the injection pressure holding process.

  Specifically, in the entire injection process, mold closing → mold touch → mold clamping → nozzle advance → injection → holding pressure → cooling → mold opening → extrusion → mold closing is fundamental. A series of “injection → holding pressure” steps in this cycle is called an injection holding pressure process. In the injection process, the interior of the cavity (not shown) is filled with a molding material, and in the pressure holding process, the cavity is further pressed to apply pressure to the interior of the cavity to increase the density of the molded product. The behavior of the screw itself operates in the forward direction, but the screw hardly operates at the time of holding pressure compared to the time of injection, and mainly applies pressure. Further, after the mold clamping process, there is a nozzle touch in which the nozzle advancement process is entered and the tip of the nozzle 2 and a mold (not shown) are joined.

  However, the technique disclosed in Patent Document 1 targets a molten metal as a molding material. Molten metal is a molding material that can be melted by reheating, and is limited only to molding at a temperature higher than a certain level. Therefore, as described above, it is impossible to eliminate the problem of scorch generation in the case of difficult-to-work molding materials using rubber or thermosetting resin.

  That is, in the case of injection molding using a metal and a thermoplastic resin as a molding material, the temperature of the cylinder 1 and the nozzle 2 is higher than the temperature of the molding die. However, when injection molding is performed using a molding material of rubber and thermosetting resin, the temperature of the cylinder 1 and the nozzle 2 is lower than the temperature of the molding die.

  Specifically, since the temperature of the cylinder 1 and the nozzle 2 is kept at a low temperature of 100 ° C. or less, the injection pressure is high and the injection time is also long. On the other hand, the temperature of the molding die needs to be a high temperature of 180 ° C. or higher because material solidification (giving shape) involves a crosslinking reaction.

  Accordingly, when the metal and thermoplastic resin are used as the molding material, it is important to heat the nozzle 2 in order to prevent the material from solidifying. However, in the case of rubber and thermosetting resin, a cooling mechanism is added. It is important to maintain the temperature at a predetermined temperature with high accuracy. That is, in order to increase the accuracy of temperature adjustment control, a cooling means is required.

  Incidentally, Patent Document 2 described below also discloses an example in which a high-frequency induction heating coil is provided, but this is only temperature control by a high-frequency induction heating coil, and no active cooling means is disclosed.

  As an injection molding machine using a cooling means, there is a technique disclosed in Patent Document 3 below. The temperature control disclosed in Patent Document 3 is a temperature control that uses both a heating action by induction heating and an endothermic action (cooling action) by cooling water, and is applied to a rubber injection molding apparatus.

  Specifically, a cooling passage is formed on the axis of the injection molding nozzle and on the outer wall, and a plurality of through holes are formed in the middle of the inner and outer double cooling passages along the axial direction and near the tip thereof. The rubber material injected from the through hole is heated to the required vulcanization temperature within a short time by induction heating, and the rubber material remaining in the plurality of through holes is cooled except during injection molding. Scorch can be prevented.

  However, in the technique disclosed in Patent Document 3, since the through holes for extruding and transferring the rubber material generate shear heat, the inner diameter of each through hole is reduced to 3.5 mm and a large number of through holes are required. Yes.

  Usually, the reason why the injection pressure increases in rubber injection molding is that pressure loss occurs in a portion that is sharply narrowed from the enlarged portion. Therefore, as disclosed in Patent Document 3, it flows from the supply side of the molding material (equivalent to the screw 3 shown in FIG. 7) to the narrowed through hole, so even if only this through hole is heated, There is a problem that it is not suitable for the current difficult-to-process molding material in which the amount of filler increases and the melt viscosity tends to increase.

  At the same time, in Patent Document 3, since the cooling water for cooling stays in the nozzle at the time of heating, the temperature of the cooling water also rises at the time of temperature rise, which requires extra heat and time, and a new production It becomes a factor of sex decline.

  An induction heating hot tip for an injection mold comprising a resin heating element for heating an injection molding resin, a heating coil for induction heating the resin heating element, and an insulating layer for covering and insulating the heating coil, Patent Document 4 below discloses an induction heating hot tip for an injection mold in which a coil bobbin having a plurality of partition walls is provided on a winding layer of a heating coil and the heating coil is wound along the partition walls of the coil bobbin.

  However, the one disclosed in Patent Document 4 stabilizes the temperature distribution in the hot chip by providing a bobbin having a partition wall for aligning and winding the induction heating coil and managing the winding position and the number of turns. Although the temperature of the resin heated by heating can be made uniform, the actual situation is that the structure does not allow rapid temperature control.

Japanese Patent Laid-Open No. 11-300462 Japanese Patent Laid-Open No. 5-159954 JP-A-8-34034 JP 2003-260728 A

  As described above, regarding the temperature management technology for ensuring the fluidity of difficult-to-process molding materials, the technology disclosed in Patent Document 1 is applied to an injection molding nozzle using rubber or thermosetting resin as a molding material. In the technique disclosed in Patent Document 2, only a temperature control by a high-frequency induction heating coil is performed, and a stacked cooling means is not disclosed. In the technique disclosed in Patent Document 3, the amount of the filler is small. It is difficult to apply to current difficult-to-process molding materials that tend to increase in melt viscosity, and the technology disclosed in Patent Document 4 enables rapid temperature control of difficult-to-process molding materials. There is a problem that it is not.

  In order to solve the above problems, the present invention uses rubber or a thermosetting resin as a molding material, and also uses a difficult-to-work material in which the viscosity of the molding material is increased to improve the quality of the molded product. It aims at providing the nozzle for injection molding which can improve the moldability.

  In order to achieve the object, an injection molding nozzle according to claim 1 includes a nozzle portion having a heating chamber for temporarily storing a molding material supplied from a screw of a cylinder portion, and an outer side of the nozzle portion. An induction heating member that is positioned and temporarily heated to the melting temperature corresponding to the material characteristics of the molding material temporarily stored in the heating chamber and maintains the temperature rising state until the completion of injection, and temporarily in the heating chamber A cooling unit that cools the heating chamber by supplying a refrigerant simultaneously with completion of injection of the stored molding material and stops supplying the refrigerant when heated by the induction heating member, and a temperature sensor that monitors the current temperature of the nozzle unit. It is characterized by.

  The nozzle for injection molding according to claim 2 is characterized in that the volume of the heating chamber is a space equal to or larger than the volume required for product molding.

  The nozzle for injection molding according to claim 3 is used for molding rubber or thermosetting resin.

  According to the temperature control method for an injection molding nozzle according to claim 4, the cooling of the nozzle portion is completed at the start of the start of the molding machine, and induction heating is performed during the period from the completion of the mold closing to the injection mold. Heating by a member is performed to lower the melt viscosity to improve the molding processability, and the nozzle portion is cooled by the refrigerant during the period from the start of injection to the start of the molding machine in the next process.

  The temperature management method for an injection molding nozzle according to claim 5 is characterized in that the refrigerant is removed from the cooling section during heating by the induction heating member.

  A temperature management method according to a sixth aspect of the present invention is used for the injection molding nozzle according to the first, second, or third aspect.

  The method for molding rubber or thermosetting resin according to claim 7 is characterized in that an injection molding nozzle temperature-controlled by the method according to claim 4, 5 or 6 is used.

  The molding method according to claim 8 is characterized in that the molding method is applied to rubber or thermosetting resin highly filled with a filler.

The molding method of claim 9, the shear viscosity at 90 ° C. is applied to 10 ⁴ Pa · s highly filled filler-containing rubber also thermosetting resin (for shear rate of ^10/2 sec) It is characterized by.

  According to the injection molding nozzle of the present invention, the molding material supplied from the screw of the cylinder part is temporarily stored in the heating chamber of the nozzle part, and is temporarily stored in the heating chamber by the induction heating member located outside the nozzle part. The molding material stored in the heating chamber is heated to the melting temperature corresponding to the material characteristics and maintained in the temperature rising state until the completion of injection. Simultaneously with the completion of injection of the molding material temporarily stored in the heating chamber, the cooling portion is supplied. The heating chamber is cooled by the supply of the refrigerant and the supply of the refrigerant is stopped when heating by the induction heating unit, and the current temperature of the nozzle unit is monitored by the temperature sensor, so that rubber or thermosetting resin is used as the molding material. The moldability can be improved while using a difficult-to-work material in which the viscosity of the molding material is increased to improve the quality of the molded product.

  More specifically, according to the injection molding nozzle 10 of the present invention, since the melt viscosity is high, molding using difficult-to-process materials that could not be achieved by a conventional molding machine has become possible. It is possible to perform molding without occurrence of. In addition, since the melt viscosity is lowered, not only the injection pressure can be lowered, but also the clamping force between the injection molding nozzle 10 and the molding die 22 can be reduced by lowering the injection pressure. This can contribute to the miniaturization of the molding machine and the reduction of the molding time. Furthermore, transferability from the mold can be improved.

  Next, the injection molding nozzle of the present invention will be described with reference to the drawings. FIG. 1 shows an injection molding nozzle according to the present invention, and is a block explanatory diagram of the main part thereof.

  In FIG. 1, an injection molding nozzle 10 is disposed at a cylinder portion 11 serving as a passage of a difficult-to-work material as a molding material, and at a tip side of the cylinder portion 11, that is, at a downstream side of the cylinder 11 in the injection direction of the molding material. And a screw 13 that is disposed in the cylinder portion 11 and pushes the molding material to the nozzle portion 12 side.

  In addition, a cooling groove 12 a is formed on the outer periphery of the nozzle portion 12 as a refrigerant portion that is recessed in an annular shape or a spiral shape. The cooling groove 12 a is sealed with a cylindrical heat-resistant cover 14. Furthermore, an induction heating coil 15 is provided on the outer periphery of the heat-resistant cover 14. Further, a temperature sensor 16 that detects the temperature of the nozzle portion 12 or the temperature of the molding material is provided at an appropriate location of the nozzle portion 12 inside the heat-resistant cover 14.

  Inside the nozzle portion 12, a heating chamber 12b is secured which is a space equal to or larger than the volume (flow rate) required for product molding. The heating chamber 12b preferably has the same volume as that required for product molding. Further, it is desirable to make the length of the nozzle as long as possible with respect to this volume (ratio of length / volume). Furthermore, the distance between the heating chamber 12b and the induction heating coil 15 as the induction heating member is preferably as close as possible. In the case where the inner diameter suddenly changes at the joint portion between the heating chamber 12b and the cylinder portion 11 and the heating chamber becomes a reduced portion, an induction heating coil and a cooling groove are also provided at the joint portion to control the temperature. It is preferable to do.

  A coolant such as water, oil, air, or gas is circulated in the cooling groove 12 a by opening and closing the electromagnetic valve 17. The refrigerant increases the temperature associated with the circulating heat absorption in the cooling groove 12a when the nozzle portion 12 is at a high temperature. Cooling means provided before and after the electromagnetic valve 17 (simple cooling such as meandering of the pipe). It is cooled when going through.

  When a normal metal material is used for the heat-resistant cover 14, the temperature of the cover itself rises when it is overheated by the induction heating coil 15, and the amount of heat and time are wasted. Therefore, the specific resistance value is large or the relative permeability is high. Is made of a small material (for example, a resin-based material having heat resistance of about 200 ° C., such as a phenol resin or a polyphenylene sulfide resin).

  The induction heating coil 15 is heated by the power supply from the low frequency power supply 18 and the nozzle portion 12 is heated by the temperature rising effect.

  On the other hand, the temperature sensor 16, the electromagnetic valve 17, and the low frequency power supply 18 are controlled by the control device 19. Further, the control device 19 is centrally managed by a computer, generally a personal computer 21, via the I / O 20. The computer 22 also controls and manages a known molding die whose configuration diagram is omitted.

  FIG. 2 shows an example of timing control by the personal computer 21. As shown in FIG. 2, the injection molding machine in this embodiment is a molding machine start → ejector return → mold closing → mold touch → nozzle advance → injection standby → injection → pressure holding → vulcanization → metering → nozzle Work as a series of injection molding routines: retreat → mold opening → ejector ejection.

  In parallel with these injection molding routines, the operation is performed as a temperature management routine in which the refrigerant is expelled → induction heating → nozzle cooling start → nozzle cooling end. At this time, the nozzle cooling end timing in the previous process is controlled to be the same as the molding machine start timing in the next process.

FIG. 3 is a graph of temperature control in temperature management according to the above embodiment. Here, in order to obtain a desired melt viscosity at the time of injection, induction heating by the induction heating coil 15 is started in advance to heat the difficult-to-work material in the nozzle portion 12, and when the melt viscosity suitable for molding is reached, injection is performed. Starts (t ₀ ).

Then, the induction heating is stopped simultaneously with the completion of the injection holding pressure (t ₁ ), and the coolant is supplied into the nozzle to rapidly cool the nozzle portion 12 to such an extent that scorch is not generated in the difficult-to-work material. When such a method is used, it is possible to complete one cycle in about 20 to 60 seconds in the case of one cycle of initial temperature → rapid heating → molding temperature → rapid cooling → initial temperature. It can be accommodated in one cycle of substantially the same time as (vulcanization) injection molding using a molding material made of a thermosetting resin. Further, during rapid heating, if the refrigerant remains in the cooling groove 12a, the induction heating coil 15 hinders the temperature of the nozzle portion 12 from rising, so the refrigerant remaining in the cooling groove 12a is expelled.

The symbols in FIG. 3 are described as follows.
T ₁ : Nozzle temperature before heating (= cylinder temperature before heating / temperature without scorch)
T ₂ : Heating temperature (flow temperature)
t ^* ₀ : Heating start time
t ^* ₁ : Heating temperature arrival time
t ^* ₂ : Heating end time
t ₀ : Injection start time
t ₁ : Injection holding pressure switching time Δt: Primary pressure injection time

Using the injection molding nozzle 10 of the present invention, the molding die 22 has a ring shape with an inner diameter of 70 mm, an outer diameter of 80 mm, and a thickness of 2 mm, and NBR rubber as a difficult-to-work material contains a large amount of ferrite as inorganic filler. (800 parts by weight per 100 parts by weight of rubber; shear viscosity 1.5 × 10 ⁴ Pa · s) is used, and the temperature of the nozzle part 12 is rapidly heated from 100 ° C. to 130 ° C. by induction heating and reaches 130 ° C. After that, it was ejected after being held for 10 seconds. And after completion | finish of the injection holding pressure, it rapidly cooled from 130 degreeC to 100 degreeC. Moreover, the temperature of the cylinder part 11 was 100 degreeC, and the temperature of the molding die 22 was 180 degreeC using the well-known means. At this time, the temperature was increased after the solenoid valve 17 was controlled to completely extrude the refrigerant in the cooling groove 12a so that the cooling water as the refrigerant did not remain as water droplets in the cooling groove 12a.

  As shown in FIG. 4, when the normal injection molding method in which the product is vulcanized and molded while keeping the temperature of the nozzle unit 12 constant at 100 ° C. without increasing the temperature of the nozzle unit 12, it is necessary for molding. The injection pressure was 200 MPa, and the injection time was 10 seconds. In contrast, when the injection molding nozzle 10 of the present invention was used, the injection pressure was 150 Mpa and the injection time was 6 seconds.

  Further, when the nozzle portion 12 was cooled without using a refrigerant at the time of cooling, the time required for cooling was about 15 minutes 30 seconds as shown in FIG. On the other hand, the rapid cooling time using the refrigerant of the present invention was less than 1 minute.

Further, when water droplets or the like of coolant (water pressure 2 kg / cm ² ) as a refrigerant remain in the cooling groove 12a at the time of temperature rise of the nozzle portion 12, as shown in the graph of FIG. Was about 25 seconds. On the other hand, when no cooling water as a refrigerant was left in the cooling groove 12a, the temperature increase could be completed in less than 10 seconds.

FIG. 3 is a block explanatory diagram of the main part of the injection molding nozzle according to the present invention. It is explanatory drawing which shows the relationship between the injection molding routine using the nozzle for injection molding of this invention, and the temperature management routine of a nozzle part. It is a graph which shows the temporal relationship of the screw stroke using the nozzle for injection molding of this invention, nozzle temperature, and injection pressure. In the case of using the nozzle for injection molding of the present invention, (A) is a graph showing the relationship between the presence / absence of induction heating and the injection pressure, and (B) shows the relationship between the presence / absence of induction heating and the injection time. FIG. FIG. 4 is a comparative graph of nozzle cooling time when forced cooling is not used and when forced cooling is used when the injection molding nozzle of the present invention is used. When using the nozzle for injection molding of this invention, it is a comparison graph figure of the temperature increase achievement time in the case of cooling water remaining and the case of no cooling water remaining. It is the longitudinal cross-sectional view of the principal part which shows the conventional nozzle for injection molding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Injection molding nozzle 11 ... Cylinder part 12 ... Nozzle part 12a ... Cooling groove (refrigerant part)
12b ... heating chamber 13 ... screw 15 ... induction heating coil (induction heating member)
16. Temperature sensor

Claims (9)

  A nozzle part having a heating chamber that temporarily stores the molding material supplied from the screw of the cylinder part, and a molding material that is located outside the nozzle part and temporarily stored in the heating chamber has the material characteristics. An induction heating member that raises the temperature to a corresponding melting temperature and maintains the temperature rise state until the completion of injection, and cools the heating chamber by supplying a refrigerant simultaneously with completion of injection of the molding material temporarily stored in the heating chamber. An injection molding nozzle comprising: a cooling unit that stops supply of refrigerant when heated by the induction heating member; and a temperature sensor that monitors a current temperature of the nozzle unit.   The nozzle for injection molding according to claim 1, wherein the volume of the heating chamber has a space equal to or larger than the volume required for product molding.   The nozzle for injection molding according to claim 1 or 2, which is used for molding rubber or thermosetting resin.   Cooling of the nozzle part is completed at the start of molding start of the molding machine, and during the period from the completion of mold closing with the injection mold to the completion of injection, heating is performed by an induction heating member to lower the melt viscosity, and molding processability In addition, the temperature control method for the nozzle for injection molding is characterized in that the nozzle portion is cooled by the refrigerant during the period from the start of injection to the start of the start of the molding machine in the next step.   The temperature management method for an injection molding nozzle according to claim 4, wherein the refrigerant is removed from the cooling section during heating by the induction heating member.   The temperature control method for an injection molding nozzle according to claim 4 or 5, wherein the injection molding nozzle according to claim 1, 2, or 3 is used.   A method for molding rubber or thermosetting resin, wherein an injection molding nozzle controlled in temperature by the method according to claim 4, 5 or 6 is used.   The molding method according to claim 7, which is applied to a rubber or a thermosetting resin that is highly filled with a filler. The molding method according to claim 8, which is applied to a rubber or a thermosetting resin containing a highly filled filler having a shear viscosity at 90 ° C of 10 ⁴ Pa · s or more (when the shear rate is 10 ² / sec).

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