JP4245435B2 - Counter pressure mold - Google Patents

Description

  The present invention relates to a counter pressure mold, and more particularly to a counter pressure mold suitable for supplying a fluid additive to a molten resin filled in a cavity.

  Conventionally, as a mold for injection molding, a counter pressure mold for injecting molten resin after pressurizing the inside of a cavity with a gas is known. By the way, when various additives are supplied to the molten resin filled in the cavity of this mold, the resin of the molten resin that is preliminarily filled with the fluid additive in the cavity and flows into the cavity. The fluid additive is impregnated from the flow front end (flow front).

  For example, as shown in FIG. 3, a gap that communicates from the cavity 100 to the outside of the mold is sealed by a sealing member 101 such as an O-ring. Thus, a structure is known that prevents the fluid additive and the counter pressure gas prefilled in the cavity 100 from flowing out of the mold (see Patent Document 1).

  There is also known a molding method in which counter pressure molding is performed by removing the seal member by setting the gas pressure condition in the cavity to a pressure within a certain range (see Patent Document 2).

Japanese Patent Laid-Open No. 11-245254 JP-A-5-269778

However, when filling the cavity with the fluid additive, there is a problem that special and complicated mold processing is required when a seal member is used to improve the airtightness in the cavity. On the other hand, when this pressure is removed and counter pressure molding is performed by adjusting the gas pressure in various ways, the pressure that can be used is about 3 to 6 kg / cm ^2, which is limited to a low pressure for general counter pressure molding. There was a problem that.

  Therefore, the problem to be solved by the present invention is to provide a counter pressure mold that can fill a cavity with a fluid additive at a relatively high pressure without using a seal member.

In order to solve the above-described problems, a counter pressure mold according to the present invention is the cavity wall surface on the axis of an ejector pin provided near the cavity formed on the parting surface of the fixed mold and the movable mold or in the vicinity of the sprue. In addition, a porous member that allows passage of the fluid additive added to the molten resin filled in the cavity but prevents the penetration of the molten resin is provided, and communicates from the cavity to the outside. All or a part of the gap (excluding the gap around the ejector pin) is bent at least once, and the porous member is provided at the final filling position of the molten resin filled in the cavity. members, and summarized in that which enables connecting the collection path for collecting the fluid-like additive became surplus is filled in the cavity That.

Further, the gist of the fixed mold or the movable mold includes a first fitting portion that covers the outer periphery of the opposed movable mold or the fixed mold with a certain depth .

In addition, the fixed mold or the movable mold includes a second fitting portion that covers an outer periphery of the opposed movable mold or the fixed mold with a certain depth .

  Further, the gist is that at least the parting surface and the ejector pin sliding surface are subjected to a low friction surface treatment and / or a hardness increasing treatment by ion implantation.

  The gist of the porous member is made of a porous metal or a porous ceramic.

  Normally, the fluid filled in the cavity flows out from the gap formed between the parting surface of the mold and the sprue bush, but according to the counter pressure mold according to the present invention, the fluid is discharged from the cavity. Since all or a part of the gap communicating with the outside of the mold (excluding the gap around the ejector pin) is bent at least once, the fluid filled in the cavity is difficult to leak to the outside.

  That is, the more the gap serving as the fluid flow path has more bends, the higher the pressure required for the fluid filled in the cavity to flow out of the mold through the gap. Therefore, even without using a seal member, the fluid filled in the cavity is difficult to leak to the outside, and therefore the pressure in the cavity can be kept relatively high.

  According to the counter pressure mold of the present invention, the fluid additive is allowed to pass on the axis of the ejector pin provided near the cavity or in the vicinity of the sprue, but the molten resin is prevented from entering. Since the porous member is provided, the fluid additive is filled into the cavity at a relatively high pressure if the supply path led out from the external fluid additive supply device is connected to the porous member. be able to.

In addition, a porous member is provided at the final filling position of the molten resin filled in the cavity, and a recovery path for collecting the excess fluid additive filled in the cavity can be connected to the porous member. In this case, the excess fluid additive can be recovered with the pressure in the cavity kept constant.

In addition, the fixed mold or the movable mold has a first fitting portion that covers the outer periphery of the opposed movable mold or the fixed mold with a certain depth, or the second is inserted into the opposed movable mold or the fixed mold by a certain depth. In the case of having a fitting part, the parting surface of the mold becomes a fitting type, and the gap formed in this parting surface is bent at least once, so that the fluid filled in the cavity is It becomes difficult to leak outside from the parting surface.

In addition, if at least the parting surface and ejector pin sliding surface are subjected to low friction surface treatment and / or increased hardness by ion implantation, it is possible to slide the mold even in a very small clearance state. It can be in a state with high sliding resistance. In addition, since the gap communicating from the cavity to the outside can be further narrowed, the outflow of the fluid filled in the cavity can be more effectively suppressed.

At this time, the porous member is preferably made of a porous metal or a porous ceramic. This is because it has excellent resistance to temperature and pressure during injection molding, and it is easy to obtain appropriate through holes.

  Hereinafter, the counter pressure mold (hereinafter, also referred to as “the present mold”) according to the present embodiment will be described in detail.

  FIG. 1 is a cross-sectional view schematically showing the internal structure of the mold. First, the structure of this metal mold | die is demonstrated. As shown in FIG. 1, the present mold 10 has a cavity 14 formed in a parting surface 13 between a fixed mold 11 and a movable mold 12.

  A fixed-side mounting plate 15 is attached to the back surface of the fixed mold 11, and a nozzle (not shown) such as a shut-off nozzle of an injection molding machine is brought into contact with the central portion of the fixed-side mounting plate 15. A sprue bushing 16 is provided so that the molten resin injected from the nozzle can be filled into the cavity 14 through the sprue 17.

  On the other hand, a receiving plate 18 is attached to the back surface of the movable mold 12, and a space portion is formed between the receiving plate 18 and the movable side mounting plate 19 with a pair of spacer blocks 20 interposed therebetween. Yes. In this space portion, an ejector retainer 21 and an ejector plate 22 are arranged, and a pair of ejector pins that pass through the receiving plate 18 and the movable mold 12 and advance toward the cavity 14 in the ejector retainer 21 and the ejector plate 22. One end of 23 is attached. Further, the other end of the ejector pin 23 faces the cavity 14.

  Here, this metal mold | die 10 has the characteristic structure in the following points. That is, in the conventionally known counter pressure mold, a seal member such as an O-ring is provided in a gap communicating from the cavity to the outside of the mold. It is not provided at all.

  Moreover, the fixed mold | type 11 has the 1st fitting part 24, and can cover the outer periphery of the movable mold | type 12 which opposes by fixed depth. On the other hand, the movable mold 12 has a second fitting portion 25 and is inserted into the fixed mold 11 facing to a certain depth. Thereby, the parting surface 13 of the fixed mold | type 11 and the movable mold | type 12 becomes a fitting type, and the clearance gap formed in this parting surface 13 will be bent at least once or more.

  At this time, the mold 10 may have a configuration in which the first fitting portion 24 is provided in the movable die 12 and the second fitting portion 25 is provided in the fixed die 11. Moreover, each fitting part 24 and 25 may be provided in any one of the fixed mold | type 11 or the movable mold | type 12, and is not specifically limited.

  Further, the sprue bushing 16 is formed with a diameter gradually increased from the cavity 14 side toward the nozzle side of the injection molding machine, and thereby formed between the fixed die 11 and the fixed side mounting plate 15. The gap is bent at least once.

  In the present mold 10, the gap formed around the ejector pin 23 is not bent. This is because in order to bend the gap formed around the ejector pin 23, it is necessary to bend the ejector pin 23. If such a configuration is used, it will hinder the extrusion of the molded product.

  Further, at least the parting surface 13 and the ejector pin 23 sliding surface of the fixed die 11 and the movable die 12 are subjected to a low friction surface treatment and / or a hardness increasing treatment by ion implantation, thereby improving the sliding resistance. It is illustrated. Here, as the low friction surface treatment, specifically, a treatment for forming a diamond-like carbon (DLC) film or the like can be given. Examples of ion implantation include fluorine ion implantation and nitrogen ion implantation.

  Further, a porous member 26 is embedded on the axis of the ejector pin 23, and a fluid additive supply device 27, which will be described later, is connected to an end of the porous member 26 opposite to the cavity 14 side. The supply path 28 of the fluid additive to be led out can be connected. Here, the porous member 26 has a large number of fine through holes, and allows the passage of low-viscosity fluid additives such as liquid and gas, but prevents the intrusion of viscous molten resin. It has a function.

  In this case, specific examples of the fluid additive to be supplied include dyes, liquid pigments, pigment solutions, nucleating agent solutions, blowing agent solutions, plasticizers, gases such as carbon dioxide and nitrogen, Examples thereof include carbon dioxide and nitrogen in a critical state or a supercritical state, and these may be used alone or in combination. Examples of the solvent for the pigment solution include lower alcohols, higher alcohols, and carbon dioxide in a subcritical or supercritical state.

  Examples of the resin include polypropylene (PP), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyamide (PA), polyphenylene sulfide (PPS), polystyrene (PS), and the like. is not.

  Here, since the pore diameter of the through hole of the porous member 26 differs depending on the fluid additive used, the viscosity and type of the molten resin, etc., various adjustments may be made in consideration of these. Moreover, although the form of a through-hole includes a continuous bubble, a small diameter hole, etc., as long as it has air permeability, any form may be sufficient and it is not specifically limited.

  Specific examples of such porous member 26 include porous metals such as porous aluminum and porous stainless steel, and porous ceramics such as zeolite. More specifically, “Metapol-METAPOR (trade name)” (manufactured by Pontc Ltd. Switzerland), “Hyporus (trade name)” (manufactured by Kobe Steel, Ltd.) and the like can be used.

  Further, the porous member 29 described above is provided at the final filling position of the molten resin filled in the cavity 14, and at least a part of the porous member 29 is filled in the cavity 14. A recovery path 30 for recovering the excess fluid additive can be connected.

  Next, a method for supplying and collecting a fluid additive using the above-described mold will be described. FIG. 2 shows an example in which a fluid additive supply / recovery circuit is connected to the mold. In FIG. 2, a fluid additive supply path 28 led out from the fluid additive supply device 27 is connected to one end of a porous member 26 provided inside the ejector pin 23 via a pressure regulating valve 31. Yes. The fluid additive recovery path 30 led out from the fluid additive recovery device 32 is connected to a porous member 29 provided inside the cavity 14 via a pressure adjustment valve 33. Further, the fluid additive supply device 27 and the recovery device 32 are connected via a flow path 34. A fluid additive storage device 35 is connected to the fluid additive supply device 27.

  And in order to supply and collect | recover fluid additive using this metal mold | die 10, first, the fixed mold | type 11 and the movable mold | type 12 were fitted, the metal mold | die was closed, and the pressure regulation valve 33 was closed. Then, the pressure adjustment valve 31 is opened. As a result, the fluid additive passes through the supply path 28 and the porous member 26 and is filled into the cavity 14.

  When it is necessary to sufficiently replace the inside of the cavity 14 with the fluid additive, the pressure adjustment valve 33 is initially opened, and the air is sufficiently pushed out to close the pressure adjustment valve 33. You can do that.

  After filling the cavity 14 with a fluid additive at a predetermined pressure (preferably about 0.5 MPa to 10 MPa) in this way, the shutoff nozzle (injection molding machine) is closed with the pressure adjustment valve 31 closed. The molten resin is injected into the cavity 14 from (not shown).

  Then, the fluid additive previously filled in the cavity is impregnated from the flow front of the molten resin flowing into the cavity 14, and the fluid additive is added to the molten resin. At this time, the surplus fluid additive is driven to the final filling position of the molten resin in the cavity 14.

  When the pressure adjustment valve 33 is opened just before the end of the injection, the excess fluid additive in the cavity 14 is recovered through the porous member 29 while keeping the pressure in the cavity 14 constant. It is discharged to the passage 30 and is recovered to the fluid additive supply device 27 via a purification filter (for example, activated carbon) of the recovery device 32. When the pressure of the fluid additive is smaller than the predetermined pressure, the fluid additive is newly replenished from the fluid additive storage device 35 and the flow rate is adjusted, and then the fluid addition is performed. It is sent out again from the agent supply device 27.

  On the other hand, on the mold side, when the mold is opened after cooling the resin in the mold, the molded product is ejected by the ejector pins 23, and a desired molded product is obtained.

  In the above, the case where the porous member 29 and the recovery path 30 connected to the porous member 29 are used has been described. However, it is possible to supply and recover the fluid additive even by other methods. is there.

  Generally, the position of the ejector pin 23 differs depending on the shape of the molded product. For example, when the end of the ejector pin 23 on the cavity 14 side is located at the final filling position of the molten resin filled in the cavity 14. Is connected to the supply path 28 via a switching cock (not shown) so that the recovery path derived from the recovery apparatus 32 is added to the fluid without using the porous member 29 and the recovery path 30 connected thereto. It is possible to supply and recover the agent.

  That is, when supplying the fluid additive into the cavity 14, the switching cock is switched to the fluid additive supply device 27 side to supply the fluid additive into the cavity 14. When the excess fluid additive is recovered, the switching cock is switched to the recovery device 32 side, and the excess fluid additive can be recovered.

  The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the case where the porous member 26 is provided on the axis of the ejector pin 23 is exemplified, but in addition to this, the porous member is provided on the wall surface of the cavity 14 near the sprue 17 to The supply channel 28 led out from the fluid additive supply device 27 may be connected to the porous member to supply the liquid additive to the molten resin filled in the cavity 14.

It is sectional drawing which showed typically the internal structure of the counterpressure metal mold | die which concerns on this invention. It is the figure which showed an example which connected the supply / collection circuit of the fluid additive to this metal mold | die. It is sectional drawing which showed typically the internal structure of the counter pressure metal mold | die using the conventional sealing member.

Explanation of symbols

10 Counter pressure mold (main mold)
DESCRIPTION OF SYMBOLS 11 Fixed type 12 Movable type 13 Parting surface 14 Cavity 17 Sprue 23 Ejector pin 24 1st fitting part 25 2nd fitting part 26 Porous member 27 Fluid additive supply apparatus 28 Supply path 29 Porous member 30 Recovery path

Claims (5)

Added to the cavity wall on the axis of the ejector pin provided near the cavity formed on the parting surface of the fixed mold and the movable mold or in the vicinity of the sprue to the molten resin filled in the cavity A porous member that allows passage of the fluid additive but prevents the intrusion of the molten resin is provided, and all or part of the gap communicating from the cavity to the outside (excluding the gap around the ejector pin) Has been bent at least once,
The porous member is provided at the final filling position of the molten resin to be filled in the cavity, and a recovery path for collecting the excess fluid additive filled in the cavity can be connected to the porous member. Counter pressure mold characterized by that. 2. The counter pressure mold according to claim 1, wherein the fixed mold or the movable mold includes a first fitting portion that covers an outer periphery of the opposed movable mold or the fixed mold with a certain depth . The counter pressure mold according to claim 1 or 2, wherein the fixed mold or the movable mold includes a second fitting portion that is inserted into the opposed movable mold or the fixed mold at a certain depth .   4. The counter pressure mold according to claim 1, wherein at least the parting surface and the ejector pin sliding surface are subjected to a low friction surface treatment and / or a hardness increasing treatment by ion implantation. .   5. The counter pressure mold according to claim 1, wherein the porous member is made of porous metal or porous ceramics.

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