JP2008120030A - Extrusion die head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extrusion die head which is mounted at the apex of an extruder and extrudes a molten resin material in a solid state, and further, can effectively avoid such a trouble that the molten resin material to be extruded from an opening of the extrusion die head, tends to curve in an indefinite direction, without being forced to undergo complicated remedial steps. <P>SOLUTION: This extrusion die head comprises a die head body 20 with an opening 30 through which the resin material is extruded and a core 10 to be fitted to the interior of the die head body 20. In addition, at least, a single strip of helical groove (11a and 11b), is nicked along the surface of the core 10. Besides, the helical groove (11a and 11b) becomes gradually shallow toward the apex side of the core 10, and an air space is formed between the inner peripheral surface of the die head body 20 and the core 10 in such a way that an interval between the inner peripheral surface of the die head body 20 and the core 10 gradually widens toward the opening 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an extrusion die head that is attached to the tip of an extruder and extrudes a molten resin material in a solid state.

  In recent years, synthetic resin containers formed by forming a synthetic resin such as polyethylene terephthalate into a bottle shape by blow molding or the like have been rapidly spread and spread as beverage containers containing various beverage products. Such a synthetic resin container is generally prepared by preparing a bottomed cylindrical molding intermediate called a preform, setting it in a mold, and using a stretching rod as needed. While being stretched in the direction, it is stretched in the transverse direction by blow air to form a predetermined container shape.

  In producing bottle-shaped synthetic resin containers in this way, many preforms have been conventionally molded by injection molding, but in recent years, they are excellent in terms of economy and production efficiency. Therefore, a preform formed by compression molding using a rotary compression molding machine (for example, see Patent Document 1 and Patent Document 2) in which a large number of molding dies are attached to a rotating disk is used. A lot has also happened.

  However, the rotary compression molding machine described in Patent Document 1 and Patent Document 2 continuously transfers a molten resin material (drop) extruded from an extrusion die head to a female mold that is rotating and moving. Need to be supplied. And, in supplying a drop to each female mold, the drop must be inserted quickly and accurately into the cavity of each female mold, and if the drop is not accurately inserted, A part of the drop protrudes outside the cavity of the female mold, and it becomes impossible to obtain a precise preform.

  In view of such circumstances, the present applicant, in mass production of preforms using a rotary compression molding machine, can quickly and more accurately supply a continuous supply of drops to a female mold. We studied earnestly to do it. As a result, when the flow path of the resin material from the extruder to the extrusion die head is changed in the middle due to the relationship with the flow path of the resin material, in particular, it crosses the extrusion direction of the extruder. When the flow path of the resin material is changed in the direction, the axial symmetry of the flow velocity distribution of the resin material in the flow path is lost, so that the molten resin material is removed from the opening of the extrusion die head. It is found that there is a problem that it is pushed out while bending in an indefinite direction without being pushed out straight, and this causes problems with accurate cutting of the drop and insertion into the female mold of the drop. A means for solving the problem was previously proposed in Patent Document 3.

  Here, in Patent Document 3, the resin flow control pin is inserted into the resin path of the extrusion die head, and the position of the resin flow control pin is adjusted to control the resin flow, thereby forming the tip of the extrusion die head. Further, it is described that the bending of the molten resin extruded from the extrusion opening is corrected.

JP 2000-25729 A JP 2000-108127 A JP 2005-319667 A

  However, as a result of further investigations by the present inventors, in the above means, a complicated operation is forced to adjust the position of the resin flow control pin, and the melt that is extruded in a solid state due to the influence of the resin flow control pin The center part of the resin material in a state has excessively raised the temperature, leading to the knowledge that the resin material may be deteriorated.

  The present invention has been made to solve such problems, and the molten resin material extruded from the opening of the extrusion die head is bent in an indefinite direction without forcing a complicated operation. It is an object of the present invention to provide an extrusion die head that can effectively avoid problems such as the above, and can easily control the temperature of the resin material and suppress excessive temperature rise.

  The extrusion die head according to the present invention is an extrusion die head that is attached to the tip of an extruder to extrude a molten resin material in a solid state, and a die head body provided with an opening through which the resin material is extruded, At least a core mounted in the die head body so that the tip side faces the opening, and the core has at least one spiral groove engraved along the surface in a spiral shape, and The spiral groove is configured such that the groove depth gradually decreases toward the tip side of the core.

By adopting such a configuration, the resin material introduced into the gap formed between the inner peripheral surface of the die head body and the core mounted in the die head body is engraved along the surface of the core. A spiral flow is generated by the spiral groove and is stirred by this spiral flow. And as the spiral groove engraved in the core becomes shallower as it approaches the opening, the spiral flow generated in the resin material is gradually converted into a flow along the axial direction.
Therefore, according to the extrusion die head according to the present invention, after the resin material is sufficiently stirred by generating a spiral flow, the shaft is pushed out from the opening by gradually moving the flow in the axial direction. It becomes possible to improve the axial symmetry of the flow velocity distribution of the resin material along the direction. For this reason, it is possible to effectively prevent the resin material from being pushed out while being bent in an indefinite direction without forcing a complicated operation when the resin material is extruded in a solid state only by being attached to the tip of the extruder. it can.

Further, in the extrusion die head according to the present invention, between the inner peripheral surface of the die head main body and the core mounted in the die head main body, the distance between the two gradually increases toward the opening. It can be set as the structure by which the space | gap is formed so that it may go.
With such a configuration, the distance between the inner peripheral surface of the die head body and the core is increased, and the cross-sectional area of the flow path is set so as not to cause an abnormal increase in resin pressure (abrupt pressure increase) in the flow path. The resin material can be directed to the opening while ensuring.

  The extrusion die head according to the present invention has a resin flow path that changes direction with respect to the extrusion direction of the extruder, and the flow path of the resin material from the extruder to the extrusion die head is changed in the middle. In such a case, the effect is particularly remarkable when the resin flow path that changes the flow direction of the resin material to cross the extrusion direction of the extruder is provided.

Moreover, the extrusion die head according to the present invention can be configured such that the core includes a cooling mechanism, and more specifically, a configuration in which a coolant injection nozzle is embedded in the core.
With such a configuration, it is possible to prevent heat from the heat-melted resin material from accumulating in the core, to easily adjust the temperature of the resin material, and to suppress excessive temperature rise.

  According to the present invention as described above, a spiral flow is generated in the resin material guided to the gap formed between the inner peripheral surface of the die head body and the core mounted in the die head body, thereby After sufficiently stirring the resin material, it is possible to increase the axial symmetry of the flow velocity distribution of the resin material along the axial direction when being pushed out from the opening by gradually moving the flow in the axial direction. . For this reason, it is possible to effectively prevent the resin material from being pushed out while being bent in an indefinite direction without forcing a complicated operation when the resin material is extruded in a solid state only by being attached to the tip of the extruder. it can.

  Hereinafter, a preferred embodiment of an extrusion die head according to the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing an extrusion die head according to this embodiment. The extrusion die head 1 according to this embodiment is attached to the tip of an extruder (not shown) for kneading and extruding a heat-melted resin material. Thus, the molten resin material is extruded in a solid state.

  In the example shown in FIG. 1, an extrusion die head 1 includes a die head main body 1 provided with an opening 30 through which a resin material is extruded, and a core 10 mounted in the die head main body 20 with the tip side facing the opening 30. And. The core 10 is pressed from above via a flow path forming member 45 by a pressing member 46 that is fastened and fixed to the die head main body 20 with a bolt or the like (not shown), and a predetermined distance between the core 10 and the inner peripheral surface of the die head main body 20. It is fixed so that a void is formed.

  As shown in FIG. 1, the inner peripheral surface of the die head body 20 has a cylindrical vertical surface 21, and a frustoconical first inclined surface 22 inclined at an angle θ <b> 1 with respect to the vertical surface 21. The second inclined surface 23 has a truncated cone shape that is inclined with respect to the surface 21 at an angle θ2 (where θ1 <θ2).

The core 10 has a tapered tip portion, and the overall shape thereof is substantially conical. And as shown in FIG.1 and FIG.2, it has the vertical part 10a, the 1st inclination part 10b, the 2nd inclination part 10c, and the 3rd inclination part 10d, and the side surface of each inclination part 10b, 10c, 10d with respect to an axial direction The inclination angle increases as it approaches the tip side.
FIG. 2 is a front view showing an outline of the core 10.

  When the core 10 is mounted in the die head body 20, the upper side of the vertical portion 10a of the core 10 is in close contact with the vertical surface 21 on the die head body 20 side. At the same time, on the lower side of the vertical portion 10a of the core 10, a certain clearance C1 is secured between the core 10 and the vertical surface 21 on the die head body 20 side.

  Further, the gap between the inner peripheral surface of the die head body 20 and the core 10 mounted in the die head body 20 gradually increases toward the opening 30 located below these. A void is formed in the surface. The gap is adjusted by appropriately adjusting the inclination angles of the outer surfaces 10bb, 10cc, 10dd of the inclined portions 10b, 10c, 10d on the core 10 side and the inclination angles of the inclined surfaces 22, 23 on the die head body 20 side. It can be formed at a predetermined interval.

For example, as shown in the figure, the angle formed between the outer surface 10bb of the first inclined portion 10b on the core 10 side and the first inclined surface 22 on the die head body 20 side is θ3, and the second on the core 10 side. An angle formed between the outer surface 10cc of the inclined portion 10c and the second inclined surface 23 on the die head main body 20 side is set to θ4, and θ3 <θ4, whereby the inner peripheral surface of the die head main body 20 and the inside of the die head main body 20 A gap formed between the outer surface of the core 10 attached to the outer surface of the core 10 can be gradually expanded toward the opening 30. By doing in this way, when the resin material flows, a rapid pressure rise in the die head can be suppressed. Here, the values of θ3 and θ4 can be adjusted as appropriate within a range in which a rapid pressure increase in the die head does not occur.
In the example shown in the figure, the outer surface 10dd of the third inclined portion 10d of the core 10 is further inclined at an angle of θ5 with respect to the side surface of the second inclined portion 10c.

  Further, when the core 10 is mounted in the die head body 20, the pressing member 46, the flow path forming member 45, and the core 10 are in close contact with each other to form a resin flow path. The resin material extruded from the extruder is guided to a gap formed between the inner peripheral surface of the die head main body 20 and the core 10 mounted in the die head main body 20 through the resin flow path. It is pushed out from the opening 30 located below the die head body 20 in a solid state.

Here, when the flow path forming member 45 and the pressing member 46 are brought into close contact with each other, a resin flow path is formed so as to extend in the horizontal direction. The main flow path 40 extending from the machine side is branched into a first horizontal flow path 41a and a second horizontal flow path 41b (see FIG. 3). Each of the first horizontal flow path 41a and the second horizontal flow path 41b is continuous with the first vertical flow path 42a and the second vertical flow path 42b that penetrate the flow path forming member 45 substantially vertically.
Further, each of the first vertical flow path 42a and the second vertical flow path 42b communicates from the flow path forming member 45 to the upper end side of the core 10 as shown in the drawing, and draws a double helix to form the core 10 It continues to the first spiral groove 11a and the second spiral groove 11b engraved along the surface.
3 is an explanatory view corresponding to the AA cross section of FIG. 1 showing the positional relationship between the resin flow paths 40, 41a, 41b, 42a, 42b and the core 10.

  As described above, the extrusion die head 1 is attached to the tip of the extruder, and the resin material extruded from the extruder is divided into the first horizontal channel 41a and the second horizontal channel 41b through the main channel 40. Go. The resin material that has flowed in each of the first horizontal flow path 41a and the second horizontal flow path 41b is transferred from the first horizontal flow path 41a to the first vertical flow path 42a and from the second horizontal flow path 41b to the second horizontal flow path 41a. To the vertical flow path 42b, the direction of the flow is changed at a substantially right angle downward so that the flow direction crosses the extrusion direction of the extruder.

A part of the resin material guided from the first horizontal flow path 41a to the first vertical flow path 42a is a clearance C1 formed between the vertical portion 10a of the core 10 and the vertical surface 21 of the die head body 20. However, most of the resin material that has flowed through the first vertical flow path 42a flows into the first spiral groove 11a without changing the flow direction. 1 and toward the near side in FIG. 1 and flows downward while turning spirally along the surface of the core 10.
Similarly, a part of the resin material guided from the second horizontal flow path 41b to the second vertical flow path 42b flows along the inner peripheral surface of the die head body 20 through the clearance C1, but many of them. Flows into the second spiral groove 11b and moves toward the back side in FIG. 1 and flows downward while spirally turning along the surface of the core 10.

  At this time, in this embodiment, the groove depths of the spiral grooves 11a and 11b are gradually reduced toward the tip side of the core 10, and the inner peripheral surface of the die head body 20 and the die head body A gap is formed between the core 10 and the core 10 mounted in the space 20 so that the distance between the cores 10 gradually increases toward the opening 30.

By doing so, the resin material introduced into the gap formed between the inner peripheral surface of the die head body 20 and the core 10 mounted in the die head body 20 is engraved along the surface of the core 10. A spiral flow is generated by the provided spiral grooves 11a and 11b and stirred by the spiral flow. As the opening 30 is approached, the resin material flowing in the spiral grooves 11a and 11b It flows out into the gap formed between the inner peripheral surface and the core 10, and the spiral flow generated in the resin material is gradually converted into a flow along the axial direction.
As described above, the gap formed between the inner peripheral surface of the die head main body 20 and the outer surface of the core 10 mounted in the die head main body 20 is gradually expanded toward the opening 30. Thus, a rapid pressure increase in the die head can be suppressed.

  Therefore, according to this embodiment, after the resin material is sufficiently stirred by generating a vortex flow, the flow is gradually directed in the axial direction, and along the axial direction when being pushed out from the opening 30. It becomes possible to improve the axial symmetry of the flow velocity distribution of the resin material. For this reason, the extrusion die head 1 of the present embodiment is simply attached to the tip of the extruder, and the resin material is extruded while bending in an indefinite direction without forcing a complicated operation when extruding the resin material in a solid state. Can be effectively avoided.

  In particular, in the case of having a resin flow path that changes the flow direction of the resin material so as to cross the extrusion direction of the extruder as in the illustrated example, in the opening 30 of the extrusion die head 1, Since there is a difference in the flow velocity of the material resin between the extruder side and the counter-extruder side across the center, there is a strong tendency for the resin material to be extruded while bending in the same direction as the extrusion direction of the extruder. The extrusion die head 1 of the present embodiment exhibits a remarkable effect in such a case.

  Further, when the melted resin material is pushed out of the opening 30 through the gap formed between the inner peripheral surface of the die head body 20 and the core 10 attached to the die head body 20, the resin material In addition to the above heat, the core 10 is stored by heat due to the shear heat generation of the resin material, and the temperature may rise to a considerably high temperature. If the temperature of the resin material is excessively increased by the heat accumulated in the core 10, the resin material may be deteriorated.

  In this embodiment, in order to prevent the heat from the resin material from accumulating in the core 10 and more positively, the resin material is cooled by the core 10 to avoid deterioration of the resin material. The core 10 can be provided with a cooling mechanism, and in the illustrated example, the refrigerant injection nozzle 60 is embedded in the core 10. That is, in the illustrated example, a refrigerant discharge hole 61 is formed in the center of the core 10, and the refrigerant injection nozzle 60 is inserted and fixed in the refrigerant discharge hole 61.

Thereby, the core 10 is cooled from the inside by the refrigerant injected from the refrigerant injection nozzle 60. In this way, heat from the heat-melted resin material is prevented from accumulating in the core 10, and further, by cooling the resin material, it is easy to adjust the temperature of the resin material and excessively increase the temperature It becomes possible to suppress.
The refrigerant injected from the refrigerant injection nozzle 60 can be discharged to the outside through the refrigerant discharge hole 61.

  In addition, the core 10 may be cooled for the entire core 10, but more heat is generated at the tip of the core 10 where the resin material that has flowed so as to cover the core 10 joins. It tends to accumulate. For this reason, it is effective to cool the core 10 with priority at the tip, and in the illustrated example, the coolant is directly injected into the inside of the tip of the core 10, or A refrigerant injection nozzle 60 is embedded so that the refrigerant circulates and is cooled. Examples of the refrigerant include compressed air, water, and oil.

  In addition, a material having a high heat transfer rate called a heat pipe can be embedded in a portion corresponding to the refrigerant discharge hole 61 to increase the cooling efficiency of the tip of the core 10. Here, examples of the material having a high heat transfer coefficient include water (steam), a material in which an alternative chlorofluorocarbon is enclosed in a vacuum pipe, beryllium copper, copper, and aluminum.

  Although the present invention has been described with reference to the preferred embodiment, it is needless to say that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. .

  For example, in the above-described embodiment, the example in which the two spiral grooves 11a and 11b are engraved on the surface of the core 10 is shown, but the spiral groove is not limited to two. The spiral groove only needs to be at least one, and three or more can be provided. Furthermore, the resin flow path for guiding the resin material to the spiral groove can be appropriately changed according to the number of the spiral grooves.

  Further, in the example illustrated in the above-described embodiment, the spiral grooves 11a and 11b have a cross-sectional shape in which a cross-section cut by a plane orthogonal to the extending direction includes a common arc having substantially the same radius of curvature at any position. However, only the groove depth gradually decreases toward the distal end side of the core 10, but the cross-sectional shape of the spiral groove is not limited to this. That is, the resistance exerted on the resin material to generate a spiral flow along the spiral groove decreases as it approaches the distal end side of the core 10, and the groove flows so that the ratio of the resin material flowing out from the spiral groove increases. If the depth is shallow, the cross-sectional shape of the spiral groove and the like can be arbitrarily set.

  As described above, the present invention provides an extrusion die head that is attached to the tip of an extruder and extrudes a molten resin material in a solid state.

It is sectional drawing which shows the outline of the extrusion die head which concerns on this invention. It is a front view which shows the outline of a core. It is explanatory drawing which shows the positional relationship of each resin flow path and a core.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extrusion die head 10 Core 11a 1st spiral groove 11b 2nd spiral groove 20 Die head main body 30 Opening part 60 Refrigerant injection nozzle 61 Refrigerant discharge hole

Claims (5)

An extrusion die head that is attached to the tip of an extruder and extrudes a molten resin material in a solid state,
A die head main body provided with an opening through which the resin material is extruded; and at least a core mounted in the die head main body so that a front end faces the opening.
The core is characterized in that at least one spiral groove is engraved spirally along the surface, and the groove depth gradually decreases toward the tip side of the core. Extrusion die head.   A gap is formed between the inner peripheral surface of the die head main body and the core mounted in the die head main body so that the distance between the two gradually increases toward the opening. Item 2. The extrusion die head according to Item 1.   The extrusion die head according to claim 1, further comprising a resin flow path that changes direction with respect to an extrusion direction of the extruder.   The extrusion die head according to claim 1, wherein the core includes a cooling mechanism.   The extrusion die head according to claim 4, wherein a coolant injection nozzle is embedded in the core.

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