JP2012111067A - Injection molding machine for preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding machine of a preform, capable of improving the productivity or the like by reducing the generation of cold slag in the injection molding of the preform.SOLUTION: The injection molding machine 1 for the preform has a bottom insert 3, a nozzle insert 4 and a needle valve 5. The needle valve 5 has, on a tip side thereof, a cylindrical straight part 51 and a truncated cone-shaped taper part 52 having a taper angle corresponding to a taper hole 41 of the nozzle insert 4. When the injection of a molten resin 109 is closed, the tip side part of the taper part 52 is inserted into a hole 31 for a gate of the bottom insert 3, and the tip side part of the straight part 51 is inserted into the taper hole 41 of the nozzle insert 4.

Description

  The present invention relates to a preform injection molding apparatus, and more particularly to a preform injection molding apparatus that can reduce the occurrence of cold slag and improve productivity when the preform is injection molded.

Plastic containers such as plastic bottles are widely used, and their production quantity is enormous. For this reason, reducing the occurrence of defective products in the manufacturing process is important for improving productivity and also from the viewpoint of effectively using resources and energy.
Said plastic container is manufactured by blow-molding the bottomed cylindrical preform by which injection molding was carried out. In the process of injection-molding a preform, one of chronic defects is cold slag. For this reason, various techniques for reducing the occurrence of cold slag have been researched and developed.
Here, the cold slag is referred to as the next appearance defect in the preform. That is, as a result of injection molding after a part of the molten resin before injection is crystallized or semi-solidified, it appears that white foreign matter is mixed in the vicinity of the gate part of the preform or the resin surface becomes uneven. The appearance is poor. When cold slag is generated, non-uniform deformation occurs in the process of blow molding the preform, resulting in perforations, poor appearance, and poor dimensions.

(Conventional example)
Next, the preform injection molding apparatus described in Patent Document 1 will be described with reference to the drawings.
FIG. 3 is a schematic cross-sectional view of a main part of an injection molding apparatus according to a conventional example.
FIG. 4 is a schematic enlarged cross-sectional view of the main part of an injection molding apparatus according to a conventional example. In FIG. 4, the molten resin 109 is omitted.
As shown in FIGS. 3 and 4, the preform injection molding apparatus 100 is attached to a bottom cavity mold 101, a bottom insert 107 in which a gate hole 171 is formed, and a nozzle 103 so as to face the bottom insert 107. A nozzle insert 108 having a tapered hole 181 and in direct surface contact with the bottom insert 107, a needle valve 105 inserted into the tapered hole 181 of the nozzle insert 108, and the like.

The bottom insert 107 is a substantially disk-shaped member, and a gate hole 171 communicating with the gate 102 is formed at the center. The bottom insert 107 is embedded in the bottom cavity mold 101, and is made of a material having low thermal conductivity and high mechanical strength (for example, titanium or titanium alloy). The diameter D ₁ (not shown) of the injection hole side of the gate hole 171 is substantially the same as the diameter d ₁ of the distal end surface of the needle valve 105.

  The nozzle insert 108 is a substantially disk-shaped member, and a tapered hole 181 communicating with the tapered hole-shaped flow path 132 is formed at the center. The nozzle insert 108 protrudes from the tip of the nozzle 103 and is made of a material having low thermal conductivity and high mechanical strength (for example, titanium or titanium alloy). Furthermore, the flow path 132 and the taper hole 181 communicate with each other so that there is almost no step, and are tapered so that the molten resin 109 flows smoothly. The nozzle 103 is heated by a heater 106.

Further, the diameter D ₃ (not shown) of the taper hole 181 on the injection machine side is substantially the same as the diameter of the flow path 132 on the preform side.
Further, the taper angle of the taper hole 181 is substantially the same as the taper angle of the flow path 132.
Further, although not shown, the end portion on the preform side of the tapered hole 181 is usually chamfered.

The needle valve 105 has a substantially cylindrical shape, and moves in the reciprocating direction by an air cylinder (not shown). This needle valve 105 has a tip end surface with a diameter d ₁ that is substantially the same as a diameter D ₂ (not shown) on the preform side of the taper hole 181. When moved to the preform side, the needle valve 105 closes the taper hole 181. The injection of the molten resin 109 is closed.
Further, when the needle valve 105 is moved to the preform side, a predetermined position (that is, a position where the needle valve 105 closes the tapered hole 181 and the injection of the molten resin 109 is closed by a stopper (not shown) or the like). ).

In the injection molding apparatus 100 having the above-described configuration, when the needle valve 105 is moved to the injector side in a state where the bottom insert 107 and the nozzle insert 108 are in direct surface contact, the molten resin 109 becomes the flow path 131 and the flow path. 132, the taper hole 181, the gate hole 171 and the gate 102 are injected into the space sandwiched between the bottom cavity mold 101 and the core mold 104 and cooled to form a preform.
Here, the hot-side nozzle insert 108 and the cold-side bottom insert 107 are in direct surface contact, but the material of the nozzle insert 108 and the bottom insert 107 has a low thermal conductivity and a high mechanical strength. Is used. As a result, when the nozzle insert 108 comes into contact with the bottom insert 107, the molten resin 109 in the tapered hole 181 is supplied to the bottom cavity mold 101 without being crystallized by cooling due to the heat insulation effect, thereby reducing the occurrence of cold slag. To do.

After the injection of the molten resin 109 is completed, the bottom insert 107 is cooled in order to solidify the resin in the gate portion of the preform. When the injected molten resin 109 is solidified, the preform is released.
Moreover, since the nozzle insert 108 and the bottom insert 107 are in contact with the injection molding apparatus 100 from the end of injection until the preform is taken out, the nozzle insert 108 is cooled by the bottom insert 107. On the other hand, the resin on the hot runner side of the nozzle insert 108 is maintained in a molten state in preparation for the next injection.

JP 2002-283396 A Japanese Patent Laid-Open No. 2002-1802 JP 2002-79570 A

  However, in the injection molding apparatus 100 described above, the hot-side nozzle insert 108 and the cold-side bottom insert 107 are in direct surface contact (without using a heat insulating material or the like), so that the vicinity of the tip of the nozzle insert 108 (the bottom) In the vicinity of the contact surface with the insert 107), the temperature rapidly decreases, and also at the distal end portion of the needle valve 105, the temperature decreases toward the distal end side (preform side). And there existed a problem that cold slug generate | occur | produced in preform and productivity etc. cannot be improved.

  In addition, although the technique of patent documents 2 and 3 is a technique of the manufacturing method of a biaxially-stretched polyester container and is a technique relevant to this invention, for example, the nozzle chip front-end | tip part is equipped with the heat insulating material layer, and this invention The basic configuration was different. Therefore, the techniques of Patent Documents 2 and 3 cannot solve the above-described problems.

  The present invention has been proposed in order to solve the above-described problems. When a preform is injection-molded, the injection of the preform can reduce the occurrence of cold slag and improve the productivity. An object is to provide a molding apparatus.

  It should be noted that chronic defects in the manufacturing process are usually associated with various factors, and some of the chronic defects seem to be almost impossible to effectively reduce the defect rate. Similarly, various factors (for example, the timing of closing the needle valve 105, the temperature and shape of the nozzle insert 108, the needle valve 105, and the bottom insert 107) are also involved in the cold slug, which is a chronic failure. In addition, the occurrence rate of cold slag varies depending on the type of resin used, and even the same type of resin is affected by differences in partial melting point, kneading degree, crystallinity, etc. It is.

  The inventors of the present invention have established a technique capable of effectively reducing cold slag by carrying out diligence, research and testing. That is, as shown in FIG. 4, when the needle valve 105 is closed (moved toward the preform side), the molten resin 109 existing in the tapered hole 181 (particularly, the molten resin 109 present on the distal end side of the tapered hole 181). The temperature decreases as the temperature of the nozzle insert 108 decreases. Then, the inventors of the present invention found that the molten resin 109 having a lowered temperature was partially solidified or crystallized, and moved to the vicinity of the outer surface of the preform and to the periphery of the gate in the next injection, and became white. The present invention is conceived by assuming that cold slag is generated because the resin flow is disturbed.

  In order to achieve the above object, the preform injection molding apparatus of the present invention is attached to a gate of a bottom cavity mold, a bottom insert having a gate hole formed therein, and a nozzle so as to be in surface contact with the bottom insert. In a preform injection molding apparatus having a nozzle insert attached and having a tapered hole and a needle valve that advances and retreats in the tapered hole of the nozzle insert, a columnar straight portion and the nozzle insert are provided at the tip side of the needle valve. When the injection of the molten resin into the bottom cavity mold is stopped, the needle valve is advanced to form a tapered cone portion having a taper angle corresponding to the taper hole of the taper hole. The tip side part protrudes from the taper hole of the nozzle insert, and the tip of the straight part It is constituted to insert the portion of the side to the tapered bore of the nozzle insert.

  According to the preform injection molding apparatus of the present invention, when a preform is injection molded, the generation of cold slag can be reduced and the productivity can be improved.

FIG. 1 is a schematic enlarged cross-sectional view of a main part of an injection molding apparatus according to an embodiment of the present invention. FIG. 2 is a schematic enlarged cross-sectional view for explaining the dimensions of the main part of the injection molding apparatus according to the embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a main part of an injection molding apparatus according to a conventional example. FIG. 4 is a schematic enlarged cross-sectional view of a main part of an injection molding apparatus according to a conventional example.

[Embodiment of preform injection molding apparatus]
FIG. 1 is a schematic enlarged cross-sectional view of a main part of an injection molding apparatus according to an embodiment of the present invention. In FIG. 1, the molten resin 109 is omitted.
In FIG. 1, the preform injection molding apparatus 1 according to the present embodiment is different from the above-described conventional example in that a bottom cavity mold 101, a bottom insert 107, a nozzle insert 108, and a needle valve 105 are replaced with a bottom cavity mold. 2, the point provided with the bottom insert 3, the nozzle insert 4, and the needle valve 5 is different. In addition, the other structure of this embodiment is as substantially the same as a prior art example.
Therefore, in FIG. 1, the same components as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
Note that the above-mentioned preform has a single-layer specification. Moreover, the capacity | capacitance of a container at the time of blow molding, a use, a shape, etc. are not specifically limited.

(Bottom cavity mold)
The bottom cavity mold 2 is different from the bottom cavity mold 101 described above in that the diameter of the gate 21 is larger than the diameter of the gate 102. Other configurations are substantially the same as those of the bottom cavity mold 101.

(Bottom insert)
The bottom insert 3 is different from the bottom insert 107 described above in that the diameter of the gate hole 31 is larger than the diameter of the gate hole 171. Other configurations are substantially the same as those of the bottom insert 107.
The material of the bottom insert 3 and the nozzle insert 4 is usually a material having low thermal conductivity and high mechanical strength (for example, titanium or titanium alloy), but is not particularly limited. Steel or the like may be used.

(Nozzle insert)
The nozzle insert 4 is substantially the same as the nozzle insert 108 described above. However, (see FIG. 2) in diameter (such as a preform side diameter) D ₂ of the taper hole 41 is set in accordance with the shape of the needle valve 5.
The taper angle α ₁ of the taper hole 41 is substantially the same as the taper angle α ₂ of the flow path 132.
Further, a step is generated between the flow path 132 and the tapered hole 41, but the structure is not limited to this structure. For example, although not illustrated, the injection machine side of the tapered hole 41 is chamfered, It is good also as a structure which makes the flow path 132 and the taper hole 41 communicate smoothly.
Further, although not shown, the end portion on the preform side of the tapered hole 41 is usually chamfered, and the shape of the chamfering is not particularly limited.

(Needle valve)
Compared with the needle valve 105 described above, the needle valve 5 has a substantially cylindrical straight portion 51 and a taper angle β corresponding to the taper hole 41 of the nozzle insert 4 on the tip side (preform side). The point which has the tapered part 52 of a head cone shape is different. Other configurations are substantially the same as those of the needle valve 105.
Straight portion 51 is located as a diameter _{d 2} of the cylindrical shape, the diameter _{d 2} is the diameter (diameter of the injection machine side) _{D 3} diameter (of the preform side diameter) _{D 2} and the tapered hole 41 of the tapered bore 41 On the other hand, there is a relationship of D ₂ <d ₂ <D ₃ . Thereby, when the injection of the molten resin 109 is closed, that is, as shown in FIG. 1, when the needle valve 5 is closed (moved toward the preform side), the tip side portion of the straight portion 51 (the straight portion 51 and A step portion at the boundary of the tapered portion 52 (appropriately abbreviated as a step) is inserted into the tapered hole 41 of the nozzle insert 4.

Further, the tapered portion 52 has a truncated cone shape having a taper angle β corresponding to the tapered hole 41 of the nozzle insert 4. That is, the tapered portion 52 has a diameter of the upper surface is d _1, the lower surface of the diameter is d _2, a frusto conical taper angle is beta. In addition, the diameter d ₁ and the diameter d ₂ have a relationship of d ₁ <D ₂ <d _{2 with} respect to the diameter D ₂ of the tapered hole 41 (the diameter on the preform side). Thereby, when injection of the molten resin 109 is closed, that is, as shown in FIG. 1, when the needle valve 5 is closed (moved to the preform side), the tip side portion of the tapered portion 52 is moved to the nozzle insert 4. Protrudes from the taper hole 41.
Further, the taper angle β of the taper surface of the taper portion 52 is substantially the same as the taper angle α ₁ of the taper hole 41.

In the injection molding apparatus 1 having the tapered hole 41, the straight portion 51, and the tapered portion 52 described above, when the needle valve 5 is closed (moved toward the preform side), the tapered portion 52 is formed on the preform side of the tapered hole 41. The molten resin 109 is almost in contact with the tapered hole 41, and there is almost no molten resin 109 between the tapered portion 52 and the tapered hole 41. That is, it is presumed that by not allowing the molten resin 109 to exist in this region (region where the temperature decreases), the generation of resin that crystallizes and becomes white is almost eliminated, and the generation of cold slag is greatly reduced. .
When the needle valve 5 is closed, the molten resin 109 exists between the straight portion 51 and the taper hole 41 on the injection machine side of the taper hole 41, but the temperature on the injection machine side of the nozzle insert 4 is The temperature is higher than the temperature on the preform side of the nozzle insert 4, and the temperature of the straight portion 51 is higher than the temperature of the tapered portion 52. Thereby, since the molten resin 109 in this region is maintained in a molten state at a high temperature, it is presumed that the generation of cold slag is greatly reduced.
As described above, the injection molding apparatus 1 reduces the amount of the molten resin 109 between the taper portion 52 and the taper hole 41 to a level that hardly exists and the straight portion 51 and the taper as compared with the injection molding device 100. It is presumed that the generation of cold slag is greatly reduced by effectively and reliably preventing the temperature drop of the molten resin 109 existing between the holes 41.

Here, preferably, when the taper angle of the taper hole 41 is α ₁ ° and the taper angle of the taper portion 52 is β °, α ₁ ° + 0.5 ° <β ° <α ₁ ° + 2 ° may be satisfied. . In this way, a minute gap is formed between the taper hole 41 and the taper portion 52, and the molten resin 109 enters the gap, so that the needle valve 5 and the nozzle insert 4 are galled or damaged (damaged). It can be effectively prevented.
The reason for limiting the above numerical values is to effectively prevent the needle valve 5 and the nozzle insert 4 from galling or damage (damage) when the taper angle β ° is α ₁ ° + 0.5 ° or less. It is because it becomes impossible. Further, when the taper angle β ° is α ₁ ° + 2 ° or more, the amount of the molten resin 109 existing between the taper portion 52 and the taper hole 41 is increased, and cold slag may be generated.

In addition, preferably, a convex portion 53 is formed on the end surface of the tapered portion 52. The convex portion 53 has a substantially conical shape. If it does in this way, when releasing a preform, stringing of resin can be prevented.
In addition, the shape of the convex part 53 is not limited above, For example, it is good also as a curved shape (shape which consists of a part of spherical shape).

Preferably, when the tip side portion (the preform side portion) of the taper portion 52 is inserted into the gate hole 31 of the bottom insert 3, the protruding amount (h) of the taper portion 52 into the gate hole 31 (h) ₁ and FIG. 2) may be 0.1 mm or more and 1.5 mm or less. If it does in this way, the temperature fall of the molten resin 109 which exists between the taper part 52 and the taper hole 41 can be suppressed, and generation | occurrence | production of cold slag can be reduced.
The reason for the above numerical limitation is that, if h ₁ is less than 0.1 mm, the molten resin 109 may not be surely cut off, and the molten resin existing between the tapered portion 52 and the tapered hole 41 is present. There is a danger that cold slag is generated due to a decrease in the temperature of 109. Moreover, h ₁ is, there is a possibility that more than 1.5mm when the molten resin in the gate hole 31 is stringiness becomes insufficient cooling occurs.

Further, preferably, when the tip side portion (preform side portion) of the straight portion 51 is inserted into the tapered hole 41 of the nozzle insert 4, the contact surface of the nozzle insert 4 (contact surface with the bottom insert 3). The distance h ₂ (see FIG. 2) from the imaginary end surface to the front end side of the straight portion 51 is preferably 0.5 mm or more and 3.5 mm or less, more preferably 0.6 mm or more and 2.5 mm or less. Good. If it does in this way, generation | occurrence | production of cold slag can be reduced.
The reason why the numerical limits, h ₂ is less than 0.5 mm, not fitting the tapered hole 41 and the tapered portion 52 is fit, there is a risk of generating resin breakage failure (stringing) Because. Further, if h ₂ exceeds 3.5 mm, the temperature of the molten resin 109 existing between the taper portion 52 and the taper hole 41 may be lowered and cold slag may be generated.

Further, the needle valve 5, the injector side of the straight portion 51 has a cylindrical portion 54 of diameter d ₂ larger than the diameter d ₃ (see FIG. 1), to improve the mechanical strength of the needle valve 5 is there. When the needle valve 5 is moved in the reciprocating direction by an air cylinder (not shown) or the like and moved to the preform side, the needle valve 5 closes the taper hole 41 and the injection of the molten resin 109 is closed.
Further, when the needle valve 5 is moved to the preform side, the needle valve 5 is moved to a predetermined position by a stopper (not shown) or the like.

When the needle valve 5 is moved to the injector side in a state where the bottom insert 3 and the nozzle insert 4 are in direct surface contact with each other, the injection molding apparatus 1 having the above configuration causes the molten resin 109 to flow into the flow path 131 and the flow path. Through 132, the taper hole 41, the gate hole 31, and the gate 21, it is injected into a space sandwiched between the bottom cavity mold 2 and the core mold 104 to form a preform.
As shown in FIG. 1, when the needle valve 5 is closed (moved toward the preform side), the preform side portion of the taper portion 52 is inserted into the gate hole 31 of the bottom insert 3, and the taper portion 52. The portion on the injection machine side is substantially in contact with the tapered hole 41, and the preform side portion of the straight portion 51 is inserted into the tapered hole 41 of the nozzle insert 4. Thereby, the injection of the molten resin 109 is closed.

Here, the temperature reduction of the molten resin 109 existing between the taper portion 52 and the taper hole 41 is suppressed by inserting the preform side portion of the taper portion 52 into the gate hole 31 of the bottom insert 3. And the occurrence of cold slag can be reduced.
In addition, since the portion on the injection machine side of the taper portion 52 is substantially in contact with the taper hole 41, there is almost no molten resin 109 between the taper portion 52 and the taper hole 41. That is, it is presumed that the generation of cold slag is greatly reduced by the fact that almost no resin that crystallizes and whitens in this region.
Further, the portion of the straight portion 51 on the preform side is inserted into the tapered hole 41 of the nozzle insert 4, thereby increasing the amount of the high-temperature molten resin 109 existing between the straight portion 51 and the tapered hole 41. Therefore, the temperature drop of the molten resin 109 can be suppressed, and the occurrence of cold slag can be reduced.

  As described above, according to the preform injection molding apparatus 1 of the present embodiment, when a preform is injection molded, the generation of cold slag can be reduced and the productivity can be greatly improved.

  The preform injection molding apparatus of the present invention has been described with reference to the preferred embodiments, but the preform injection molding apparatus according to the present invention is not limited to the above-described embodiments, It goes without saying that various modifications can be made within the scope of the present invention.

1,100 Injection molding equipment 2 Bottom cavity mold
3 Bottom insert
4 Nozzle insert
5 Needle valve
21 Gate
31 Gate hole
41 Tapered hole
51 Straight part 52 Tapered part
53 Convex
54 Cylinder part 101 Bottom cavity mold
102 gate
103 nozzles
104 core mold
105 Needle valve
106 Heater
107 Bottom insert
108 Nozzle insert
109 Molten resin
131 flow path
132 flow path
171 Hole for gate
181 Taper hole

Claims (3)

A bottom insert that is attached to the gate of the bottom cavity mold and has a hole for the gate, a nozzle insert that is attached to the nozzle so as to be in surface contact with the bottom insert, and that has a tapered hole, and in the tapered hole of the nozzle insert In a preform injection molding apparatus having a needle valve that advances and retracts,
Formed on the tip side of the needle valve is a frustoconical tapered portion having a taper angle corresponding to a cylindrical straight portion and a tapered hole of the nozzle insert;
When stopping injection of the molten resin into the bottom cavity mold, the needle valve is advanced so that the tip side portion of the taper portion protrudes from the taper hole of the nozzle insert, and the tip side of the straight portion The preform injection molding apparatus, wherein the portion is inserted into the tapered hole of the nozzle insert.   2. The preform injection molding according to claim 1, wherein the needle valve has a cylindrical portion on an injector side of the straight portion, and the diameter of the straight portion is smaller than the diameter of the cylindrical portion. apparatus.   The preform injection molding apparatus according to claim 1, wherein a convex portion is formed on an end surface of the tapered portion.

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