JPH11105082A - Hot runner mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of the turnup of a surface layer causing the damage of appearance and the plateout of the pattern of the surface layer and the surface of a molded product. SOLUTION: A low heat conductive material 8 is present between a fixed mold M1 and the gate part 2 provided therein. The gate part 2 and the low heat conductive material 8 are set to a state drawn into the fixed mold M1 from a movable mold M2 and a cavity 1 formed by mold closing. A filling resin bringing about a slip in the vicinity of the gate part 2 remains in a stepped shape and the surface of the cavity 1 achieves a resin flow becoming a fountain flow. After the cavity is filled with the resin not precipitating inorg. matter from the outlet of a resin passage to form a surface layer, a product is internally filled with the resin from which inorg. matter is precipitated. In order to obtain good appearance, difference in level is provided to the cavity 1 within a range of 0.5-1.5 mm. The taper angle of the outlet of the resin passage at the tip part of a nozzle is set to 40-50 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hot runner mold capable of improving the appearance of a molded product.

[0002]

2. Description of the Related Art As a countermeasure against poor appearance due to a decrease in resin temperature at the nozzle tip of a hot runner mold, there is, for example, a mold insulated between a nozzle tip and a cavity with a synthetic resin having low thermal conductivity. (JP-A-8-332653).
Due to this heat insulation, the temperature difference between the molten resin at the nozzle tip and the nozzle body can be reduced, and the temperature of the mold near the tip of the gate does not rise. There is no occurrence of molding failure or jetting due to cold slug or the like.

[0003]

However, as shown in FIG. 3, the cavity opening surface 10 consisting of the gate end surface 9 and the lower surface of the low thermal conductive material 8, which is a part of the smooth cavity 1, has a design temperature. When the temperature rises as described above, the surface layer is turned up near the gate portion by the filling resin R that has caused the sliding flow, and a surface layer pattern is generated. In addition, when a hard vinyl chloride resin is used as the resin material, a plate-out phenomenon occurs in which inorganic substances such as lead and titanium added as a stabilizer or a pigment precipitate on the product surface. Therefore, an object of the present invention is to provide a hot runner mold that does not have a surface turn-up or a surface pattern and does not cause a plate-out phenomenon on the surface of a molded product.

[0004]

The invention according to claim 1 comprises a fixed mold and a movable mold, and a nozzle provided in the fixed mold has a gate portion and a periphery of the gate portion. There is a low thermal conductive material provided, a cavity is formed between the fixed die and the movable die, and the surface of the cavity opening made of the gate and the low thermal conductive material is the fixed die. A hot runner mold provided with a step toward the inside of the fixed side mold with respect to the cavity surface, wherein the step is 0.5 mm or more and 1.5 mm or less. Hot runner mold.

According to the first aspect of the present invention, the step is 0.5 m.
m and 1.5 mm or less. When a step of less than 0.5 mm is provided, the surface of the resin is turned up by the sliding flow of the filled resin,
Surface pattern and plate out occur. Also, 1.5
If a step exceeding mm is provided, resin shrinkage occurs in the vicinity of the gate portion, and sink marks occur around the gate portion.

According to a second aspect of the present invention, there is provided a hot runner mold according to the first aspect, wherein a taper angle of a resin flow path outlet at a nozzle tip portion is 40 ° or more and 50 ° or less.

[0007] The taper angle is the throttle angle at the outlet of the resin flow path at the tip of the nozzle. According to the second aspect of the present invention, the tapered angle of the outlet of the resin flow path at the tip of the nozzle is set to 40 ° or more and 50 ° or less. When the taper angle is less than 40 °, the resin easily flows out from near the wall surface of the flow path,
Plate-out is likely to occur, and the cut position of the gate portion varies, particularly when the product is released from the mold. On the other hand, if the taper angle exceeds 50 °, it becomes difficult for the resin to flow out from the vicinity of the wall surface of the flow path, and the resin burns.

(Operation) As shown in FIG.
Surface 1 of cavity opening formed by the lower surface of low thermal conductive material 8
If there is a level difference between the mold resin 0 and the cavity surface 11 of the fixed mold, the filled resin R which has caused the sliding flow near the gate portion 2 remains in the step shape, and the cavity surface 11 of the fixed mold has a fountain. The flow of the resin becomes the flow.

Further, by setting the taper angle W to an appropriate value, resistance to the flow of the resin is applied, and the resin on which the inorganic substance is precipitated flows later than the resin without the precipitation. Is filled to form a surface layer, and the resin on which the inorganic substance is precipitated is filled inside the product. Therefore, even if plate-out occurs, it enters the inside of the molded article and does not impair the appearance.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The hot runner mold of the present invention has a moving mold M2 having a cavity 1 as shown in FIG. 1, a gate 2 opening to the cavity 1, and a flow path 3 communicating with the gate 2. Injection in which a stationary mold M1 containing a hot runner H including a sprue 4, a manifold 5, and a nozzle 6 is accommodated, and an air heat insulating layer 7 is formed between the hot runner H and the stationary mold M1. The apparatus includes a molding die M, and an injection molding machine N that mounts the injection molding die and injects a molten resin into the die.

Further, PI (Mitsui Toatsu, grade: Aurum, between the outer periphery of the gate portion 2 and the fixed mold M1)
Thermal conductivity: 0.174 W / mK, thermal deformation temperature: 238
C.) is provided. The low heat conductive material 8 has a structure in which it contacts the outer periphery of the gate portion 2 and the fixed mold M1 to seal the inside of the air heat insulating layer 7.

As shown in FIG. 2, the structure of the tip of the nozzle is such that the gate portion 2 and the low thermal conductive material 8 are drawn into the fixed mold M1 from the cavity 1, and the gate end surface 9 and the lower surface of the low thermal conductive material 8 are formed. A stepped shape is formed between the cavity opening surface 10 made of the above and the cavity surface 11 of the fixed mold M1. The filling resin R which caused the sliding flow in the vicinity of the gate portion due to this step shape remains in the step shape.

At the tip of the nozzle, a taper angle W is provided. If the taper angle W is appropriate, the resin on which the inorganic substance has precipitated flows later than the resin without the precipitation. Thereby, an appropriate resin flow can be secured. Next, as an example using the apparatus of the present invention and a comparative example using the conventional apparatus, when a hard vinyl chloride resin was used as a raw material resin and a 3.3 mm-thick flat plate was injection-molded, As shown in Tables 1 and 2, the step size between the gate end surface 9 and the cavity opening surface 10 made of the low thermal conductive material 8 and the cavity surface 11 of the fixed mold and the resin flow outlet at the nozzle tip end are respectively shown. The occurrence of defects in molded products obtained by changing the taper angle was examined.

Table 1 shows the relationship between the appearance of the step when the step is formed between the end face 9 of the gate part, the cavity opening surface 10 made of the low thermal conductive material 8 and the cavity surface 11 of the fixed mold. The relationship between the taper angle W at the exit of the resin flow path at the nozzle tip and the appearance was examined from the failure occurrence situation of No. 2.

[0015]

[Table 1] In Table 1, the taper angle W at the outlet of the resin flow path at the tip of the nozzle was set to 40 °.

[0016]

[Table 2] In Table 2, the step between the cavity opening surface 10 made of the gate end face 9 and the low thermal conductive material 8 and the cavity surface 11 of the fixed mold was set to 1.0 mm.

According to the results shown in Table 1, the cavity opening surface 10 made of the gate end face 9 and the low thermal conductive material 8 is provided with a step in the range of 0.5 mm to 1.5 mm with respect to the cavity surface 11 of the fixed mold. As a result, the appearance was improved.

When there was no step corresponding to the conventional mold and when a step of 0.3 mm was provided, the solidified resin flowed out to the cavity surface, causing surface turn-up, surface pattern, and plate out. Also, 1.7 mm, and 2.
When a step of 0 mm was provided, resin shrinkage occurred near the gate portion 2 and sink marks occurred around the gate portion 2.

From the results shown in Table 2, the taper angle W at the outlet of the resin flow path at the tip of the nozzle of the hot runner mold is 40 ° to 50 °.
°, the appearance improved. When the taper angle W is 30 °, the resin easily flows out from the vicinity of the wall surface of the flow path 3, so that the plate-out easily occurs, and particularly, the cut position of the gate portion varies when the product is released from the mold. Further, when the taper angle W was set to 60 °, it was difficult for the resin to flow out from the vicinity of the wall surface of the flow path 3, and resin burns occurred.

From these results, it is found that the step is 0.5 mm or more.
The outer appearance is improved by providing the gap between the nozzles at 1.5 mm and setting the taper angle W of the outlet of the resin flow path at the tip of the nozzle between 40 ° and 50 °.

[0021]

By providing a step between the surface of the cavity opening formed by the end surface of the gate portion and the surface of the low thermal conductive material and the surface of the cavity of the fixed mold, it is possible to prevent appearance defects occurring on the surface layer of the product. . In addition, by appropriately setting the taper angle of the resin flow path outlet at the nozzle tip,
No plate-out on the surface of the molded product.

[Brief description of the drawings]

FIG. 1 is a schematic view of the entire hot runner mold of the present invention.

FIG. 2 is an enlarged view schematically showing a nozzle tip of the present invention.

FIG. 3 is an enlarged view schematically showing a nozzle tip of a conventional hot runner mold.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 Cavity 2 Gate part 3 Flow path 4 Sprue 5 Hot runner 6 Nozzle 7 Air insulation layer 8 Low heat conductive material 9 Gate part end face 10 Cavity opening surface 11 Cavity surface M1 Fixed side mold M2 Moving side mold M Hot runner N Injection Molding machine R Filled resin that caused sliding flow W Taper angle

Claims (2)

[Claims] 1. A fixed-side mold and a movable-side mold, wherein a nozzle provided on the fixed-side mold has a gate portion and a low heat conductive material provided around the gate portion. A cavity is formed between the side mold and the moving mold, and the surface of the cavity opening made of the gate portion and the low heat conductive material is fixed to the surface of the cavity of the fixed mold. A hot runner mold provided with a step toward the inside, wherein the step is 0.5 mm or more and 1.5 m or more.
m or less. 2. The hot runner mold according to claim 1, wherein a taper angle of a resin flow path outlet at a nozzle tip portion is 40 ° or more and 50 ° or less.