JPH09193199A - Hot runner mold - Google Patents

Abstract

(57) [PROBLEMS] To provide a manifold type hot runner die for injection molding in which the temperature drop of these portions is suppressed so that the molten resin is less likely to stay at the branch portion or the corner portion of the runner. SOLUTION: A manifold 6 includes a branch portion 9 of a runner 9.
1 and a hot runner die 1 supported by a fixed die plate 4 via four support portions 14 having a small support area and located away from the corner portion 92.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hot runner die used for injection molding of synthetic resin.

[0002]

2. Description of the Related Art In injection molding of synthetic resin, usually,
The molten and plasticized resin is injected into the mold-clamped cavity through the nozzle of the injection molding machine, the mold sprue, runner, and gate, cooled and solidified, and then the mold is opened to mold the sprue and runner. Molding is performed in a cycle of protruding with the gate, protruding with a pin and dropping. However, in the case of such ordinary injection molding, the sprue and runner are collected separately from the molded product, pulverized, and then granulated again before use, resulting in a high recovery cost and in the case of granulation again. Physical properties deteriorate due to heating. Further, particularly in the case of multi-cavity molding, there is a problem that the sprue and runner become large and the time required for cooling becomes long, so that the molding cycle becomes long and the productivity is remarkably reduced.

Therefore, a hot runner die a as shown in FIG. 3 has come to be used ("Plastic Molding Technology" Vol. 7, No. 9). This mold is referred to as a manifold type hot runner mold, and is a manifold m in which a sprue e, a branch part f, and a runner d including a corner part g are incorporated between a fixed side mounting plate b and a fixed mold plate c. A hot runner nozzle n is incorporated at the end of the manifold m. Then, by covering the periphery of the manifold m with a heat insulating material (not shown) to improve heat insulation,
The resin in the manifold m is kept in a molten state even during the cooling of the molded product so that the injection molding can be continuously performed without taking out the sprue or the gate for each shot.

In such a manifold type hot runner die, the temperature of the manifold m is fixed to the fixed side mounting plate b.
Since the temperature of the main mold body including the fixed mold plate c and the stationary mold plate c is always higher, the heat is conducted away from the manifold m toward the main mold body, and the temperature of the manifold m decreases.

Therefore, the manifold m is fixed to the fixed side mounting plate b.
And so as not to directly contact the fixed mold plate c in a large area,
The manifold m is supported by a plurality of steel bolts h floating from the fixed side mounting plate b, and by a thrust ring spacer i surrounding the hot runner nozzle n from the fixed mold plate c, and the thrust ring spacer i is supported. It is made of a material having a low thermal conductivity, or the periphery thereof can be heated by a heater j.

[0006]

However, in the case of the mold as shown in FIG. 3, since the thrust ring spacer i is close to the branch part f and the corner part g and the supporting cross-sectional area thereof is large, the runner d is branched. The temperature drop of the part f and the corner part g is large, and the fluidity of the molten resin in contact with this part is deteriorated.

The branch portion f and the corner portion g are originally places where the flow direction and the flow velocity of the molten resin suddenly change. Therefore, the molten resin is likely to stay in the branch portion f and the corner portion g, and in the case of a resin having low thermal stability such as a vinyl chloride resin, the staying resin is thermally decomposed and discolored, or further carbonized, The appearance of the product may be impaired, and the strength and function may be reduced. Further, when the color of the resin is changed, the retained resin before the color change may be mixed with the resin after the color change.

The present invention has been made in view of the problems of the prior art as described above, and the temperature drop in these portions is reduced so that the molten resin is less likely to stay at the branch portion or the corner portion of the runner. The present invention aims to provide a hot runner die.

[0009]

To achieve the above object, the present invention is a manifold type hot runner mold for injection molding, wherein a plurality of manifolds are separated from the branch portion and the corner portion of the runner. Is supported by a fixed mold through a supporting portion having a small supporting area.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a hot runner die of the present invention, (A) is a sectional view, (B) is XX of (A).
It is sectional drawing along the line. As shown in FIG. 1, the hot runner mold 1 includes a fixed side mounting plate 2, side plates 3 and 3 on both sides, a fixed type plate 4, a movable type plate 5, and a movable side mounting plate (not shown) from the injection molding machine side. And a manifold 6 supported in a space surrounded by the fixed-side mounting plate 2, the side plates 3 and 3, and the fixed mold plate 4, and the like.

A sprue bush 7 is fitted on the manifold 6, and a sprue 8 extending from the sprue bush 7 branches rightward and leftward in the middle at right angles into runners 9 and 9. The runners 9 and 9 are joined to the sprue 8 from the middle again. The hot runner nozzles 10, 1 are bent at right angles to the direction and are connected to the hot runner nozzles 10, 10 provided through the fixed mold plate 4.
The cavities 12 and 1 formed between the fixed mold plate 4 and the movable mold plate 5 through the gates 11 and 11 formed at the end of 0.
2 are connected.

The periphery of the manifold 6 is kept warm by a heat insulating material such as asbestos, rock wool, glass wool or the like, which prevents heat radiation from the surface. It should be noted that the manifold 6 may have a built-in heater or a heater provided on the outer surface thereof so that the manifold 6 can be heated.

The manner of supporting the manifold 6 is as follows. That is, the manifold 6 is fixed to the fixed side mounting plate 2 by the plurality of adjusting bolts 13 provided on the fixed side mounting plate 2.
And four support parts 1 having a small support area at a constant distance from the branch part 91 and the corner part 92 of the runner 9 near the center of the hot runner die 1.
It is supported in a state of maintaining a distance from the fixed mold plate 4 via 4.

The support portion 14 is made of a material (for example, polyimide) having a low thermal conductivity and an excellent heat resistance temperature and mechanical strength, and a heat insulating material is laid between the support portion 14 and the manifold 6. Preferably. Further, in the vicinity of the support 11, the exposed portion between the fixed mold plate 4 of the hot runner nozzle 10 and the manifold 6 and the gate 11,
A heater 15 for heating is provided.

Since the hot runner die 1 constructed as described above is supported by the fixed die plate 4 at a distance from each other via the support portion 14 having a small cross-sectional area, the hot runner die 1 is fixed to the fixed die from the manifold 6. Since the heat conduction loss to the plate 4 is small and the support portion 14 is located far from the branch portion 91 and the corner portion 92, the temperature decrease of the branch portion 91 and the corner portion 92 is suppressed.

2A and 2B show another example of the hot runner die of the present invention. FIG. 2A is a sectional view, and FIG. 2B is a sectional view taken along line YY of FIG. Hot runner die 1a shown in FIG.
Are supported via narrow support portions 16 provided at both ends of the manifold 6. Support 16
Since is far from the branch portion 91 and the corner portion 92 and has a small cross-sectional area, the heat conduction loss from the manifold 6 to the fixed mold plate 4 is small, and the temperature decrease of the branch portion 91 and the corner portion 92 is suppressed.

[Embodiment] Next, an embodiment of the present invention will be described. [Example] A resin obtained by adding 0.88 parts by weight of a yellow pigment (titanium yellow) to 100 parts by weight of a vinyl chloride resin, and a predetermined heat stabilizer, lubricant, filler, etc. was plasticized by an injection molding machine. A hot runner mold 1 as shown in FIG. 1 was injected and filled. Then, vinyl chloride resin 10
A resin obtained by adding 0.88 parts by weight of a white pigment (titanium oxide) and predetermined heat stabilizers, lubricants, fillers, etc. to 0 parts by weight is plasticized by an injection molding machine, and 10 shots (2.00
0 cm ³ ) After injection molding, the resin in the manifold 6 was cooled and solidified. Then, the temperatures of the branch portion 91 (point P) and the corner portion 92 (point Q) immediately before the opening of the mold of each shot were measured.

The molding conditions are the temperature of the nozzle of the injection molding machine =
190 ℃ (setting), Manifold 6 temperature = 185 ℃
(Setting), injection amount = 40 cm ³ / sec. In addition, a polyimide resin is used for the support portion 14, and the dimensions of the manifold 6 and the support portion 14 are the diameter d of the runner 9.
= 10 mm, L ₁ = 270 mm, L ₂ = 120 mm, L
_{3 = 110mm, L 4 = 19mm} , was L ₅ = 40 mm.

Next, the solidified resin in the manifold 6 was taken out, the resin was sliced into slices at the branch portion 91 and the corner portion, the thickness of the yellow colored portion was measured by a CCD camera, and the average value was obtained.

[Comparative Example] Molding was performed in the same manner as in Example except that the conventional hot runner die shown in FIG. 3 was used, and the branch portion f (point P) and the corner portion g (point Q) were formed. The temperature was measured, and the thickness of the yellow portions of the branch portion f and the corner portion g were also measured to obtain the average value. The support portion (thrust ring spacer j) has a diameter D = 60 mm.
Other than the circular shape, the structure and dimensions of the mold and the manifold, the heat insulation state, the position and capacity of the heater, etc. were the same as those of the example.

The above results are summarized in Table 1.

[0022]

[Table 1]

[0023]

As is apparent from the above description, in the hot runner mold of the present invention, since the manifold is supported by the fixed mold through the plurality of supporting portions having a small supporting area, the hot runner mold is high in temperature. Since the heat conduction loss from the manifold to the mold body is small and the support is located far from the branch and the corner, the temperature drop at the branch and the corner is suppressed.

As a result, the resin stays in the branch portion or the corner portion where the flow direction and flow velocity of the molten resin drastically change, and the staying resin is thermally decomposed to cause discoloration or carbonization, and the strength and function are It is prevented from falling. Further, even when the color of the resin is changed, it is possible to prevent the resin before the color change and the resin after the color change from being mixed.

[Brief description of the drawings]

1A is a sectional view showing an example of a hot runner die of the present invention, and FIG. 1B is a sectional view taken along line XX of FIG.

FIG. 2A is a sectional view showing another example of the hot runner die of the present invention, and FIG. 2B is a sectional view taken along line YY of FIG.

3A is a cross-sectional view of a conventional hot runner die, and FIG. 3B is a cross-sectional view taken along line ZZ of FIG.

[Explanation of symbols]

 1,1a Hot runner mold 2 Fixed side mounting plate 4 Fixed mold plate 6 Manifold 9 Runner 91 Branch section 92 Corner section 10 Hot runner nozzle 14, 16 Support section

Claims (1)

[Claims] 1. A hot runner mold for injection molding of a manifold type, wherein the manifold is supported by a fixed mold through a plurality of supporting parts having a small supporting area separated from a branch part and a corner part of the runner. A hot runner mold characterized by