JPH02307719A - Reaction injection mold - Google Patents

Abstract

PURPOSE:To obtain a reaction injection mold, in a resin item molded with which pin holes are prevented from developing at the thick wall part of the item by a structure wherein a springing means is provided at an enlarged part so as to narrow the crosssection of flow of filling resin at the enlarged part. CONSTITUTION:As mixed liquid 66 is filled in a cavity, a slide plate 64 releases the locking of a piston 59. As a result, the residual flow pressure and blowing pressure of the mixed liquid 66 is applied through an elastic membrane 58 and silicone oil 61 to the piston 59 so as to push up the piston 59, resulting in gradually pulling the elastic membrane 58 in a first recess 55 in order to form a thick wall part 68 in a resin molded part 67. As a result, since the boundary layer of the mixed liquid 66 is not disturbed at the end part of the cavity 31, pin holes due to the disturbance of the boundary layer of the mixed liquid 66 does not develop on the surface of the thick wall part 68 of the resin molded item 67 after molding.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a reaction injection mold.

(Prior art) As shown in Japanese Patent Application Laid-Open No. 62-30010, a reaction injection mold is provided with a gas vent passage on the mold mating surface that communicates the cavity with the outside of the mold.
It is generally known that gas venting passages are used to sufficiently vent gas to ensure good fluidity of the filled resin.

By the way, in resin molded products molded using reaction injection molds, in order to maintain the shape and ensure the rigidity of the product,
In particular, thick portions may be provided at the ends. In such a case, the reaction injection mold has a mold corresponding to the thick part,
The cavity is to be provided with an enlarged portion that enlarges the flow cross-sectional area of the filled resin.

(Problems to be Solved by the Invention) However, in the reaction injection mold described above, when the filled resin flows into the expanded portion, the resin flow rate decreases in the expanded portion, while the resin pressure increases. become. Therefore, in the boundary layer formed by the resin near the cavity surface, velocity energy is lost due to friction between the resin and the cavity surface, and the flow finally stops.After that, the flow is caused by a reverse flow caused by the reverse gradient of the resin pressure. will peel off from the cavity surface, which will disturb the boundary layer, and as a result, air bubbles mixed in the filled resin will appear on the surface of the thick part of the molded product, creating bottle holes on the surface. may occur.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a reaction injection mold that prevents pinholes from forming in the thick portion of a resin molded product.

(Means/effects for solving the problem) In order to achieve the above object, the present invention provides a reaction injection molding mold in which the cavity is provided with an enlarged section for enlarging the flow cross-sectional area of the filled resin. 1. An elastic means is disposed in the enlarged part so as to narrow a flow cross-sectional area of the filled resin in the enlarged part.

With the above configuration, at the start of resin filling, the flow cross-sectional area is narrowed by the elastic means, so the decrease in resin flow velocity is suppressed and the boundary layer of the resin flow is prevented from peeling (to prevent the boundary layer from being disturbed). (b) Velocity energy can be secured, and as the resin filling progresses, the elastic means is elastically deformed by the effects of the resin's residual flow pressure, foaming pressure, etc.
It is possible to widen the flow cross-sectional area of the resin, and it is possible to form thick parts in the resin molded product. Therefore, it is possible to form a thick interior in the resin molded product that does not have pinholes due to disturbances in the flow of the resin.

(Example) Embodiments of the present invention will be briefly described below with reference to the drawings.

1 to 5, reference numeral 1 denotes a reaction injection molding apparatus, and as shown in FIG. , 3b, an injection head 4, and a mold 5.

In the raw material tank 2a, liquid A is stored as a resin raw material, and in the raw material tank 2b, liquid B is stored as a resin thickness I.

For example, the A solution is composed of 80 parts by weight of polypropylene glycol, 20 parts by weight of ethylene glycol, 0.1 part by weight of dibutyl tin dilaure-1, and 1 part by weight of DΔB C0-33LV. For example, one consisting of 98 parts by weight of galbodiimide-modified MDI and 112 parts by weight of Freon is used. Air bubbles are mixed into the A and B liquids by a known method in order to foam the resin molded product.

1. The injection cylinder device 3a is located below the raw material tank 2a, and the injection cylinder device 3b is located below the raw material tank 2b. Both injection cylinder devices 3a and 3b have the same configuration, and each injection cylinder device 3a (3b) is capable of displacing and moving the injection piston 9 in the direction of exiting from the inside (upward in FIG. 1). The liquid A (liquid B) in the raw material tank 2a (2b) is drawn into the injection cylinder device 3a (3b), and the liquid A (liquid B) in the injection cylinder device 3a (3b) is drawn into the injection cylinder device 3a (3b) by moving the injection piston 9 inside. It has a function of extruding liquid B) to the injection head 4.

The injection head 4 has an injection port 1 as shown in FIG.
7, and an injection passage 18 that guides the liquid A to the injection port 17;
A return passage 19 for returning the A liquid, and the B
An injection passage 20 that leads the liquid to the injection port 17 and a return passage 21 that returns the B liquid are provided. The injection passage 18 and the outlet of the injection cylinder device 3a (7) are connected via a passage 22, the return passage 19 and the raw material tank 2a are connected via a passage 23, and there is a A valve 24 is interposed. On the other hand, the injection passage 20 and the outlet of the injection cylinder device 3b are connected via a passage 25, and the return passage 21 and the raw material tank 2b are connected via a passage 26, and a valve is provided in the middle of the passage 26. 27 is interposed (first
(see figure).

Furthermore, as shown in FIG. 2, a plunger 28 is provided within the injection head 4 as a valve body. This plunger 28 is to be driven in the vertical direction by a hydraulic drive mechanism 29 (in Fig. 2, arrows indicate oil supply and discharge).
By vertically displacing the plunger 28, the injection port 17 is opened and closed to the outside.

As shown in FIGS. 2 and 3, the mold 5 has an upper mold 4.
0 and a lower mold 41, and the upper mold 40 and the lower mold 41 form a runner 30, a gate part 32, and a cavity 31 inside. When the injection head 4 is set, the distal end surface of the injection head 4 is brought into contact with the mold 5 so that the injection port 17 and the runner 30 fit together.

The lower mold 41 has a cavity 3 as shown in FIG.
A first recess 55 that opens into the cavity 31 at the end of the cavity 31 to form an enlarged portion, and a first recess 55 that opens upward outside the first recess 55 (on the left side in FIG. 3). Two recesses 56 and a communication path 57 that communicates the first recess 55 and the second recess 56 are formed. First recess 55
and the cavity 31 are defined by an elastic membrane 58 as a component of the elastic means, and the elastic membrane 58
It is continuously attached to the entire inner wall of the second recess 55, 56 and the communication passage 57. Silicone resin is used for this elastic film 58, thereby ensuring the releasability of this elastic film 58 and a mixed liquid 66, which will be described later. A long piston 59 is provided in the second recess 56 with its axis directed in the vertical direction. One end of the piston 59 is always slidably fitted into the second recess 56, and the other end of the piston 59 projects upward from the second recess 56. One end side of this piston 59 and the elastic membrane 58 are
A sealed space 60 is formed between the first and second recesses 55 and 56 and the communication path 57, and silicone oil 61 is sealed within the sealed space 60.

The upper mold 40 has a recess 62 opened toward the lower mold 41, as shown in FIG. This recess 62 corresponds to the second recess 56, and when the lower mold 41 and the upper mold 40 are clamped, the other end side of the piston 59 can slide into the recess 62. It is supposed to be mated. An air passage 63 is opened at the bottom of the recess 62, and compressed air is supplied to and discharged from the inside of the recess 62 through the air passage 63.

In this case, since the cross-sectional area of the air passage 63 is extremely small compared to the cross-sectional area of the recess 62, air is not rapidly supplied and discharged, and the piston 59 moves up and down slowly.

Further, a slide plate 64 is slidably held on the lower surface of the upper die 40, and this slide plate 64
Accordingly, the piston 59 can be placed in the locked state as shown in FIG. 4, or the piston 59 can be placed in the unlocked state as shown in FIGS. 3 and 5. When the piston 59 is in the locked state, one end of the piston 59 is pushed down to the bottom of the second recess 56, as shown in FIG. The silicone oil 61 is pressed so that the elastic membrane 58 protrudes into the cavity 31 over the entire opening of the first recess 55 . At this time, the distance I21 between the elastic membrane 58 and the lower surface of the upper mold 40 and the vertical distance β of the cavity at other locations. Which ratio A, /(2,
In this example, it is assumed that the flow pressure of the mixed liquid in the cavity 31 is 5 kg/cm2.
1/Flood.

= 1/3, and this ratio is set as R1/I2. : It is allowed to increase to about 4/3.

On the other hand, as shown in FIGS. 3 and 5, when the piston 59 changes from the locked state to the unlocked state, the air passage 63 is simultaneously opened to the atmosphere. When an external force is applied to the elastic membrane 58 from the cavity 31 side, the neutral membrane 58 can be drawn into the first recess 55, and as shown in FIG. 3, one end of the piston 59 When the side is in its highest raised position, the ratio ff, /I2. is I21/l2o=5
/3.

In addition, 65 is a heater, and the heater 65 is filled with silicone oil 6.
It is provided to make the temperature of No. 1 the same as the mold temperature (for example, 70° C.).

Next, 10' will explain resin filling using the above device 1. Ru.

First, the injection head 4 is set in the mold 5 as shown in FIG. 2, and then the piston 59 is locked by the slide plate 64 as shown in FIG.

As a result, as described above, the silicone oil 61 receives a pressing force from the piston 59, and the elastic membrane 58 moves from the first recess 55 into the cavity 31 at the ratio ff, /βo=
It will protrude by 1/3, and the flow cross-sectional area will be in a narrowed state.

Next, liquid A in the raw material tank 2a and liquid B in the raw material tank 2b are
The liquid is supplied to the injection head 4 at a constant high pressure (for example, 150 kg/cm2) by the injection cylinder devices 3a and 3b.
Accordingly, the plunger 28 of the injection head 4 opens the injection lower part. As a result, liquid A and liquid B are mixed in the injection head 4, and the mixed liquid 6
6 is filled into the cavity 31 through the gate portion 32.

By filling this mixed liquid 66, the mixed liquid 66 enters the cavity 3.
The liquid mixture 66 also flows to one end, and reaches onto the elastic membrane as shown in FIG. At this time, as described above, since the flow cross-sectional area is narrowed by the elastic membrane 58, the flow velocity of the mixed liquid can be made higher than in other cavity parts, and the boundary layer of the flow of the mixed liquid 66 increases. Velocity energy can be secured to prevent separation (so that the boundary layer is not disturbed).

On the other hand, as the liquid mixture 66 is filled, the slide plate 64 unlocks the piston 59. As a result, the residual flow pressure and foaming pressure (for example, 5 to 10 kg/cm2) of the mixed liquid 66 acts on the screws 1 to 59 via the elastic membrane 58 and the silicone oil 61 to push the piston 59. As a result, the elastic membrane 58 gradually retracts into the first recess 55 as shown in FIG. Finally, as shown in FIG. 3, the ratio 12. /f2. = 5/3, and the thick portion 68 is formed in the resin molded product 67 by IFF.

Therefore, since the boundary layer of the mixed liquid 66 is not disturbed at the end of the cavity 31, the boundary layer of the mixed liquid 66 is not disturbed on the surface of the thick part 68 of the resin molded product 67 after molding. Based on the disturbance (no pinholes will occur).

An experiment was actually conducted under the conditions described in the above example, and no pinholes were generated on the surface of the thick portion 68 of the resin molded product 67, and a good surface was obtained.

On the other hand, from the beginning to the end, the ratio of the enlarged part to the vertical spacing of other cavities is,! , /f2o=5/3 in the conventional case, pinholes with a diameter of 10 to 80 LLm were generated.

Although the embodiments have been described above, the present invention includes the following.

(2) Utilize only the elastic force of an elastic body such as the elastic membrane 58 without using the force of the screws 59, silicone oil 61, etc.

(2) The aforementioned ratio JQ, /92o can be arbitrarily determined depending on the injection pressure of the mixed liquid 66, etc.

(Effects of the Invention) As described below, the present invention can provide a reaction injection mold that prevents the formation of pinholes in the thick interior of a resin molded product.

Brief explanation of the four sections FIG. 1 is a diagram conceptually showing a reaction injection molding apparatus in which a reaction injection mold according to an embodiment of the present invention is used, FIG. 2 is an enlarged explanatory diagram illustrating an injection head, FIG. 3 is an enlarged longitudinal cross-sectional view of a main part showing a reaction injection mold according to an embodiment of the present invention, and FIGS. 4 and 5 are operating state diagrams explaining the operating state of FIG. 3.

5...Molding mold 31...Cavity 55...first recess 58...Elastic membrane Patent distributor: Mazda Motor Corporation

Claims (1)

[Claims] (1) In a reaction injection mold in which the cavity is provided with an enlarged part for enlarging the flow cross-sectional area of the filled resin, the enlarged part has an elastic means so as to narrow the flow cross-sectional area of the filled resin in the enlarged part. A reaction injection mold characterized in that: