JPS6230009A - Reaction injection molding device - Google Patents

Abstract

PURPOSE:To drain gas sufficiently to secure a good fluidity of resin materials and keep off foams getting mixed by providing detecting means which detect the flow-in of resin materials from the cavity of mold into the venting passage and also providing an on-off valve to close the venting passage when the said detecting means detect the flow-in of resin materials. CONSTITUTION:The foaming resin materials P, being injected into the cavity 2 and filled up therein, flow through the gas drainage line 4. When the resin materials come up to the detecting means 5 set up in the said line, the detecting means 5 detect the flow and actuate the closing valve 6 to close the gas drain age line 4. Thus, by draining the gas sufficiently at the time of injection and filling, the fluidity of resin materials P is secured, and the density and yield of molding product are increased by the pressure rise during foaming and harden ing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a reaction injection molding apparatus that injects a resin stock solution into a mold cavity and foams and hardens the resin stock solution.

(Prior art) Generally, in a reaction injection molding apparatus for molding, for example, a foamed urethane molded product, a mixed resin stock solution is injected into a mold cavity using a mixing head and foamed and hardened. It is necessary to provide a gas vent passage in the mold that communicates with the cavity (Utility Model Publication No. 59-1318)
(See No. 13).

This gas venting passage performs gas venting during injection so that the resin stock solution flows with good fluidity within the cavity, and prevents air bubbles (air voids) from being drawn into the molded product.

Therefore, in order to obtain sufficient fluidity of the resin stock solution during injection and to uniformly foam and mold a molded product with a uniform density, the gas vent passage must be formed to be large enough to allow rapid gas venting. There is a need. However, if the gas venting passage is large, there is a problem that the resin material flows out from the gas handling passage during foaming and curing, lowering the density of the molded product, making it impossible to ensure desired material properties, and lowering the material yield. On the other hand, if the gas vent passage is made smaller, the pressure inside the cavity during foaming and curing increases, making it possible to obtain the desired molded product with high density. There is a risk that molding defects such as surface defects and underfilling may occur.

(Object of the Invention) In view of the above circumstances, the present invention focuses on the fact that degassing is necessary when the resin stock solution injected into the cavity is in a fluid state when it is filled into the cavity, and uses this degassing passage. The object of the present invention is to provide a reaction injection molding apparatus which can be opened and closed to obtain a good molded product.

(Structure of the Invention) The reaction injection molding apparatus of the present invention is provided with a detection means for detecting the inflow of resin material from the cavity of the molding die into the gas vent passage, and when the inflow of the resin material is detected by the detection means, the above-mentioned This device is characterized by being provided with an on-off valve that closes the gas vent passage.

(Effects of the Invention) According to the present invention, gas is sufficiently vented by opening the gas vent passage until the resin material injected into the cavity foams and the entire cavity is filled with the resin material. This ensures good fluidity of the resin material and prevents the inclusion of air bubbles. In addition, the detection means detects when the foaming progresses and the resin material flows into the gas venting passage, and in response, the on-off valve is activated to close this gas venting passage, which reduces the pressure inside the cavity. increases, the molded product is cured at a predetermined density without decreasing its density, and a molded product of excellent quality can be obtained. Furthermore, the amount of resin material flowing out from the gas venting passage is reduced, increasing the material yield, and the process of deburring molded products becomes easier and easier, thereby reducing product costs.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

Figure 1 shows the main structure of the mold of the reaction injection molding device.
The mold 1 is configured as an open/close mold consisting of an upper mold 1A and a lower mold 1B, and a cavity 2 is provided between both molds 1A and 1B. For example, a urethane stock solution (a mixed solution of a polyol stock solution and an isocyanate stock solution) is injected into the cavity 2 as a resin stock solution. The resin stock solution injected into the cavity 2 foams, fills the cavity 2, and hardens.

The mold 1 is provided with a gas vent passage 4 on its mold mating surface, which communicates the cavity 2 with the outside of the mold. A detection means 5 for detecting passage of the resin material P (foamed resin stock solution) is disposed in the middle of the gas venting passage 4, and an on-off valve 6 for opening and closing the gas venting passage 4 is installed.

The detection means 5 includes a light source 5a facing the gas vent passage 4.
and a photosensor 5b are arranged, and their signals are input to the control circuit 7. The resin material P flows into the gas vent passage 4, and the presence or absence of the resin material P is detected from the change in the amount of detected light due to the presence of the resin material P between the light source 5a and the photosensor 5b.

As shown in FIG. 2, the control circuit 7 includes a photosensor 5 whose electrical characteristics change depending on the amount of light from the light source 5a.
The signal b is input to the transistor 8, and the transistor 8 performs a switching operation in accordance with the set value adjusted by the variable resistor 9, thereby activating the relay 10 for driving the on-off valve 6.

On the other hand, the on-off valve 6 includes a slide member 12 having a ball body 12a that opens and closes the opening of the gas vent passage 4, and a drive cylinder 13 that moves and operates the slide member 12. The fluid pressure from the pressure source 15 is switched by a solenoid valve 14. A signal from the control circuit 7 corresponding to the signal from the detection means 5 is outputted to the solenoid valve 14 .

This 171 opening valve 6 opens the gas vent passage 4 when the resin stock solution is injected into the cavity 2, that is, when the detection means 5 does not detect it, and when the detection means 5 detects the inflow of the resin material P into the gas vent passage 4. It operates to close the gas vent passage 4. Note that the open operating state of the on-off valve 6 may be detected and inputted to the control circuit 7 to be compared with the detected state of the detection means 5.

With the above configuration, the resin material P injected into the cavity 2 and foamed flows into the gas venting passage 4 after filling the cavity 2, but the resin material P flows into the gas venting passage 4 up to the position of the detection means 5. When the inflow occurs, this is detected by the detection means 5.
is detected and operates the on-off valve 6 to close the gas vent passage 4.

This ensures the fluidity of the resin material P through sufficient degassing during injection and filling, while improving the density and yield of the molded product due to the pressure increase during foaming and curing.

The test results confirming the effects of the above-mentioned molding apparatus of the present invention are shown below. As a comparative example in this test, in Comparative Example 1, the injection □, that is, the resin injection amount was standard (90% of the cavity volume).
The degassing passage is small and the amount of degassing during injection and filling is insufficient. Comparative example 2
The standard injection m is that the gas venting passage is large so that a sufficient amount of gas can be handled during injection and filling. Furthermore, in Comparative Example 3, the injection amount was larger than the standard, and the gas venting passage was large like Comparative Example 2. On the other hand, in the embodiment of the present invention, the injection amount is standard, and the gas vent passage 4 is large.
Moreover, the on-off valve 6 is closed by the detection means 5 provided in the gas vent passage 4.

The average density, density distribution, and material yield of the molded products molded by each side above are as shown below, and the surface quality of the molded products is the product of Comparative Example 1, which has defects such as air bubbles on the surface. There were no defects in other products.

■This invention (outgassing amount 2 large 20% amount: standard) average density
1.05g/cm3 density distribution 1.03
~1.07 a/cm3 material yield 99
% ■Comparative example 1 (gas venting position: small, injection amount: standard) Average density 1.07g/Cl113 density distribution 0
．． 98-1.15 g/cm3 Material yield 99
% ■ Comparative Example 2 (Two major gas vent gates, Injection j: Standard) Average density 1,020/cm3 Density distribution 1.00
~1.04 g/cm March yield 90
% ■Comparative example 3 (gas venting: large, injection ω: large) average density
1.03 g/c, rn3 density distribution
1.01~1.05 g/cm3 material yield
85% As can be seen from the above results, in Comparative Example 1, since the degassing interval was small, the internal pressure was large and a molded product with a high average density and high yield was obtained, but the density distribution In addition to being widely lacking in uniformity, molded products have defects in surface texture. In Comparative Example 2, the amount of gas removed is large and the surface quality is good, but the density and material yield are reduced due to the outflow of the resin material from the gas removal passage. Furthermore, in Comparative Example 3, the amount of gas vented is large and the surface quality is good, and the injection amount is large and the density is also high, but the resin m flowing out from the gas venting passage increases and the material yield decreases. It has decreased significantly.

On the other hand, in the case of the embodiment of the present invention, the amount of degassing during injection and filling is large and the surface quality is good.Moreover, the gas handling passage 4 is closed during foaming and curing, and the pressure inside the cavity 2 increases. Even if the injection amount is standard, a homogeneous molded product with a high average density can be obtained, the material yield is also good, and costs can be reduced and deburring work can be simplified.

In the above embodiment, the detection means 5 is an example of optical detection that detects a change in light amount due to the blocking of light by a resin material. Conventionally known detection means can be employed, such as one that detects using a change in ultrasonic wave reflection due to the presence or absence of a resin material.

Furthermore, as for the structure of the on-off valve 6, in addition to one having a valve body that directly opens and closes the opening of the gas vent passage, there are also those that open and close this passage by operating a valve member interposed in a passage communicating with the gas vent passage. , a conventionally known air passage opening/closing mechanism can be employed. Furthermore, when a plurality of gas vent passages are provided, it is necessary to provide an on-off valve to open and close each passage.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a partially sectional view of a mold of a reaction injection molding apparatus according to an embodiment of the present invention, and FIG. 2 is an electric circuit diagram showing an example of a control circuit for a detection means. 1... Molding mold 1A... Upper mold 1B... Lower mold 2... Cavity 4... Gas vent passage 5...
...Detection means 6...Opening/closing valve P...
...Resin material Figure 1 Old Figure 2

Claims (1)

[Claims] (1) In a reaction injection molding device that injects a resin stock solution into the cavity of a mold provided with a gas vent passage and foams and hardens it, a detection means for detecting that the resin material has flowed into the gas vent passage is installed in the mold. 1. A reaction injection molding apparatus, further comprising an on-off valve that closes a gas vent passage in response to an output signal from the detection means.