JPS63199616A - Monolithic foam molding method - Google Patents

Abstract

PURPOSE:To constitute the title method so that a molded product generates neither flashes nor surface swelling, by a method wherein pressure of a urethane foam is detected by a pressure sensor provided within a foam mold and at the same time when a differential value of the pressure becomes zero or negative, the foam mold is unclamped. CONSTITUTION:After setting-up of a skin material 3 and core material 1 respectively in a bottom force 5 and top force 4 and casting of a urethane stock solution onto the skin material 3, the mold is closed by descending a top force 4 through rotation and clamped. The bottom force 5 is provided with a pressure sensor 15 and the pressure sensor 15 measures skin pressure p. The single is subjected to exponential treatment by a detector 16 of a control device 19,then a command signal is sent to an operating instrument 18 when DELTAp/DELTAt<=0 is discriminated by an arithmetic unit 17, and the mold is made into an unclamped state by actuating a hydraulic cylinder 14. The top force 4 is pushed up a little by a urethane foam 2, and high-pressure blowing gas is fled through a mold seal part 9. Therefore, the skin pressure is reduced. A defect such as peeling of the skin material or flashes are not seen on a product obtained in this manner.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a molding method for obtaining a product by injecting a urethane stock solution between a skin material and a core material, foaming and integrating the materials.

(Prior art) Integral foam molding is already a known technology (for example, "Dictionary of Production Terminology", Toyota Motor Corporation, Toyota Technical Association, 1932).
(Refer to page 381, published on December 24, 2013). For example, the integral foam-molded instrument panel safety pad, which is widely used in the manufacture of interior parts for automobiles, etc.
A foam material is formed between the skin material and the core material. Semi-rigid urethane foam is generally used as the foam material, and material made by injection molding of thermoplastic resin is used as the core material.
As the skin material, a material formed by slush molding using vinyl chloride as a raw material is generally used. Since such integrally foamed molded products have high compressibility and resilience, they are useful for reducing impact in the event of a collision between an occupant and the passenger compartment due to an accident.

Conventionally, the integrally foamed instrumental panel safety pad as described above has been manufactured as follows using a foaming mold consisting of an upper mold and a lower mold.

First, as shown in FIG. 4, the slush-molded skin material 3 is placed on the molding surface of the lower mold 5, and the core material 1, which has also been preformed, is placed on the molding surface of the upper mold 4 with fixing pins (not shown). Next, a predetermined amount of urethane stock solution 2a mixed with, for example, polyether polyol, diisocyanate, etc., is supplied from the injection machine 6 onto the skin material 3, and then the upper mold 4 is rotated down to close the mold.

Then, as shown in FIG. 5, the volume of the foam 2 increases due to the action of the blowing agent mixed in the foaming raw material liquid, and the space formed by the core material 1 and the skin material 3 is filled, and a polymerization reaction occurs. 0 foam 2 that hardens due to external heating.
After the material has sufficiently hardened, the upper mold 4 is opened and removed as shown in FIG. 6, thereby obtaining an instrument panel safety pad 8 consisting of a core material 111 (foamed urethane foam) 2b and a skin material 3. .

By the way, if the foam that causes the leakage of foam occurs in the parting part 9 (Fig. 5) between the upper mold 4 and the lower mold 5, voids and cell roughness will occur in the molding area in the vicinity, resulting in poor quality. Not only does it become a finished product, but the foam is also highly adhesive, making cleaning the mold time-consuming. As a countermeasure, conventionally, a foam mold with good sealing properties was used, and the upper and lower molds were fixed by clamping during molding.

(Problem to be solved by the invention) However, when an integral foam molding system with improved mold sealing performance is adopted, the urethane foam and skin material of the molded product peel off when the mold is removed after molding is completed, resulting in surface blisters. There was a problem that occurred. The reasons for this can be explained using Fig. 6: 1. There is foaming gas in the urethane foam 2b that could not escape sufficiently, and its residual pressure n is large; 2. This is due to the fact that a vacuum space 7 of negative pressure P2 is instantaneously generated between the lower mold 5 due to good sealing performance. FIG. 7 shows a time-skin pressure curve in conventional integral foam molding. This pressure is the pressure between the skin material 3 and the lower mold 5, and is equal to the internal pressure of the foam 2 until demolding 1. In Fig. 7, To is the pressure when the mold is set, and T1 is the foaming raw material pressure. At the time of injection, 1 indicates the end of foaming,
1 to T1 is the curing time, during which time the gas in the foam 2 escapes out of the mold little by little (because it is not completely sealed).

As can be seen from Figure 7, during demolding 1, P is instantaneously applied to the epidermis.
When a pressure of 10 B is applied, the adhesive force between the skin and the urethane foam is weakened by the pressure, pH -+4, and the skin material peels off from the urethane foam, causing surface blistering.

The present invention has been made to solve the above problems, and its purpose is to provide an integral foam molding method that does not cause flakes or surface blisters in a molded product.

(Means for Solving the Problems) Therefore, in the integral foam molding method of the present invention, in the skin material core integral foam molding method, the pressure of the urethane foam is detected by a pressure sensor attached in the foam mold, and the pressure is It is characterized in that the foaming mold is unclamped at the same time that the differential value (Δp/Δt) of becomes 0 or negative.

Yet another method of the present invention to achieve the same objective is to
In the skin and core integral foam molding method, offline data is input into the control device in advance, and the foam mold is unclamped when the pressure differential value (Δp/Δt) of the urethane foam becomes O or negative. It is characterized by

That is, the present invention allows unclamping (releasing the clamp), which was conventionally performed during demolding, to be performed by the control device immediately after the internal pressure of the foam reaches its maximum value, and without demolding. , the timing can be detected by the control device using an online method using a pressure sensor, or various data such as the mixture composition ratio of the urethane stock solution, injection amount, temperature, pressure changes due to degree of sealing, etc. and rise time (foaming reaction time) can be used. ) This can be done by inputting the unclamping timing calibrated based on the relevant data into the control device.

In the method of the present invention as described above, it is preferable to make ventilation holes in the foam mold in order to prevent negative pressure generated between the foam mold and the molded product during demolding. Pressurized air may be sent into the mold through the holes.

(Function) The pressure inside the foam increases with the reaction of the foaming raw materials, reaches a peak with the completion of foaming, and then gradually decreases, until the pressure differential value (Δp/Δt) becomes O or negative. When unclamped, the upper mold is pushed up by the pressure of the foam, creating a slight gap in the sealing part of the mold. Since the gas is rapidly released from the foam, the pressure due to the residual gas in the foam drops significantly by the time of demolding. Note that unclamping is performed after the above-mentioned pressure differential value (Δp/Δt) becomes 0 or negative.

The rate at which gas escapes is extremely reduced. This is because the set gas release clearance between the core material and the skin material is blocked by the foam that is being cured.

In addition, since the foam has sufficiently increased viscosity at the time when it should be unclamped, it will not leak out from the gaps in the mold seal created by unclamping.

(Example) The present invention will be described below in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 FIG. 1 is a sectional view showing a foam mold during integral foam molding according to an example. This is done by setting a slush-molded vinyl chloride skin material 3 in the lower mold 5 and a core material 1 made of 7-crylonitrile-styrene resin reinforced with glass fiber in the upper mold 4, and then placing urethane resin on the skin material 3. After injecting the stock solution, the upper mold 4 is rotated down via the hinge lO to close the mold.
This figure shows the state where the foaming reaction is about to end after clamping.

As shown in FIG. 2 (partial change diagram of FIG. 1), this foam-type clamp part has a tapered groove 11 and a tapered hole 12 provided in each of the upper mold 4 and lower mold 5, and the tip of the rod 13 is tapered. It consists of a hydraulic cylinder 14 in the shape of a hydraulic cylinder 14, and a clamping operation is performed by expanding and contracting the rod 13. And lower mold 5
is provided with a pressure sensor 15, and the sensor 15 detects skin pressure (the pressure at which the sensor 15 is pressed from the skin material 3) p.
Measure. The signal is subjected to index processing by the detector 18 of the control device 18, and then when the calculator 17 determines that Δp/Δt≦O, it sends a command signal to the operating device 18 to operate the hydraulic cylinder 14, as shown in FIG. Unclamp the mold as shown. Then, the upper mold 4 is pushed up slightly by the urethane foam 2, and a gap is created in the mold seal portion 9, through which the high-pressure foaming gas escapes.

Therefore, the skin pressure sensed by the sensor 15 rapidly decreases as shown by the solid curve in FIG. After that, the foam 2 that is curing begins to block the gas outlet between the core material 1 and the skin material 3, so the rate of decrease in pressure p decreases, but the residual pressure n inside the foam 1 at the time of demolding is lower than that of the previous one. considerably lower than that of Furthermore, the third
The dotted line curve in the figure shows the skin pressure p when unclamping at the point indicated by the black arrow, and it can be seen that in this case, gas does not escape sufficiently outside the mold.

Demolding is carried out by rotating the upper mold 4 upward using a device not shown. At this time, the negative pressure R generated between the skin material 3 and the lower mold 5 is extremely small. This is because the upper mold 4 has ventilation holes 20. This is because the air that has entered the mold passes through the non-product cavity (not shown) and goes around to the back side.

The product obtained in this way has surface blisters (peeling of the skin material).
There are no defects such as or Paris.

Example 2 A number of foam molds similar to those used in Example 1, except for the absence of a pressure sensor, are used to produce identical molded products on a continuous mass production line. At that time, various data obtained in advance at a different location using the same model are input into the control computer of the production robot. As a result, the robot performs the same steps as in Example 1, such as setting the core material, injecting the urethane stock solution, closing the mold, clamping, demolding, etc. Furthermore, unclamping is performed based on the above offline data, Δp/Δt≦ Although this is carried out at the point when the temperature becomes 0, molded products of constant quality with no defects can be obtained with good productivity even in this way.

(Effects of the Invention) The integral foam molding method of the present invention has the following effects.

First, it becomes possible to produce an integrally foamed molded product without surface blistering defects without causing flakes.

Furthermore, since the residual gas in the foam can be removed extremely effectively and in a short time, the time for demolding can be brought forward. That is, the degassing time, which is one of the main factors determining the molding cycle time, can be shortened, so the molding cycle can be accelerated.

Furthermore, since degassing is performed at the most effective time, communication of the urethane layer (elimination of closed cells) is promoted, and a good urethane foam can be formed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the integral foam molding method of the present invention, FIG. 2 is a partial change diagram of FIG. 1, FIG. 3 is a diagram showing the effect of unclamping according to one embodiment, 4, 5, and 6 are explanatory diagrams sequentially showing the conventional integral foam molding method, and FIG. 7 is a diagram illustrating changes in the wind force applied to the skin material over time in the conventional molding method. In the figure, 1...core material 2...urethane foam 3.
...Skin material 4...Upper mold 5...Lower mold
7... Vacuum space 9... Parting part (mold seal part) 14... Hydraulic cylinder 15... Pressure sensor 19... Control device 20... Ventilation hole patent author Toyota Motor Corporation Company (and 2 others) ゛1 figure, 3 figures

Claims (6)

[Claims] (1) In the skin and core integral foam molding method, the pressure of the urethane foam is detected by a pressure sensor attached to the foam mold, and as soon as the differential value (Δp/Δt) of the pressure becomes 0 or negative, the foam mold An integral foam molding method characterized by unclamping. (2) Integral foam molding according to claim 1, characterized in that the foam mold is provided with ventilation holes to prevent negative pressure generated between the foam mold and the molded product during demolding. Method. (3) The integral foam molding method according to claim 2, characterized in that pressurized air is sent into the mold from the ventilation holes as necessary. (4) In the skin and core integral foam molding method, offline data is input into the control device in advance, and the foaming mold is started when the pressure differential value (Δp/Δt) of the urethane foam becomes 0 or negative. An integral foam molding method characterized by unclamping. (5) Integral foam molding according to claim 4, characterized in that the foam mold is provided with ventilation holes to prevent negative pressure generated between the foam mold and the molded product during demolding. Method. (6) The integral foam molding method according to claim 5, characterized in that pressurized air is sent into the mold from the ventilation holes as necessary.