JPH0679817B2 - Integrated foam molding method - Google Patents

Description

The present invention relates to a molding method for obtaining a product by injecting an undiluted urethane solution between a skin material and a core material to foam and integrate them.

(Conventional technology) Integrated foam molding is a known technology (for example, "Production term dictionary" Toyota Motor Corporation Toyota Technical Association, Showa 60).
Issued December 24, 2014, see page 391), it is widely used in the manufacture of interior parts for automobiles. For example, an instrumental panel safety pad integrally formed by foaming has a foam material formed between a skin material and a core material. Semi-rigid urethane foam is generally used as the foaming material, thermoplastic resin is injection molded as the core material, and slush molded material is generally used as the skin material as vinyl chloride. There is. Since such an integral foam-molded product is rich in compressibility and resilience, it is useful for mitigating impact in the event of a collision between an occupant and a passenger compartment due to an accident or the like.

Conventionally, the integral foam molding instrumental panel safety pad as described above has been manufactured as follows using a foam mold composed of an upper mold and a lower mold.

First, as shown in FIG. 4, the slush-molded skin material 3 is arranged on the molding surface of the lower mold 5, while the pre-formed core material 1 is fixed to the molding surface of the upper mold 4 by fixing pins (not shown). No.) etc. Next, a predetermined amount of urethane stock solution 2a mixed with, for example, polyether polyol, diisocyanate or the like is supplied from the pouring 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 is increased by the action of the foaming agent mixed in the foaming raw material liquid, and the space formed by the core material 1 and the skin material 3 is filled with the polymerization reaction. And it is hardened by heating from the outside. Foam 2
After fully cured, the upper mold 4 is opened and released from the mold as shown in FIG. 6, whereby the instrumental panel safety pad 8 including the core material 1, the foam material (urethane foam) 2b, and the skin material 3 is formed. can get.

By the way, the parting portion 9 (the fifth mold) between the upper mold 4 and the lower mold 5 is
If the leakage of the foam that causes burrs occurs in the figure, voids and cell roughening will occur at the molding site in the vicinity, resulting in poor quality products and because the foam is highly adhesive, Cleaning will be time-consuming. As a countermeasure against this, conventionally, a foaming mold having a good sealing property was used, and the upper mold and the lower mold were fixed by clamping during molding.

(Problems to be solved by the invention) However, when the integrated foam molding system with improved mold sealing property is adopted, the urethane foam and the skin material of the molded product are peeled off at the time of demolding after completion of molding, and surface blisters are generated. There was a problem that it would occur. The reason for this will be explained with reference to FIG. 6. In the urethane foam 2b, there is a foaming gas that could not escape sufficiently, the residual pressure P ₁ thereof is large, and at the time of demolding This is because a vacuum-like space 7 having a negative pressure P ₂ is instantaneously generated between the molds 5 due to the good sealing property. FIG. 7 shows a time-skin skin pressure curve in the conventional integral foam molding. This pressure is the pressure between the skin material 3 and the lower die 5, and is the internal pressure of the foam 2 up to T ₃ at the time of demolding. equal. In addition, in FIG. 7, T ₀ is when the mold is set,
T ₁ indicates the time when the foaming raw material was injected, T ₂ indicates the time when the foaming was completed, and the curing time was between T _{2 and} T ₃ , during which the gas in the foam 2 escaped little by little to the outside of the mold (not completely sealed). For).

As can be seen from FIG. 7, at the time of demolding T ₃ , the epidermis momentarily P ₁
The pressure of + P ₂ is applied, and the adhesive force between the skin and the urethane foam is defeated by the pressure P ₁ + P ₂ , so that the skin material is separated from the urethane foam and surface blister occurs.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an integral foam molding method which does not cause burrs and surface blisters in a molded product.

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

Yet another method of the present invention to achieve the same purpose is:
In the foam molding method with integrated skin and core material, offline data is input in advance to the control device, and the foam mold is unclamped when the pressure differential value (Δp / Δt) of the urethane foam becomes 0 or negative. It is characterized by

That is, the present invention is to perform the unclamping (to release the clamp), which was conventionally performed at the time of demolding, immediately after the internal pressure of the foam reaches the maximum value by the control device and without demolding. , The timing is detected by the control device by an online system using a pressure sensor, or various data such as the mixture composition ratio of the urethane raw solution, the injection amount, the temperature, the pressure change due to the sealing degree, and the rise time (foaming reaction time). It can be performed by inputting the unclamp timing calibrated based on the relevant data of 1) to the control device.

In the method of the present invention as described above, it is preferable to form a vent hole in the foam mold to prevent negative pressure generated between the foam mold and the molded product at the time of mold release, and as another means. Pressurized air may be sent into the mold through the ventilation holes.

(Function) The pressure in the foam rises with the reaction of the foaming raw material, reaches a peak with the completion of foaming, and then gradually decreases, but when the pressure differential value (Δp / Δt) becomes 0 or negative, When clamped, the upper mold is pushed up by the pressure of the foam,
There is a slight gap in the mold seal. Since the gas suddenly escapes from there, the pressure due to the residual gas in the foam is
By the time it is released from the mold, it drops significantly. If the pressure differential value (Δp / Δt) is unclamped after the time when the differential pressure value (Δp / Δt) becomes 0 or a negative value, the gas escape speed extremely decreases. This is because the set gas release clearance between the core material and the skin material is blocked by the foaming material being cured.

Further, at the time of unclamping, since the foam has sufficiently increased in viscosity, it does not leak out from the gap between the mold seal portions caused by unclamping.

(Examples) Hereinafter, the present invention will be described 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 foaming mold during integral foam molding according to an example. In this, a slush-molded vinyl chloride skin material 3 is set in the lower mold 5, and a core material 1 formed by strengthening acrylonitrile-styrene resin with glass fiber is set in the upper mold 4, and then a urethane stock solution is placed on the skin material 3. After injection, the upper mold 4 is rotated down through the hinge 10 to close the mold, and after clamping, the state where the foaming reaction is about to end is shown.

As shown in FIG. 2 (partial change diagram of FIG. 1), this foam-type clamp portion has a taper groove 11 and a taper hole 12 provided in each of the upper die 4 and the lower die 5, and the tip of the rod 13 is tapered. The hydraulic cylinder 14 has a shape, and the rod 13 is expanded and contracted to perform a clamping operation. The lower die 5 is provided with a pressure sensor 15, and the sensor 15 measures a skin pressure (pressure at which the sensor 15 is pressed by the skin material 3) p. The signal is exponentially processed by the detector 16 of the control device 19, and then when the computing unit 17 determines Δp / Δt ≦ 0, a command signal is sent to the operation unit 18 to operate the hydraulic cylinder 14 to operate it, as shown in FIG. Unclamp the mold as shown in. Then upper mold 4
Is slightly pushed up by the urethane foam 2, and a gap is generated in the mold seal portion 9, and high-pressure foaming gas escapes from there.

Therefore, the skin pressure sensed by the sensor 15 sharply decreases as shown by the solid curve in FIG. Since then the foam 2 during curing will block the gas outlet between the core 1, the skin material 3, but the rate of decrease in the pressure p decreases, the foam residual pressure P ₁ demolding time T ₃ Is considerably lower than before. The dotted curve in FIG. 3 shows the skin pressure p when unclamped at the time of the black arrow, and it can be seen that in this case the gas does not sufficiently escape to the outside of the mold.

The demolding is performed by raising and rotating the upper mold 4 by a device (not shown), but at this time, the negative pressure P ₂ generated between the skin material 3 and the lower mold 5 is extremely small. This is because the upper die 4 is provided with the vent hole 20 and the air that has entered the die passes around the back side through the cavity (not shown) of the non-product portion.

The product obtained in this way has skin blisters (peeling of the skin material).
No defects such as burrs are seen.

Example 2 A large number of foam molds similar to those used in Example 1 are used except that there is no pressure sensor, and the same molded product is manufactured in a continuous mass production line. At that time, various data previously obtained at another place using the same model are input to the control computer of the production robot. As a result, the robot performs the setting of the core material and the like, the injection of the undiluted urethane solution, the closing mold, the clamping operation, the demolding, etc. in the same manner as in the procedure of the first embodiment. Although unclamping is performed at the time when Δp / Δt ≦ 0 based on the above-mentioned offline data, a molded product of constant quality with no defects can be obtained with good productivity even in this case.

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

First, it is possible to manufacture an integral foam-molded product without surface blister defects without generating burrs.

In addition, since the residual gas in the foam can be removed very effectively in a short time, it is possible to accelerate the demolding time. That is, the degassing time, which is one of the main factors that determines the molding cycle time, can be shortened, so that the molding cycle can be accelerated.

Furthermore, since degassing is performed at the most effective time, the urethane layer is made to communicate (elimination of closed cell), and a good urethane foam can be formed.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the integral foam molding method of the present invention, FIG. 2 is a partial change view of FIG. 1, FIG. 3 is a view showing an effect of unclamping according to the embodiment, 4, FIG. 5 and FIG. 6 are explanatory views showing the conventional integral foam molding method continuously, and FIG. 7 is a view showing the pressure change to the skin material with time in the conventional molding method. In the figure, 1 ... Core material, 2 ... Urethane foam material, 3 ... Skin material, 4 ... Upper mold, 5 ... Lower mold, 7 ... Vacuum space 9 ... Parting part (mold sealing part) 14 ...... Hydraulic cylinder, 15 ...... Pressure sensor 19 ...... Control device, 20 ...... Vent hole

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Claims (6)

[Claims] 1. In the method of foaming a skin material core material integrally, the pressure of the urethane foam is detected by a pressure sensor provided in the foaming mold, and at the same time the differential value (Δp / Δt) of the pressure becomes 0 or negative. An integral foam molding method comprising unclamping a foam mold. 2. The integrated structure according to claim 1, wherein a ventilation hole is formed in the foam mold for preventing a negative pressure generated between the foam mold and the molded product at the time of releasing the mold. Foam molding method. 3. The integrated foam molding method according to claim 2, wherein pressurized air is sent into the mold through the ventilation hole. 4. A skin material core material integrated foam molding method, wherein offline data is input in advance to the control device, and foaming is carried out when the pressure differential value (Δp / Δt) of the urethane foam becomes 0 or negative. An integral foam molding method comprising unclamping a mold. 5. The integrated structure according to claim 4, wherein a ventilation hole is formed in the foam mold to prevent a negative pressure generated between the foam mold and the molded product when the mold is released. Foam molding method. 6. The integrated foam molding method according to claim 5, wherein pressurized air is sent into the mold through the ventilation hole.