JPH02187312A - Foam molding - Google Patents

Abstract

PURPOSE:To mold an extremely excellent urethane foam having no flashes, no sink marks and no voids by using a mold provided with a urethane skeleton foam impregnated with a foam breaker at the end of a cavity and carrying out foam molding of urethane. CONSTITUTION:A Scott foam 7 impregnated with a foam breaker is used as a variable sealing section at the terminal of a cavity formed with a top force 1 and a bottom force 2 for sealing the terminal of the cavity. As the cavity terminal is sealed with air permeable Scott foam 7 impregnated with the foam breaker, gas in the cavity can be released out of the mold at the time of foam molding, and voids are not generated. The foams of urethane foam 5 reaching the cavity terminal is destroyed by the foam breaker applied to the Scott foam 7 to prevent said urethane foam from expanding. Thus, the urethane foam is prevented from flowing out of the cavity to eliminate the generation of flashes and sinking marks.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for foam molding urethane.

(Prior Art) Recently, lightweight and soft-feeling integrally foamed molded products have been increasingly used as interior components for automobiles and the like.

The molded product is highly compressible and resilient, so it is useful in mitigating the impact of a collision between an occupant and the passenger compartment due to an accident or the like.

Conventionally, this integrally foamed molded product has an upper mold 1 as shown in Fig. 2.
It was manufactured in the following manner using a foam mold consisting of a lower mold 2 and a lower mold 2.

That is, a skin material made of a soft vinyl sheet or the like is placed on the molding surface of the lower mold 2, and on the other hand, a skin material 1O made of, for example, acrylonitrile-styrene resin (ASG) reinforced with glass fiber is placed on the molding surface of the upper mold 1. Then, a foaming stock solution, for example, a urethane stock solution 5 mixed with polyether polyol, diisocyanate, etc., is poured into the lower mold 2.The mold is closed and the above stock solution is poured between the core material 9 and the skin material lO. It was manufactured by foaming and curing.

At this time, if the foam leaks out from the cavity, sink marks (cavity missing parts) will occur in the molded area in the vicinity, reducing the commercial value and requiring deburring work.

Figures 3 (a) to (d) show the process in which cracks and sink marks occur during urethane foam molding. Urethane stock solution is poured into the lower mold 2, the mold is closed, and the core material 9 and the skin material are removed. When foaming of the above stock solution is started between 1O and 5 foam 8
As shown in figure (a), it rises while expanding inside the mold, and the third
The filling in the mold is completed as shown in Figure (b). However, if there is a gap in the bartending part of the mold, the expanding foam 8 will flow into the gap and form a gap 11, as shown in FIG. 3(C). As the powder flows out, the uncured urethane foam is pushed out four times in the direction of the arrow in Figure 3 (C), resulting in sink marks 12 in the molded area in the vicinity as shown in Figure 3 (D). will occur. In order to prevent such cracks and sink marks from occurring, it is possible to seal the gap between the upper and lower molds around the cavity with an elastic sealant (Japanese Utility Model Publication No. 60-14914), but If the mold is made too heavy, there will be no place for the gas generated within the mold to escape.

Normally, the gas generated during foam molding reaches 2 to 4 times the mold cavity volume, so if the gas is not released outside the mold, the foam will contain high-pressure gas, and the boundary between the skin material and the urethane foam will This results in the disadvantage that voids are generated in areas such as the above.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a method for molding a urethane foam that does not cause the outflow of Paris and the generation of sink marks associated with it, and also does not generate voids.

(Means for Solving the Problems) The above-mentioned problems of the present invention are solved by performing foam molding of urethane using a mold in which the end of the cavity is provided with a urethane skeleton foam impregnated with a foam-breaking agent. .

In the present invention, the urethane skeleton foam refers to a urethane foam in which the membrane between the cells is removed using a chemical or the like, leaving only the skeleton.

An example of such a foam is Scotto foam, which is commercially available from Bridgestone Tire Company. The foam-breaking agent impregnated into the urethane skeleton foam has a foam-breaking effect on the foam of the urethane foam during one foaming process;
For example, polybutene is used.

In the present invention, a skeletal foam impregnated with such a foam-breaking agent is provided at the end of the cavity. It may be provided.

(Function) The urethane skeleton foam provided at the end of the cavity of the mold for foam molding has high air permeability because it consists only of the skeleton from which the cell membrane has been removed. During the process in which the stock solution foams and expands, filling the inside of the cavity and reaching the end of the cavity, the gas inside the cavity that causes voids is exhausted to the outside of the mold through the skeleton foam. Further, since the urethane skeleton foam is impregnated with a foam-breaking agent, the foam of the urethane foam that reaches the end portion is destroyed by the action of the foam-breaking agent, and the foam no longer expands. Therefore, since the urethane foam does not flow out to the outside more than the skeleton foam, the urethane foam is prevented from flowing out of the cavity in the form of flakes, and the generation of sink marks associated with this is also prevented.

(Example) Polyether polyol (SANNIX FA-718, manufactured by Sanyo Chemical Industries, Ltd.) 10 as a urethane raw material blend
0 parts, triethanolamine 4.0 parts, jetanolamine 1.0 parts, water 2.4 parts and DABGO-33LV
(manufactured by Sankyo Air Products Co., Ltd.) was mixed to prepare a polyol premix, and this and 61.6 parts of polyisocyanate (MDI-CR200, manufactured by Mitsui Toatsu Chemical Co., Ltd.) were used.

Mix the above polyol premix and polyisocyanate using a stirrer (4000 rpm xlosec
) L, as shown in FIG.
Urethane foam molding was performed by injecting it into a mold equipped with

During molding, the following four molding patterns were set for the variable seal portion 3 at the end of the cavity.

Molding pattern 1: Acceptable as shown in FIG. 1 (b) (Comparative example 1) The end of the cavity is completely sealed by the modified seal portion 3.

Molding pattern 2: Acceptable as shown in FIG. 1 (c) (comparative example) A gap 4 of 1 mm is provided between the variable seal portion 3 and the upper mold 1.

Molding pattern 3: Possible as shown in FIG. 1(d) (comparative example) The end of the cavity is sealed using Scotto foam 6 as a modified sealing part.

Molding pattern 4: As shown in FIG. 1 (E) (invention) As the deformed seal part, Scotto foam 7 impregnated with a foam-breaking agent such as Ssan, polybutene, and New Glide U (manufactured by Nippon Oil & Fats Co., Ltd.) was used. Seal the end of the cavity.

Table 1 shows the evaluation of the amount of flash, void defects, and sink mark defects of the molded products molded with the above four molding patterns.

Table 1 Evaluation of poor foaming As can be seen from the results in Table 1 above, in the case of molding pattern 1, the end of the cavity is sealed by the variable seal part 3, so the urethane foam does not flow out from the end of the cavity. Although there is no outflow and associated sink marks, on the other hand, voids occur because the gas inside the cavity cannot escape outside the mold. Molding pattern 2
In the case of , a gap 4 of 1 mm is provided between the variable seal part 3 and the upper mold 1, so the gas inside the cavity can escape to the outside of the mold and no voids are generated. Since it flows out of the cavity through the above-mentioned gap, the occurrence of sparks and associated sink marks can be seen.

Also, in the case of molding pattern 3, the end of the cavity is sealed by the breathable Scotto foam 6, so the gas inside the cavity can escape to the outside of the mold and no voids are generated. As the liquid flows out of the cavity through the pores in the cavity, the occurrence of sparks and associated sink marks can be seen.

On the other hand, in the case of molding pattern 4 of the present invention, the cavity end is sealed by the air-permeable Scotto foam 7 impregnated with a foam-breaking agent, so that the gas in the cavity escapes outside the mold during foam molding. The urethane foam that reaches the end of the cavity is destroyed by the foam-breaking agent impregnated in Scotto foam 7, and therefore no voids are generated.
Therefore, the urethane foam is prevented from flowing out of the cavity, and no cracks or sink marks occur.

(Effects of the Invention) According to the foam molding method of the present invention, the gas in the cavity that causes voids is discharged to the outside of the mold, and the urethane foam foamed and expanded in the cavity fills the inside of the cavity, but does not flow outside the cavity. Since it does not flow out, it is possible to mold an extremely excellent urethane foam that is free of cracks, sink marks, and voids.

[Brief explanation of the drawing]

Figure 1 (a) is a schematic cross-sectional view of the mold used in the examples, (b) to (e) are explanatory diagrams of molding patterns of the present invention and comparative examples, and Figure 2 is an illustration of the integral foam molding method. A cross-sectional view showing the injection of the foaming stock solution in the process diagram, and FIGS. 3(a) and 3(d) are explanatory diagrams of the process of occurrence of cracks and sink marks during foam molding. ...Upper die 2...Lower die 3...Variable seal portion 4...Gap 5...Urethane stock solution 6...Scotto foam 7...Scott foam impregnated with foam-breaking agent Patent applicant Toyota Motor Corporation Co., Ltd. (and 2 other people) Figure 2 Figure 1 (A) A-shaped mold (d) Diagonal pattern 3 (e) Hex-shaped butterfly 4 Figure 3 (a) Filling process (b) Filling completed ( C) Go out to Ha'suj (d) Moss occurs

Claims (1)

[Claims] A method for foam molding urethane, characterized in that foam molding of urethane is performed using a mold having a urethane skeleton foam impregnated with a foam-breaking agent at the end of the cavity.