JPS6283111A - Mold for manufacture of urethane foam molding - Google Patents

Abstract

PURPOSE:To suppress the generation of flash as well as cracks and voids in a urethane foam molding by a method in which a bent hole of a specific diameter is provided in the upper one of split molds and a low gas-permeable sheet is provided on the tip of the hole on the mold side. CONSTITUTION:A split mold for casting a raw material and taking out a molding is divided into an top force 1 and a bottom force 2. Bend holes 3 of a diameter of 10-40m/m are provided in the top force 1, having a round or slit shape preferably, through which reaction gases in the system are discharged over a wide range from the system. A low gas-permeable sheet 4 used is preferably made of a nonwoven fabric, Kraft paper, polyethylene, etc., which is separable after taking out the molding.

Description

[Detailed Description of the Invention] E-Industrial Field of Application The present invention relates to a mold for producing a urethane foam molded body, and more specifically, the molded body is free from cracks and voids, and is free from protruding parts that occur at the joints of the molds. The present invention relates to the structure of a mold for manufacturing vehicle seat cushions that suppresses the occurrence of dust particles.

[Prior art] In the conventional manufacturing method of vehicle cushion bodies, the pressure inside the mold changes as shown in Fig. 3, and if the acid gas generated by the formation of urethane is not released to the outside of the system, the product will deteriorate. Because voids and cracks occur,
If necessary, about 5 to 10 vent holes with a diameter of 2 to 5 m/m are opened in the upper mold to vent gas.

It is also known to provide a low air permeability sheet inside the upper mold in order to reduce the amount of debris (benthole debris) that protrudes from the vent hole due to the foaming pressure.

Problems to be Solved by the Invention J However, even with these techniques, there is a problem in that it is insufficient to prevent voids and cracks from occurring in the cushion body.

Therefore, as a result of intensive research to solve the above problem, the inventor of the present invention found the following.

That is, the acid gas generated by the chemical reaction of the urethane foam within the mold continues to release reaction gas for about 3 to 4 minutes from the start of the reaction, as shown in Figure 4.
It has been found that when these reactive gases accumulate and the pressure inside the mold exceeds a certain level, troughs and voids occur. To be more specific, if the mold is simply filled with foam (it takes about 50 to 60 seconds, depending on the reaction rate and amount of filling, see section C shown in Figure 4), no cracks or voids will occur. , 80 seconds to 1 after foam filling
Cracks or voids occur over 10 seconds (4th
(See section D shown in the figure).

Therefore, when a small vent hole is provided in the upper part of the mold as in the past, as the foam rises, it comes into contact with the foam while it is still fluid, and that part quickly comes into contact with the high temperature in the curing furnace, which accelerates curing. Therefore, it is effective to expel the air in the mold and prevent voids, and to vent gas in the vicinity, but it is effective in releasing the entire reaction gas to the outside of the system and preventing cracks caused by the pressure of the reaction gas. It turned out to be ineffective.

Also, reactive gases are generated over a wide range.

If possible, it would be possible to prevent degassing by creating numerous vent holes in the upper mold and approaching free foaming, but this would require a lot of man-hours to remove the foam debris that fills the vent holes, and could result in product failure. There are too many and it's not realistic.

Furthermore, with conventional hot molding, in addition to gas venting from the upper mold vent hole, the pressure inside the mold increases compared to the area where the upper mold and lower mold meet (the smaller the vent hole, the higher the pressure), causing the foam to protrude. It has also been found that there is a problem in that this occurs, and that it requires many man-hours to cut off the protruding portion after demolding.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a mold for producing a urethane foam molded body that does not generate cracks or voids in the molded body and can suppress the occurrence of protruding parts or cracks that occur at the mating parts of the molds.

Means for Solving Problem E] The present inventor has conducted further research based on the above knowledge, and as a result, has arrived at the present invention. That is, the mold for producing a urethane foam molded body according to the present invention is a split mold for manufacturing a urethane foam molded body by combining two or more divided molds, and the upper die of the split combination mold has substantially 10 to A vent hole with a diameter of 40+w/m is provided, and a low air permeability sheet is provided at the end of the vent hole on the mold side.

The present invention will be explained in detail below with reference to the accompanying drawings.

In the mold of the present invention, the number of divisions in which a divided and combined mold is used is arbitrary for the convenience of injection of raw materials and handling of molded products, and it is sufficient that the mold is divided into at least two parts. This shows the case where the mating mold divided into the lower mold 2 was made last month.

Molded products obtained using the mold of the present invention are primarily vehicle seat cushions, but are not limited thereto, and include various urethane foam molded products.

The upper mold 1 of the mold of the present invention has a length of approximately 10 to 40 m.
A vent hole 3 with a diameter of /m, preferably 15 to 30 m/@ diameter is provided.

In the Mokmei Rules, "substantially 10 to 40 m/m diameter" means that the shape of the vent hole 3 is not necessarily limited to a circle, and if the opening area of the vent hole is not circular, the opening area of the vent hole is circular. #F4Fa>10~4 when replaced
This means that the opening area should be approximately the same as the opening area of 0 m/m diameter.

The shape of the vent hole 3 is preferably circular, but it may also be triangular, square, or slit.If the shape of the vent hole 3 is circular, the opening diameter is 10 to 40+w.
10r diameter and conventional vent hole opening diameter 2-5Il/
By making the width much larger than Ilφ (the cross-sectional area of one 20m/mφ vent hole is equivalent to the cross-sectional area of 100 2m/mφ vent holes), the reactant gas in the system can be released from the mold to the outside of the system over a wide range. can.

The number of vent holes 3 varies depending on the size of the sheet to be manufactured, but preferably 1 to 1 for separator types.
5 pieces, and 5 to 15 pieces for bench type seats. -For sword slit 0.5~2+s/■×100~200
It is sufficient to provide two to three pieces of m/m shape.

The low air permeability sheet 4 used in the present invention includes: 2-
The urethane foam of 3Ill-11 may be used, but this part hardens due to impregnation with the raw material during foaming, which impairs the cushioning properties of the product. Desirable materials include non-woven fabric, kraft paper, polyethylene sheet, etc.
It is even more desirable to be able to peel off the sheet after demolding.

In terms of air permeability, it is effective even if it exceeds 80 cc/crrf/sea, and although it is not limited to this, if the air permeability is increased by 1, the foam will protrude more from this area and there will be more so-called failures, so 80 cc/crrf/sea is effective. c go/s
Desirably less than ec, -10,000, 10 cc/crn'/
Seawater has poor gas permeability and is less effective.

In the present invention, when manufacturing a product using a mold with a large vent hole 3, hot molding involves raising the temperature of the mold in a heating furnace (120 to 150°C), curing the product, removing the mold, and then removing the mold for 30 minutes. The material is cooled to ~40°C to perform a raw material discharge cycle, and the upper and lower molds are cooled using water cooling,
There is an air cooling method, but when using water cooling, by providing the vent hole of the present invention, cooling water enters the lower mold through the vent hole, and it is necessary to remove this cooling water before injecting the raw material. In order to improve this problem, a vibrator 5 with the same diameter as the vent hole 3 (length 1
It is also preferable to provide a cover having other vent holes (0 to 100 m/m) in the vent hole 3 of the upper mold 1, which can prevent cooling water from entering.

Although the combination of the vent hole 3 and the sheet 4 of the present invention has a remarkable degassing effect, the larger the vent hole, the more the corresponding portion swells due to the foaming pressure, which may be detrimental to the appearance of the product. In order to prevent this, as shown in FIG. 2, it is effective to use a nipple 6 or the like to extend the sheet 4 toward the inner part of the mold with a length CM) of 3 to 5 m/m'A, and then paste the sheet 4 thereon.

Furthermore, it is also effective to provide a wire-like object (not shown) at the mouth of the vent hole 3 to receive pressure.

"Effects of the Invention" According to the present invention, no cracks or voids occur in the molded product, and it is possible to suppress the occurrence of protrusions or cracks that occur at the mating portions of the molds.

[Brief explanation of drawings]

Fig. Ei1 is a sectional view showing one embodiment of the present invention, Fig. 2 is an enlarged sectional view of main parts showing another embodiment of the present invention, and Fig. 3 is a graph showing the relationship between elapsed time and pressure change in the mold. , A shows the case where the mold seal is completely clamped, and B shows the case where the reaction gas slightly escapes from the mold seal part. 4th rf4 is a graph showing the relationship between the reaction time and the amount of reaction gas generated. In the figure, l indicates the upper mold, 2 indicates the lower mold, 3 indicates the vent hole, and 4 indicates the low air permeability sheet.

Claims (4)

[Claims] (1) In a split joining mold in which a molded urethane foam is produced by combining two or more split molds, the upper die of the split joining mold is substantially 10 to 40 m long.
1. A mold for producing a urethane foam molded body, characterized in that a vent hole with a diameter of /m is provided, and a low air permeability sheet is provided at the end of the vent hole on the mold side. (2) The mold for producing a urethane foam molded body according to claim 1, wherein the vent hole is substantially circular and has a substantial diameter of 10 to 40 m/mφ. (3) The mold for producing a urethane foam molded body according to claim 1, wherein the vent hole is a slit. (4) The mold for producing a urethane foam molded body according to claim 1 or 2, wherein a pipe protruding to the outside is fixed to the vent hole.