JPS628784A - Production of seat cushion pad having different hardness layers - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing a seat cushion pad having plastic foam layers of different hardness, including a relatively hard layer and a soft layer. The present invention relates to a method of manufacturing a seat cushion pad in which layers are simultaneously foam-molded.

(Prior Art) In cushion pads used for automobile seats, the upper layer that comes into contact with the occupant is made of flexible plastic foam such as polyurethane foam to provide a good feeling when sitting on the seat. It is desirable that the lower layer be formed from a relatively rigid plastic foam to ensure its support. When trying to obtain a seat cushion pad having such layers of different hardness, conventionally, for example, the upper layer is pre-molded from a soft plastic foam, and then this is molded in a mold with the cushion pad upside down. Put it in
On top of that, a relatively hard plastic foam was foamed and molded.

However, this manufacturing method not only requires a separate mold for the upper layer, but also impregnates the surface of the pre-molded soft plastic foam layer with the foaming solution for the hard plastic foam layer, resulting in a poor quality of the product. There is a problem in that an extremely hard boundary layer is formed between the soft layer and the hard layer, which deteriorates the feel when sitting on the seat and also results in poor durability.

In view of these problems, a method has been proposed in which a layer made of soft plastic foam and a layer made of relatively hard plastic foam are simultaneously foam-molded, as shown in Japanese Patent Application Laid-Open No. 55-98195. There is. In this method, a first foaming solution that foams twice to form a hard plastic foam layer is poured into a mold, and after this first foaming solution foams to some extent, a second foaming solution forms a soft plastic foam layer. The second foaming stock solution is injected and the first and second foaming stock solutions are foamed and hardened.

By using such a method, the second foaming stock solution is injected when the first foaming stock solution partially foams and expands inside the mold and its specific gravity becomes small.
The foaming stock solution sinks below the first foaming stock solution to form a layer due to the difference in specific gravity. Therefore, if these first and second foaming stock solutions are foamed and hardened in that state,
It is possible to obtain a single-layer plastic foam molded product of different hardness, in which the lower layer is a soft plastic foam layer and the upper layer is a hard plastic foam layer. When used as a cushion pad for a sheet, the obtained product may be turned upside down.

However, in this method, the first foaming stock solution floats on top of the second foaming stock solution by utilizing the difference in specific gravity between the first foaming stock solution and the second foaming stock solution. , the second foaming stock solution must be injected after foaming and expanding until its specific gravity becomes reliably lower than that of the second foaming stock solution. The timing for injecting the first foaming stock solution is when the first foaming stock solution has foamed and expanded to 10% or more of its potential expansion amount.

The time when the foam reaches about 10% of the potential expansion amount is the time when the first foaming solution has been foamed and hardened to a considerable extent. Therefore, if the second foaming stock solution is injected at such a time, there will be a difference in the degree of foaming progress between the second foaming stock solution and the first foaming stock solution, making it difficult to obtain a uniform layer throughout. becomes.

In view of these problems, the inventor of the present invention injected a second foaming stock solution at high speed through a nozzle while the first foaming stock solution was almost in a liquid state, and poured it under the first foaming stock solution. proposed a method to infiltrate the
issue).

(Problems to be Solved by the Invention) By the way, when molding a seat cushion pad having a plastic foam layer of different hardness by such a method, the mold used for the molding is such that the cushion pad is molded with the cushion pad upside down. Normally, the top surface of the seat cushion pad is flat.

The upper surface of the mold is formed as a horizontal plane, and even if an inclined surface is provided, the inclination is extremely gentle. Therefore, even when the foaming solution in the mold is in a liquid state, it takes a considerable amount of time for the foaming solution to spread throughout the mold.

On the other hand, the foaming stock solution injected into the mold immediately begins foaming. Therefore, there is a problem in that the foaming stock solution foams and loses fluidity before reaching every corner of the mold, causing air pockets to form in the corners of the mold, resulting in the resulting product having an irregular shape.

In addition, since the foaming stock solution flows and spreads while foaming, the cells formed become flat along the direction of flow, resulting in the resulting cushion pad having poor cushioning properties. , its strength also decreases.

The present invention was made in view of these problems, and its purpose is to prevent the foaming stock solution from remaining in a liquid state even when using a mold having a nearly horizontal upper surface. so that it spreads over the entire mold, thereby giving it an accurate shape.
It is an object of the present invention to provide a seat cushion pad that is favorable in terms of strength and has good cushioning properties.

(Means for solving the problem) In order to achieve this object, in the present invention, the second foaming stock solution injected after the injection of the first foaming stock solution is directed to the upper surface of the mold by a nozzle. The inclination angle is set to allow high-speed injection.

(Function) By injecting the second foaming stock solution at high speed while tilting it at a predetermined angle with respect to the upper surface of the mold, the second foaming stock solution can rapidly inject the first foaming stock solution. It passes through, forms the underlying layer, and flows rapidly along the direction of injection. The first foaming solution in the upper layer is dragged by the flow of the second foaming solution. In this way, these first and second foaming stock solutions reach the periphery of the mold while remaining in a liquid state and having high fluidity. Therefore, air pockets do not form at the corners of the mold.

Since foaming will proceed after these foaming stock solutions have spread throughout the mold, the cells formed will be long in the vertical direction. Therefore, the resulting seat cushion pad is.

It has good strength and cushioning properties.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

Among the figures, FIG. 1 shows an embodiment of the method for manufacturing a seat cushion pad according to the present invention. In order to explain the manufacturing process of the cushion pad, FIG. FIG. 4 is a vertical cross-sectional view showing states at different stages. Further, FIG. 2 is a perspective view of the mold, and FIG. 3 is a partially cutaway perspective view showing a cushion pad for an automobile seat obtained by the manufacturing method.

As is clear from FIG. 3, the target automobile seat cushion pad l has a center support part 1a that supports the weight of the occupant, and is formed on both sides higher than the center support part 1a to prevent the occupant from moving laterally. The upper part of the center support part 1a is formed of a soft polyurethane foam layer 2 to provide soft support for the occupant, and the lower part and the side support part 1b have a reliable supporting force. In order to achieve this, it is formed by a relatively rigid polyurethane foam layer 3.

In order to mold such a cushion pad 1, an aluminum alloy mold 4 as shown in FIG. 2 is used. In this mold 4, a lower mold 5 molds the upper surface side of the cushion pad 1, and an upper mold 6 molds the lower surface thereof. Therefore, the cushion pad 1 is molded by this mold 4 in an upside-down state.

The upper surface of the lower mold 5 is provided with a central molding part 5a for molding the center support part 1a of the cushion pad l, and both side molding parts 5b for molding the side support parts 1b.

The central molded portion 5a has a substantially horizontal wide flat surface 5f extending in the front-rear direction. Further, a protruding weir 7 is provided between the central molded portion 5a and both side molded portions 5b.

Next, a method for manufacturing the cushion pad 1 using such a mold 4 will be described.

Keep mold 4 in a heated state.

First, as shown in FIG. 1(A), the upper mold 6 is opened and the first mixing head is placed near the rear end (left end in the figure) of the flat surface 5f of the lower mold 5. A predetermined amount of the first foaming stock solution 3a is injected from the nozzle 8. This first foaming stock solution 3a is foamed to form a relatively hard polyurethane foam. At this time, the nozzle 8 is tilted forward (to the right in the figure) so as to form a predetermined angle θ with respect to the flat surface 5f of the lower mold 5, and the first foaming stock solution 3 is discharged.
Most of a flows forward on the flat surface 5f.

Within a short time after injection of the first foaming stock solution 3a.

From above, the second
A predetermined amount of the second foaming stock solution 2a is injected through the nozzle 9 of the mixing head. This second foaming stock solution 2a foams to become a flexible polyurethane foam.

At this time, the nozzle 9 is also tilted forward so as to form a predetermined angle θ with respect to the flat surface 5f of the lower mold 5. The discharge pressure of the second foaming stock solution 2a discharged from is set high.

When discharging the second foaming stock solution 2a, the first foaming stock solution 3a
Foaming has hardly progressed and remains in a liquid state, or only a portion of it has been cleaned. Therefore, the second foaming stock solution 2a injected at high speed is
As shown in Figure (B), the second foaming stock solution 2a quickly passes through the first foaming stock solution 3a, hits the flat surface 5f of the lower mold 5, and spreads. It sneaks under 3a and forms the lower layer. At this time, a part of the first foaming stock solution 3a overflows over the weir 7 and flows into both side molding parts 5b.

. . In the meantime, since the nozzle 9 is tilted forward, the discharged second foaming stock solution 2a is given kinetic energy to flow forward. Therefore, a part of the foaming stock solution 2a spreads backward and in the left-right direction, but most of it quickly flows forward and reaches the front end of the flat surface 5f within a short time. The first foaming stock solution 3a on the second foaming stock solution 2a also flows and spreads as it is dragged by the flow of the second foaming stock solution 2a.

In this way, the first and second foaming stock solutions 3a, 2a
The liquid flows smoothly and reaches every corner of the mold 4 within a short period of time while maintaining high fluidity. During this time, the foaming of each of the foaming stock solutions 2a and 3a continues, so that the portions where fluidity has decreased due to foaming to some extent remain in their original positions. Therefore, Fig. 1(C)
As shown in FIG. 2, layers of the first and second foaming stock solutions 3a and 2a are formed throughout the mold 4.

After the first and second foaming stock solutions 3a and 2a have finished flowing,
Close the upper mold 6 and completely foam.

Then, as shown in FIG. 1(D), the first and second foaming stock solutions 3a and 2a fill the entire inside of the mold 4,
It is molded into a predetermined shape by the mold 4.

In this way, the first and second foaming stock solutions 3a.

When 2a is completely foamed and cured, these become a relatively hard polyurethane foam layer 3 and a soft polyurethane foam layer 2, respectively, and these layers 3 and C! A laminate molded product in which 2 parts are successively integrated is obtained.

When this molded product is removed from the mold 4 and turned upside down, the upper surface of the center support portion 1a is a soft polyurethane foam layer 2, and the surrounding area is a relatively hard polyurethane foam layer, as shown in FIG. 3 can be obtained.

In this way, by injecting the second foaming stock solution 2a at high speed at a predetermined inclination angle θ to the flat surface 5f that is the upper surface of the mold 4, the first and second foaming stock solutions 3
While both a and 2a are in a highly fluid state that is almost in a liquid state or has partially progressed to a creaming state, they flow and spread to every corner of the mold 4, and the mold Air pockets will no longer be formed around the 4. Therefore, the degree of freedom in the shape of mold 4 increases,
For example, it is possible to mold a heavy pad 7 in which the flexible polyurethane foam layer 2 has an overhanging portion. Further, the second foaming stock solution 2a is applied to the flat surface 5f.
By injecting at an angle to will no longer be disturbed.

Furthermore, since each of the foaming stock solutions 2a and 3a finishes flowing within a short time, the time for foaming while flowing is short, and the time from finishing flowing until complete foaming and hardening is sufficiently long.

Therefore, the cells formed in each polyurethane foam layer 2, 3 have a vertically elongated shape, making it possible to obtain a cushion pad 1 with good cushioning properties and good strength.

Using a mold 4 with a horizontal flat surface 5f and a length of 400 mm, an experiment was conducted to determine the optimal inclination angle θ of the nozzle 9 by injecting the second foaming stock solution 2a at a speed of 2130 g per second for 1.3 seconds. As a result, it was found that in that case, the nozzle 9 should be inclined by 5° to 10° with respect to a plane perpendicular to the flat surface 5f.

In addition, in the above embodiment, the first foaming stock solution 3a also
Although the injection is performed at an angle with respect to the flat surface 5f of the lower mold 5, since the first foaming stock solution 3a flows along with the flow of the second foaming stock solution 2a as described above, the first foaming stock solution 3a flows with the flow of the second foaming stock solution 2a. The injection nozzle 8 for the stock solution 3a does not necessarily need to be tilted, but if it is done as in the above embodiment, each of the foaming stock solutions 2a and 3a will flow more smoothly.

Further, the nozzle 9 that discharges the second foaming stock solution 2a is not necessarily held at a constant inclination angle θ during the discharge, but may be adjusted as appropriate during that time.

The inclination angle θ of the nozzle 9 also varies depending on the inclination angle of the flat surface 5f of the lower die 5 with respect to the horizontal plane.

(Effect of the invention) As is clear from the above explanation, according to the present invention, the first
While the foaming stock solution is almost in a liquid state, the second foaming stock solution is injected at high speed at a predetermined angle of inclination to the upper surface of the mold. These foaming solutions form a layer inside the mold and foam almost simultaneously, and while having high fluidity, they spread throughout the interior of the mold. It is thus possible to obtain a seat cushion pad having a precise shape and a predetermined thickness of a soft plastic foam layer and a hard plastic foam layer.

Further, since the time for foaming while flowing is short and the time for foaming after flowing is sufficiently long, it is possible to obtain a seat cushion pad with good cushioning properties and favorable strength.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the method for manufacturing a seat cushion pad according to the present invention, and (A) to (D) show the states of the mold and the foaming solution inside the mold at different stages of the manufacturing process. FIG. 2 is a perspective view of a mold used for manufacturing the seat cushion pad, and FIG. 3 is a cross-sectional view of the automobile seat cushion pad obtained by the manufacturing method. FIG. l... Seat cushion pad 2... Soft polyurethane foam layer 2a... Second foaming stock solution 3... Rigid polyurethane foam layer 3a... First foaming stock solution 4... Mold 5... Lower mold 5f...
Flat surface (upper surface of mold) 8.9... Nozzle θ... Nozzle inclination angle

Claims (1)

[Claims] A first material that expands into a relatively hard plastic foam.
A foaming stock solution 3a is injected onto the upper surface 5f of the mold 4, and a second foaming stock solution 2a that foams into a soft plastic foam is injected from above the first foaming stock solution 3a. The stock solution 2a is converted into the first foaming stock solution 3a.
These first and second foaming stock solutions 3a,
2a is formed and foamed and cured to form a seat cushion pad 1 having a plastic foam layer of different hardness; While the first foaming stock solution 3a is almost in a liquid state, it is injected at a high speed through the nozzle 9 at a predetermined inclination angle θ to the upper surface 5f of the mold 4, and these first and second foaming solutions A method for manufacturing a seat cushion pad having layers of different hardness, characterized in that the stock solutions 3a, 2a are allowed to reach the periphery of the mold 4 while having high fluidity.