JPS625042B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a soft polyurethane foam molded article, specifically a soft polyurethane foam molded article used as a cushion material for automobile seats, etc. for the purpose of preventing the occurrence of cracks during foam molding. The present invention relates to a manufacturing method.

Soft polyurethane foams are often used as cushioning materials for automobile seats, etc., but these cushioning materials are usually provided as molded bodies molded into a desired shape, and the method for manufacturing them is A desired shape is formed by injecting a stock solution of flexible polyurethane foam into a mold made of aluminum or plastic, and foaming the stock solution so as to completely fill the space formed by the mold. Manufacturing methods for obtaining the body are known.

In such manufacturing methods, there has conventionally been a problem that, depending on the shape of the molded product, cracks may occur in the foam, impairing its physical properties.

For example, from the viewpoint of improving cushioning properties and saving raw materials, it is common practice to provide a large number of protrusions on the desired surface of a molding die to give an uneven pattern to the surface of the molded product. Cracks occur in the form at the part that touches the protrusion of the mold.

The present invention has been made to solve such problems. That is, the present inventor believes that such a phenomenon occurs in a specific shaped part of a molding die.
Focusing on the fact that this occurs when the rise of the stock solution during foaming is significantly inhibited in some parts, leading to stress concentration, we found a method to alleviate the stress applied to the stress concentration area, and completed the present invention. be.

In the present invention, after a soft foam having open air cells is attached to the stress concentration area, that is, the protrusion of the molding die, a stock solution of soft polyurethane foam is injected into the mold and foamed, and the foam is integrated with the attached foam. The present invention relates to a method for producing a molded article for a cushion, the main material of which is a soft polyurethane foam used for automobile seats and the like.

According to the present invention, when the undiluted solution is foamed, locally concentrated stress is relaxed, and the undiluted solution also impregnates and fills the mounting foam to form a strong portion, thereby significantly reducing the occurrence of cracks.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Reference numeral 1 is a lower die of an aluminum alloy molding die, which is used to form the upper and side surfaces when the molded body is used as a cushion, and 2 is an aluminum alloy molding die used to form the lower surface shape. This is the upper mold for the mold. 3 is a protrusion provided on the upper die 2;
is a needle for attaching a soft foam having open air bubbles provided at the tip of the protrusion 3. Reference numeral 5 denotes a soft foam having open air cells, which is inserted into the needle 4 when the upper die 2 is open. The attachment location and size of the soft foam 5 may be determined as appropriate depending on the shape of the mold, but if you want to prevent cracks from occurring at the protrusions 3, it may be necessary to cover the peaks of the individual protrusions. Installing. In this case, it is not necessarily necessary to attach the soft foam 5 along the slope of the mountain, but an adhesive tape is used to attach it to a shaped part where attachment with the needle 4 is inconvenient. In addition, the soft foam 5
The thickness of the cushion varies depending on the concentrated stress generated, but it is 3 m/m for a normal car seat cushion molded product.
A certain amount is enough. In addition, the soft foam 5 only needs to be installed at stress concentration points, but if the protrusions 3 are aligned, a band-shaped soft foam can be used to connect the protrusions. It's okay. In this case, the band-shaped foam crosses the space within the mold, but this does not pose an obstacle during foaming of the raw solution.

When the attachment of the soft foam 5 is completed, the upper mold 2 is closed and set, and a soft polyurethane foam stock solution is injected and foamed to produce a molded body of a desired shape.

Comparative Example As a molding die, an aluminum alloy die (width 520 m/m x length 1250 m/m) shown in FIGS. 1 and 2 was used. The upper mold has a protrusion (bottom diameter 90m/m x height
50m/m) were arranged in a row.

A stock solution with a free foaming density of 30 Kg/m ³ was poured into the mold and foamed, and after heating in an atmosphere of 200° C. for 10 minutes, the molded product was taken out. Fifty pieces of the molded body were manufactured in the same manner and the form of the portions corresponding to the protrusions was observed, and cracks were found at 320 locations.

Example On the other hand, as a soft foam with open cells, the density
20Kg/ ^m3 band-shaped flexible polyurethane foam (width
30 m/m x thickness 3 m/m) was attached to the protrusion of the upper mold used in the comparative example, and then 50 molded bodies were manufactured under the same conditions as the comparative example, and the part corresponding to the protrusion was When observing the form, cracks were found in 89 locations.

That is, the reduction rate of crack occurrence compared to the conventional method was about 72%.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the inner surface of the upper mold of the molding die, and Fig. 2 is a sectional view taken along line A-A in Fig. 1. 1...Lower die, 2...Upper die, 3...Protrusion, 4...Needle ,5
...Soft foam with open cells.

Claims (1)

[Claims] 1. In a method of manufacturing a soft polyurethane foam molded article of a desired shape by injecting and foaming a stock solution of flexible polyurethane foam into a molding die, a flexible foam having open air cells is attached to a protruding portion of the molding die. A method for producing a soft polyurethane foam molded article, which comprises subsequently injecting and foaming a stock solution of the soft polyurethane foam, and molding it integrally with the soft foam.