JPS6183010A - Molding of urethane foam - Google Patents

Abstract

PURPOSE:To reduce remaining amount of air in expandable stock solution and prevent generation of air pockets by a method wherein baffle plate is provided at the rear side of a protrusion in a cavity from reflecting side so as to be protruded out of said protrusion. CONSTITUTION:A bottom force 1 is provided with the protuberance 3, not arriving at a top force 2 but dividing the cavity into two parts. The protuberance 3 may be provided in the whole width of the cavity or may be provided partially. It is necessary to mount the baffle plate 6 so that the tip end thereof is projected more deeply than the tip end of the protuberance 3 and the other end there of is inscribed with the inner surface of the top force. The top force is closed and the stock solution for urethane foam is poured into the mold. The expandable stock solution collides against the baffle plate and is reflected toward the root of the protuberance while air is ground due to the provision of the baffle plate, provided at the rear side of the protuberance and projected from the reflecting side so as to be projected deeper than said protuberance, therefore, generation of air pockets may be prevented.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention is a method for foam molding polyurethane foam molded products having complex external shapes, such as seat cushions for automobiles and furniture, and packaging materials for various types of equipment. It relates to a molding method.

(Prior art) When molding polyurethane foam, there are two methods: one method is to open the lid wall and inject the foaming stock solution into the cavity, and then close the lid mold. One of the methods used is to provide an injection port at a suitable location and press-inject the foaming stock solution through the injection port.

Regardless of which method is used, if there are protrusions on the cavity surface, air may remain at the base of the protrusions, causing large cavities or air pockets in the foam molded product. Measures have been taken to provide vent holes for venting air, as shown in FIG. 5, near the bases of recesses and protrusions where air is likely to remain.

(The problem to be solved by the invention) If a vent hole is provided to prevent air from remaining in the mold, it is possible to reduce the occurrence of large cavities and air pockets that cause defects in foam molded products. It is difficult to completely remove the remaining air.

A crushed core of air bubbles forms in the vent hole area, causing a significant difference in hardness, so when covered with a cloth or synthetic resin cover material, the core of the vent hole area will rise to the surface of the cover. There are some difficulties. Therefore, it is necessary to cut and remove the core of the vent hole part, and there is also the problem that the normal form is gouged out, and when it is covered with a cover material, it becomes a dent and spoils the appearance of the product.

(Objective of the Invention) The present invention can be applied even when using a mold in which projections are provided over a wide range on the inner surface of the cavity.

There is no need to provide a Ben 1 hole near the protrusion.

It is an object of the present invention to provide a method that can prevent the formation of cavities and air pockets due to residual air.

(Structure of the Invention) The structure of the present application will be explained with reference to the drawings. Fig. 1 is a sectional view showing an example of the mold used in the molding method of the present application, in which the lower mold (1) has a cavity that does not reach the upper mold (2), but has two cavities.
A dividing protrusion (3) is provided. This protrusion (3) may be provided over the entire width of the cavity, or may be provided only partially.

The upper mold (2) at the rear of the protrusion (3) when viewed from the injection port (4) side.
), one or more needle-shaped bodies (5) for attaching the baffle plate (6) are planted in the protrusion (3). In this embodiment, the needle-shaped body (5) is used as a method of attaching the baffle plate (6), but it may be temporarily fixed using adhesive, for example, or the baffle plate (6) can be attached to the upper mold (2). A groove may be provided to insert the
In short, when demolding the foam molded product, any method may be used for temporary fixing as long as the baffle plate (6) can be easily removed from the upper mold (2) when the upper mold (2) is opened. The baffle plate (6) is preferably a plate-shaped rubber or synthetic resin foam, but it may also be a synthetic resin board, a tangled body of fiber material such as palm rock or nonwoven fabric, or a wood material such as plywood or cork. It may be a material.

What is important in this application is that the tip of the baffle plate (6) is shaped like a protrusion (
It is necessary to attach it so that it protrudes deeper than the tip of 3), and the other end is inscribed in the inner surface of the mold.

In this case, it is desirable to adjust the distance that the projection (3) projects from the projection (3) depending on the depth of the cavity. Preferably, as shown in FIG.
, the distance that the protrusion (3) of the baffle plate projects from the top is D2.
When 1/2D is in the range of ≧D2〉0, it is better to set one end of the baffle plate to the inner surface of the mold, otherwise some of the foaming stock solution will pass through the gap and the tip of the baffle plate will This is because it collides with the foaming stock solution that has been turned around and breaks the normal foam. It is desirable that the width of the baffle plate (6) be as close as possible to the width of the projection (3) of the mold.

There is no particular limit to the thickness of the baffle plate, but in order to change the flow of the foaming urethane stock solution, in the case of a soft material such as flexible urethane foam, the thickness should be 10ml1! The above thickness is desirable, and in the case of a relatively rigid material such as semi-rigid urethane foam, polyethylene foam, or palm board, it may be around 51 mm. In addition, when using a hard plate-like body, one as thin as about 0.1 to 1 mm can also be used.

There are no restrictions on the material of the mold to be used, and all known materials can be used, and the foamable urethane stock solution can be applied to everything from soft foam to #quality foam.

Fig. 2 is a sectional view showing an example of a case where the upper die has protrusions, contrary to Fig. 1, but it can be applied whether the protrusions are located on the top or bottom or on both sides. Although the number is shown for the case of one protrusion in the examples of Fig. 1 and Fig. 2, it can also be applied to the case of two or more protrusions. All you have to do is increase the number of plates. In addition, when it is necessary to provide baffle plates at symmetrical positions such as vertically or horizontally, porous materials are preferable as the material for the baffles. When using porous materials such as open-cell urethane foam, nonwoven fabric, or palm rock as baffles, vent holes may not be necessary if the internal volume of the mold is small, but if the mold has a complex shape or When the internal volume is large, it is desirable to provide a vent hole, and in that case, it is better not to provide a vent hole near the baffle plate.

This is because the provision of vent holes makes it easier for the foaming urethane stock solution to penetrate into the pores of the baffle plate made of porous material.
This is because it forms an impregnated hardened layer and impairs cushioning properties.

When using a non-porous material or a closed-cell material for the baffle plate, unlike open-cell porous materials, it does not have the ability to absorb residual air in the mold or air drawn in when mixing the foaming g-liquid. Since the foaming stock solution only has the effect of being crushed as it flows over the surface of the baffle plate, it is necessary to place the waste surface area near the joint of the upper and lower molds, for example, near the joint of the upper mold and the lower mold, for air venting, so that the product appearance is less affected. It is desirable to provide a vent hole.

(Example) Example 1 An aluminum mold having the cross-sectional shape shown in Fig. 1 was used, and a soft urethane foam with a foam density of 0.018 g/cd and a foam thickness of 15 mm was used as a baffle plate as shown in Fig. 4. Attach the same width as the protrusion (3) and keep the mold temperature at 60℃.
Close the upper mold at ℃ and mold clamping pressure of 2z.

Injection pressure of undiluted solution for soft urethane foam with cream time of 4 seconds and rise time of 30 seconds up to 80, shot time of 3.
Injected in 5 seconds. The distance 11D, which is projected from the projection (3) of the baffle plate (6), was set to 1/3 DL. When the upper mold was opened 2 minutes after injection, a cushion body was obtained in which the soft urethane foam used as the baffle plate was integrated into the foam molded body. In particular, there were no air pockets or cavities in the recessed part of the form corresponding to the protrusion (3) of the mold, and the integrated baffle plate part was a good cushion molded product with no strange appearance.

Comparative Example 1 As shown in Fig. 5, four vent holes (7) with a diameter of 3+m were provided along the protrusion near the protrusion (3) at 10 cm intervals, and no baffle plate was provided. A cushion molded article was foam-molded in exactly the same manner as in Example 1. In this case as well, the appearance was good with only a few inconspicuous small air pockets formed near the concave part of the foam, but there was an extremely hard core in the vent hole (7) part, making it difficult to touch. It was something that felt strange.

Comparative Example 2 A cushion molded body was foam-molded in the same manner as in Example 1 while the vent hole (7) of the upper mold in Fig. 5 was filled with urethane resin. Many air pockets and cavities with diameters of 5 to 15+ am were generated in the recessed portions, resulting in a molded product with an appearance that could not be put to practical use.

Examples 2 to 4 The distance D2 of the baffle plate (6) protruding from the protrusion (3) is
Table 1 summarizes the results of foam molding carried out in the same manner as in Example 1 except that the values were changed to 0, L/2D 1 and 2/3D t, respectively.

As seen in the results of Examples and Comparative Examples, when there is a protrusion with a width that forms the inner surface of the cavity, the air at the base of the protrusion remains without being completely removed by the flow of the foaming stock solution. This causes the generation of air pockets, and when the polyisocyanate component, polyol component, and other compounding agents are mixed, such as in the case of urethane foam, the foaming stock solution flows while entraining air, causing an increase in reaction progress. Due to viscosity, the foam tends to become sticky and cause air bubbles, but by providing a baffle plate at the rear of the protrusion so as to protrude from the protrusion from the opposite side, the foaming stock solution is As shown in.

When it collides with the baffle plate, the flow is directed toward the base of the protrusion, and at the same time, the air is rubbed between the baffle plate surface and the wall of the protrusion, and the air is crushed during that time, or in the case of porous materials, the air is absorbed into the pores. It is believed that this reduces the amount of air remaining in the foamable stock solution, thereby preventing the formation of air pockets and providing a foam molded product with a good appearance.

Note that the length of the protruding distance of the baffle plate, that is, the depth, is determined when it does not reach the tip of the protrusion, in other words, when D2 in Fig. 3 is smaller than O, the flow of the foaming stock solution is determined by the injection pressure from the injection port and the foaming pressure. Due to the foaming pressure of the stock solution, it advances without changing its direction too much, making it impossible to prevent the formation of air pockets, and if D2 in Figure 3 protrudes too deep than 1/2D1, it has already increased due to the progress of foaming and reaction. Because the viscous stock solution is under pressure and cannot quickly slide through the narrow gap, the foam that has begun to form runs in a crushed form, causing bubbles to rise. It is assumed that

Therefore, by attaching a baffle plate that is inscribed on the inner surface of the mold on the opposite side to the protrusion provided on the inner surface of the mold and protrudes deeper than the top of the protrusion, air pockets can be created on the surface of the recessed part of the foam molded body corresponding to the protrusion. The formation of urethane is prevented, and it is possible to easily obtain a foam molded product that does not have the strange feeling of a core that is created when a vent hole is provided, without significantly changing the mold. This can be said to be an extremely useful technology for foam molding.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a mold showing one embodiment for molding the urethane foam molded article of the present invention, Fig. 2 is a cross-sectional view of a mold showing another embodiment, and Fig. 3 is a cross-sectional view of a mold showing another embodiment. An explanatory diagram of the relationship between the protruding distance of the baffle plate, FIG. 4 is a plan view taken along the line X--X in FIG. 1, and FIG. 5 is a sectional view of a mold used in the conventional method. l: Lower mold 2: Upper mold 3: Protrusion 4: Inlet 5: Needle-shaped body 6: Baffle plate 7, F: Vent hole

Claims (1)

[Claims] When foam-molding urethane foam using a mold having protrusions on the inner surface of the mold, a mold is placed at a position behind the protrusions on the inner surface of the mold with respect to the flow direction of the foaming stock solution, and inside the inner surface of the mold on the opposite side of the protrusions. A method for molding urethane foam, characterized by providing a baffle plate that is in contact with the protrusion and protrudes deeper than the top of the protrusion.