JPS588620A - Molding of foamed object of soft urethane resin - Google Patents

Abstract

PURPOSE:To reduce a molding manpower and improve a yield of raw material, by pouring a mixed liquid of raw material in a mold of which a plurality of molding spaces is drilled, being arranged perpendicularly on the same axis and molding a foamed object. CONSTITUTION:Split molds 1A, 1B are clamped by uniting the parting faces and also positioned in their longitudinal direction making an axis 5 to coincide with a perpendicular direction and a pouring port 8 to be on a top. Then, a liquid mixture of which a soft urethane raw material and a foaming agent are mixed in a required ratio is poured from the pouring port 8 and foaming proceeds and finishes. clamping of split molds 1A, 1B is released, the molds are opened in an arrow direction and a molded, solidified foamed object is drawn out. A number of cavities is varied according to a shape and size of a molded product and multiple molding of 2-15 pieces become possible as conception.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new method for molding a flexible urethane resin foam into a large number of molds using a single mold.

Conventionally, cushioning foams made from soft urethane have been widely used in automobiles, toys, and the like. However, all of these products are molded into the desired shape using a single-piece molding method.

That is, a mixture of a soft urethane raw material and a foaming agent in a desired ratio is injected into a mold that can be divided into two and has a molding space of a desired shape, and a foaming action is performed in the space in the mold (hereinafter referred to as the cavity). At the same time, the excess raw material and foaming gas containing rough foaming gas, which will result in a defective foam, are discharged from the injection port, and the foam is solidified and taken out.
During the above-mentioned foaming action, the fine bubbles generated by the foaming gas accumulate in the cavity and become large, forming large cavities that remain in the foam, resulting in a cavitation phenomenon, or variations in the hardness of the foam (elasticity due to uneven distribution of cell density). There is an extremely high risk of producing defective products due to
It is considered extremely difficult to put so-called multi-piece production into practice as a mass production method. Therefore, soft urethane foams have the disadvantage of inevitably being expensive due to the high unit cost of raw materials and high molding costs.

The present invention aims to solve the above-mentioned difficulties, and provides a new multi-cavity molding method that significantly reduces molding costs.

The present invention will be described below with reference to drawings of embodiments.

First of all, the mold 1 used in the present invention shown in the first to fourth figures consists of a combination of two divided molds IAIB divided into two at the center plane 4, and a connecting piece 2A2 is attached to the lower end of each divided mold IAIB.
The split type IAIB is connected by a connecting pin 8 so as to be rotatable in the direction of the arrow shown in the figure, and is tightened by appropriate means so that the surfaces come into close contact during molding. On the other hand, mold 1
As shown in Fig. 2, a large number of cavities 6A6B6 (3---6N) are arranged on the same axis in the vertical direction. each cavity is arranged in series such that its center lies on a central axis 5 lying on a central plane 4;
A short and narrow through hole 7A7B with a circular cross section centered at the top
7C--- respectively communicate with the adjacent cavities. The through hole 7A at the uppermost end is configured to communicate with an injection port 8 which opens upward in a hole shape. The mold 1 described above is used to mold the required foam according to the following method. That is, as shown in FIG. 1, the split type IAIBs are joined in contact with each other and tightened, the axes 5 are aligned vertically, and the inlet 8 is positioned vertically with the inlet 8 upward.
A mixture of soft urethane raw materials and a foaming agent in the required ratio is injected into the mold, and the foaming action is completed within the mold. Then, the tension of the split type one-person IB is released and opened in the direction of the arrow in FIG. 1, and the molded and solidified foam is extracted. At this time, the required amount of the above-mentioned mixed liquid is injected based on the predicted volume expansion due to the foaming action. The required amount of waste remains. Therefore, due to the presence of the through holes 7A7B7G--- and the surplus at the injection port 8, the extracted foam has a continuous skewer-like shape as shown in FIG. 5, and after extraction, Code 9 A 9 B
9 (cutting from parts 3--- to obtain individual foam products. Note that the reference numeral 10 is a thin film formed by the contact surface of the split type IAIB, which is usually removed after molding. .

Further, the mold 1 may be coated with a mold release agent on the inner surface of the cavity to facilitate mold release of the foam, and may be slightly preheated and molded in a heated state to promote the foaming action.

Generally, in the foaming process of soft urethane, smooth flow and discharge of the foaming gas within the cavity are the most important requirements for obtaining a quality product. However, in the above-mentioned new method, since the mold 1 is configured vertically with the axis 5 in the vertical direction, the foaming gas flows smoothly upward from the lowermost cavity by following the volume expansion of the mixed liquid due to buoyancy. As it moves, the through holes 7B7cj--- are extremely short and have an appropriate cross-sectional area, so that the foaming action proceeds without interfering with the above-mentioned expansion and rising action, resulting in the continuous foam shown in Figure 6. can be efficiently molded.

Therefore, applying a mold release agent, injecting a mixed liquid, separating the mold,
The number of man-hours required for all molding operations, such as taking out the foam, is significantly reduced, resulting in a mass production effect. On the other hand, since the above-mentioned surplus amount that is discarded as a necessary evil is a fixed amount regardless of the number of molded products, the amount of waste per product unit is significantly reduced in the method of the present invention that uses multiple products, and the yield of raw materials is reduced. This has the effect of improving the rate.

Note that in the present invention, the number of cavities varies depending on the shape, dimensions, etc. of the intended molded product, but conceptually it is 2 to 15.
It becomes possible to take out many pieces. In a specific example of one embodiment, nine cavities each having a diameter of 40 mm are bored, and the diameter of the through hole is approximately 12 mm, and the length of the through hole is approximately 2 mm, so that the cavitation phenomenon and hardness variation described above do not occur. , it was possible to stably mold a high-quality foam.

Next, preferred embodiments of the present invention will be described. With reference to FIG. 6.7, this embodiment
~In the mold 1 shown in Figure 4, the through hole 7A is formed along the axis 5.
7B70--- Small diameter guide shaft 11 having a curve and a gap
It is characterized in that the same molding operation as described above is performed. The guide shaft 11 has a special function of smoothing the upward movement of the mixed liquid containing foaming gas in the upward movement of the mixed liquid into the cavity as the foaming action of the mixed liquid progresses. That is, the sixth
As shown in the figure, the mixed liquid 12 in contact with the inner surface of the cavity and the guide shaft 11 slows down its rising speed due to expansion due to contact resistance, so that it rises while producing two mid-height phenomena 18A and 18B in the longitudinal section. Therefore, when the guide shaft 11 is not present, the through hole 7B7C-m- is quickly closed due to the large mid-high portion 180 indicated by the dotted line in the figure, which naturally occurs, and this blocks the flow path of the mixed liquid containing the foaming gas, causing an excess amount to flow into the cavity. It is possible to prevent the harmful phenomenon of residual foaming gas and further promote high-quality foam molding. Note that the guide shaft 11 may be a shaft body having an extremely small diameter compared to the diameter of the through hole 7 A 7 B, and the above-mentioned specific effect can be fully expected. In urethane foam molding, it enables multi-cavity molding with excellent productivity, which significantly reduces molding man-hours and improves raw material yield, making it an industrial product that provides high-quality and inexpensive urethane foam. This is a useful invention.

[Brief explanation of the drawing]

1N: Front view of the mold used in the present invention - Examples, Figure 2: Vertical sectional view of the mold shown in Figure 1, Figure 8: Plan view of Figure 1, Figure 4: Figure 1 AA sectional view, FIG. 5: A front view of the foam showing the shape formed by foam molding with the mold shown in FIG. 1, FIG. 6: A longitudinal sectional view of the mold showing one embodiment of the present invention, FIG. 7: BB sectional view in Fig. 6 Main symbols: 1: Molding die, IAIB = divided portion of forming die 1, 2A2B: connecting piece, 8: connecting bottle, 4: central plane, 5
: Meticulous, 6A6B60---: Cavity, 7A7B7
0---: Through hole, 8: Inlet, 11: Guide shaft, 12:
Mixed liquid patent applicant Nippon Chemical Industries Co., Ltd. Patent attorney Masami Oka 0 70 11 6 [3 Figure 7 Figure 6

Claims (2)

[Claims] (1) In molding a foam by injecting a raw material mixture into a mold in which a molding space is bored, a large number of the molding spaces are arranged in series on the same axis, and adjacent molding spaces are The mold, which is communicated by a short, narrow, and shaded through hole centered on the axis, and the molding space at the uppermost end communicates with the injection port through the through hole, is placed vertically with the axis in the vertical direction. 1. A method for molding a soft urethane resin foam, the method comprising the steps of: arranging the foam in the same direction, and then injecting a raw material mixture from the injection port to perform foam molding to obtain a large number of required foams. (2) Claim (1) states that molding is performed by inserting a guide shaft that has a gap with the circumferential surface of the through hole that communicates with the molding space and that penetrates vertically along the axis of the molding space. Foam molding method.