JPH0688274B2 - Method for manufacturing urethane foam molded product - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a urethane foam molded product having a central hole.

(Prior Art) Urethane foam 32 with a hole 30 in the center, as shown in FIG.
For example, a foam used for an earphone cover is manufactured by using a molding die in which a columnar projection 36 for forming a hole 30 is provided in the center of the die surface of a lower die 34 as shown in FIG.
It is carried out by injecting a urethane foam raw material 20 and foaming the raw material in the cavity after the mold is closed.

(Problems to be Solved by the Invention) Incidentally, in the production of a urethane foam molded article using a molding die, it is preferable to perform single-point injection in which the injection position is fixed from the point of view of work.

However, in the method for producing a urethane foam molded product having a hole in the center, since the lower mold surface has columnar projections, it is difficult to uniformly disperse the raw material into the cavity 38 by single-point injection, Not only is it difficult to obtain a molded product of uniform quality, but there is also the problem that a molded product with a lack of wall tends to be formed.

Therefore, in the manufacturing method, in order to make the dispersion of the raw material 20 in the cavity 38 uniform, the raw material 20 must be injected while moving the injection position, which complicates the work.

The present invention aims to solve the above-mentioned problems, and an object of the present invention is to provide a manufacturing method capable of uniformly dispersing a raw material into a cavity even by single-point injection.

(Means for Solving Problems) In the present invention, a urethane foam raw material discharged from a pouring machine nozzle is injected into a cavity of a molding die having a columnar protrusion on a lower die surface, and a hole is opened in the center. In a method for foam-molding a urethane foam molded product, the shape is such that the diameter from the upper end of the columnar projection to the predetermined lower position is gradually enlarged, while a plurality of vertical grooves is provided on the inner peripheral surface of the injection machine nozzle, It is characterized in that the enlarged shape portion of the columnar protrusion is inserted into the nozzle to discharge the raw material, thereby injecting into the cavity.

(Operation) The raw material discharged from the nozzle of the injection machine collides with the peripheral surface of the enlarged shape portion of the columnar projection, then spreads along the enlarged shape portion, and is dispersed and flows into the cavity. At that time, if a normal nozzle with a substantially smooth inner surface is used, the flow of the discharged raw material is likely to be disturbed, and a large amount of raw material collides with a part of the enlarged shape part, and a small amount of raw material collides with the other part. easy. As a result, it becomes impossible to uniformly disperse the raw material in the cavity. Therefore, in the present invention, by providing a plurality of vertical grooves on the inner peripheral surface of the nozzle, the disturbance of the flow of the raw material is prevented, the uniform collision of the raw material with the enlarged shape portion is ensured, and the raw material is uniformly distributed into the cavity. It was possible to disperse easily.

(Example) Hereinafter, the present invention will be described based on an example with reference to the drawings.

1 to 3 relate to an embodiment of the present invention, in which FIG. 1 is a perspective view of a urethane foam raw material before being discharged, FIG. 2 is a view of the tip of an injector nozzle seen from the direction A, and FIG.
The figure is a cross-sectional view at the time of injecting a urethane foam raw material.

Reference numeral 10 is a lower die of a forming die having a structure of being divided into upper and lower parts.
The lower mold 10 has a columnar protrusion 12 at the center of the mold surface and a cavity 14 around the columnar protrusion 12. Cavity 14
When the upper mold (not shown) and the lower mold 10 are closed, the upper mold surface has the same shape as the desired molded product. The columnar protrusion 12 is for forming a hole in the molded product, and the upper end 12
The diameter from a to the lower predetermined position 12b is gradually enlarged. The diameter of the upper end 12a of the enlarged shape portion 13 and the distance from the upper end 12a to the predetermined lower position 12b are determined according to the shape of the molded product.

16 is a nozzle of the injector. The nozzle 16 is provided with a plurality of vertical grooves 17 on its inner peripheral surface. It is preferable that the vertical grooves are evenly spaced. Further, the inner diameter of the nozzle 16 is larger than the diameter of the upper end 12a of the enlarged shaped portion 13 of the columnar projection and smaller than the diameter of the lower end (that is, the lower predetermined position 12b). The injector used is not a so-called high-pressure type for RIM but is usually called a low-pressure type.

Insert the enlarged shape portion 13 of the columnar protrusion into the nozzle 16,
The polyurethane foam raw material 20 is discharged to produce a desired polyurethane foam molded article. At this time, the tip of the nozzle 16 is located between the upper end 12a and the lower end 12b of the enlarged shape portion. Further, the tip of the nozzle and the peripheral surface of the enlarged shape portion 13 are in contact with or separated from each other depending on the discharge amount of the raw material, the depth of the vertical groove 17, and the like.

The raw material 20 passing through the nozzle 16 is discharged from the nozzle tip without the flow being disturbed by the vertical groove 17 on the inner peripheral surface of the nozzle, uniformly collides with the peripheral surface of the enlarged shape portion 13 of the columnar projection, and the enlarged shape thereof. Flow along the section and uniformly flow into the cavity 14.

The raw material 20 uniformly dispersed and injected into the cavity 14 is foamed in the cavity of the closed mold to become a urethane foam having a hole in the center, and then when the mold is removed, a desired molded product 32 is obtained as shown in FIG. obtain. The obtained molded product has a uniform quality and has a good appearance with no wall thickness.

Depending on the intended use of the molded product, an insert is appropriately placed in the molding die. Further, the raw material 20 is discharged with the molding die opened or with the molding die closed depending on the structure of the molding die and the like.

(Effect of the Invention) This invention inserts an upper enlarged shape portion of a columnar protrusion protruding from a lower mold surface into an injector nozzle having a plurality of vertical grooves on its inner peripheral surface to discharge a urethane foam raw material. It is something to do. Therefore, it is possible to cause the raw material discharged from the nozzle to uniformly collide with the peripheral surface of the enlarged shape portion and spread it evenly along the enlarged shape portion, and as a result, to uniformly disperse the raw material into the cavity. I was able to do it.

Therefore, according to the present invention, it is possible to uniformly disperse the raw material into the cavity even with a single-point injection, and to manufacture a urethane foam molded product having a uniform quality and having a hole without defective appearance such as lack of wall. And the work becomes extremely easy.

[Brief description of drawings]

1 to 3 relate to an embodiment of the present invention,
FIG. 1 is a perspective view of a lower mold and a nozzle before discharging urethane foam raw material, and FIG. 2 is a front view of the nozzle as viewed from the direction A.
FIG. 3 is a cross-sectional view of the lower mold and the nozzle at the time of raw material injection,
Fig. 4 is a perspective view of a urethane foam molded product with holes.
FIG. 5 is a cross-sectional view of a lower mold when a raw material is injected by a conventional manufacturing method. 12 …… Column protrusion, 13 …… Enlarged shape part, 14 …… Cavity, 16 …… Nozzle, 17 …… Vertical groove

Claims (1)

[Claims] Claims: 1. A urethane foam raw material discharged from an injection machine nozzle is injected into a cavity of a mold having a columnar protrusion on a lower mold surface to foam-mold a urethane foam molded product having a hole in the center. In the method, the diameter from the upper end of the columnar projection to the lower predetermined position is gradually enlarged, while a plurality of vertical grooves are provided on the inner peripheral surface of the injector nozzle, and the enlarged shape of the columnar projection is formed in the nozzle. A method for manufacturing a urethane foam molded article, characterized in that a part is inserted and the raw material is discharged, whereby the raw material is injected into the cavity.