JPH0483613A - Rim wing method of dicyclopentadiene - Google Patents

Abstract

PURPOSE:To constitute the title method so that a sink corresponding to a thick part is not generated on an external appearance side even if a thick part such as a rib is on the inside, by a method wherein an appropriate number of platelike pieces are fitted beforehand under a state where a rib forming recessed part of a mold is closed partly and in a dispersed state and then RIM molding is performed. CONSTITUTION:Three sheets of platelike pieces 5 are fitted to a male mold 2 (ordinarily this become a top force) forming the inside of a molded product at intervals so that they close partly and in a dispersed state a recessed part 4 to form a rib 3. A cavity 7 is formed of the male mold (top force) 2 and a female mold (bottom force) 6 by putting them together and RIM molding resin is cast under low pressure. At a buried position of the platelike piece 5 an influence of contraction following cooling and solidification of the rib 3 is interrupted by the platelike piece 5 so that an ordinary thick part, 8 is not influenced by separating the ordinary thick part 8 and rib 3 partly from each other by the platelike piece 5. Therefore, the external side of the ordinary thick part 8 develops no sinks 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is characterized in that the main component is dicyclopentadiene (hereinafter referred to as rDC).
It is abbreviated as PDJ. ) using the raw material resin, DCP
This relates to the RIM molding method of D.

[Conventional technology]

RIM molding (reaction injection molding) involves passing multiple low-molecular-weight, low-viscosity liquids through a mixing chamber under pressure, injecting them simultaneously into a closed mold as a mixed liquid, and causing the liquid components to react quickly within the mold. The liquid mixture has good fluidity and can be filled into the mold with a small pressure, so the molding pressure applied to the mold is small (and cheap synthetic resin molds are used). It has characteristics such as being suitable for molding medium-sized and large-sized articles.

In particular, in DCPD RIM molding using Metone (trade name, sold by Teijin Vercules) whose main component is DCPD as the RIM molding resin, the molding pressure is approximately 2) cgf/
cj is small, and the molding pressure in general injection molding is approximately 400
kgf/alt, it can be molded at much lower pressure, and molding shrinkage is small and sink marks are less likely to occur.
It is also possible to mold objects with a thickness of 500 m. So, the bulldozer
Medium and dog-shaped grain members that require strength, such as the upper outer panels of cars, the bodies of agricultural machinery, and the bodies of floating tools, are now formed using DCP, instead of being formed by pressing steel plates.
It has also come to be manufactured by RIM molding of D.

When forming a medium/dog-shaped grain member by RIM molding, ribs are often provided at appropriate locations in order to achieve a predetermined strength. These ribs are generally provided on the inner surface so as not to spoil the appearance of the product. In RIM molding, it is easy to increase the thickness, so there is a tendency to increase the thickness of the ribs.

[Problem to be solved by the invention]

When molding medium-sized and large-sized parts using DCFD RIM molding, when the resin filled in the mold and reacted cools and solidifies,
As shown in Fig. 5, if the rib 3 is thick, it will contract later than the surrounding generally thick part 8, so the shrinkage of the rib 3 will cause one of the surrounding partial force bows to be stretched, corresponding to the rib on the external side. There was a drawback that sink marks 9 were caused. Although this sink mark is less noticeable than injection molding, medium-sized and
This cannot be ignored for large parts.

The present invention has been developed based on the above circumstances, and an object of the present invention is to provide a DCPD RIM molding method in which sink marks are not noticeable on the external appearance of the product even when molding a product having thick ribs. do.

[Means to solve the problem]

RI of DCPD according to the present invention to achieve the above object
The M molding method is characterized in that an appropriate number of plate-shaped pieces are installed in advance on the inner surface of the mold in a state that partially and dispersedly closes the rib-forming recesses of the mold, and then RIM molding is performed. do.

[For production]

The present invention improves the appearance of the product by partially embedding a plate-like piece between the general thick part and the rib so as not to cause a decrease in strength, and blocking the influence of rib shrinkage during molding with the plate-like piece. This prevents noticeable sink marks from forming on the surface.

〔Example〕

Below 5. The DCPD RIM molding method according to the present invention will be specifically explained with reference to the drawings.

In the method of the present invention, first, three molds are placed in a male mold 2 (usually the upper mold) that forms the inner surface of the molded product 1 so as to partially and dispersely close the recesses 4 for forming the ribs 3. plate-like piece 5
Attach them with a gap between them. A high-strength adhesive tape or a metal plate, specifically, a so-called cloth tape, a thick aluminum foil, or the like is attached to the plate-like piece 5. The adhesion strength may be such that it does not peel off when the DCPD is filled, and the number, shape, and dimensions of the plate-like pieces 5 can be changed as appropriate to correspond to the ribs.

After this, as in normal DCPD RIM molding, a cavity 7 is formed by combining the male mold (upper mold) 2 and the female mold (lower mold) 6, and the main component is DCFD as the RIM molding resin. Metone (trade name) is injected at low pressure. Since metone is a low viscosity liquid, it quickly flows into the recess 4 between the plate-shaped pieces 5 and is filled. Furthermore, since metone is injected at low pressure, the plate-like piece 5 attached to the male mold 2 will not come off.

Metone is sold by Teijin Vercules Co., Ltd., and is an olefin-based crosslinked thermosetting resin that uses DCPD as its main raw material. Liquid A and DCP
It consists of liquid B, which is made by adding a stabilized catalyst and additives to liquid D, and the properties of both liquids are almost the same.As a resin for RIM molding, it is easier to handle than polyurethane, etc. Since the mixture is mixed at a ratio of 1:1 and injected into a mold at low pressure, an inexpensive RIM machine and mold can be used.

After injection into the cavity 7, the male and female molds 6, 2 are held closed for the time required for the reaction of liquids A and B and for cooling and solidification.

Then, the male and female molds 6 and 2 are opened, and the molded product 1 is taken out. At this time, since the plate-shaped piece 5 attached to the recess 4 of the male mold 2 does not have very high attachment strength, it comes off from the male mold 2 while being embedded in the molded product 1 and remains in the female mold 6. Therefore, the molded product 1 with the plate-like piece 5 is taken out.

In the molded article 1 formed by the above method, when the resin is cooled and solidified in the cavity 7, the thick crotch portion 8 is solidified first, and then the rib 3 formed by the recess 4 is solidified. Here, by partially separating the crotch thick portion 8 and the rib 3 by the plate piece 5, the plate piece 5 blocks the effect of shrinkage due to cooling and solidification of the rib 3 at the location where the plate piece 5 is buried. General thick part 8
I'm trying not to let it get to that point. Therefore, sink marks 9 do not occur on the external side of the thick crotch portion 8. Further, although the thick crotch portion 8 and the rib 3 are partially separated by the plate-like pieces 5 provided in a dispersed manner, they are continuous at other locations, so the rib 3
A reinforcing effect can be achieved.

Furthermore, in the case where a metal plate is buried as the plate-like piece 5, a reinforcing effect by the plate-like piece 5 can be expected.

〔Effect of the invention〕

In the RIM molding method of DCPD according to the present invention, as described above, a plate-like piece is attached in advance to the rib forming portion of the mold so as to partially close the recess, so that the RIM molding is performed within the mold.
When the molding resin is cooled and solidified, the influence of the shrinkage of the resin filled in the recesses is blocked by the plate-like piece, and the external appearance of the molded product is hardly affected.

Therefore, in the method of the present invention, even if there is a thick part such as a rib on the inner surface side, sink marks corresponding to the thick part will not occur on the external side, and medium-sized and large-sized parts that require a thick part for strength. can be formed in an attractive manner.

In addition, in the method of the present invention, the injection pressure of the resin raw material into the mold is considerably lower than that in general injection molding, so it can be easily installed by simply pasting the plate-like piece in a predetermined position of the mold, and after molding. It is also easy to remove the plate-like piece from the mold while it is embedded in the molded product.

As described above, in the present invention, by simply adding the simple process of attaching the plate piece to the mold to the conventional RIM molding method, there is no sink mark on the outside that is a problem with the conventional method. , it is possible to easily form medium-sized and large-sized members with good appearance.

[Brief explanation of drawings]

FIG. 1 is a front view showing the main steps of the DCPD RIM molding method according to the present invention, FIG. 2 is a sectional view thereof, FIG. 3 is a perspective view showing an example of a molded product according to the method of the present invention, and FIG. FIG. 5 is a cross-sectional view of the periphery of the thick-walled part of a molded product produced by the method of the present invention. FIG. FIG. 2 is a perspective view of a molded product. 1... Molded product, 2... Mold, 3... Rib, 4...
・Concavity, 5...Plate piece

Claims (1)

[Claims] 1. Place an appropriate number of plate-like pieces (5) on the inner surface of the mold (2) in advance so as to partially and dispersely close the rib (3) forming recesses (4) of the mold (2). A RIM molding method for dicyclopentadiene, which comprises performing RIM molding after mounting.