JPH0620788B2 - RIM molding method for dicyclopentadiene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention mainly uses dicyclopentadiene (hereinafter referred to as "DC
Abbreviated as "PD". ) DCP using the raw material resin
The present invention relates to a DIM RIM molding method.

[Conventional technology]

RIM molding (reaction injection molding) allows multiple low-molecular-weight, low-viscosity liquids to pass through a mixing chamber under pressure, and is simultaneously injected as a mixed liquid into a closed mold to rapidly react the liquid components in the mold. This is a method of forming a polymer, and the fluidity of the mixed liquid is good, and the mold can be filled with a small pressing force, so the molding pressure applied to the mold is small and an inexpensive synthetic resin mold is used. It has the characteristics that it can be formed, and that it is suitable for molding medium and large-sized articles.

In particular, in the RIM molding of DCPD using Meton (trade name, sold by Teijin Hercules Co., Ltd.) containing DCPD as a main component as the RIM molding resin, the molding pressure is as small as about 2 kgf / cm ^{2, which} is the same as that in general injection molding. Molding pressure is about 400 kgf / cm ²
However, molding can be performed at a much lower pressure, shrinkage is less likely to occur, and sink marks are less likely to occur, and molding of thick-walled products of about 10 mm is also possible. Therefore, instead of forming medium- and large-sized grain-shaped members that require strength, such as the upper skin of bulldozers, the bodies of agricultural machines, the bodies of watercrafts, etc., by pressing steel plates, DCPD It has also come to be manufactured by RIM molding.

When forming a medium- or large-sized grain-shaped member by RIM molding, it is often practiced to provide ribs at appropriate places in order to achieve a predetermined strength. This rib is generally provided on the inner surface side so as not to impair the appearance of the product. Since it is easy to increase the wall thickness by RIM molding, the wall thickness of the rib tends to increase.

[Problems to be Solved by the Invention]

In the molding of medium and large-sized members by RIM molding of DCPD, when the resin filled and reacted in the mold is cooled and solidified,
As shown in FIG. 5, when the rib 3 has a large thickness, the rib 3 contracts later than the surrounding general thick portion 8. Therefore, the contraction of the rib 3 pulls the peripheral portion, and the sink mark 9 corresponding to the rib on the appearance side.
There was a drawback that caused. Although the sink marks were less noticeable than those obtained by injection molding, they were not negligible for medium- and large-sized members that required large ribs in terms of strength.

Therefore, the present invention has been made based on the above circumstances, and an object thereof is to provide a RIM molding method of DCPD in which a sink mark is not noticeable on the appearance side of the product even when a product having a large rib is molded.

[Means for Solving the Problems]

RI of DCPD according to the present invention for achieving the above object
The M-molding method is characterized in that a plate-shaped piece having an enemy number is preliminarily mounted on the inner surface of the mold in a state in which the rib-forming recesses of the mold are partially and dispersedly closed, and then RIM molding is performed. To do.

[Work]

The present invention partially embeds the plate-shaped piece between the general thick portion and the rib so as not to reduce the strength, and shields the influence of the rib shrinkage during molding by the plate-shaped piece, thereby improving the appearance of the product. It prevents the occurrence of a noticeable sink mark on the surface.

〔Example〕

Hereinafter, a method for forming a DCPD RIM according to the present invention will be specifically described with reference to the drawings.

According to the method of the present invention, first, the male die 2 (which is usually the upper die) forming the inner surface side of the molded article 1 is provided with three pieces so as to partially and disperse the concave portions 4 for forming the ribs 3. Plate piece 5
Install with a gap. A high-strength adhesive tape or a metal plate, specifically, a so-called cloth tape or thick aluminum foil is attached to the plate-like piece 5. The attachment 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 appropriately according to the ribs.

After this, like the ordinary RIM molding of DCPD, a cavity 7 is formed by combining a male mold (upper mold) 2 and a female mold (lower mold) 6, and DCPD is used as a main component for RIM molding. Inject Metton® at low pressure. Since the methone is a low-viscosity liquid, it rapidly flows into the recess 4 from between the plate-like pieces 5 and is filled therein. Further, since the methone is injected at a low pressure, the plate-shaped piece 5 attached to the male mold 2 does not peel off.

Meton is a product sold by Teijin Hercules Co., Ltd. It is an olefin-based cross-linking type thermosetting resin that uses DCPD as a main raw material, and a catalyst activator, a polymerization initiation time regulator and additives are added to DCPD. Liquid A and DCP
It consists of a stabilized catalyst and a liquid B with additives added to D, and since the properties of both liquids are almost the same, it is easier to handle as a resin for RIM molding than polyurethane etc. Since it is mixed at a ratio of 1 and injected into the mold at a low pressure, an inexpensive RIM machine and mold can be used.

After the injection into the cavity 7, the male and female molds 6 and 2 are held in the closed state for the time required for the reaction between the A liquid and the B liquid and the 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-like piece 5 attached to the concave portion 4 of the male mold 2 does not have a very high attachment strength, it is removed from the male mold 2 and left in the female mold 6 while being embedded in the molded product 1. Therefore, the molded product 1 with the plate-shaped 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 general thick portion 8 is solidified first, and then the rib 3 formed by the recess 4 is solidified. Here, the general thick portion 8 and the rib 3 are partially separated by the plate-like piece 5, so that at the place where the plate-like piece 5 is embedded, the effect of shrinkage due to cooling and solidification of the rib 3 is blocked by the plate-like piece 52. So that it does not reach the general thick portion 8. Therefore, the sink mark 9 does not occur on the appearance side of the general thick portion 8. Also, the general thickness part 8
Although the ribs 3 and the ribs 3 are partially divided by the plate-shaped pieces 5 provided in a dispersed manner, the ribs 3 are continuous at other places, so that the reinforcing effect by the ribs 3 can be achieved. Further, a metal plate embedded as the plate-shaped piece 5 can be expected to have a reinforcing effect by the plate-shaped piece 5.

〔The invention's effect〕

In the DCPD RIM molding method according to the present invention, a plate-shaped piece is preliminarily attached to the rib forming portion of the mold as described above so as to partially close the recess, and thus the RIM is formed in 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 it hardly reaches the appearance side of the molded product. Therefore, according to the method of the present invention, even if there is a thick portion such as a rib on the inner surface side, a sink mark corresponding to the thick portion does not occur on the appearance side, and a medium- or large-sized member requiring a thick portion for strength. Can be formed in a good appearance.

Further, in the method of the present invention, since the injection pressure of the resin raw material into the mold is considerably smaller than that of general injection molding, it is possible to simply attach the plate-shaped piece to the predetermined position of the mold, and after molding, It is also easy to remove the plate-shaped piece from the mold with the plate-shaped piece embedded in the molded product.

As described above, by simply adding the simple step of mounting the plate-shaped piece to the mold in the present invention to the conventional RIM molding method,
Medium and large-sized members can be formed easily and easily without causing sink marks, which have been a problem in the conventional method, on the appearance side.

[Brief description of drawings]

FIG. 1 is a front view showing the main steps of a DCPD RIM molding method according to the present invention, FIG. 2 is a cross-sectional view thereof, FIG. 3 is a perspective view showing an example of a molded article according to the present invention, and FIG. FIG. 5 is a cross-sectional view around the thick part of the molded product by the method of the present invention. FIG. 5 is a cross-sectional view around the thick part of the molded product manufactured by the conventional RIM molding method. It is a perspective view of a molded product. 1 ... Molded product, 2 ... Mold, 3 ... Rib, 4 ... Recess,
5 ... plate-shaped piece

Claims (1)

[Claims] 1. An appropriate number of plate-shaped pieces (5) on the inner surface of a mold (2).
RIM of dicyclopentadiene, characterized in that RIM molding is performed after pre-mounting the ribs (3) forming recesses (4) of the mold (2) partially and dispersedly to close them.
M molding method