JPH0620798B2 - 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 simultaneously inject 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 body that is rich in elasticity or rigidity, and has good fluidity of the mixed liquid, and can be quickly filled into a large mold with a small pressing force, so it is suitable for molding medium and large-sized articles. In addition, the molding pressure applied to the mold is small, and an inexpensive synthetic resin mold can be used.

Especially, in the RIM molding of DCPD using Meton (trade name, sold by Teijin Hercules Co., Ltd.) whose main component is DCPD as the resin for RIM molding, the molding pressure is as small as about 2 kgf / cm ^2, and the injection molding is performed. Molding pressure is about 400k
It can be molded at a much lower pressure than gf / cm ² , and
Molding shrinkage is small and sink marks are unlikely to occur, making it possible to mold thick products of about 10 mm. Therefore, middle- and large-sized shell-shaped members that require strength, such as the upper skin of a bulldozer, the body of an agricultural machine, or the body of a watercraft, are sometimes divided into several parts by press working of steel plates. Instead of being manufactured, it has also come to be integrally molded by RIM molding of DCPD.

Further, in RIM molding of DCPD, the outer surface side of the molded product is often formed by a lower fixed mold (lower mold) and the inner surface side is formed by an upper movable mold (upper mold), as shown in FIG. Article 4
A method of projecting a protrusion 6 such as a boss, a holed protrusion, or a rib for coupling with another member is also commonly used on the inner surface side of the.

[Problems to be Solved by the Invention]

When the protrusion 6 is provided on the back surface side of the general thick portion 5 apart from the peripheral portion 13 for the convenience of design, the protrusion 6 is the eighth.
As shown in the figure, where the shape should project from the general thick portion 5 by a predetermined length, a void (defective portion) 14 is formed at the tip of the protrusion 6 as shown in FIG. There is also a possibility that the bond strength may be reduced or the bond itself may be impossible.

The reason why the void 14 is formed at the tip of the protrusion 6 is that the mixed solution before the reaction injected into the mold at the time of RIM molding passes from the one peripheral portion 13 through the horizontal general thick portion 5 and the protrusion 6. When the gas in the mold is extruded and flows into the other peripheral edge portion 13, the concave portion corresponding to the protrusion 6 in the mold has a blind alley in the inflow direction (upward direction) of the mixed liquid. This is because the gas at that location is not completely extruded, and the reaction of the mixed solution proceeds while leaving the gas at the upper end.

Therefore, the present invention has been made based on the above-mentioned circumstances, and even in the case of a molded product having a projection portion on the inner surface side of a general thick portion, which is separated from the peripheral edge portion, a thin wall portion is formed at the tip of the projection portion. It is an object of the present invention to provide a RIM molding method of DCPD that can be molded into a predetermined shape without any need.

[Means for Solving the Problems]

RI of DCPD according to the present invention for achieving the above object
According to the M-molding method, a horizontally separable insert core is magnetically attached to a recess formed on the inner surface of the upper mold, and the insert core has a space corresponding to a protrusion protruding toward the inner surface of the molded product. A void reservoir is formed on the upper side of the upper mold over the lower mold to perform RIM molding, and an enlarged portion is extended above the protrusion through a thin wall. Then
It is characterized in that the upper and lower molds are opened and the molded product and the insert core are taken out as they are, and the insert core is laterally divided from the molded product and removed, and the enlarged portion is cut off with the thin portion.

[Work]

In the present invention, an extra bulge is provided on the upper end of the protrusion that is turned upward during molding via a thin portion to be cut later, and a void is generated in the uppermost bulge to be cut later.

By forming a bulge, a thin portion and a protrusion with a core fixed to the upper mold with magnetic force, even if the bulge is undercut, the molded product and the core are handled as one It can be taken out.

The insert core is a piece that is divided laterally and removed from the molded product so that the bulge does not undercut.

Since the filling core fixed by magnetic force to the upper mold has a small filling pressure in the RIM molding of DCPD, until the mold is opened,
It is fixed immovably.

〔Example〕

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

In the case of manufacturing a molded product 4 having two bosses as the protrusions 6 in the central portion on the inner surface side of the general thick portion 5 as shown in FIG. 6, first, the pair of placing cores 3, 3 are laterally arranged. Butt and mount in the recess 2 provided in the lower surface of the upper mold 1. here,
Between the abutting cores 3 and 3, the protrusions 6 are arranged in order from the bottom.
The space 7 corresponding to the above, the constricted portion 8 and the void reservoir portion 9 are formed in communication with each other, and the pin 16 for forming the boss hole 15 is inserted into the central portion thereof. Further, an iron plate 17 is attached to the upper end of each core 3, and a magnet 18 is fitted into the recess 2 of the upper mold 1 in correspondence with each iron plate 17, and the core 3 is moved upward by the attraction force of the two 17, 18. It is fixed in place on the mold 1. here,
It goes without saying that the iron plate 17 may be arranged on the upper mold 1 and the magnet 9 may be arranged on the storage core 3.

Next, the upper mold 1 having the placement core 3 mounted thereon is superposed on the lower mold 10 to form a cavity 19, and RI is formed in the cavity 19.
Meton (trademark) is filled as the M molding resin. At this time, the meton rises in the space 7 and flows into the void reservoir 9 from the constricted portion 8. However, the gas in the space 7 is trapped in the void reservoir 9.
The void 14 is generated in the void reservoir 9 due to the reaction of the metaltone and the solidification by cooling. Further, since the filling pressure of the meton is small, the core 4 fixed by the magnetic force does not move during this.

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

Then, the upper and lower molds 1 and 10 are held in a closed state for a time required for the reaction and cooling and solidification of the metal, and the protrusion 6 is formed in the space 7 between the storage cores 3 and 3, the thin portion 11 is formed in the constricted portion 8, and the void is formed. Enlarged portions 12 are formed in the reservoirs 9, respectively.

Then, the upper and lower molds 1 and 10 are opened. Then, the molded product 4 includes the protrusion 6 to the thin-walled part 11 and the enlarged part 1 to be an undercut.
Removed from the upper mold 1 with the storage core 3 still fitted over 2
It remains on the lower die 10 side. At this time, since the placement core 3 is only fixed to the upper mold 1 by the magnetic force, it can be easily removed.

Next, the molded product 4 in which the storage core 3 is fitted is raised from the lower mold 10 and taken out.

Then, the insert cores 3, 3 fitted in the molded product 4 are divided in the lateral direction (direction of the arrow in FIG. 3) and pulled out. In addition, boss hole 1
The pin 16 for forming 5 is removed after this, but the pin 16 may be fixed to the upper mold 1 so as to come out of the molded product 4 when the upper and lower molds 1 and 10 are opened.

After that, the enlarged portion 12 extending above the protruding portion 6 via the thin portion 11 is formed as the thin portion 11, and preferably, as shown in FIG. 4A-A.
Cut off with a line. At this time, the thin portion 11 makes the cutting position clear and facilitates the cutting.

〔The invention's effect〕

As described above, the RIM molding method for DCPD according to the present invention provides an extra bulge through the thin portion at the tip of the protrusion that faces upward at the time of molding, causes a void in the bulge, and then enlarges the bulge. Since a part is cut off, if a product having a protrusion such as a boss or a rib is formed by this method, a product having a protrusion with a proper shape without voids can be reliably formed, and the strength as designed and A combined state can be realized.

Further, in the method of the present invention, the above-mentioned enlarged part is formed by the magnetic core mounted in the concave portion of the lower surface of the upper die by magnetic force, and the molded product is taken out while the elastic core is fitted in the enlarged part, and then the elastic core is removed. Since it is divided in the lateral direction and removed, it is possible to form without difficulty even if the enlarging portion is undercut.

Moreover, in RIM molding of DCPD, since the filling pressure of the resin raw material is low, it is possible to immobilize the insert core to the upper mold immovably by the magnetic force, so that even if there is an enormous portion that is an undercut in the molded product,
There is no need to use expensive split molds with a complicated structure,
A desired product can be easily manufactured by using a die having a relatively simple structure and being inexpensive.

[Brief description of drawings]

1 to 4 are longitudinal sectional views showing the main working steps of the RIM molding method for DCPD according to the present invention, FIG. 5 is a longitudinal sectional view in the superposed state of the insert core, and FIG. 6 is according to the method of the present invention. FIG. 7 is a perspective view showing an example of a molded product to be manufactured, FIG. 7 is a sectional view taken along the line BB of FIG. 6, FIG. 8 is an enlarged sectional view of an essential part showing an example of good formation of a portion C of FIG. 7, and FIG. FIG. 7 is an enlarged sectional view of an essential part showing an example of defective formation of the part C in FIG. 7; 1 ... Upper mold, 2 ... Recessed portion, 3 ... Storage core, 4 ... Molded product, 6 ... Projection portion, 7 ... Space, 8 ... Constricted portion, 9 ...
... Void reservoir, 10 ... Lower mold, 11 ... Thin wall, 12 ...
… Huge part

Claims (1)

[Claims] 1. A recess (2) formed on the inner surface of an upper mold (1).
A core (3) which can be divided in the lateral direction is attached by magnetic force, and the core (3) is a space (7) corresponding to a protrusion (6) protruding to the inner surface side of the molded product (4). And a void reservoir (9) which is connected to the lower mold (10) via a constriction (8). The upper mold (1) is overlapped with the lower mold (10) to perform RIM molding, and the protrusion ( 6) above the thin portion (1
1) to extend the enlarging part (12) through the upper and lower molds (1, 1
0), the molded product (4) and the storage core (3) are taken out as a unit, and the molded core (3) is laterally divided from the molded product (4) and removed, and the thin portion (11) is an enlarged portion. RIM molding method of dicyclopentadiene characterized by cutting off (12)