JPH0211309A - Production of curable resin molded product - Google Patents

Abstract

PURPOSE:To produce a molded product contg. no void by rotating a mold around a feeding hole as a center and performing degassing from the feeding hole as air bubbles are gathered to the feeding hole in the central part even if air bubbles are included when a resin is poured-in. CONSTITUTION:A mold constitutes a top force 1 and a bottom force 2 and a cavity 3 is thereby formed in this mold. The top force 1 and the bottom force 2 are positionally fixed on a rotating table 6 through pins 5 and they can be integrally rotated with the rotating table 6 by driving a motor 7. The position of the mold is fixed in such a manner that a pouring hole 4 is positioned on the rotating axis 10 of the rotating table 6. As the curable resin to be used, a prepolymer of thermosetting resins and acrylic resin syrups well known as epoxy resins, unsatd. polyester resins and various amino resins can be used. Number of revolutions of the mold etc., can be properly determined in accordance with the kind of the curable resin of the raw material in such a manner that degassing and shrinkage of the resin can be effectively performed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a curable resin molded product such as an epoxy resin, and more specifically, a method for manufacturing a curable resin molded product such as a flat plate or a flat plate having unevenness or protrusions. This invention relates to a manufacturing method particularly useful for manufacturing molded articles.

(Prior Art) Conventionally, curable resin molded products such as epoxy resins have been manufactured by methods such as press molding, transfer molding, injection molding, and cast molding, and have been applied as industrial members.

With this type of curable resin, if the resin and curing agent are selected well, molded products with excellent properties such as transparency, weather resistance, and heat resistance can be obtained, and they have extremely high properties compared to thermoplastic resins. Since it is possible to perform molding in a low viscosity state, it has started to attract attention in the field of optoelectronics, such as optical disks, which require low optical distortion (birefringence).

However, when manufacturing molded products with the above characteristics using molding methods such as press molding, transfer molding, and injection molding, all molding methods involve molding the resin under considerable stress. In addition, the production capacity of the equipment will be stopped until the injected resin gels, and as the resin contracts, it is necessary for the mold to follow this contraction, so pressurize the mold. There are various disadvantages in that additional steps are required. Particularly in transfer molding, there is a restriction that the mold must be held while applying plunger pressure.

Furthermore, the casting method, which performs molding under normal pressure, can produce molded products with the most excellent properties as described above, but there are problems such as air bubbles getting mixed in when resin is injected, and problems when producing thin-walled molded products. However, there is a drawback that it takes time to inject the resin.

(Problems to be Solved) Therefore, the present invention uses a curable resin to significantly improve workability, and makes it possible to obtain molded products with excellent wall thickness accuracy and optical properties, and without voids. The purpose is to provide a manufacturing method.

(Means for Solving the Problems) The method for manufacturing a cured resin molded product of the present invention uses a mold having an injection port in the center and a cavity inside, and while rotating the mold, liquid is poured from the injection port. It is characterized by injecting a curable resin and curing it.

(Function) In the present invention, since the mold rotates around the injection port, even if air bubbles are mixed in during resin injection, the air bubbles are concentrated at the injection port in the center of the mold, and as a result, the injection port Gas is removed from the mold, and a void-free molded product can be obtained.

Furthermore, since centrifugal force acts on the resin filled in the mold, the resin shrinkage until gelation is compensated for by the centrifugal force.

(Preferred embodiment of the invention) FIG. 1 shows a mold used in the manufacturing method of the present invention.

That is, this mold consists of an upper mold 1 and a lower mold 2, and a cavity 3 is formed in these molds.

In addition, an injection port 4 is formed in the center of the upper mold 1.
The curable resin is injected through the injection port 4.

Further, the upper mold 1 and the lower mold 2 are fixed in position on a rotary table 6 via a bin 5, and can rotate together with the rotary table 6 as a motor 7 is driven. In this case, the injection port 4 is connected to the rotating shaft 10 of the rotating table 6.
The mold is fixed in position at the top.

It should be noted that the cavity 3 does not necessarily have to be planar as shown in FIG. 1, as long as the spout 4 is formed in the center, and may have, for example, an uneven shape.

According to the present invention, liquid hardening resin is injected into the mold from the injection port 4 while rotating the mold.

The curable resins used include well-known thermosetting resins such as epoxy resins, unsaturated polyester resins, and various amino resins, as well as prepolymers such as acrylic resin syrup. A curing agent, a curing accelerator, a polymerizable additive, etc. can also be blended.

Furthermore, if the raw resin is highly viscous and difficult to handle, a diluent may be added as necessary.

Furthermore, colorants, lubricants,
Of course, it is also possible to incorporate various compounding agents known per se, such as fillers.

When injecting the cured resin, it is preferable to heat the mold in advance; for example, when a combination of an alicyclic epoxy resin and an alicyclic acid anhydride is used, the temperature is usually 100 to 180°C. It is desirable to heat it to a temperature range of .

The number of rotations of the mold may be appropriately determined depending on the type of curable resin used as the raw material so that gas release and resin contraction are effectively performed.

According to the present invention, since resin is injected while rotating the mold, air bubbles mixed in during injection are concentrated near the injection port 4, and as a result, the air bubbles are quickly removed, resulting in a molded product. The product will be completely free of voids.

In the present invention, the mold may be rotated for a certain period of time after the resin is injected, for example, until gelation has progressed to the extent that the shrinkage of the resin has subsided (usually about several minutes, although this varies depending on the type of resin); There is no need to continue rotating until curing is complete.

Thus, according to the present invention, it is possible to effectively prevent distortion of the molded body due to resin contraction.

When the production method of the present invention described above is applied to a combination of an alicyclic epoxy resin and an alicyclic acid anhydride, a molded article extremely useful for optical purposes can be obtained.

(Example) A mold with a clearance of 1.21 am, a cavity of 200φ, and an injection port in the center was heated at 180°C.
This was preheated to 100 mL, set on a rotary table as shown in FIG. 1, and while rotating at a speed of 500 rpm, a resin composition having the following formulation was injected.

The molded product was then heated to 180°C for an additional 5 minutes, and removed from the mold to obtain a disc-shaped molded product.

The obtained molded product was completely free of voids and optical distortion and was ideal for use as an optical disc.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a mold for suitably implementing the method of the present invention.

Claims (2)

[Claims] (1) A curable resin characterized by using a mold having an injection port in the center and a cavity inside, and injecting liquid curable resin from the injection port and curing the mold while rotating the mold. Method of manufacturing molded products. (2) The manufacturing method according to claim (1), wherein the curable resin is an epoxy resin.