JPH10156859A - Manufacture of reaction injection molding and mold therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and mold where in a micro cell is not generated on a surface of a reaction injection molding. SOLUTION: Molds 4, 6 wherein a cavity 8 is formed inside by being clamped; a cushioning tank 26 wherein it is communicated to a vent opening 20 formed to the molds 4, 6, and dwelling gas of a pressure higher than atmospheric pressure around the mold and lower than clamping pressure of the molds 4, 6 is supplied to an inside of the cavity 8 before filling stock solution through the bent opening 20; control valves 30, 32 which control an inside of the cushioning tank 26 within a specific pressure range; and a stock solution feed means 10 wherein reaction stock solution is casted into the cavity 8 of the molds 4, 6 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a reaction injection molded article and a mold apparatus used for the method.

[0002]

2. Description of the Related Art Reaction injection molding (hereinafter also referred to as RIM).
In the method, two reaction stock solutions are mixed in a mixing chamber, fed into a cavity of a mold, and injection-molded while reacting in the mold. This RIM method is suitably used when a polymer (molded article) is formed from a norbornene-based monomer.

[0003] In the RIM method, molding is performed by sending a reaction stock solution stored in a stock solution tank to a mixer and a mold by a pump.

[0004]

However, fine bubbles may be generated on the surface of the molded article depending on the shape and molding conditions of the molded article to be obtained. When this foam is generated on the surface of the molded article, swelling occurs at the time of coating the surface of the molded article, thereby deteriorating the appearance of the surface of the molded article. In addition, when bubbles are generated in the molded body, the electrical characteristics of the molded body become unstable.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a method for preventing micro bubbles from being generated on the surface of a reaction injection molded article. By filling the cavity with a holding pressure gas, it was found that fine bubbles were not formed on the surface of the obtained reaction injection molded article, and the present invention was completed.

That is, in the method for producing a reaction injection molded article according to the present invention, before injecting the unreacted solution into the cavity of the mold, the inside of the cavity of the mold is higher than the atmospheric pressure around the mold. It is characterized by filling with a holding pressure gas having a pressure lower than the mold clamping pressure, then injecting a reaction solution into a cavity of the mold, and performing reaction injection molding.

[0007] A mold apparatus according to the present invention further comprises: a mold having a cavity formed therein by being clamped;
A holding pressure gas having a pressure higher than the atmospheric pressure around the mold and lower than the mold clamping pressure of the mold is communicated with the inside of the cavity through the vent hole formed in the mold. It has a cushion tank to be supplied, a control means for controlling the inside of the cushion tank to a predetermined pressure range, and a stock solution supply means for injecting a stock solution into the cavity of the mold.

The pressure-holding gas for filling the cavity of the mold is not particularly limited, but is preferably an inert gas such as nitrogen gas. The pressure of the holding gas is set to be higher than the atmospheric pressure around the mold and lower than the mold clamping pressure of the mold. Specifically, the lower limit of the pressure of the holding gas is preferably 0.1 kgf / cm ² or more, more preferably 0.3 kgf / cm ² or more, and particularly preferably 0.4 kgf / cm ² or more. If the pressure of the holding gas is too low, the method becomes almost the same as the conventional method, and fine bubbles tend to be formed on the surface of the molded body. The upper limit of the pressure of the holding pressure gas is determined according to the mold clamping pressure, and the mold clamping pressure during the reaction injection molding is 3 kgf / kg.
cm ² , preferably 2 kgf / cm 2
² or less, more preferably 1.5 kgf / cm ² or less,
Particularly preferably, it is 1.0 kgf / cm ² or less. This is to prevent the mold from opening.

The mold clamping pressure during reaction injection molding is 0
Since the pressure can be set freely within the range of １００100 kgf / cm ² , when the mold clamping pressure is high, the holding pressure can be set high. However, since the filling pressure of the reaction solution into the cavity of the mold is generally set lower than the mold clamping pressure, the pressure of the holding gas is preferably lower than the filling pressure of the reaction solution.

In the present invention, the reaction stock solution used for the reaction injection molding is not particularly limited, but includes urethane-based, urea-based, nylon-based, epoxy-based, unsaturated polyester-based, phenol-based, and norbornene-based solutions. As general molding conditions, the reaction stock solution temperature is 20 to 8
At 0 ° C., the viscosity of the reaction stock solution is, for example, 5 cps to 3000 cps, preferably 100 cps at 30 ° C.
It is about 1000 cps. In such molding,
Reinforcement polymer (molded product) by placing a reinforcing material in a mold in advance and supplying a reaction solution into it and polymerizing it
Can be manufactured.

Examples of the reinforcing material include glass fiber, aramid fiber, carbon fiber, ultra high molecular weight polyethylene fiber, metal fiber, polypropylene fiber, aluminum coated glass fiber, cotton, acrylic fiber, boron fiber, silicon carbide fiber, and alumina fiber. And the like. These reinforcing materials can be used in various shapes, such as those obtained by forming a long fiber or chopped strand into a mat, woven into a cloth, or remaining in a chopped shape. It is preferable that the surface of these reinforcing materials is treated with a coupling agent such as a silane coupling material in order to improve the adhesion to the resin. The amount is not particularly limited, but is usually 10% by weight of the total weight of the molded article
As described above, the content is preferably 20 to 60% by weight.

Further, various additives such as an antioxidant, a filler, a pigment, a colorant, a foaming agent, a flame retardant, a sliding agent, an elastomer, a dicyclopentadiene-based thermopolymerized resin and a hydrogenated product thereof are blended. Thereby, the properties of the obtained polymer can be modified. As the antioxidant, there are various antioxidants for plastics / rubbers such as phenol type, phosphorus type and amine type. Filled with milled glass,
There are inorganic fillers such as carbon black, talc, calcium carbonate, aluminum hydroxide and mica. Examples of the elastomer include natural rubber, polybutadiene, polyisoprene, styrene-butadiene copolymer (SBR), and styrene-butadiene-styrene block copolymer (SB).
S), styrene-isoprene-styrene block copolymer (SIS), ethylene-propylene-diene terpolymer (EPDM), ethylene-vinyl acetate copolymer (EV
A) and hydrides thereof.

The additive is usually mixed in advance with one or both of the reaction solutions. The mold used for the reaction injection molding does not necessarily need to be a rigid and expensive mold, and is not limited to a metal mold, but may be a resin mold or a simple mold. This is because reaction injection molding can be performed at a relatively low temperature and a low pressure by using a low viscosity reaction liquid.
The components used for the polymerization reaction are preferably stored and operated under an atmosphere of an inert gas such as nitrogen gas.

The mold temperature is preferably from 10 to 150
° C, more preferably 30 to 120 ° C, still more preferably 50 to 100 ° C. Mold pressure is usually 0-100
Kgf / cm ² . The polymerization time may be appropriately selected, and is usually from 20 seconds to 20 seconds after the completion of the injection of the reaction solution.
Minutes.

[0015]

According to experiments by the present inventors, before injecting the unreacted solution into the mold cavity, the inside of the mold cavity is
It was confirmed that by filling with a holding pressure gas having a predetermined pressure, no fine bubbles were formed on the surface of the reaction injection molded article after molding.

In the mold apparatus according to the present invention, by using a cushion tank communicating with a vent port formed in the mold as a pressure holding source, the inside of the cavity of the mold before injection of the unreacted solution is maintained at a predetermined pressure. Can be filled, and at the time of injecting the undiluted reaction solution, the pressure holding gas in the mold is conveniently pushed back from the vent port to the cushion tank. When the internal pressure of the cushion tank is going to be higher than the predetermined pressure due to the held back gas,
The holding gas is released to the outside or another tank by a control means (for example, a safety valve), and the internal pressure of the tank is kept substantially constant. Therefore, the internal pressure of the cavity does not suddenly increase (cushion action), and does not adversely affect the filling of the reaction solution.

In order to stabilize the pressure inside the cavity as described above, in the mold device according to the present invention, it is preferable that the inner volume V ₁ of the cushion tank has a certain volume. ₁ is determined in accordance with the internal volume V ₂ of the mold cavity, the relationship of V ₁ and V ₂ is preferably V ₁ = V ₂ × 1 to 5, more preferably V ₁ = V ₂ × (2 to 4). If the volume of the tank is too small, the cushioning effect of the cushion tank tends to be insufficient, and if the volume is too large, it is uneconomical.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for producing a reaction injection molded article and a mold apparatus according to the present invention will be described in detail based on an embodiment shown in the drawings.

FIG. 1A is a schematic view of a mold apparatus used in a method of manufacturing a reaction injection molded article according to one embodiment of the present invention, and FIG. 1B is a main part of the mixer shown in FIG. It is sectional drawing.

As shown in FIG. 1A, a mold apparatus 2 for performing reaction injection molding has a mold 4 and a mold 6, which are provided so as to be relatively close to and separated from each other. . Mold 4,6
Are combined, a cavity 8 is formed inside the mold. The cavity 8 communicates with a mixer 10 serving as a stock solution supply means, from which a reaction stock solution is injected into the cavity 8. Molds 4 and 6
It is not always necessary to use an expensive mold having high rigidity, and the invention is not limited to a metal mold, and a resin mold or a simple mold can be used. This is because reaction injection molding has a lower filling pressure and mold clamping pressure than ordinary injection molding.

The mixer 10 includes a reaction solution A in a tank 14.
And a reaction liquid B in a tank 16 for mixing and discharging, and has an advancing / retracting rod 12 at the center. And FIG.
In the state before the injection shown in FIG. 1A, the reaction liquid A and the reaction liquid B circulate in the closed circulation circuits, respectively, without being mixed by the advance / retreat rod 12 moving forward.
At the time of the injection shown in (B), the reaction liquid A and the reaction liquid B are mixed in the mixer 10 by the reciprocation rod 12 retreating, and filled into the cavity 8 through the injection port.

In the present embodiment, a vent port 20 communicating with the cavity 8 of the dies 4 and 6 is formed in the split surface of the dies 4 and 6, and the vent port 20 communicates with the pressure holding line 22. It is. The pressure holding line 22 is connected to a cushion tank 26 via a three-way valve 24. The three-way valve 24 is controlled so as to enable communication between the cushion tank 26 and the cavity 8, cut off the communication by a switching signal, and open the interior of the cavity 8 to the atmosphere.

The cushion tank 26 is connected to a holding gas supply source (not shown) through a holding gas supply line 28. A control valve 30 is mounted on the supply line 28. The control valve 30 opens the pressure-holding gas supply line 28 when the pressure of the pressure-holding gas in the cushion tank 26 falls below a predetermined pressure, and replenishes the pressure-holding gas in the cushion tank 26. A safety valve 32 is attached to a pressure-holding line 28 between the control valve 30 and the cushion tank 26. When the pressure of the pressure-holding gas in the cushion tank 26 becomes higher than a predetermined pressure, the safety valve 32 Pressure is released to the outside. In the present embodiment, the control valve 30 and the safety valve 32 correspond to control means in the present invention.

In the present embodiment, the inner volume V ₁ of the cushion tank 26 is determined according to the inner volume V ₂ of the mold cavity 8 and the like, and a relationship of about V ₁ = V ₂ × 1 to 5 is preferable. V ₁ = V ₂ × (2-4) is more preferable. If the capacity of the tank 26 is too small, the cushioning effect of the cushion tank 26 tends to be insufficient, and if the capacity is too large, it is uneconomical.

The reaction injection molding performed in the present embodiment is a reaction injection molding using a norbornene-based monomer, and the monomer used is a norbornene such as dicyclopentadiene, dihydrodicyclopentadiene, tetracyclododecene, tricyclopentadiene or the like. It is a cycloolefin having a ring.

A metathesis catalyst that can be used in reaction injection molding using a norbornene-based monomer is
There is no particular limitation on the metathesis catalyst known as a catalyst for bulk polymerization of norbornene-based monomers such as organic ammonium molybdates such as tungsten hexachloride, tridodecyl ammonium molybdate, and tri (tridecyl) ammonium molybdate. Organic ammonium salts are preferred.

Examples of the activator (cocatalyst) include alkylaluminum halides such as ethylaluminum dichloride and diethylaluminum chloride, alkoxyalkylaluminum halides, and organotin compounds.

As preparations for the reaction injection molding, a reaction injection molding material mainly composed of a norbornene-based monomer, a metathesis catalyst and an activator was used as a solution A comprising a norbornene-based monomer and a metathesis catalyst; Divided into two stable liquids, liquid B and activator,
Keep each in a separate tank. In this embodiment,
The liquid A is stored in the tank 14 and the liquid B is stored in the tank 16.

Next, a method for producing a reaction injection molded article according to the present embodiment will be described.

The molds 4 and 6 are clamped. The mold clamping pressure is 3 kgf / cm ² in the present embodiment. Also,
The temperature of the molds 4 and 6 is preferably 10 to 150 ° C, more preferably 30 to 120 ° C, and still more preferably 5 to 150 ° C.
It is set to 0-100 ° C.

Thereafter, the three-way valve 24 is controlled to communicate the cushion tank 26 with the inside of the cavity 8, and the inside of the cavity 8 is filled with a holding pressure gas. In the present embodiment, nitrogen gas is used as the holding pressure gas. Cushion tank 2
The pressure of the nitrogen gas in 6 is 0.4 to 1.0 kgf / cm.
² (gauge pressure). By controlling the three-way valve 24, the inside of the cavity 8 becomes 0.4 to 1.0 kgf / c.
Filled with nitrogen gas at a pressure of m ² (gauge pressure).

Thereafter, the advancing / retreating rod 12 of the mixer 10 is controlled to mix the liquid A and the liquid B from the tanks 14 and 16 and fill the cavity 8 as a reaction stock solution. The filling pressure is ² to 4 kgf / cm ² in the present embodiment.
At that time, the nitrogen gas inside the cavity 8 is pushed back toward the cushion tank 26 through the vent port 20 and the pressure holding line 22. When the internal pressure of the cushion tank 26 is going to be higher than a predetermined pressure due to the pushed back nitrogen gas, the holding pressure gas is released to the outside or another tank by the safety valve 32, and the internal pressure of the tank 26 is substantially constant. Is kept. Therefore, the internal pressure of the cavity 8 does not suddenly increase (cushion action), and does not adversely affect the fillability of the reaction solution.

The three-way valve 24 may be controlled to release the inside of the cavity 8 to the atmosphere simultaneously with or immediately after the start of the charging of the reaction solution. In this case, the holding pressure by the nitrogen gas inside the cavity 8 is released simultaneously with or immediately after the start of the filling.

However, the timing for releasing the holding pressure in the cavity 8 is preferably 5 to 30 seconds from the time when the filling of the reaction stock solution into the cavity 8 is completed.
The holding pressure release in this case is also performed by the three-way valve 24. After the inside of the cavity 8 returns to the normal pressure by the three-way valve 24, preferably after 10 to 60 seconds, the mold is opened, and the molded body is taken out of the molds 4 and 6.

It was confirmed that fine bubbles were not formed on the surface of the reaction injection molded article obtained by the method for producing a reaction injection molded article according to the present embodiment.

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention.

For example, in the above embodiment, a nitrogen gas is used as the pressure-holding gas, but an inert gas such as an argon gas or a helium gas may be used instead of the nitrogen gas. However, nitrogen gas is economical.

[0038]

EXAMPLES Hereinafter, the present invention will be described with reference to more specific examples, but the present invention is not limited to these examples. Parts and percentages are by weight unless otherwise specified.

Example 1 Plate-forming dies 4 and 6 of 300 mm × 300 mm × 10 mm were prepared. FIG. 1 (A) shows the vent holes 20 of the molds 4 and 6.
As shown in the figure, a cushion tank 26 was attached via a pressure holding line 22 and a three-way valve 24. The internal volume of the cushion tank 26 was 1500 cc. The tank 26 is provided with a safety valve 3 so that the inside of the cushion tank 26 is always maintained at 0.5 kgf / cm ² (gauge pressure).
2 and a holding pressure gas supply line 28 having a control valve 30 were connected.

On the other hand, dicyclopentadiene (DCP) 9
A norbornene-based monomer composed of 0% and 10% of asymmetric cyclopentadiene trimer and 3 parts by weight of vinylnorbornene with respect to the monomer are placed in each of two tanks, and one of them is provided with diethylaluminum chloride (DEAC). ) Was added to give a 40 molar concentration and a 1,4-dichloro-2-propanol (dcPrOH) 48 molar concentration (Solution A). On the other hand, tri (tridecyl) ammonium molybdate per monomer is
The solution was added to a concentration of 0 mmol (solution B). These A liquid and B liquid are supplied to tank 14 and tank 1 respectively.
Stored at 6.

First, the dies 4 and 6 were clamped. The mold clamping pressure was 3 kgf / cm ² . The temperature of the mold 4 was 50 ° C., and the temperature of the mold 6 was 80 ° C.

Thereafter, the three-way valve 24 was controlled to communicate the cushion tank 26 with the inside of the cavity 8, and the inside of the cavity 8 was filled with nitrogen gas. Cushion tank 2
The pressure of the nitrogen gas in 6 was 0.5 kgf / cm ² (gauge pressure). By controlling the three-way valve 24, the inside of the cavity 8 was filled with nitrogen gas having the same pressure as the internal pressure of the tank 26.

Thereafter, the advancing / retracting rod 12 of the mixer 10 was controlled to mix the liquid A and the liquid B from the tanks 14 and 16 and to fill the cavity 8 as a reaction solution. The filling pressure was 3 kgf / cm ² . At that time, the nitrogen gas inside the cavity 8 was pushed back toward the cushion tank 26 through the vent port 20 and the pressure holding line 22. Although the internal pressure of the cushion tank 26 was going to become higher than the predetermined pressure due to the pushed back nitrogen gas, the pressure-holding gas was released to the outside by the safety valve 32, and the internal pressure of the tank 26 was kept substantially constant. Therefore, the internal pressure of the cavity 8 did not suddenly increase, and did not adversely affect the fillability of the reaction solution.

Twenty seconds after the completion of filling of the cavity 8 with the undiluted reaction solution, the three-way valve 24 was driven to open the cavity 8 to the atmosphere. After the inside of the cavity 8 returned to the normal pressure by the three-way valve 24, the mold was opened 30 seconds later, and the molded body was taken out of the molds 4 and 6.

In the molding of 100 shots, a flat molded body having the same dimensional accuracy as the first shot could be obtained.

In addition, almost no voids (bubbles) were observed on the surface of the molded article, and no swelling or the like occurred even when painted. In addition, it was confirmed that the volume resistivity of the molded article was stable, and the odor peculiar to the reaction injection molded article could be reduced. The number of voids having a diameter of 1 μm or more per unit surface area of the surface of the molded product was visually observed, and the average of 100 molded products was 3. The variation in the volume resistivity of the molded product is 1 × 10 ^{16 to} 5 × 10 ¹⁶ cmΩ (measurement temperature 23 °
C). The measurement of the volume resistivity is ASTM D25
7 was performed.

Comparative Example 1 Molding was carried out in the same manner as in Example 1 except that molding was carried out using a conventional reaction injection molding machine without holding pressure as shown in Example 1. The number of voids having a size of 1 μmφ or more per unit area on the surface of the molded product was visually observed, and the average of 100 molded products was 52. The variation in the volume resistivity of the molded product was 3 × 10 ¹⁵ to 8 × 10 ¹⁵ cmΩ (measuring temperature 23 ° C.).

[0048]

As has been described above, according to the present invention, before the injection of the unreacted solution into the mold cavity, the inside of the mold cavity is filled with a holding gas at a predetermined pressure to form the mold. Fine bubbles are not formed on the surface of the subsequent reaction injection molded article. As a result, even if the surface of the molded body is coated, swelling or the like does not occur, and the appearance of the surface of the molded body is improved. In addition, the electrical properties of the molded body are improved.

Further, in the mold apparatus according to the present invention, by using a cushion tank communicating with a vent port formed in the mold as a pressure holding source, the inside of the cavity of the mold before the unreacted solution is injected. The gas can be filled with a pressure-holding gas of a predetermined pressure, and at the time of injecting the reaction solution, the pressure-holding gas in the mold is conveniently pushed back from the vent port to the cushion tank. Therefore, there is no adverse effect on the filling property of the reaction solution.

[Brief description of the drawings]

FIG. 1A is a schematic view of a mold apparatus used in a method for producing a reaction injection molded article according to one embodiment of the present invention, and FIG. 1B is a schematic view of a mixer shown in FIG. It is a fragmentary sectional view. It is.

[Explanation of symbols]

 2 mold apparatus 4,6 mold 8 cavity 10 mixer 12 reciprocating rod 14,16 tank 20 vent port 22 pressure-holding line 24 three-way valve 26 cushion tank 28 pressure-holding gas supply line 30 ... control valve 32 ... safety valve

Claims (2)

[Claims] 1. A pressure-holding gas having a pressure higher than the atmospheric pressure around the mold and lower than the mold-clamping pressure inside the mold cavity before injecting the unreacted solution into the mold cavity. And then injecting the undiluted reaction solution into the mold cavity and performing reaction injection molding. 2. A mold in which a cavity is formed by clamping the mold, and a vent port formed in the mold, and through the vent port, the inside of the cavity is surrounded by a mold surrounding the mold. A cushion tank for supplying a holding pressure gas having a pressure higher than the atmospheric pressure and lower than the mold clamping pressure; a control means for controlling the inside of the cushion tank to a predetermined pressure range; And a stock solution supply means for injecting a stock solution into the mold.