JPH07137069A - Reaction injection molding and mold therefor - Google Patents

Abstract

PURPOSE:To obtain a method for reaction injection molding which enables suppression of voids occurring in collision and mixing of a reaction stock solution in a mixing chamber. CONSTITUTION:A method for reaction injection molding wherein an auxiliary injection solution is injected in a mixing chamber before a reaction stock solution is mixed in the mixing chamber, and then the reaction injection molding is executed. The auxiliary injection solution is preferably a liquid not producing an adverse effect on the reaction injection molding and a liquid being mixed easily with the reaction stock solution. Mold equipment 2 has the mixing chamber 12 for mixing at least two reaction stock solutions, mold tools 4 and 6 wherein a cavity 8 into which the mixture prepared by mixing in the mixing chamber 12 is injected is formed, and an auxiliary injection pipe 42 for injecting the auxiliary injection solution into the mixing chamber 12 before the reaction stock solution is sent into this mixing chamber 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reaction injection molding method and a mold device, and more particularly, to a reaction injection molding method capable of suppressing bubbles generated by collision mixing of a reaction stock solution in a mixing chamber. And a mold device.

[0002]

2. Description of the Related Art Reaction injection molding (hereinafter also referred to as RIM)
The method is a molding method in which a reaction solution obtained by mixing two undiluted reaction solutions is fed into a cavity of a mold, and molding is performed while causing reaction in the mold. This RIM method is preferably used when molding a polymer (molded product) from a norbornene-based monomer.

However, the RIM method has a problem that bubbles and deficiency are likely to occur on the surface of a molded product.
In order to solve such a problem, for example, Japanese Patent Laid-Open No. 63-63
As shown in Japanese Patent Laid-Open No. 112124, a method of injecting a mixed reaction solution of a reaction stock solution from a position below a mold has been developed. Further, as disclosed in JP-A-63-104010, the cross-sectional shape of the end portion of the cavity formed in the mold is L-shaped to suppress the generation of bubbles and lack of thickness on the surface of the molded product. The way to do is being developed.

According to these methods, since the flow state of the mixed reaction solution in the mold is improved, it is possible to suppress the occurrence of voids and the like due to it.

[0005]

However, in the above-mentioned method, it is difficult to suppress bubbles generated during collision mixing of the reaction stock solution in the mixing chamber in RIM molding by the collision mixing method. Since it remains in the mold cavity, it is difficult to completely remove the voids on the surface of the molded product. The present invention has been made in view of such circumstances, and it is possible to suppress the voids that cannot be removed by the method according to the related art, specifically, the voids caused by the bubbles generated by the collision mixing of the reaction stock solutions in the mixing chamber. It is an object to provide a possible reaction injection molding method and a mold device.

[0006]

In order to achieve the above object, the reaction injection molding method according to the present invention, in the reaction injection molding by the collision mixing method, in the mixing chamber,
The auxiliary injection liquid is injected in advance, and then the reaction injection molding is performed.

To achieve the above object, the mold apparatus according to the present invention comprises a mixing chamber for collision-mixing at least two reaction stock solutions, and a cavity into which the mixed solution mixed in the mixing chamber is injected. It has a formed mold and an injection means for injecting an auxiliary injection liquid into the mixing chamber before the reaction stock solution is fed into the mixing chamber.

The injection of the mixed solution into the cavity of the mold is
Specifically, it is usually performed through a sprue portion provided at a position communicating with the mixing head of the mold and a gate portion communicating between the sprue portion and the cavity portion. When these are provided separately from these or in these sites, the reaction solution can be mixed more effectively.

The mold may be provided with a purge port for purging the inside of the cavity, a vent port for discharging gas such as air in the cavity, and the like. The mold used for the reaction injection molding does not necessarily have to be an expensive mold having high rigidity, and is not limited to a metal mold, and a resin mold or a simple mold can be used. This is because the reaction injection molding can be performed at a relatively low temperature and low pressure using a low-viscosity reaction liquid. It is preferable that the mold is sealed with an inert gas, and the components used for the polymerization reaction are stored and operated in an atmosphere of an inert gas such as nitrogen gas.

As the reaction stock solution used in the reaction injection molding,
Although not particularly limited, reaction stock solutions such as urethane series, urea series, nylon series, epoxy series, unsaturated polyester series, phenol series, and norbornene series may be mentioned.
In particular, the present invention exhibits a particularly remarkable effect when a norbornene-based reaction stock solution, which has a low viscosity and is apt to generate bubbles during collision mixing, is used.

When the reaction injection molding is a reaction injection molding using a norbornene-based monomer, the monomers used in the present invention include dicyclopentadiene, dihydrodicyclopentadiene, tetracyclododecene and tricyclopentadiene. It is a cycloolefin having a norbornene ring.

Metathesis catalysts that can be used in reaction injection molding with norbornene-based monomers are:
There is no particular limitation as long as it is a metathesis catalyst known as a catalyst for bulk polymerization of norbornene-based monomers such as organic molybdate ammonium salts such as tungsten hexachloride, tridodecyl ammonium molybdate, tri (tridecyl) ammonium molybdate, etc. Acidic ammonium salts are preferred.

Examples of the activator (cocatalyst) include alkyl aluminum halides such as ethyl aluminum dichloride and diethyl aluminum chloride, alkoxyalkyl aluminum halides thereof, and organic tin compounds. At the time of reaction injection molding, in the present invention, the auxiliary injection liquid is injected in advance into the mixing chamber. The auxiliary injection liquid is preferably a liquid which does not adversely affect reaction injection molding and which is easily mixed with the reaction stock solution.

The viscosity of the auxiliary injection liquid is not particularly limited as long as it is a viscosity that can be uniformly mixed with the reaction liquid, but is usually 3
At 0 ° C, 1 to 10000 cps, preferably,
5 cps to 3000 cps, particularly preferably 100 cps
It is about ps to 1000 cps. Above all, it is particularly preferable that the viscosity is equal to or less than the viscosity of the reaction stock solution.

The maximum injection amount of the auxiliary injection liquid is determined within a range not exceeding the sum of the respective volumes of the mixing chamber and the sprue part of the mold, and the minimum amount is sufficient if a part of the mixing chamber is filled, Usually 0.5-10 of its volume
Times, preferably 1 to 3 times. When the volume exceeds the volume of the mixing chamber, the auxiliary injection liquid is injected into the sprue part of the mold communicating with the mixing chamber. If the amount of the auxiliary injection liquid used is too small, voids are likely to occur in the molded product, and if it is too large, the auxiliary injection liquid is not uniformly mixed, and there is a high possibility that a partially defective molded product is produced. There is a tendency.

The method of injecting the auxiliary injection liquid into the mixing chamber in advance is not particularly limited, but the following three methods can be exemplified. The first method is
There is a method of inserting from the vent port of the mold device. The second method is to insert it through the purge port of the mold device.
As a third method, a three-liquid injection unit is built in the mixing head, and immediately before the reaction stock solution is injected into the mixing head, the auxiliary injection liquid is relatively supplied into the mixing head from one inlet of the three-liquid injection unit. There is a method of injecting at low pressure.

The mold temperature is preferably 10 to 150.
C., more preferably 30 to 120.degree. C., still more preferably 50 to 100.degree. Mold pressure is usually 0.1 to 1
00 Kg / cm ² , mixing pressure is 20-200 Kg / cm
It is in the range of ² . The polymerization time may be appropriately selected,
Usually, it is 30 seconds to 20 minutes, preferably 5 minutes or less after the completion of the injection of the reaction solution.

In such molding, a reinforcing material (molded product) can be produced by previously installing a reinforcing material in a mold and supplying a reaction solution therein to polymerize. As the reinforcing material, for example, glass fiber, aramid fiber, carbon fiber, ultra high molecular weight polyethylene fiber,
Examples thereof include metal fibers, polypropylene fibers, aluminum coated glass fibers, cotton, acrylic fibers, boron fibers, silicon carbide fibers, alumina fibers and the like. Further, whiskers such as potassium titanate and calcium sulfate can also be mentioned. Further, these reinforcing agents can be used in various shapes such as those obtained by matting long fiber-shaped or chopped strand-shaped materials, cloth-woven materials, and chopped materials.
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 with the resin. The blending amount is not particularly limited, but is usually 10% by weight or more, preferably 20 to 60% by weight.
Is.

Further, antioxidants, fillers, pigments, colorants, void generating agents, flame retardants, sliding imparting agents, elastomers,
By blending various additives such as a dicyclopentadiene-based thermopolymerization resin and its hydrogenated product, the properties of the obtained polymer can be modified. As antioxidants, there are various antioxidants for plastics and rubber such as phenol-based, phosphorus-based, amine-based and the like. Fillers include inorganic fillers such as milled glass, carbon black, talc, calcium carbonate, aluminum hydroxide and mica. As the elastomer, natural rubber, polybutadiene, polyisoprene, styrene-butadiene copolymer (SB
R), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), ethylene-propylene-diene terpolymer (EPDM), ethylene vinyl acetate copolymer (EVA) and These include hydrides.

The additives are usually mixed in advance with either or both of the reaction solutions.

[0021]

In the reaction injection molding according to the present invention,
The reaction stock solution is collision-mixed in the mixing chamber in which the auxiliary injection solution is injected. By doing so, it is possible to prevent bubbles from being generated by the reaction liquid entraining the surrounding gas at the time of collision mixing. Therefore, according to the present invention, it is possible to suppress the generation of bubbles in the mixing chamber, and it is possible to manufacture a reaction injection molded product having a good appearance and surface shape without voids caused thereby.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in the drawings. 1 and 2 are schematic views of a mold apparatus for realizing a reaction injection molding method according to an embodiment of the present invention, and FIG. 3 is a schematic view of a mold apparatus according to another embodiment of the present invention.

As shown in FIG. 1, the mold device 2 has a first mold 4 and a second mold 6. The first mold 4 is a movable mold, and the second mold 6 is a fixed mold. A cavity 8 for reaction injection molding a molded product is formed between the molds 4 and 6. A sprue portion 10 and a runner portion 7 are formed on the second mold 6 so as to communicate with the cavity 8. A mixing head 14 is connected to the sprue portion 10 of the second mold 6.

The mixing head 14 is supplied with a reaction stock solution by a pump 18 from an A tank 16 in which one reaction stock solution (solution A) necessary for reaction injection molding is stored.
Liquid supply pipe 20 and liquid B supply pipe 2 in which the reaction liquid is sent from pump 24 from B tank 22 in which the other reaction liquid (B liquid) necessary for reaction injection molding is stored.
And 6 are connected. Further, the mixing head 14 is connected to an A liquid return pipe 28 for returning the A liquid to the A tank 16 and a B liquid return pipe 30 for returning the B liquid to the B tank 22.

A piston rod 32 is reciprocally mounted in the mixing chamber 12 of the mixing head 14. The piston rod 32 includes an A liquid return passage 34 that connects the A liquid supply pipe 20 and the A liquid return pipe 28 in a standby state for reaction injection molding, and a B liquid supply pipe 26.
A B liquid return passage 36 that connects the B liquid return pipe 30 and the B liquid return pipe 30 in a standby state of reaction injection molding is formed.

In the standby state of the reaction injection molding, the piston rod 32 is located at the upper position as shown in FIG.
The reaction stock solution stored in the tank 16 and the B tank 22 is the A solution return passage 3 formed in the piston rod 32.
4 and the B liquid return passage 36, respectively, and return to the respective tanks 16 and 22.

During reaction injection molding, the piston rod 32
2 retreats to the rear of the outlet holes of the A liquid supply pipe 20 and the B liquid supply pipe 24 to form the mixing chamber 12, as shown in FIG. Each of the outlet holes is set to have a predetermined diameter by an orifice, the liquids A and B are injected at a predetermined pressure, and the liquids A and B are collided and mixed with each other while sprue,
It is transported to the cavity through the runner.

When a norbornene-based monomer is used as a reaction stock solution, a solution A composed of the norbornene-based monomer and the metathesis catalyst and a solution B composed of the norbornene-based monomer and the activator are prepared as a preparation for the reaction injection molding. Divide into two stable liquids and store them in separate tanks 16 and 2, respectively.
Put in 2.

At the time of reaction injection molding, these two liquids are mixed in the mixing chamber 12, and then the mixed liquid is injected into the cavity 8 of the mold and bulk polymerized,
Obtain a molded product. In this embodiment, the mixing chamber 12 and the sprue portion 1 located above the mixing chamber 12 are mixed before the two liquids are mixed.
The auxiliary injecting liquid 40 is pre-injected into 0. The positional relationship between the sprue portion 10 and the mixing chamber 12 is preferably such that the mixing chamber 12 is located below the sprue portion 10, and may be a positional relationship in which the mixing chamber 12 is slightly inclined with respect to the vertical direction. As for the positional relationship between the sprue portion 10 and the cavity 8, from the viewpoint of the technique disclosed in Japanese Patent Laid-Open No. 63-112124, the cavity 8 has the sprue portion 10 in its position.
However, the present invention can be arranged horizontally as in the illustrated embodiment. Further, in the present invention, the sprue portion 10 and the cavity 8 are
It is preferable to provide a runner 7 having a mixing function such as an after-mixer between them.

The auxiliary injection liquid 40 is preferably a liquid which does not adversely affect the reaction injection molding and which is easily mixed with the reaction stock solution. When the reaction injection molding is a reaction injection molding of a norbornene-based monomer, the auxiliary injection liquid 40 is specifically a liquid that does not adversely affect the metathesis polymerization activity and that is easily mixed with the reaction stock liquid, for example, A norbornene-based monomer, a liquid A-side reaction stock solution, a solution B-side reaction stock solution, a hydrocarbon-based solvent such as toluene or xylene, and the like are used. From the viewpoint of maintaining the glass transition temperature and mechanical properties, norbornene-based monomers,
The liquid A side reaction stock solution and the solution B side reaction stock solution are preferable, and it is particularly preferable to use a norbornene-based monomer from the viewpoint of being less affected by the injection amount and the atmosphere.

The injection amount of the auxiliary injection liquid 40 is an amount for replacing at least a part of the mixing chamber in the mixing head with the auxiliary injection liquid, and is usually 0.5 to 10 times the volume of the mixing chamber 12, and preferably 1 to 10. 3 times. The auxiliary injection liquid 40 is introduced into the sprue 10 from the vent port 42 or the purge port 44 of the mold apparatus 2 shown in FIG. 1 immediately before the injection molding is started every injection molding. This work may be performed manually, but is preferably performed automatically.

When the auxiliary injection liquid is injected from the purge port 44, a three-way valve 48 is provided in the N ₂ purge line 46,
The valve 48 is controlled to switch N ₂ purge and injection of injection liquid. When the injection molding is started, the piston rod 32 is pushed down to a predetermined position as shown in FIG.
Mixing chamber 12 and liquid A supply pipe 20 and B
The liquid supply pipe 26 is communicated. As a result, the two reaction stock solutions (solution A and solution B) collide and mix in the mixing chamber 12 in the presence of the auxiliary injection liquid 40. However, since the auxiliary injection liquid 40 is injected into the mixing chamber 12 in advance, it is possible to significantly reduce the generation of bubbles due to collision mixing, as compared with the case without the auxiliary injection liquid 40.

Next, the mixed reaction stock solution mixed in the mixing chamber 12 is injected into the cavity 8 through the sprue section 10. At that time, since the mixed reaction stock solution does not contain bubbles, the cavity 8 is filled well,
Voids, defects in outer shape, etc. do not occur in the reaction injection molded product molded in the cavity 8.

The temperature of the mold device 2 is preferably 10 to 10.
The temperature is 150 ° C, more preferably 30 to 120 ° C, and further preferably 50 to 100 ° C. The mold clamping pressure of the mold device 2 is usually in the range of 0.1 to 100 Kg / cm ² .
The polymerization time may be appropriately selected, but is usually 30 seconds to 20 minutes, preferably 5 minutes or less after the completion of the injection of the reaction solution.

After the reaction injection molding, the first mold 4 of the mold device 2 is separated from the second mold 6 to open the mold, and the molded product is pushed out of the cavity 8 by an ejector pin (not shown). . The molded product also has an extra molded portion molded by the sprue portion 10, but these are removed in a later step.

The present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the present invention. For example, as shown in FIG. 3, a mold in which the mixing head 14a is improved and an auxiliary injection pipe 42 for injecting an auxiliary injection liquid into the mixing chamber 12 immediately before injection molding is connected to the upper position of the mixing head 14a. The reaction injection molding according to the present invention can also be performed using the apparatus 2a. An auxiliary tank 44 that stores an auxiliary injection liquid is connected to the auxiliary injection pipe 42. Since other configurations are similar to those of the mold apparatus 2 of the embodiment shown in FIGS. 1 and 2, the same members as those shown in FIGS. 1 and 2 are designated by the same reference numerals, and the description thereof is partially omitted. .

In the standby state of the reaction injection molding using the mold apparatus 2a according to this embodiment, the piston rod 32 is located at the upper position and stored in the A tank 16 and the B tank 22 as shown in FIG. The reaction stock solution thus formed passes through the A liquid return passage 34 and the B liquid return passage 36 formed in the piston rod 32, respectively, and the respective tanks 16, 2
It is supposed to return to 2.

Further, since the outlet of the auxiliary injection pipe 42 is in contact with the outer circumference of the piston rod 12, the auxiliary injection liquid is not injected into the mixing chamber 12 from the auxiliary injection pipe 42. The piston rod 32
It is also possible to form an auxiliary injecting liquid return passage similar to the A liquid returning passage 34 and the B liquid returning passage 36 on the outer circumference of, and to return the auxiliary injecting liquid to the auxiliary tank 44.

Immediately before starting the reaction injection molding, the piston rod 32 is pushed down to a position where only the outlet of the auxiliary injection pipe 42 communicates with the inside of the mixing chamber 12, and the auxiliary injection liquid is mixed from the auxiliary injection pipe 42 with the auxiliary injection liquid.
Inject into 2. The injection amount of the auxiliary injection liquid is approximately the same as in the above-mentioned embodiment.

After that, the piston rod 32 is further pushed down to connect the mixing chamber 12 with the A liquid supply pipe 20 and the B liquid supply pipe 26. The subsequent steps are the same as those in the above-mentioned embodiment. This embodiment has the same effects as the above embodiment, and facilitates the automation of the injection work of the auxiliary injection liquid into the mixing chamber 12.

Next, more specific examples of the present invention will be described. Example 1 85% of dicyclopentadiene (DCP) and 15% of asymmetric cyclopentadiene trimer were used, and 5% of styrene-isoprene-styrene block copolymer (Kreton 1170, manufactured by Shell Co.) and phenol type were used. 2% of Irganox 1010 (manufactured by Ciba Geigy), which is an antioxidant of, is dissolved in 2 containers, and this is placed in two containers. One is diethyl aluminum chloride (DE).
AC) was added at a concentration of 40 mmol, n-propanol was added at a concentration of 44 mmol, and silicon tetrachloride was added at a concentration of 20 mmol (solution A). On the other hand, tri (tridecyl) ammonium molybdate was added to the monomer so as to have a concentration of 10 mmol (Liquid B). These A liquid and B liquid were stored in A tank 16 and B tank 22 shown in FIG. 1, respectively.

Gears 1 for A liquid and B liquid, respectively
At 8, 24, liquid was sent to the mixing head 14 so that the volume ratio was 1: 1 and circulated to the respective tanks 16, 22 through the return passages 34, 36 of the piston rod 32. In addition, before injection molding, the auxiliary injection liquid 40 was previously injected into the sprue portion 10 located above the mixing chamber 12 through the vent port of the mold device 2. While the internal volume of the mixing chamber 12 was 2 cc, the injection amount of the auxiliary injection liquid 40 was 3 cc. DCP monomer was used as the auxiliary injection liquid.

After that, as shown in FIG. 2, the piston rod 32 is pushed down to a predetermined position, and the mixing chamber 1
2 was connected to the A liquid supply pipe 20 and the B liquid supply pipe 26. As a result, two reaction stock solutions (A solution and B solution)
Liquid) was impingingly mixed in the mixing chamber 12 in the presence of the auxiliary injection liquid 40. Next, the temperature 7 of the molds 2 and 6
At 0 ° C. and an injection pressure of 2.0 Kg / cm ² or less,
Mix reaction stock solution in mixing chamber 12 to sprue section 1
0 to fill the cavity 8. The molded product was taken out 3 minutes after the filling. These series of operations were performed under a nitrogen atmosphere. The reaction injection-molded product obtained by taking out from the cavity 8 had almost no voids and no defect in external shape was observed.

Comparative Example 1 Reaction injection molding was carried out in the same manner as in Example 1 except that the auxiliary injection liquid was not injected into the mixing chamber before injection molding. The reaction injection molded product obtained by taking out from the cavity 8 had many voids and defective outer shape was observed.

[0045]

As described above, according to the reaction injection molding according to the present invention, since the auxiliary injection liquid is injected into the mixing chamber in advance, the reaction stock solution collides and mixes in the mixing chamber. However, bubbles will not be generated by entraining the surrounding gas. Therefore, according to the present invention, it is possible to suppress the occurrence of entrained voids in the mixing chamber, and it is possible to manufacture a reaction injection molded product having a good appearance and surface shape without voids caused by this.

In the mold apparatus according to the present invention, since the injection means for injecting the auxiliary injecting liquid is installed in the mixing chamber, the operation of injecting the auxiliary injecting liquid can be automated.

[Brief description of drawings]

FIG. 1 is a schematic view of a mold apparatus for realizing a reaction injection molding method according to an embodiment of the present invention, showing a standby state of injection molding.

FIG. 2 is a schematic view of a mold apparatus for realizing the reaction injection molding method according to the embodiment, showing a state immediately before injection molding.

FIG. 3 is a schematic view of a mold device according to another embodiment of the present invention.

[Explanation of symbols]

 2, 2a ... Mold device 4 ... 1st mold 6 ... 2nd mold 7 ... Runner 8 ... Cavity 10 ... Sprue part 12 ... Mixing chamber 14, 14a ... Mixing head 16 ... A tank 20 ... A liquid supply pipe 22 B tank 26 B liquid supply pipe 28 A liquid return pipe 30 B liquid return pipe 32 Piston rod 42 Auxiliary injection pipe 44 Auxiliary tank

Continuation of the front page (72) Inventor Yasumasa Wada 1-2-1 Yokou, Kawasaki-ku, Kawasaki-shi, Kanagawa Nihon Zeon Co., Ltd. Research and Development Center

Claims (3)

[Claims] 1. The reaction injection molding method according to the collision mixing method, which comprises preliminarily injecting an auxiliary injection liquid into the mixing chamber, and then performing the reaction injection molding. 2. The reaction injection molding method according to claim 1, wherein the reaction injection molding method is a reaction injection molding of a norbornene-based monomer in the presence of a metathesis catalyst system. 3. A mixing chamber for mixing at least two reaction stock solutions, a mold having a cavity for injecting the mixed solution mixed in the mixing chamber, and the reaction stock solution fed into the mixing chamber. A mold device having injection means for injecting an auxiliary injection liquid into the mixing chamber.