JP2000309044A - Production of molded object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a molded object reduced in possibility such that a sink or a thin skin is generated on the upper and rear surfaces thereof other than fine bubbles and excellent in appearance as a whole on its upper and rear surface sides. SOLUTION: When a reactive raw soln. containing a norbornene monomer is supplied into the cavity 8 of a mold to be subjected to bulk polymn., a reinforcing material is arranged in the cavity 8 of the mold before the reactive raw soln. is supplied into the cavity 8 of the mold. Subsequently, gas is supplied from the gate opening 62 communicating with the cavity 8 of the mold to hold the pressure in the cavity to 0.5-10 kgf/cm2.

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 molded article, in which bubbles, sink marks and skins are less likely to be formed on the entire front and back surfaces of the molded article.

[0002]

2. Description of the Related Art The reaction injection molding (RIM) method is a method in which two or more reaction stock solutions are mixed by a mixing head, fed into a cavity of a mold apparatus, and injection-molded while reacting in the mold apparatus. This RIM method is suitably used, for example, when molding a polymer (compact) from a norbornene-based monomer. RIM moldings have excellent impact resistance,
Moreover, since the molding pressure is low and the molding is easy, it is used in various technical fields.

[0003] In such RIM molding, fine bubbles may be generated on the surface of the molded article depending on the shape of the molded article to be obtained, molding conditions, and the like. When this foam is generated on the surface of the molded body, swelling occurs during surface coating of the molded body,
It reduces the appearance of the surface of the molded article.

Therefore, in order to solve such a problem,
Before injecting the unreacted solution into the mold cavity, the applicant fills the inside of the mold cavity with a holding gas at a predetermined pressure from the vent port, and then injects the unreacted solution into the mold cavity and molds It has been proposed to produce a body (Japanese Patent Application Laid-Open No. H10-156859). In addition, the applicant of the present invention has also proposed that a molded body is manufactured by advancing polymerization while applying a holding pressure gas of a predetermined pressure from a vent port during injection of a reaction stock solution into a cavity of a mold (particularly). Further, it is described that the holding pressure may be applied through an introduction line provided in a mold (for example, a mold) different from a mold having a gate port (for example, a core mold). ing. According to the techniques described in these publications, the formation of minute bubbles on the surface of the molded article after molding is reduced.

[0005]

However, even in the method described in the above publication, bubbles may be mixed into the molded article depending on molding conditions, and a molding method capable of further reducing bubbles has been demanded. . In addition, in the RIM method, molding defects such as sink marks and skins may occur on the back surface of the molded product, and improvement is required. Depending on the use of the molded article, it may be required to be excellent not only on the front surface but also on the entire appearance including the back surface.

[0006] In particular, when a reinforcing material is placed in a mold in advance and molded, bubbles are difficult to fall out of the vent port, and it is difficult to reduce bubbles.

[0007] The present inventors have found that a molded product without sink marks can be obtained by injecting a reaction stock solution into a mold and then additionally injecting a reaction stock solution corresponding to the sink volume under a constant pressure. Molding method (Japanese Patent Laid-Open No. 63-112126)
Japanese Patent Laid-Open No. 2-239915), and a method for producing a thick molded product in which a polymerization reaction proceeds while pressurizing after injecting a reaction stock solution into a mold (Japanese Patent Application Laid-Open No. 2-239915). However, even with the techniques described in these publications, it is still difficult to reduce bubbles on the surface of the molded body when the reinforcing material is placed in a mold in advance and molded.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to reduce the risk of sink marks and skins being generated on the front and back surfaces of the molded product, in addition to the formation of fine bubbles. It is an object of the present invention to provide a method capable of producing a molded article having excellent appearance on the entire front and back surfaces even when the molded article is molded.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, after supplying a reaction solution to a cavity of a mold, a predetermined pressure is maintained by using gas from a gate port. By applying pressure, there is little possibility that sinks and skins are generated in addition to fine bubbles on the front and back surfaces of the molded body reinforced by the reinforcing material, and the molding reinforced by the reinforcing material that is excellent in the overall appearance of the front and back surfaces Finding that the body can be obtained,
The present invention has been completed.

That is, the method for producing a molded article of the present invention comprises:
The undiluted solution containing the norbornene-based monomer is poured into a mold
When the mold is fed into the
After placing the reinforcing material inside the tee, the undiluted reaction solution is poured into the mold cap.
Supply into the cavity and then into the mold cavity
0.5kgf / cm using gas from the gate opening² Less than
Top 10kgf / cm²Features applying the following packing pressure
And

Undiluted Reaction Solution The undiluted reaction solution used in the present invention generally contains a metathesis catalyst and an activator as main components in addition to the norbornene-based monomer.

The norbornene-based monomer may be any as long as it has a norbornene ring. Examples thereof include bicyclics such as norbornene and norbornadiene, and tricyclics such as dicyclopentadiene (cyclopentadiene dimer) and dihydrodicyclopentadiene. , Tetracyclics such as tetracyclododecene, pentacyclics such as cyclopentadiene trimers, heptacyclics such as cyclopentadiene tetramers, and bicyclics thereof.
Heterocyclic alkyl substituents (eg, methyl, ethyl,
Propyl, butyl substituents, etc.), alkenyl substituents (eg, vinyl substitutions, etc.), alkylidene substitutions (eg, ethylidene substitutions, etc.), aryl substitutions (eg, phenyl, tolyl, naphthyl substitutions, etc.), and the like. Examples thereof include substituted compounds having a polar group such as an ester group, an ether group, a cyano group, and a halogen atom of these bicyclic to heptacyclic compounds. Among these, polycyclic norbornene-based monomers having three or more rings are preferable because they are easily available, have excellent reactivity, and are excellent in heat resistance of the obtained molded body, and are more preferably tricyclic and tetracyclic. Alternatively, it is a pentacyclic norbornene-based monomer.

These norbornene monomers may be used alone or in combination of two or more.

In addition, monocyclic cycloolefins such as cyclobutene, cyclopentene, cyclopentadiene, cyclooctene, cyclododecene and the like which can be ring-opened polymerized with at least one of the above-mentioned norbornene-based monomers are used as comonomer as long as the object of the present invention is not impaired. May be used.

The metathesis catalyst is not particularly limited as long as it is capable of ring-opening polymerization of a norbornene-based monomer, and may be a known one. For example, 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 ammonium molybdate such as tungsten hexachloride, tridodecyl ammonium molybdate, or tri (tridecyl) ammonium molybdate. However, an organic ammonium molybdate is preferred. The amount used is usually 0.01 to 50 mmol, preferably 0.1 to 20 mmol, per 1 mol of the monomer used in the whole reaction stock solution.

The activator (cocatalyst) is not particularly limited, and a known activator is used. Examples thereof include organic aluminum compounds such as alkylaluminum halides such as ethylaluminum dichloride and diethylaluminum chloride, and organictin compounds such as alkoxyalkylaluminum halides. The amount used is usually 0.1 mol per 1 mol of the metathesis catalyst used in the whole reaction stock solution.
１００100 mol, preferably 1-10 mol.

These metathesis catalysts and activators are usually used by dissolving them in monomers, but they may be suspended in a small amount of solvent and then mixed with the monomers.

The reaction stock solution includes, for example, antioxidants, fillers, elastomers, pigments, colorants, foaming agents, flame retardants,
Various additives such as a sliding imparting agent, a dicyclopentadiene-based thermopolymerized resin and a hydrogenated product thereof can be further blended. Thereby, the characteristics of the obtained molded body can be modified. As the antioxidant, there are various antioxidants for plastics and rubbers such as phenol, phosphorus and amine. Fillers include inorganic fillers such as milled glass, carbon black, talc, calcium carbonate, aluminum hydroxide, mica, potassium titanate, calcium sulfate, and the like. Examples of the elastomer include natural rubber, polybutadiene, polyisoprene, styrene-butadiene copolymer (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and ethylene- Examples include propylene-diene terpolymer (EPDM), ethylene-vinyl acetate copolymer (EVA), and hydrides thereof.

Such a reaction stock solution is usually a solution containing a norbornene monomer and an activator (Solution A) and a solution containing a norbornene monomer and a metathesis catalyst (Solution B).
And two liquids, each of which is stored in a separate container. When the additive is blended, the additive is mixed in advance with one or both of the liquid A and the liquid B.

The unreacted solution is preferably stored and operated under an atmosphere of an inert gas such as nitrogen gas.

At the time of reaction injection molding, the above-mentioned solution A and solution B are mixed in a mixing head and then supplied into a cavity of a mold to undergo bulk polymerization (curing) to obtain a molded body. The temperature of the reaction solution before it is supplied to the inside is preferably 20 to 80 ° C., and the viscosity of the reaction solution is, for example, at 30 ° C., preferably 5 to 300 ° C.
0 cps, more preferably 100 to 1000 cps.

The polymerization time may be appropriately selected, but is usually about 20 seconds to 20 minutes after the completion of the injection of the reaction solution.

The reaction solution starts flowing from the start of the injection of the reaction solution into the mold cavity, and the reaction proceeds rapidly, and the time t 'from when the white smoke slightly rises above the surface of the produced resin.
(SMT) and filling time t from the start of injection to the completion of filling
Is preferably determined according to the size of the obtained molded body. The SMT time t 'is always longer than the filling time t, preferably 10 to 300 seconds, and the filling time t at that time is preferably about 1 to 50 seconds. Also,
The SMT time t ′ is more preferably 20 to 200 seconds, and the filling time t at that time is more preferably 5 to 2 seconds.
It is about 0 seconds. t '/ t depends on the temperature, but is preferably about 1.5 to 20.

Mold The mold used in the present invention 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 it may be a simple mold, but preferably a non-adhesive material with good release properties for the obtained molded body,
For example, metals such as cast iron, iron, stainless steel, aluminum, and nickel electroformed are preferred. However, a synthetic resin or another material may be used as long as the material does not adhere to the molded body. Since the RIM uses a low-viscosity reaction stock solution and can be molded at a relatively low temperature and a low pressure, it is not always necessary to use a highly rigid mold.

The mold temperature is not particularly limited, but is preferably 10 to 150 ° C., more preferably 30 to 120 ° C.
C, more preferably 50 to 100 ° C. The mold clamping pressure of the mold is usually 0 to 100 kgf / cm ² .

[0026] In the reinforcing material present invention, prior to feeding the reaction stock solution into the mold cavity, it should be installed in advance reinforcement into the mold cavity. Thereby, a molded article having excellent mechanical strength can be obtained.

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 in the form of a chop.

It is preferable that the surface of these reinforcing materials is treated with a coupling agent such as a silane coupling agent in order to improve the adhesion to the resin.

The amount of the reinforcing material used is not particularly limited, but is usually 10% by weight or more, preferably 20 to 60% by weight, based on the total weight of the molded product. If the amount of installation in the cavity of the mold is too small, the rate of improvement in mechanical strength will be small, and if the amount of installation is too large, the molded product tends to be uneven or installation is hindered. By installing the reinforcing material within the above range, the mechanical strength of the obtained molded body is improved.

After the reinforcing material is previously installed in the cavity, the inside of the mold is preferably sealed with an inert gas.

[0032]Holding pressure In the present invention, the "holding pressure" means that the pressure is kept inside the mold cavity.
After supplying the undiluted solution, constant using gas from the gate opening side
The pressure that can be applied over time, depending on the shape and size of the molded product.
In the present invention, the lower limit of the holding pressure is selected.
Is 0.5 kgf / cm², Preferably 1 kgf / c
m², More preferably 2 kgf / cm ²And that
Is 10kgf / cm², Preferably 8kg
f / cm ², More preferably 5 kgf / cm²In
You.

The pressure-holding time is not particularly limited, and is usually from the completion of the charging of the reaction stock solution to the SMT, but is preferably about 5 to 30 seconds after the completion of the charging.

A gas is used as a means for applying the holding pressure. The type of gas is not particularly limited, and includes, for example, nitrogen, an inert gas, a gas other than oxygen, and the like, and is preferably nitrogen, an inert gas, or a gas other than oxygen, and more preferably nitrogen. is there. Such a gas is supplied from a cylinder or the like to a predetermined pressure via a pressure reducing valve.

The gas introduction section is not particularly limited as long as it can be pressurized from the gate port of the mold, but it is preferable that the gas introduction section is provided on the injection line extending from the mixing head to the mold.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a schematic view of a mold apparatus used for carrying out the method for manufacturing a molded article according to the present invention, and FIG. 2 is a sectional view of a main part of the mixing head shown in FIG.

As shown in FIG. 1, the mold apparatus 2 for performing reaction injection molding in the present embodiment has a core mold 4 (upper mold) and a mold mold 6 (lower mold). It is provided so that it can be approached and separated. In a state where the core mold 4 and the mold mold 6 are combined, a cavity 8 is provided inside the mold.
Is formed.

The cavity 8 is connected to a mixing head 10 as a means for supplying an undiluted reaction solution through a gate port 62 and a pipe 50 provided in the mold 6, from which the undiluted reaction solution is supplied. Is to be injected.

The mixing head 10 mixes and discharges the reaction liquid A in the tank 14 and the reaction liquid B in the tank 16 and has a rod 12 at the center. A holding pressure supply tank 40 is connected to the middle of the pipe 50 to which the mixing head 10 is connected, so that a predetermined pressure can be applied from the gate port 62 into the cavity 8 through the control valve 30. is there. In this manner, by applying a pressure to the inside of the cavity 8 from the gate port 62, it is possible to prevent generation of minute bubbles particularly on the surface of the molded body reinforced by the reinforcing material.

The control valve 30 is provided at the gate port 62 of the mold 6.
In addition, the communication between the pressure holding tank 40 and the pressure holding tank 40 is enabled, and the communication is interrupted by the switching signal so that the pressure holding is stopped.

In the mold apparatus 2 having such a configuration, the reaction liquid A and the reaction liquid B can be moved by the advancing and retreating rod 12 of the mixing head 10 in a state before the stock solution is injected as shown in FIG.
Are not mixed by circulating through the circulation closed circuit, but during the injection of the undiluted solution shown in FIG. 2, the reaction liquid A and the reaction liquid B are mixed in the mixing head 10 by the reciprocation of the advance / retreat rod 12, and Gate port 62 provided in mold 6
Is filled into the cavity 8 through the hole.

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

As RIM preparation, a RIM mainly composed of a norbornene monomer, a metathesis catalyst and an activator is used.
The materials for use are divided into two stable liquids, a liquid A composed of a norbornene-based monomer and a metathesis catalyst, and a liquid B composed of the above-mentioned norbornene-based monomer and an activator, each of which is placed in a separate tank. In the present embodiment, the liquid A is stored in the tank 14 and the liquid B is stored in the tank 16.

First, a reinforcing material is placed in the cavity 8 in advance. Then, the core mold 4 and the mold mold 6 are clamped. The pressure of this mold clamping is 0 to 100 kgf / cm ²
Is appropriately set within the range. Core type 4 and mold type 6
Is preferably set at 10 to 150 ° C. The cavity 8 may be filled with a gas such as nitrogen or an inert gas as needed before injecting the reaction solution. By previously filling the cavity 8 with the gas before injecting the reaction solution, it is possible to further prevent the generation of fine bubbles on the surface of the obtained molded body.
The gas pressure at this time is 0.4 to 1.0 kgf / cm ²
(Gauge pressure) is appropriately determined. Then, the control unit controls the reciprocating rod 12 of the mixing head 10 and
The solution A and the solution B from 16 are mixed and filled into the cavity 8 as a reaction stock solution.

The filling pressure (injection pressure) P1 for filling the reaction solution into the cavity 8 is usually 5 to 100 kgf / c.
m ² , preferably 10 to 50 kgf / cm ² . If the filling pressure P1 is too low, the transfer of the transfer surface formed on the inner peripheral surface of the cavity 8 tends to be poorly performed. If the filling pressure P1 is too high, the rigidity of the mold must be increased. Not economic. When the reaction solution is filled, the control valve 41 of the vent port 42 shown in FIG. 1 is open.

In the present embodiment, after the filling of the cavity 8 is completed, the control valve 30 is released to activate the holding pressure supply tank 40, and the holding pressure P2 is applied from the gate port 62. At the timing of applying the holding pressure P2, it is preferable that the control valve 41 of the vent port 42 is closed. The holding pressure P2 is
It is 0.5 kgf / cm ² or more and 10 kgf / cm ² or less. By applying the holding pressure P2 in this range, there is less danger that sinks and skins are generated in addition to minute bubbles on the front and back surfaces of the molded body, and as a result, the appearance of the entire front and back surfaces of the molded body is improved. The holding pressure P2 is preferably 5 to 100%, more preferably 10 to 70%, and still more preferably 20 to 50% of the injection pressure P1.

The means for applying the holding pressure P2 uses gas. As the type of gas, more preferably, nitrogen is economical. The holding pressure P2 is released after a lapse of a predetermined time, but it is preferable that the release timing is about 5 to 30 seconds after the completion of filling the cavity 8 with the undiluted reaction solution. If the time until the release is too short, the effect of the present invention cannot be obtained, and if it is too long, it is uneconomical. The holding pressure is released by closing the control valve 30.

After the inside of the cavity 8 returns to the normal pressure, preferably after 10 to 60 seconds, the mold is opened, and the molded body is taken out of the core mold 4 and the mold 6. On the front and back surfaces of the RIM molded body reinforced with the reinforcing material obtained by the manufacturing method according to the present embodiment, in addition to fine bubbles, the risk of sink marks and skins being reduced is reduced. An RIM molded body having excellent appearance can be obtained.

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

[0050]

EXAMPLES The present invention will be described below with reference to more specific examples, but the present invention is not limited to these examples.
Note that “parts” and “%” are based on weight unless otherwise specified.

Example 1 A 500 mm × 500 mm × 7 mm plate-forming mold (corresponding to the core mold 4 and the mold mold 6 in FIG. 1) was prepared.
As shown in FIG. 1, the core mold 4 was provided with a vent port 42 so as to communicate with the atmosphere via a control valve 41. A mixing head 10 (PE) having an advancing / retracting rod 12 at the center is connected to a gate port 62 of the mold 6 via a pipe 50.
C-RTM, RIM molding machine collision mixing type). In addition, the pipe 5 to which the mixing head 10 is attached
0, via the control valve 30, the holding pressure supply tank 4
0 was attached. A glass mat (product number M9600, manufactured by Asahi Fiberglass Co., Ltd., made by bundling glass fibers with a mat binder and having the surface treated with a coupling agent) in advance inside the cavity 8 is used in advance. I left it.

On the other hand, dicyclopentadiene (DCP) 9
A norbornene-based monomer mixture consisting of 0% and 10% of an asymmetric cyclopentadiene trimer, and 3 parts of vinylnorbornene with respect to the monomer mixture are each added to 2 parts.
Into one tank, one containing 40 mmol of diethylaluminum chloride (DEAC) based on the monomer mixture, 1,3-dichloro-2-propanol (dcP).
(rOH) to a concentration of 48 mmol (A
liquid). On the other hand, tri (tridecyl) ammonium molybdate was added to the monomer mixture to a concentration of 10 mmol (Solution B). In addition, these A solution and B solution
The SMT of the liquid alone was 90 seconds. These A liquid and B
The liquid was stored in the tank 14 and the tank 16, respectively.

First, the core mold 4 and the mold mold 6 were clamped. The mold clamping pressure was 10 kgf / cm ² .
The temperature of the core mold 4 (upper mold) was 55 ° C, and the temperature of the mold mold 6 (lower mold) was 30 ° C. Thereafter, the advancing / retreating rod 12 of the mixing head 10 was controlled to mix the A liquid and the B liquid from the tanks 14 and 16 and to fill the cavity 8 as a reaction stock solution. At this time, the control valve 41 on the side of the vent port 42 was released to the atmosphere. Filling pressure P1 is 10kg
f / cm ² , and the injection rate was 100 g / sec.
The filling time t was 20 seconds. 1 from the completion of this filling
By flowing nitrogen through the gate port 62 for 0 seconds, 1 kgf /
A holding pressure P2 of cm ² was applied. Thereafter, the control valve 41 on the vent side was closed, and then the control valve 40 on the holding pressure supply tank 40 side was closed. Then, after the inside of the cavity 8 returned to normal pressure, the mold was opened, and the molded product was taken out from the core mold 4 and the mold 6.

Table 1 shows the evaluation results of surface foams, cross-sectional foams, sink marks, thin skins, and molding thickness accuracy of the molded articles reinforced by the obtained reinforcing material.

The surface bubbles are bubbles existing on the core mold surface (front surface) and the mold mold surface (back surface) of the molded article.
Cross-sectional foam is a foam that exists inside the molded body,
The sink is a dent formed by the surface being pulled by the shrinkage of the part that has not solidified when the reaction stock solution filled in the mold reacts and solidifies, and the skin is the surface of the molded body. This is a state in which a double-layered surface is seen as if a single piece of resin skin was covered on the back surface.

The molding thickness accuracy was measured by measuring the thickness of the end portion and the central portion of the molded product five times each, and evaluating whether or not the measured values were within the design dimensions. When all the measured values are within the range of the design dimensions, it is regarded as “good” and 1
A case where one or more measured values were out of the range of the design dimensions was defined as “defective”.

Example 2 A molded product was obtained in the same manner as in Example 1 except that a pressure of 3 kgf / cm ² was applied from the gate opening. Table 1 shows the results of evaluating the obtained molded body for surface foam, cross-sectional foam, sink marks, thin skin, and molding thickness accuracy.

Example 3 A molded product was obtained in the same manner as in Example 1, except that a pressure of 5 kgf / cm ² was applied from the gate opening. Table 1 shows the results of evaluating the obtained molded body for surface foam, cross-sectional foam, sink marks, thin skin, and molding thickness accuracy.

Example 4 A molded product was obtained in the same manner as in Example 1 except that a pressure of 8 kgf / cm ² was applied from the gate opening. Table 1 shows the results of evaluating the obtained molded body for surface foam, cross-sectional foam, sink marks, thin skin, and molding thickness accuracy.

Comparative Example 1 No holding pressure was applied after the injection of the undiluted reaction solution (0 kgf / cm).
Except for ² ), a molded article was obtained in the same manner as in Example 1. Table 1 shows the results of evaluating the obtained molded body for surface foam, cross-sectional foam, sink marks, thin skin, and molding thickness accuracy.

Comparative Example 2 A molded product was obtained in the same manner as in Example 1, except that a pressure of 15 kgf / cm ² was applied from the gate opening. Table 1 shows the results of evaluating the obtained molded body for surface foam, cross-sectional foam, sink marks, thin skin, and molding thickness accuracy.

[0062]Comparative Example 3 After filling the reaction stock solution into the cavity, the vent port 4 shown in FIG.
2 to 5kgf / cm ²Example except that the holding pressure was applied
A molded product was obtained in the same manner as in Example 1. About the obtained molded body
Surface foam, cross-sectional foam, sink, thin skin, and molding thickness accuracy.
Table 1 shows the results of all the evaluations.

[0063]

[Table 1]

[0064] As can be seen from Discussion Table 1, the obtained molded body according to Example 1-4, the surface bubbles, cross bubbles, sink, for any assessment of the thin skin and a molded thickness accuracy, "slightly small", It was "less", "none", or "good", and it was confirmed that the appearance of the entire front and back surfaces was good.

On the other hand, in the case of Comparative Example 1 in which no dwelling pressure was applied from the gate opening, the evaluation of the sink marks and skins generated was “small” on both the front and back surfaces, and the molding thickness accuracy was “good”. Although it was good, the evaluation of surface foam was "slightly large" on both the front and back surfaces, and the evaluation of cross-sectional foam was "many" on both the front and back surfaces. In this regard, the superiority of Examples 1 to 4 was confirmed.

In the case of Comparative Example 2, since the pressure of the holding pressure P2 was too high, the superiority of Examples 1 to 4 in terms of the evaluation of the molding thickness accuracy was confirmed.

In the case of Comparative Example 3, since the pressure was maintained from the vent port 42, the superiority of Examples 1 to 4 in terms of the evaluation of surface foam was confirmed.

[0068]

As described above, according to the present invention, not only fine bubbles but also sink marks and skins are generated on the front and back surfaces of a molded article, particularly a molded article reinforced with a reinforcing material. Is less likely to occur. As a result, the appearance of the entire front and back surfaces of the molded body is improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a mold apparatus used for carrying out a method of manufacturing a molded article according to the present invention.

FIG. 2 is a sectional view of a main part of the mixing head shown in FIG.

[Explanation of symbols]

 2 Mold device 4 Core mold 41 Control valve 42 Vent 6 Cab type 62 Gate opening 8 Cavity 10 Mixing head 12 Advance rod 14 and 16 Tank 30 Control valve 40 Holding pressure supply Tank 50 ... piping

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B29K 105: 06 C08L 65:00 (72) Inventor Toshinobu Otsuki 2-6-1 Marunouchi, Chiyoda-ku, Tokyo F-term within Zeon Corporation (reference) 4F071 AA69 AF27 AG02 AG22 BA02 BB01 BB12 BC00 BC08 4F206 AA12L AD04 AD16 AM34 JA01 JB12 JL02 JM05 JN27 4J032 CA23 CA24 CA25 CA27 CA28 CA34 CA35 CA36 CA38 CA43 CA45 CA46 CD03 CD03 CE03 CD03 CE03 CG07

Claims (1)

[Claims] 1. A reaction stock solution containing a norbornene-based monomer is supplied into a mold cavity to perform bulk polymerization, and after a reinforcing material is installed in the mold cavity, the reaction stock solution is supplied into the mold cavity. Then, using a gas from the gate opening communicating with the cavity of the mold using a gas, 0.5 kg
A method for producing a molded article, comprising applying a holding pressure of f / cm ² or more and 10 kgf / cm ² or less.