JP2698666B2 - Manufacturing method of curable mold - Google Patents

Description

The present invention relates to a method for producing a thermosetting mold. More specifically, a mixture of an acid-curable resin and a salt of a strong acid and a weak base mixed with a refractory granular aggregate is filled in a mold for mold production, and the mold is heated to mold the mold. The present invention relates to a method for producing a cured mold.

[Problems to be solved by conventional technology and invention]

Conventionally, as a method for producing a heat-curable mold, there is a so-called shell mold method in which a phenol novolak resin is coated on a refractory granular aggregate and heated and cured at about 300 ° C. using hexamethylene tedramine as a catalyst. This heat-curing method is currently used most frequently as a heat-curing mold manufacturing method because of its advantages such as simple equipment and easy operation. However, since the curing time is long and the curing temperature is high, the distortion of the mold and the distortion of the mold are large, the deburring work of the mold is indispensable, and the dimensional accuracy is insufficient. Furthermore, the working environment is poor due to the high curing temperature, and the working environment is significantly contaminated by the thermal decomposition odor of the phenol resin and hexamethylenetetramine.

At around 250 ° C, a mixture of a refractory granular aggregate and an acid-curable resin such as a phenol resole resin or a phenol or a urea / formalin-modified furan resin containing a small amount of furan, and a curing catalyst such as ammonium chloride or oxalic acid. There is a so-called hot box method of curing by heating. The curing time is shorter than that of the shell mold method, and although the distortion and dimensional accuracy due to temperature and the thermal working environment are improved, they are still insufficient, and the working environment is significantly contaminated by the pyrolytic odor. There were many defects and defects in the product, and a great improvement was desired.

Recently, a refractory granular aggregate, an acid-curable resin and a strong acid and at least one selected from the group IB, IIB, IIIB, and IVB of the fourth period or more, and the group VIII. There is a so-called foam box method in which a metal salt is cured by heating at about 150 to 200 ° C. This greatly improved the disadvantages of the conventional method, and is now attracting attention. However, there is a demand for further shortening of the curing time, improvement of the physical properties of the mold, and improvement of the working environment.

[Means for solving the problem]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found a method for producing a curable mold capable of dramatically improving the curing time, mold properties, and working environment, and have completed the present invention.

That is, the present invention fills a refractory granular aggregate, a curable mixture of an acid-curable resin and a salt of a strong acid and a weak base with a mold for mold production, and heats the mold. In the production of a heat-curing mold for molding a mold, air is introduced into the mixture filled in the mold in a direction opposite to the filling direction of the mixture (from the back of the mold to the mixture filling / blowing port). It is intended to provide a method for producing a curable mold, which is characterized in that the mold is heated and molded.

Hereinafter, the manufacturing method of the present invention will be described in detail with reference to the drawings.

In the conventional method, it is general that air does not flow into the mixture, or even if it does, air flows in the same direction as the mixture is filled as shown in FIGS.

FIG. 5 is a cross-sectional view showing a sand filling and molding step of a conventional horizontal mold making machine, wherein (a) shows a sand filling step and (b) shows a molding step. Normally, in the case of horizontal splitting, the sand is filled from the blow head 2 into the mold 1, and the surface of the lower mold 3 is often more complicated and more important due to the characteristics of sand filling. However, in the conventional method, the pressurized air 5 is sent from the ventilation head 6, and the hardening of the pressurized air 5 is larger on the surface of the upper mold 4 than on the surface of the lower mold 3.
Since the air flow is from the upper mold 4 to the lower mold 3, the air flow also reverses the direction of the upward propagation of heat.

FIG. 6 is a cross-sectional view showing a sand filling and molding step of a conventional vertical mold making machine, wherein (a) shows a sand filling step and (b) shows a molding step. Also in this case, the propagation of heat from the heat sources (the left mold 7 and the right mold 8) is opposite to the flow of the pressurized air, as in the case of the horizontal split.

The inflow of air into the mixture was not only because the heat supply to the mold was not only conducted from the mold surface, but also due to the heat propagation by the air, which had a considerable effect. It was noted that the direction of heat transfer to and from the incoming air was opposite.

In addition, the present inventors have noticed that the amount of air flowing into the mixture is the same even when the flowing direction is changed, and arrived at the present invention.

FIGS. 1 and 2 are cross-sectional views showing a sand filling and molding step of a horizontal mold making machine according to the method of the present invention, wherein (a) shows a sand filling step and (b) shows a molding step. First
In the method shown in the figure, pressurized air 5 is pumped from the back of the mold in the direction of the sand inlet. In the method shown in FIG. 2, the air in the atmosphere is sucked from the back surface of the mold by the suction blower 9 and flows in the direction of the sand blowing port.

FIGS. 3 and 4 are cross-sectional views showing a sand filling and molding step of a vertical split molding machine according to the method of the present invention, wherein (a) shows a sand filling step and (b) shows a molding step. .
In the method shown in FIG. 3, pressurized air 5 is pumped from the back of the mold in the direction of the sand blowing port. In the method shown in FIG. 4, the air in the atmosphere is sucked from the back of the mold by the suction blower 9 and flows in the direction of the sand blowing port.

The refractory granular aggregate used in the present invention is not particularly limited, and those generally used conventionally can be used.

The acid-curable resin used in the present invention is at least one cocondensate or mixture of furfuryl alcohol / formalin, urea / formalin, phenols / formalin, melamine / formalin, or a mixture with furfuryl alcohol. What is a component is mentioned. Natural resins such as rosin and shellac to this acid-curable resin,
Acrylic resin, vinyl acetate resin, petroleum resin, epoxy resin, butyral resin, urethane resin, synthetic resin such as polyester resin, silane coupling agent, surfactant,
It may contain a solvent or the like, and does not limit the present invention. Preferably, raw furfuryl alcohol, a so-called high-furanic acid-curable resin having a furan content of 50% or more, is used.

In the present invention, as a salt of a strong acid and a weak base, organic sulfonic acid, sulfuric acid, perchloric acid, at least one of hydrochloric acid,
Those whose main component is a salt with at least one metal selected from the fourth period or more of Group IB, Group IIB, Group IIIB and Group IVB of the Periodic Table and those of Group VIII are used. Preferably, one containing at least one salt of an organic sulfonic acid and the above-mentioned metal as a main component is used. More preferably, an organic sulfonic acid containing at least one salt of copper, aluminum, iron, and zinc is used.

In the present invention, the mold is heated at a heating temperature of 100 to 250 ° C, preferably at 150 to 220 ° C. As the air temperature, air at room temperature to 300 ° C. is allowed to flow.

[Action and effect]

According to the manufacturing method of the present invention, by effectively flowing air into the mixture (mold), heat supply to the mold not only heat conduction from the mold surface, but also heat propagation by air proceeds simultaneously. In addition, the heat transfer to the mold is made uniform, curing unevenness is reduced, the curing time is shortened, and the cured state is stabilized. In addition, the dehydration condensation reaction of the acid-curable resin is promoted by the inflow of air, and the odor component in the mold is removed by the inflow of air, thereby reducing the pollution of the working environment.

Further, in the method of sucking air in the atmosphere by using a suction blower or the like, since the airtightness of the mold is not required, the cost for manufacturing the mold can be reduced.

The effect of the present invention is that, for example, if the curing time is the same as the conventional one, the mold heating temperature can be greatly reduced, so that energy cost, mold distortion, heat work, etc. can be reduced. Becomes In this way, the quality,
Cost, productivity, working environment, etc. are greatly improved.

〔Example〕

Hereinafter, the effects of the present invention will be described with reference to examples, but the scope of the present invention is not limited by the examples.

Examples 1-4 and Comparative Examples 1-2 cuboid 250 × 250 × 50 ^t mm, a mold weighing approximately 5 kg, was prepared by method shown in Table 1.

The curable mixtures used in Examples and Comparative Examples were all 1000 parts by weight of refractory granular aggregate, 16 parts by weight of urea / formalin / furfuryl alcohol resin, and a curing agent mainly composed of copper toluene sulfonate. 5 parts by weight.

As a part of the effect of the present invention, evaluation was made based on the time during which a good mold, which is a decisive factor in productivity, can be released from the mold.

 Table 1 shows the results.

[Brief description of the drawings]

FIGS. 1 and 2 are cross-sectional views showing a sand filling and molding step of a horizontal mold making machine according to the method of the present invention, wherein (a) shows a sand filling step and (b) shows a molding step. Third
FIG. 4 and FIG. 4 are cross-sectional views showing a sand filling and molding step of a vertical split molding machine according to the method of the present invention.
Indicates a sand filling step, and (b) indicates a molding step. FIG. 5 is a cross-sectional view showing a sand filling and molding step of a conventional horizontal mold making machine, wherein (a) shows a sand filling step and (b) shows a molding step. FIG. 6 is a cross-sectional view showing a sand filling and molding step of a conventional vertical mold making machine, where (a) is a sand filling step and (b)
Indicates a molding step. 1: Mold, 2: Blow head 3: Lower mold, 4: Upper mold 5: Pressurized air, 6: Vent head 7: Left mold, 8: Right mold 9: Suction blower

Claims (3)

(57) [Claims] 1. A mold-making mold is filled with a curable mixture obtained by mixing an acid-curable resin and a salt of a strong acid and a weak base with a refractory granular aggregate, and heating the mold to mold the mold. In the production of a heat-curing mold for molding a mold, air is introduced into the mixture filled in the mold in a direction opposite to the filling direction of the mixture (from the back of the mold to the mixture filling / blowing port). A method for producing a curable mold, wherein the molding is performed while heating. 2. The mixture filled in a mold for mold production,
Compressed air is sent from the back of the mold toward the mixture inlet.
2. The method according to claim 1, wherein the inflow is carried out. 3. The method according to claim 1, wherein the mixture filled in the mold for producing a mold comprises:
2. The method according to claim 1, wherein air in the atmosphere is sucked from the back surface of the mold by using a suction blower and flows toward the mixture blowing port.