JPH0381045A - Manufacture of mold - Google Patents

Abstract

PURPOSE:To easily release a pattern without collapse in a mold by mixing a liquid binder of thermosetting resin blending a thickner with sand, and molding this sand and hardening the binder after releasing the pattern. CONSTITUTION:The sand is damped with polyvalent alcohol and the liquid binder of thermosetting resin blending the thicken is mixed with his sand. The sand is selected from among zircon sand, ceramic sand, etc. Resol type phenol resin. is used for the binder. The thickner is the one having reactivity to the thermosetting resin binder. The liquid thermosetting resin binder is increased in viscosity with the thickner and action for bonding the sand is improved and shape holding property can be given to the sand mold. The pattern can be easily released from the sand mold under the condition having plasticity before hardening the binder without collapse in the mold. Furthermore, the binder of thermosetting resin can be quickly hardened and the mold can be manufactured with good productivity by hardening before starting the collapse of sand mold.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a method for manufacturing a mold suitable for casting a three-dimensionally structured casting using sand with a heavy specific gravity.

[Conventional technology J] The molds currently in use include ordinary molds that use clay as a binder, such as green sand molds, high-pressure molding molds, and high-speed molding, thermosetting molds, self-hardening molds, gas hardening molds, and electron beam molds. hardening mold,
They are classified into special molds that use hardening binders, such as volatilization hardening molds and precision casting molds, and other molds.

Ordinary molds are the most common type of mold, but ordinary molds, typically green sand molds, use clay, linseed oil, etc. as a binder, so when heating and setting the mold, 170 ml of mold is used.
Productivity is low because it requires a long time of several tens of minutes to several hours at a temperature of ~180°C, and in addition, a lot of gas is generated during casting, and the gas pressure can easily damage the mold or cause many defects in the casting. There is a problem.

On the other hand, since special molds use a thermosetting resin binder, the binder can be cured quickly by heat curing or room temperature curing using a curing agent, resulting in high productivity and stable quality. In particular, shell molds that use phenolic resin as a binder are rapidly progressing as mold cores. This special mold is manufactured by hand molding, casting, blow molding, etc. to harden the thermosetting resin binder, and then horizontally splitting, vertically splitting, dump box method, etc., and removing the horizontal mold. However, since horizontal extraction must be performed from a mold that has already been hardened, it is difficult to cast objects whose surfaces are not two-dimensionally simple, such as three-dimensional impellers. If the surface of the object is complicatedly curved three-dimensionally, it is not possible to extract the horizontal model.In this case, the horizontal model is divided into several to dozens of pieces and each divided model is handcrafted. The design is such that each horizontal mold is removed after the mold is molded and the binder is cured.

However, in the case of this special mold, it is necessary to remove the model from the mold in which the thermosetting resin binder has hardened, so it is difficult to release the horizontal mold from the hardened binder, and the binder has hardened. It was difficult to pull out a model with a complex shape from a mold with no plasticity, and sometimes it became impossible to pull out the model.

Therefore, the present applicant proposed a method for manufacturing a mold using a thermosetting resin as a binder by removing a horizontal mold from a sand mold before hardening the binder. It was provided in Japanese Patent No. 68240. In other words, in this method, a liquid binder made of thermosetting resin containing a thickener is mixed with sand, and the binder is hardened after the sand is molded and a horizontal mold is extracted. It is characterized by adding a thickener to the liquid binder of thermosetting resin to increase the viscosity of the binder and improve the shape retention of the sand mold that is placed on the binder. Horizontal molds can be extracted without fear of deformation such as sagging deformation or collapse. In this way, the model can be easily extracted from the sand mold in a plastic state before the binder is hardened,
Furthermore, since the thermosetting resin binder hardens quickly, it is possible to harden the sand mold and manufacture the mold before the sand mold collapses.

Problems to be Solved by the Invention [1] The method for manufacturing young molds provided in this VF Publication No. 63-68240 is very useful when sand with relatively low specific gravity such as silica sand is used. However, it has been found that problems may occur when using sand with a high specific gravity such as Zolcon sand.

In other words, if you mix a thermosetting resin liquid binder containing a thickener with, for example, zircon sand and leave it for several hours, the mixture will harden into blocks and have very low fluidity. It has been found that a problem arises in that it becomes extremely difficult to mold into a mold, and that after several hours, molding becomes completely impossible. It is not clear why the fluidity is so low, but the reason is that zircon sand has a high specific gravity (the bulk specific gravity of silica sand is 1.4
In contrast, zircon sand is about 2.6 to 2. a
This is thought to be due to the sedimentation and agglomeration of zircon sand particles. Therefore, when using sand with a high specific gravity such as zircon sand, it must be used immediately after being mixed with a binder, which poses problems in terms of workability.

The present invention has been made in view of the above points, and when manufacturing a mold for casting a casting having a three-dimensional shape, even if a sand with a high specific gravity such as zircon sand is used, the fluidity is maintained. It is an object of the present invention to provide a method for manufacturing a mold that can easily produce a mold without causing problems.

[Means for Solving Problem 11] The mold manufacturing method according to the present invention involves moistening sand with a polyhydric alcohol, and applying a liquid binder of thermosetting resin containing a thickener to the sand. The method is characterized in that the sand is mixed, then the sand is molded and a horizontal mold is extracted, and then the binder is hardened.

The present invention will be explained in detail below.

As a binder, thermosetting resins such as 7-el resin and 7-run resin, which harden quickly, are used.
Among these, phenolic resins, which are commonly used in shell molds, are preferred; they have a fast curing speed among the 7-el resins, do not require the addition of a curing agent such as hexamethylenetetramine, and do not generate ammonia gas. This thermosetting resin binder is used in liquid form, so if it is liquid at room temperature, it can be used as is, or if it is solid at room temperature, it can be mixed with a solvent. It is used after it becomes liquid at room temperature, such as when it is dissolved.

A thickener is added to this thermosetting resin binder to make it sticky and uniformly dissolved. The thickener is preferably one that dissolves well in the liquid thermosetting resin binder, does not separate, and does not significantly change the temperature-viscosity curve, especially one that reacts with the thermosetting resin binder used. It is not preferable to use a thermosetting resin binder which is more preferable if it becomes too stringy even if the viscosity is increased or if it has high adhesion to horizontal molds. Furthermore, when a low boiling point solvent is used together, the viscosity can be changed arbitrarily by adjusting the volatilization of the solvent after mixing with the sand, and one thickener can be used depending on the shape and size of the mold. It can be used as Specific examples of preferred thickeners include a-starch, beta-starch, carboxymethyl cellulose (CMCL, polyvinyl alcohol, polyethylene oxide, guarpom, etc.), and commercially available ones include isopane (Kuraray Co., Ltd.), Cyril (
(Kanefuchi Chemical Industry Co., Ltd.), Pullulan (Hayashibara Biochemical Research Institute), Kaneki Zemurafuku (Kanejiki Chemical Industry Co., Ltd.), and the like. Inpan is a copolymer of imbutylene and maleic anhydride, has a white appearance, and is generally used after being dissolved in an alkaline aqueous solution. Cylyl is a modified silicone liquid polymer with a main chain of polypropylene oxide and a reactive silyl group at the end, and is a pale yellow transparent liquid with a molecular weight of about 8,000 and a viscosity of about 230 voids (at 23°C). This cylyl has reactivity with phenolic resin, and even if the temperature becomes higher than room temperature, it can maintain its thickening effect by reacting with the 7㎥/-l resin as the temperature rises. Therefore, pyryl is one of the most preferred thickeners. Pullulan is a natural polysaccharide whose smallest unit is glucose.
It is a water-soluble viscous substance that does not undergo deltation and has a linear structure in which liose is repeated in α-1,6 bonds. Kaneka Zemlac is made from acrylic acid-modified silicone oligomer (Acryli).
cS 1licone OliHomer).

Prior to modeling, the sand is first wetted with the polyhydric alcohol by mixing the sand with the polyhydric alcohol. Polyhydric alcohols include ethylene glycol,
Glycols such as propylene glycol, glycerin, etc. can be used. The amount of polyhydric alcohol added is preferably in the range of about 0.1 to 1.0 parts by weight per 100 parts by weight of sand. The present invention can obtain favorable effects when using sand with a high specific gravity such as zircon sand, and if the specific gravity is greater than silica sand, alumina sand can be used in addition to zircon sand. Cerabeads, which are spherical ceramic sand obtained by firing raw materials (for example, Naiga Icerabeads manufactured by Naigai Ceramics Co., Ltd.), and other alumina (R-treated aluminum)
, magnesia (magnesium oxide), etc. can also provide suitable effects. After the surface of the sand is moistened with the polyhydric alcohol in this way, a liquid thermosetting resin binder containing the above-mentioned thickener is mixed with the sand and kneaded. If sand with a high specific gravity such as Norcon sand is used as the sand for this mixed material, even if it is left for a long time, the fluidity of the mixed material will not decrease, and the mixed material will remain for a long time. liquidity can be maintained. The reason for this is not clear, but it is thought that the action of polyhydric alcohols moistened on the surface of the sand prevents the sand from coagulating with each other, preventing the sand from coagulating and hardening into blocks.

As described above, a kneaded mixture of 'I49I sand and a thermosetting resin binder is filled into a horizontal mold and shaped. At this time, when the object to be cast has a three-dimensionally complex shape, such as a three-dimensional impeller, the horizontal mold is divided into several to several dozen pieces, and each of these IF molds is molded. The viscosity of the liquid thermosetting resin binder that has been kneaded with the mold is increased by the action of a thickener, and it does not have the effect of binding sand well in the same way as the binder in ordinary molds such as green sand molds. ,
Can provide shape retention to sand molds. Therefore, unlike special molds such as shell molds, there is no need to harden a binder to maintain the shape of the sand mold, and the mold is made from a sand mold that is bound by a thermosetting resin binder and has plasticity. It can be extracted. In this way, since the horizontal mold is removed before the binder is cured, as in the case of special molds, the hardened binder adheres to the surface of the horizontal mold, making it difficult to release the horizontal mold, or molds with no plasticity Extracting a horizontal mold with a complicated shape from a sand mold will not result in VAu, and there is no risk that it will become impossible to extract the horizontal mold, and the horizontal mold can be easily extracted as in the case of a normal mold. be able to.

After the model is removed in this way, the thermosetting resin binder in the sand mold is hardened, but since the thermosetting resin binder contains a thickener to increase its viscosity. This viscosity improves the shape retention of the sand mold, making it difficult to cause deformation such as sagging or collapse, and prevents deformation during the process of curing the thermosetting resin binder.

In particular, the binder of thermosetting resin is quickly cured by heating, etc., and there is no risk of deformation occurring during this long period of time, unlike in the case of ordinary molds that require a long time to cure. Here, the amount of the thickener is set within a range that increases the viscosity of the thermosetting If fat binder to a viscosity that can effectively prevent the sand mold from deforming.
Although it cannot be determined unconditionally depending on the shape and size of the mold, it is generally about 0.5 to 50 parts by weight per 100 parts by weight of the liquid thermosetting resin binder. The amount of thermosetting IIM fat binder mixed into the sand varies depending on the specific gravity of the sand, but is 0.5 to 3.0 parts by weight of binder per 100 parts by weight of sand. I is common.

After each model divided as described above is extracted from the sand mold, the binder is hardened and molded, and then the parts are assembled to form a casting with a complex shape such as a three-dimensional impeller. It can be finished into a mold for.

【Example] The invention will now be illustrated by examples.

100 parts by weight of phenol and 100 parts by weight of 37% formalin were placed in a reaction vessel, and 50 parts by weight of 28% aqueous ammonia was added thereto, stirring well for about 60 minutes. The temperature was raised to 70°C and the reaction was continued for 4 hours. After the reaction, vacuum dehydration was started and dehydration was carried out at 100 Torr until the internal temperature reached 90°C.
parts by weight of ethylene glycol and 500 parts by weight of meta/-
Added ru. Resol type 7e obtained in this way)
The resin had a reddish brown color and a viscosity of 30 poise at 25°C.

1 part of 7 E/-le 9401ij and 37% formalin 689
parts by weight and 4.7 parts by weight of oxalic acid were charged into a reaction vessel,
It took about 60 minutes to reflux, and the reaction was continued for 2 hours. After the reaction was completed, dehydration was carried out at normal pressure to 150°C, and further dehydration was carried out under reduced pressure at 1°0 Torr until the internal temperature reached 150°C. The softening point of the solid novolac type phenol resin thus obtained was 97°C.

Next, 450 parts by weight of ethylene glycol was added to 550 parts by weight of this novolac type phenol resin and dissolved well to prepare a liquid resin having a viscosity of 60 poise at 25°C.

Wall layer 11-14 ・25% aqueous solution of polyvinyl alcohol...thickener N
ol ・25% water Fs solution of isopane #06 ... Thickener No.
2. Cyryl 5^03 ... Thickener No. 3 - 25% aqueous solution of pullulan ... Thickener N
o4〈Examples 1 to 4〉 Thickeners No.1 to No.4 were first added to the binder obtained in Production Example 1.
The amounts shown in the table were added and dissolved. By adding this thickener, the viscosity of the binder at 25°C increased to the values shown in Table 1.

On the other hand, zircon sand (produced in Australia)
was used. The particle size distribution of this Norcon sand is 28-3
5 mesh 0.5%, 35-48 mesh 5.1%, 4
8-65 mesh 35.5%, 65-100 mesh 5
0.2%, 100-150 mesh 8.4%, 150-
200 mesh 0°2%, 200-270 mesh 0.
1%, the particle size index is 63.69, and the bulk specific gravity of insects is 2.
．． It was 75.

Then, 1000 parts by weight of this zircon sand was placed in a universal mixer, 2 parts by weight of ethylene glyfur was added thereto, and the mixture was kneaded with a ladle for 1 minute to wet the surface of the zircon sand with ethylene glycol. A caking agent containing the following was added in the amount shown in Table 1, and mixing was performed for about 8 minutes to obtain kneaded sand. Various tests were conducted using this kneaded sand. The results are shown in Table 1.

■ Adhesiveness to hands After picking up the mixed sand and squeezing it tightly, I opened my hand and rubbed it with another hand to check for adhesion.

■Adhesion to a wooden horizontal model The kneaded sand was strongly pressed against a wooden model and then rubbed by hand to check for adhesion.

(2) Molding property Immediately after kneading, 200 g of the kneaded sand was filled into a 50-diameter pipe, hardened with a rammer five times, and then removed from the mold, and the bulk specific gravity was measured. The higher the bulk specific gravity, the higher the density and the higher the moldability.If the bulk specific gravity is 2.8 or more, the moldability is "good", and if the bulk specific gravity is less than 2.8, the moldability is good. Rated as "bad". *When it comes to octopus, the appearance is also 1! This was taken into account as an element of the evaluation.

(2) Green Strength Immediately after kneading, 200 g of kneaded sand was filled into a 50-1 mold, the bottom was shaped with a press so that the bulk specific gravity was 2.94, and after demolding, the green strength was measured using an Amsler.

② Corner defects: The test piece prepared in the measurement of green strength in ① above was placed in a blow dryer set at 200°C in advance, and allowed to harden for 1 hour.The condition of the corner defects on the test piece was visually observed.

■Compressive strength The compressive strength of the test piece cured in the same manner as in (■) above was measured using an Amsler.

■ Amount of gas generated Crush the test piece cured as described in ■ above,
About 51? The sample was accurately weighed and placed in a misfire oven preset at 1000°C, and the amount of soot generated was measured to show the maximum amount.

■Pouring test A mold for a three-dimensional impeller was formed using the mixed sand immediately after mixing, dried and hardened at 200°C for 30 minutes, and poured without applying a molding agent. After cooling, the casting surface was observed and evaluated using a casting surface roughness standard board (JISBO601).

Comparative Example 1 Kneaded sand was prepared in the same manner as in Examples 1 to 4 except that a binder without the addition of a thickener was used. Using this kneaded sand, various tests similar to those in Examples 1 to 4 were conducted. The results are shown in Table 1.

Comparative Example 2> PAW by adding 1 ethylene glycol to Norcon Sand
Kneaded sand was prepared in the same manner as in Examples 1 to 4 except that the sand was not subjected to R treatment. Using this kneaded sand, the same seeds as in Examples 1 to 4 were prepared (Examples 5 to 8). The amounts shown in the table were added and dissolved. By adding this thickener, the viscosity of the binder at 25° C. increased to the values shown in Table 2. Then, using the same zircon sand as in Examples 1 to 4, this zircon sand was moistened with ethylene glycol as in Examples 1 to 4, and mixed with the above-mentioned thickener-containing caking agent to form kneaded sand. Prepared. Using this kneaded sand, various tests similar to those in Examples 1 to 4 were conducted.

The results are shown in Table 2.

Comparative Example 3 Kneaded sand was prepared in the same manner as in Examples 5 to 8 except that a binder without a thickener was used. Using this kneaded sand, various tests similar to those in Examples 5 to 8 were conducted. The results are shown in the $2 table.

<Comparative Example 4> Norcon sand was used without being wetted with ethylene glycol, and the other conditions were the same as in Examples 5 to 8, and the kneading sand was ill! ! did. Using this kneaded sand, various tests similar to those in Examples 5 to 8 were conducted. The results are shown in Table 2.

<Examples 9 to 12> Thickeners No. 1 to No. 4 were added to the binder obtained in Production Example 1 as a third layer.
The amounts shown in the table were added and dissolved. By adding this thickener, the viscosity of the binder at 25°C increased to the value shown in Table WS3.

On the other hand, ceramic beads (Naigai Ceramics 60 #750 manufactured by Naigai Ceramics Co., Ltd.) were used as the sand. These ceramic beads are made of alumina raw material at a temperature of 1680℃.
The structure is a perfect mullite crystal (3A#20°/2SiOz). The shape is spherical, and the particle size distribution is 36-50 mesh 0.6%, 50-70 mesh 28.7%, 70-70 mesh
100 mesh 37.6%, 100-140 mesh 2
4.5%, 140~200 meshure, 8%, 200~
280 mesh was 0.8%, the particle size index was 77.9, and the bulk specific gravity was 1.69.

And use these ceramic beads as an all-purpose mixer for 1000
The surface of the ceramic beads was moistened with ethylene glycol by adding 2 parts by weight of ethylene glycol and kneading for about 1 minute. The mixed sand was added in a blended amount and kneaded for about 8 minutes to obtain kneaded sand. Using this kneaded sand, various tests similar to those in Examples 1 to 4 were conducted. The results are shown in Table 3. Among the tests, in the formability test (■), those with a bulk specific gravity of 1.7 or more were evaluated as "good," and those with a bulk specific gravity of less than 1.7 were evaluated as "good." The moldability is
It was rated as "bad". In addition, in the green strength test (2), test pieces were prepared by press molding so that the bulk specific gravity was 1.8.

Comparative Example 5 Kneaded sand was prepared in the same manner as in Examples 9 to 12 except that a binder without a thickener was used.

Using this kneaded sand, various tests similar to those in Examples 9 to 12 were conducted. The results are shown in Table 3.

<Comparative Example 6> Ceramic beads were used without being wetted with ethylene glycol, and the other examples were <Examples 9 to 12>.
Kneaded sand was prepared in the same manner.

Using this kneaded sand, various tests similar to those in Examples 9 to 12 were conducted. The results are shown in Tables 1 to 3 of Table tIS3.The results are shown in Tables 1 to 3 of tIS3. Comparative example 1.3.5 using binder
It has been confirmed that it is superior in adhesion, moldability, corner notch quality, and casting tests compared to those of conventional moldings, making it easier to manufacture molds for three-dimensional castings. Furthermore, by using a resol type 7 phenol resin as a binder as in Examples 1 to 4, hexamethylenetetramine It was possible to reduce gas generation mainly caused by , improve workability, and reduce casting defects.

<Example 13> The above Example 9 Kneaded sand was obtained in the same manner as in steps 12 to 12>.

<Example 14> As sand, the particle size is 0.8 to 0.2 am, and the specific gravity is 3.3 to
Using sintered magnesia (M, 099% or more) of 3.4,
Make sure to use No. 4 thickener as above.
Kneaded sand was obtained in the same manner as in Examples 9 to 12>.

Of the kneaded sands prepared in Examples 1 to 14 and Comparative Examples 2 and 4.6, 290 g of the sands immediately after kneading, 1 hour after kneading, 2 hours after 3 hours, and 4 hours after kneading were taken, and 45 g of this was taken. 180kg/am”
A cylindrical tablet was prepared by pressurizing the mixture at a pressure of . The height and compressive strength of this cylindrical tablet were measured. The height of the resulting tablet indicates the filling state, and the smaller the height, the better the filling.

In addition, the compressive strength of a tablet is a value that indicates its softness.
The higher the value, the more agglomeration of sand particles progresses and the harder the mass of kneaded sand becomes.

As seen in the results in Table 4, in Comparative Examples 2 and 4.6, which used zircon sand and ceramic beads that were not wet-treated with ethylene glycol, the compressive strength increased over time after cross-crossing. However, as time passes, agglomeration progresses and the mass of kneaded sand becomes hard.In contrast, each example uses zircon sand, ceramic beads, alumina, and magnesia that have been wet-treated with ethylene glycol in advance. The compressive strength after 4 hours of kneading is almost the same as that immediately after mixing.
It is confirmed that agglomeration hardly progresses and the mass of kneaded sand does not become hard despite the AII time.

[Effect of the invention 1 As described above, in the present invention, a liquid binder made of a thermosetting resin containing a thickener is mixed with sand, and after shaping the sand and removing a horizontal mold, Since the binder is made to harden, the viscosity of the liquid thermosetting resin binder increases due to the thickener, increasing its ability to bind the sand and giving it shape retention properties in the sand mold. The model can be easily removed from the plastic sand mold before the binder is hardened without fear of deformation, and the viscosity of the thermosetting resin can be easily removed. Since the binder can be hardened quickly, it can be hardened before the sand mold begins to lose its shape, allowing the hook mold to be manufactured with high productivity. In addition, in the present invention, since the sand is moistened with polyhydric alcohols, it is possible to prevent the sand particles from agglomerating even if sand with a high specific gravity is used. Even if you mix it with sand and leave it for a long time, it will not solidify and lose its fluidity.
This can prevent problems such as not being able to mold.

Claims (4)

[Claims] (1) Wet sand with polyhydric alcohol, mix a liquid binder made of thermosetting resin with a thickener into the sand, then mold the sand and remove the model. A method for manufacturing a mold, which comprises curing a binder. (2) The method for manufacturing a mold according to claim 1, wherein the sand is selected from zircon sand, ceramic sand, alumina, and magnesia. (3) The method for manufacturing a mold according to claim 1 or 2, wherein the binder is a resol type phenolic resin. (4) The method for manufacturing a mold according to any one of claims 1 to 3, wherein the thickener is reactive with a thermosetting resin binder.