JP3132990B2 - Mold material for shell mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel mold material for shell molds, and more particularly, it is used for producing molds (main molds and cores) used in shell mold casting.
In particular, the present invention relates to a mold material for a shell mold which is excellent in disintegration property of a mold when casting a metal having a low melting point.

[0002]

2. Description of the Related Art Conventionally, in sand casting of non-ferrous castings such as aluminum alloys, magnesium alloys, and copper alloys, and iron castings such as cast steel and cast iron, thermosetting particles formed by coating refractory particles with a phenolic resin. Shell molds made of mold materials are widely used as main molds and cores.

[0003] However, when a shell mold made of a conventional mold material is used as a core of a non-ferrous casting, since the phenolic resin is a binder having excellent heat resistance, the core has high strength even after casting. , And often remains without collapse inside the casting. Therefore, in order to remove the residual core sand, the casting after the casting is subjected to an impact treatment, for example, by a chipping machine or a heat treatment at a temperature of 400 to 500 ° C., which consumes a great deal of labor and energy. ing. Above all, aluminum hollow castings for automobiles are becoming thinner with the recent trend toward weight reduction, and thus improving the collapse property of the core after casting has become an increasingly important issue. It is also required to improve the difficulty of breaking the main mold after casting and to reduce the burden of labor when removing a casting.

[0004] In order to meet such needs, for example, additives for accelerating the decomposition of the resin binder at the time of casting, weakening the strength of the mold and improving the disintegration property, specifically, potassium nitrate powder, A method using sodium nitrate or the like has been proposed (Japanese Patent Publication No. 31-7256). However, a mold material using this type of additive shows good mold disintegration at a place where a sufficient amount of heat is supplied from the molten metal to the mold (a place where the temperature reached by the mold is high).
There is a drawback that the disintegration of the mold is insufficient at locations where a sufficient amount of heat is not supplied from the molten metal to the mold (where the temperature reached by the mold is low).

[0005]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional shell mold mold material,
It is used for the production of mold materials (main molds and cores) used in shell mold casting methods for shell molds that have excellent mold disintegration properties, especially non-ferrous castings such as aluminum alloys.
It is an object of the present invention to provide a mold material for a shell mold that exhibits a good mold disintegrability even at a location where a sufficient amount of heat is not supplied from the molten metal to the mold, that is, even at a low temperature range.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to develop a mold material for a shell mold having the above-mentioned preferable properties. As a result, the refractory particles, the phenolic resin, and the specific It has been found that a material containing an enhancer as an essential component can be suitable for the purpose, and based on this finding, the present invention has been completed.

That is, the present invention relates to a mold material for shell mold comprising refractory particles, a phenolic resin and a mold disintegration enhancer as essential components, wherein (A) an oxygen content of 25% by weight is used as the mold disintegration enhancer. The oxygen-containing hydrocarbon compound and the alkali metal nitrate (B) are each contained in an amount of 2 to 30% by weight and 2 to 30% by weight based on the weight of the phenolic resin.
It is intended to provide a mold material for a shell mold, which is used at a ratio of 50% by weight.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The refractory particles used in the mold material of the present invention, which form the base material of the mold, are inorganic particles having fire resistance enough to withstand casting and a particle size suitable for mold formation. There is no particular limitation. Examples of such refractory particles, other than silica sand, olivine sand, zircon sand, chromite sand, special sand such as alumina sand, ferrochrome-based slag, ferronickel-based slag, slag-based particles such as converter slag, Examples include porous particles such as nigaicera beads or regenerated particles obtained by collecting and regenerating them after casting. These may be used alone or in combination of two or more.

On the other hand, the phenolic resin used in the mold material of the present invention functions as a binder for binding and holding the refractory particles, and mainly comprises a reaction product of a phenol and an aldehyde. The resin is not particularly limited as long as it has a property of being cured by heating in the presence or absence of a curing agent. Examples of such phenolic resins include novolak-type phenolic resins, resol-type phenolic resins, nitrogen-containing resole-type phenolic resins, benzyl ether-type phenolic resins, and these phenolic resins and, for example, epoxy resins, urea resins, melamine resins, xylenes Modified phenolic resins formed by mixing or reacting with a resin, a polyamide resin, an epoxy compound, a melamine compound, a urea compound, and the like.
These may be used alone or in combination of two or more. When the novolak-type phenol resin is used alone, it is necessary to impart thermosetting properties by using a curing agent such as hexamethylenetetramine at the time of producing the mold material.

The amount of such a phenolic resin is as follows:
It is selected in consideration of required strength, disintegration and other properties, but is generally 0.5 to 5 parts by weight, preferably 1.5 to 5 parts by weight in terms of solid content, based on 100 parts by weight of the refractory particles. ~
It is selected in the range of 2.5 parts by weight. The use form of the phenolic resin is not particularly limited, but is generally a solid having an appropriate shape, and is used as a resin liquid or a solution as needed. In addition, solid-liquid may be used in combination.

In the mold material of the present invention, the phenolic resin improves the quality of the mold material (strength, lubricity, etc.).
It is preferable to use in combination with amino-, epoxy-, and vinyl-based silane coupling agents and lubricants that are useful for the above. As a typical example of the silane coupling agent,
γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β
-(3,4-epoxycyclohexyl) -ethyltrimethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxy) silane, vinyltris (β-methoxyethoxy) silane and the like. Representative examples of the lubricant include ethylene bisstearic acid amide, methylene bisstearic acid amide, oxystearic acid amide, and methylol stearic acid amide.

The mold disintegration improver used in the mold material of the present invention has a function of thermally deteriorating the cured phenolic resin to which the refractory particles are bound to reduce the strength of the mold. (A) having an oxygen content of 2
A combination of 5% by weight or more of an oxygen-containing hydrocarbon compound and (B) an alkali metal nitrate is used.

If the oxygen content of the oxygen-containing hydrocarbon compound of the component (A) is less than 25% by weight, the function of reducing the strength of the mold during casting is not sufficiently exhibited in a low temperature range, and the object of the present invention is achieved. Absent. Examples of the oxygen-containing hydrocarbon compound having an oxygen content of 25% by weight or more include lower carboxylic acids, polyvalent carboxylic acids, corresponding organic sulfonic acids, their esters or inorganic acid esters, lower alcohols, and polyhydric alcohols. Alcohols, lower ethers,
Peroxides and the like can be mentioned. Among them, carboxylic acids and polyhydric alcohols are preferable from the viewpoint of safety during handling.

The lower carboxylic acids and polycarboxylic acids are not particularly restricted but include, for example, solid carboxylic acids such as maleic acid, fumaric acid, citric acid, malic acid, succinic acid, benzoic acid and adipic acid. preferable. Examples of the organic sulfonic acids include lower alkanesulfonic acids such as ethanesulfonic acid, propanesulfonic acid, and butanesulfonic acid, and examples of the inorganic acid esters include sulfuric acid esters and phosphorus acids having a lower alkyl group. Acid esters can be mentioned. Among them, Chemical Handbook (revised 3)
Edition) Solid carboxyl groups such as succinic acid, benzoic acid and adipic acid having a pKa (logarithm of the reciprocal of the acid dissociation constant of an organic compound in an aqueous solution) of 4.0, especially 4.2 or more, described in Basic Edition II. Acids are preferred. Examples of the polyhydric alcohols include, but are not limited to, propylene glycol, glycerin, neopentyl glycol, trimethylolpropane, pentaerythritol, and polyvinyl alcohol. Among these, solid polyhydric alcohols such as neopentyl glycol, trimethylolpropane, pentaerythritol, and polyvinyl alcohol are preferred from the viewpoint of the fusion point of the template material. These oxygen-containing hydrocarbon compounds may be used alone or in combination of two or more.

On the other hand, examples of the alkali metal nitrate as the component (B) include potassium nitrate, sodium nitrate, lithium nitrate, and cesium nitrate. Of these, commercially available and economical ones are preferred. Thus, potassium nitrate and sodium nitrate are preferred. These alkali metal nitrates may be used alone or in combination of two or more. In view of safety during handling, an aqueous solution having an appropriate concentration, for example, 10 to 50% by weight.
It is advantageous to use it as a concentrated aqueous solution.

The amount of the mold disintegration improver in the mold material of the present invention is 2 to 30% by weight based on the weight of the phenolic resin (in terms of solid content), and 2% to 30% by weight of the component (B). It is blended at a ratio of 2 to 50% by weight.
When the amount of the component (A) is less than 2% by weight, the effect of improving the disintegration of the mold in a low temperature range is not sufficiently exhibited, and the amount of the component is 30% by weight.
If it exceeds 300, the mold strength will be significantly reduced. If the amount of the component (B) is less than 2% by weight, the effect of improving the disintegration of the mold is not sufficiently exhibited, and if it exceeds 50% by weight, the effect of improving the disintegration is improved although the added amount increases. It is economically disadvantageous. From the viewpoint of the balance between the mold disintegration improving effect and the mold strength, the more preferable compounding amount of the mold disintegrable improver is 2 to 20% by weight of the component (A) and 2 to 2 of the component (B).
The range is 0% by weight.

In the mold material of the present invention, in addition to the above-mentioned essential components, various additives may be used as necessary, for example, an anti-caking agent such as calcium stearate, a releasing agent, a deodorant, a red iron oxide,
It can be mixed with iron sand.

The mold material for a shell mold of the present invention can be produced by any of the methods conventionally used in the art, such as a dry hot coating method, a semi-hot coating method, a cold coating method, and a powdered solvent method. However, it is preferable to use a dry hot coating method from the viewpoint of productivity, quality and the like.

[0019]

According to the mold material for shell molding of the present invention, the temperature is lower than that of the conventional mold material (300 to 350).
C) can be improved. Therefore, it is possible to contribute to the improvement of the production efficiency of the casting, the improvement of the working environment (noise and high heat), and the accompanying energy saving.

The mold material for a shell mold of the present invention is suitably used for producing a mold (main mold or core) used in a shell mold casting method for a non-ferrous casting such as an aluminum alloy.

[0021]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The following tests were performed on the obtained shell mold material. (1) Flexural strength Measured according to JIS K-6910. (2) Strength Degradation Rate (%) The strength degradation rate (%) is an index for judging whether or not the disintegrability of the mold is good. Specifically, first, JIS K-691
A test piece for bending strength measurement (thickness: 10 mm × width: 10 mm × length: 60 mm) is formed in accordance with 0 and its bending strength (normal strength A) is measured. Next, the test piece was completely wrapped with an aluminum foil (100 mm long × 150 mm wide) to prepare a mold collapsible specimen, and then the specimen was placed in a hot air circulating electric furnace maintained at a predetermined temperature for a predetermined time. After leaving it, it is taken out, left to cool to room temperature, and then the aluminum foil is removed. The bending strength (residual strength B) of the test piece is measured, and the strength deterioration rate is calculated by the following equation. Strength degradation rate (%) = [(normal strength A−residual strength B) / normal strength A] × 100 The larger the value of the strength degradation rate (%), the better the disintegration of the mold.

Example 1 5 kg of silica sand preheated to about 150 ° C. in a whirl mixer manufactured by Enshu Tekko Co., Ltd., 85 g of a novolak type phenol resin containing a silane coupling agent and a lubricant, and as a component (A) of a mold disintegration improver After adding 8.5 g of adipic acid and kneading for 60 seconds, 42.5 g of an aqueous solution of 8.5 g of potassium nitrate dissolved in 34 g of water and 63 g of an aqueous solution of 13 g of hexamethylenetetramine dissolved in 50 g of water were added as the component (B). . Knead while blowing with a blower until the lump of sand collapses, then calcium stearate 5
g was added and mixed for another 15 seconds, and the mixture was discharged from the mixer to obtain a mold material for shell molding (hereinafter, simply referred to as a mold material). The bending strength and strength deterioration rate of this mold material were measured. Table 1 shows the results.

Examples 2 to 8 The same procedures as in Example 1 were carried out except that the components (A) and (B) of the mold disintegration improver were changed to the types and amounts shown in Tables 1 to 3. Seven types of mold materials were obtained.
In Example 6, 42.5 g of an aqueous solution in which 8.5 g of pentaerythritol (A) was dissolved in 34 g of hot water (temperature of 80 ° C. or higher) was used. With respect to these mold materials, the bending strength and the strength deterioration rate were measured. The results are shown in Tables 1 to 3.

Example 9 5 kg of silica sand preheated to about 140 ° C. and 85 g of a silane coupling agent and an ammonia resol type phenol resin containing a lubricant were put into a whirl mixer manufactured by Enshu Tekko Co., Ltd., and kneaded for 40 seconds. (A) of mold disintegration improver
40.8 g of an aqueous solution obtained by dissolving 6.8 g of pentaerythritol as a component in 34 g of hot water (temperature of 80 ° C. or higher) and 8.5 g of sodium nitrate as a component (B) in 37.5 water
46 g of an aqueous solution dissolved in g. After the mixture was kneaded with a blower until the lump of sand collapsed, 5 g of calcium stearate was added and mixed for 15 seconds, and the mixture was discharged from the mixer to obtain a mold material. The bending strength and strength deterioration rate of this mold material were measured. Table 3 shows the results.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

Comparative Examples 1 to 4 In the same manner as in Example 1, except that the components (A) and (B) of the mold disintegration improver were changed to the compounding amounts shown in Tables 4 and 5, Different mold materials were obtained. With respect to these mold materials, the bending strength and the strength deterioration rate were measured. The results are shown in Tables 4 and 5.

Comparative Example 5 A mold material was obtained in the same manner as in Example 9 except that the component (A) of the mold disintegration improving agent was not used. The bending strength and strength deterioration rate of this mold material were measured. Table 5 shows the results.

[0030]

[Table 4]

[0031]

[Table 5]

As is clear from Tables 1 to 5, the mold material of the present invention is 300 to 300 times more than the conventional material without the component (A).
It was confirmed that the disintegration of the mold in a low-temperature range of 350 ° C. was improved, and that the mold had a practically acceptable mold strength (Examples 1 to 9). However, when stearic acid having an oxygen content of less than 25% by weight was used as the component (A), it was confirmed that the effect of improving the disintegration of the template in a low temperature range was insufficient (Comparative Example 4).

Continued on the front page (72) Inventor Isao Kai 26-fourth Niitsu, Minamiyama, Fuso-cho, Fuwa-cho, Niwa-gun, Aichi Prefecture Asahi Organic Materials Industry Co., Ltd. Inside the Aichi factory (56) References JP-A-7-124685 JP-A-60-108138 (JP, A) JP-B-49-31178 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22C 1/00-1/26

Claims (3)

(57) [Claims] 1. A mold material for shell mold comprising refractory particles, a phenolic resin and a mold disintegration enhancer as essential components, wherein (A) an oxygen-containing material having an oxygen content of 25% by weight or more is used as the mold disintegration enhancer. Hydrocarbon compounds and (B)
A mold material for shell molds, wherein alkali metal nitrates are used in proportions of 2 to 30% by weight and 2 to 50% by weight, respectively, based on the weight of the phenolic resin. 2. The mold material for a shell mold according to claim 1, wherein the oxygen-containing hydrocarbon compound as the component (A) is at least one selected from carboxylic acids and polyhydric alcohols. 3. A carboxylic acid and a polyhydric alcohol,
3. The mold material for a shell mold according to claim 2, which is a solid material.