JPS62203635A - Molding material for shell mold - Google Patents

Abstract

PURPOSE:To obtain a casting mold which has an excellent collapsing property after casting and cold strength which has no problems in practicability by using a specific component as a collapsing property improving agent which is an essential component of a molding material for shell molds. CONSTITUTION:The collapsing property improving agent of the molding material for shell molds essentially consisting of molding sand, phenolic resin and the collapsing property improving agent is the resultant product of decomposition obtd. by subjecting an alkali metal salt of permanganic acid or alkaline earth metal salt of permanganic acid to a heating treatment at the decomposition temp. thereof or above. One kind of such collapsing property improving agent may be used and >=2 kinds thereof may be used in combination. The collapsing property of the casting mold is thereby improved and the time, labor, etc., required for the collapse of the casting mold are lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mold used in a shell mold casting method, mainly to a mold material suitable for manufacturing cores. More particularly, the invention relates to the casting of low melting point light alloys such as aluminum alloys.

This invention relates to a mold material for shell molds that provides a core with good collapsibility and which allows for easy sand removal work after I molding.

Conventional technology Conventionally, as a binder for the main mold or core (mold) used in shell mold casting of V# iron, cast steel, aluminum alloy, etc., it has excellent thermal stability during S/'I construction. Thermosetting phenolic vI41Il is widely used.

However, on the other hand, the property that the core can be easily discharged and removed from the cast product after casting, that is, the easy disintegration of the core, is not necessarily fully satisfied, and in particular, In light metals with a low melting point, such as aluminum alloys, the core tends to remain in the casting without almost collapsing after '6/7 casting. For this reason, when manufacturing light metal castings, the current process involves applying an impact to the casting using a knockout machine to roughen the core, and then heat-treating it in a high-temperature firing furnace for several hours. A method has been implemented to remove residual gold dust from castings by providing a. However, such a method has drawbacks such as consuming a huge amount of energy and requiring a great deal of labor and time.

Furthermore, recent automobile castings are thinner than YJ products to improve fuel efficiency! ! ! As there is a trend toward increasing the weight of the core, making the structure more complex, or using light alloys such as aluminum alloys instead of conventional cast iron, the development of technology regarding the easy disintegration of cores after casting is an important and important issue in this technical field. This is considered an urgent issue.

To address these technical issues, many technologies have been developed to improve disintegration, such as shell sand, hot box sand, and oil sand, which contain potassium permanganate, a strong oxidizing agent, as a disintegration improver. A method has been proposed to improve the disintegrability of the mold by
Volume 6, page 180 (1979)].

If you follow this method, the mold will not disintegrate.

Although it may still be insufficient depending on the shape of the mold, it can be significantly improved. however.

The resulting bending strength of type 17 is significantly reduced, so during use, it is necessary to increase the amount of resin added to maintain the strength, which inevitably increases manufacturing costs, and furthermore, the collapsibility itself deteriorates. There is a problem of deterioration, and even at present it has not reached a practical level.

Problems to be Solved by the Invention Under these circumstances, the object of the present invention is to provide a shell suitable for manufacturing a vI type, which has In particular for its disintegrability after casting, and has room temperature strength that does not pose any practical problems. The purpose of the present invention is to provide mold materials for molds.

Means for Solving the Problems The present inventors have conducted intensive research to develop a chisel-shaped material that satisfies the above requirements.As a result, the present inventors have developed a method of heat-treating a certain type of permanganate above its decomposition temperature. It has been found that the decomposition products obtained by this process exhibit a remarkable catalytic effect in the thermal decomposition reaction of phenolic resins.

It was discovered that the objective could be achieved by blending this decomposition product total disintegration improver with foundry sand together with a phenolic resin as a binder, and based on this knowledge, the present invention was completed. Ta.

That is, 1 the present invention provides a molding material for a shell mold comprising foundry sand, a phenolic resin, and a disintegration improver as essential components, wherein the disintegration improver includes an alkali gold scrap salt and an alkaline earth metal salt of permanganate. The present invention provides an fli-type material for a shell mold, characterized in that it uses a thermal decomposition product of at least one salt selected from the following.

The phenolic resin used in the present invention is not particularly limited; for example, phenols such as phenol, resorcinol, catechol, and hydroquinone, metacresol, 3,5-xylenol, or 1 to 4 carbon atoms (7 ) At least one phenolic compound such as a furkyl group, an attached alkylphenol, bisphenols such as bisphenol A1, bisphenol F and bisphenol S, and M residues produced as by-products in the production of the above phenols, alkylphenols or bisphenols. , formaldehyde, paraformaldehyde, trioxa/, benzaldehyde, glyoxal, aldehydes such as furfural, or at least 1a compounds such as furfuryl alcohol. Oxalic acid, hydrochloric acid, sulfuric acid as a catalyst. , novolak-type phenolic fat obtained using acidic substances such as zinc acetate, zinc borate, zinc chloride, and para-toluenesulfonic acid, and inorganic alkaline substances such as sodium hydroxide, calcium hydroxide, and magnesium oxide. Nitrogen-containing resol-type phenolic resins obtained using amine compounds such as ammonia, triethylamine, ethylenediamine, hexamine, etc., and also nitrogen-containing resol-type phenolic resins obtained using amine compounds such as ammonia, triethylamine, ethylenediamine, and hexamine, and even zinc borate and zinc chloride. Rube/diether type phenolic resins obtained using inorganic acid salts or divalent metal salts of organic carboxylic acids such as zinc acetate or lead naphthenate, and mixed resins thereof, and uses 1) Modified phenol resin 1 modified as appropriate, for example, thermosetting resin such as epoxy resin, xylene resin, urea resin, melamine resin, vinyl acetate resin, polyamide lff411, acrylic resin, polyethylene resin at any stage of producing phenol resin. Thermoplastic resins such as urea, melamine, aniline, furfural, furfuryl alcohol, cashnut oil, tall oil, etc., or modified phenolic resins made by completely mixing or reacting them are used. These phenolic resins are produced by known production methods and used in solid, liquid or sheet form.

The blending amount of the phenolic resin in the Wj sand is normally selected as appropriate within the range of 0.2 to 10% by weight, preferably 0.5 to 5% by weight, based on the 177 sand.

The disintegration improver used in the present invention is a decomposition product obtained by heat-treating an alkali metal salt of permanganate or an alkaline earth metal salt of permanganate at a temperature higher than its decomposition temperature. In the present invention, one type of disintegration improver may be used, or
Two or more types may be used in combination.

Specific examples of the permanganate include potassium permanganate, sodium permanganate, potassium permanganate, and strontium permanganate.

Cal/um permanganate, barium permanganate.

Magnesium permanganate etc.1. In particular, potassium permanganate and sodium permanganate are preferably used because they are easily available as commercial products.

When these permanganates are used as a second agent with a tendency to disintegrate, as mentioned above, it is necessary to heat treat them at a temperature higher than their thermal decomposition temperature.
Approximately 300 to 9, considering processing costs, processing efficiency, etc.
Processing temperatures in the range of 0.000C can be used.

On the other hand, the processing time is 7 stems (batch type, continuous type),
It varies depending on various conditions such as heat source (electricity, gas, hot air) unit processing amount, etc., but it is usually about L
Q - Selected within the range of 180 minutes.

In addition, manganates such as potassium manganate, sodium manganate, and barium manganate, which are one of the components of the heat-treated product obtained according to the above method and are produced as intermediate products in the process of manufacturing the permanganate, are Although it has the disadvantage that it is difficult to obtain as a commercial product, it can be used in the same way as the thermal decomposition product.

The amount of the disintegration improver according to the present invention is usually 0.5 to 30 parts by weight based on the phenolic resin, preferably 1.
The content is appropriately selected within the range of 20% by weight.

If this amount is less than 0.5% by weight, the disintegration after casting cannot be improved, and if it exceeds 30ffl, the bending strength of the mold will drop significantly, making it impossible to put it to practical use.

When manufacturing the mold material for shell mold of the present invention,
The above-mentioned disintegration improver is usually blended.

(1) A method of adding disintegration improvers f, v, and i to the sand in advance, and then adding and mixing 1ff (fat); (2)
A method of adding and mixing a disintegration improver to the foundry sand at the same time as the resin, and (3) a method of mixing the resin and foundry sand in advance and then adding and mixing two agents for improving the disintegration property.

In addition, methods for producing the mold material for shell molds of the present invention include dry hot coating method, semi-hot coating method,
Any method such as a cold coat method or a powder solvent method may be used.

Furthermore, in addition to the above-mentioned components, the molding material for a 7-Elmold according to the present invention may contain any compounding agent commonly used in the past. Ring agents, stearic acid mono- or bisamides, amides such as methylolamide, aromatic carboxylic acids such as benzoic acid and salicylic acid, hexamethylenetetramine, calcium stearate, red iron sand, iron sand, etc., all within the range that does not impair the purpose of the present invention. It can be blended with

In addition, these additives are usually added during the production of mirror-shaped materials, but silane coupling agents, amides, or aromatic carboxylic acids may not be added during the production of phenolic resins. desirable.

Effect: Due to the thermal decomposition products of peroxide alkali metal salts and alkaline earth metal salts (hereinafter referred to as permanganates) contained in the mold manufactured using the shell mold mold material of the present invention, after casting. Although the mechanism of action that improves the disintegration properties of long-life molds is not necessarily clear, it is speculated as follows.

That is, the permanganate is subjected to a heat treatment to be decomposed by oxidative oxidation to form a mixture containing manganate and manganese dioxide as main components.

When this mixture is used as a disintegration improver, when molten metal is poured, the manganate acts catalytically on the alkaline thermal decomposition reaction of the phenolic resin, and the coexisting manganese dioxide is also affected. Since it supplementarily promotes the oxidative decomposition reaction of the resin, this synergistic effect promotes mold disintegration more than conventional permanganates (which mainly involve oxidative decomposition reactions due to released oxygen), resulting in lower disintegration properties. It is inferred that the

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited in any way by these examples. In addition, the physical property values in each example are as follows. It was carefully measured.

(1) f! ? Mold bending strength: JIS-6910
Measured using a method similar to K.

(2) Bend: Measured according to JACT test method 5M-3.

Note that bending is an evaluation of curing properties. The lower the number in the method, the faster the curing speed. was judged to be fast.

(3) Disintegration: rll 40 am length 75mm
A dogbone type tensile strength test piece having a thickness of 25 m1+ and having a shape as shown in (1) in FIG. 1 was made from resin coated sand and used as a core for the collapsibility test.

Furthermore, 125 mx8 (1+i+X75mm,
A separate outer mold [Fig. 1 (2)] having a space slightly larger than the core test piece was prepared, the core test piece was set therein, and an aluminum alloy molten at 720±5°C was cast. After forming the casting 3 and cooling it, vibration is applied to the casting 301 (Fig. 2) using ethanol at a pressure of o, 4 kg, /cyJ, and the sand is discharged from the outlet of the casting with a diameter of 161 fl+. The weight was measured every hour, divided by the total weight when all was discharged, and the risk was expressed as weight %, which was defined as disintegration.

Example 1 Foundry sand (product name Pearl Sand) sooor heated to 140-150°C was placed in a speed mixer (manufactured by Enshu Tekko Co., Ltd.)
In addition, novolac type phenol resin (Asahi Yokuzai Kogyo Co., Ltd. Gp690) was added as a binder.
Qf (1.2% by weight based on the foundry sand) and potassium permanganate as a disintegration improver were heat-treated at 200°C for 1 hour. 11% by weight) and kneaded in a mixer for 50 seconds. Next, the entire amount of an aqueous solution of hexamethylenetetramine (15 parts by weight relative to the binder) dissolved in 752 parts of water was added, and mixing was continued for about 40 to 60 seconds, followed by adding 5 parts of calcium stearate as a lubricant. After mixing for about 15 seconds, the mixture was discharged from the mixer to obtain a mold material for a shell mold.

Examples 2 to 6 Potassium permanganate as a disintegration improver at 200°C
The same procedure as in Example 1 was carried out, except that instead of the pyrolysis product obtained by heat treatment for 1 hour, a pyrolysis product of potassium permanganate treated under the heat treatment conditions listed in the attached table was used. A mold material for a shell mold was obtained.

Example 7 Disintegration improver and 1. The thermal decomposition product of potassium permanganate obtained by heat treatment at 200°C for 1 hour 6.6
In place of 9 (11% by weight based on the binder), the thermal decomposition product 39 of potassium permanganate obtained by heat treatment at 600°C for 1 hour (5% by weight based on the binder) was used. A mold material 14 for a shell mold was obtained in the same manner as in Example 1 except that

Example 8 Thermal decomposition product 6.6 of potassium permanganate obtained by heat treatment at 200°C for 1 hour with the same disintegrating agent
Except that potassium manganate 37 (5% by weight, based on the binder), which is a component of the thermal decomposition product of potassium permanganate, was used instead of r (11% by weight, based on the binder). A mold material for a shell mold was obtained in the same manner as in Example 1.

Comparative Example 1 A mold material for a shell mold was obtained in the same manner as in Example 1 except that no disintegration improver was used.

Comparative Example 2 In order to obtain mold bending strength equivalent to that of Example 1-6 without using a disintegration promoter, the amount of binder was increased to 1.
A mold material for a shell mold was obtained in the same manner as in Example 1 except that 1% W was used.

Comparative Example 3 A mold material for a shell mold was obtained in the same manner as in Example 1, except that potassium permanganate without heat treatment was used as the disintegration improver.

Comparative Example 1 To obtain mold bending and strength equivalent to Examples 1-6 and Comparative Example 2, the amount of binder t - 1.451 for molding sand.
A disintegration improver and 1. An Fj-shaped material 'R for Nermold was obtained in the same manner as in Example 1, except that 111% by weight of potassium permanganate, which was not subjected to heat treatment, was used as the binder.

Comparative Example 5 Examples 7 and 8. In order to obtain mold bending strength equivalent to Comparative Example 1, the amount of binder was 1.45% of the foundry sand, and potassium permanganate, which had not been heat-treated, was added to the binder as a disintegration improver. A mirror-shaped material for a shell mold was obtained in the same manner as in Example 1, except that 5% by weight was used.

Comparative Example 6 As a disintegration improver, a thermal decomposition product of potassium permanganate obtained by heat treatment at 100° C. for 1 hour was used in an amount of 11% by weight based on the binder.

A mold material for a shell mold was obtained in the same manner as in Example 1.

Examples 1-8. For comparison, the mold bending strength and collapsibility of the mold materials for shell molds obtained in 111-6 were investigated. The results are shown in the attached table. Also potassium permanganate and
The hydrogen ion concentration (pH) Th of an aqueous solution of which was heat-treated under various conditions was measured using the following method. The results are also shown in the table.

Method for measuring the hydrogen ion concentration (pH) of an aqueous solution of a disintegration improver A 200 cc beaker was heated under various conditions, and the thermal decomposition product of potassium permanganate (LO) was added.
100 cc of distilled water was added to 7'L of this solution, and after stirring for about 20 minutes, the solution was allowed to stand, and the pH of this solution was measured using a pH meter (manufactured by Toa Electronics Co., Ltd.).

In Examples 1 to 6, in which the disintegration improver obtained by heat treatment at a temperature higher than the thermal decomposition temperature of potassium permanganate was used in an amount of 11% by weight based on the binder as in the present invention, the disintegration improved. Although the mold bending strength is slightly lower than that of Comparative Example 1 in which no agent was used, Comparative Example 31 in which potassium permanganate was not heat-treated and potassium permanganate were heated below its thermal decomposition temperature for 1 hour. Comparative example 6 using heat treated material
In contrast, the decrease in mold bending strength is very small.

In addition, in order to obtain mold bending strength equivalent to Examples 1 to G,
The amount of binder in Comparative Example 2 without using a disintegration improver was 1
．． Comparative Example 4 using potassium permanganate, which was 1.455% by weight and not heat treated, required 1.455% by weight of binder.

In addition, a heat-treated product of potassium permanganate obtained by heat-treating at a temperature higher than the pyrolysis temperature (with respect to the i-binder, 5
Example 7, which used heavy weight, had almost the same mold bending strength as Comparative Example 1, which used the same amount of binder and did not use a disintegration enhancer.
In the case of Comparative Example 5 using unheated potassium permanganate, 1.45% of binder was required to obtain mold bending strength equivalent to that of Example 7 and Comparative Example 1.

Regarding the disintegration property, Example 1 has the same mold bending strength.
~6. Comparing Comparative Examples 2 & 4, Examples 1 to 6 had significantly better disintegration properties than Comparative Example 2, which did not use a disintegration improver. Furthermore, the disintegration properties were also improved compared to Comparative Example 4, which used potassium permanganate that was not heat-treated.

This can be seen in Example 7. This is also clear from the comparison with Comparative Example 1.5.

In addition, MA/GA/, which is one component of the disintegration improver obtained by heat-treating potassium permanganate at a temperature higher than the thermal decomposition temperature, is also used.
Also in Example 8 using potassium acid.

Almost the same effect as in Example 7 was obtained.

Effects of the Invention As is clear from the above explanation, when molding the 7-elmold mold material Fi mold of the present invention containing a heat-treated product of permanganate, the mold bending strength is prevented from deteriorating,
It also improves mold properties such as increasing curing speed,
In addition, since the disintegration properties of the i-type after Ki production are greatly improved, the 11'i-time required for the disintegration of the νI-type, labor, and energy costs are greatly reduced, and production efficiency is increased and productivity is increased. Significantly improved.

In addition, since the impact pressure required to collapse the mold can be lowered, there is less damage to cast products, which increases the product yield, and it also reduces the sound and improves the working environment. It has many features and offers full industrial utility.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are cross-sectional views showing a test device for measuring disintegration described in Examples and its usage state.

Claims (1)

[Claims] 1. In a molding material for a shell mold containing foundry sand, a phenolic resin, and a disintegration improver as essential components, the disintegration improver is selected from alkali metal salts and alkaline earth metal salts of permanganic acid. A molding material for a shell mold, characterized in that it uses a thermal decomposition product of at least one salt.