JPH10193033A - Resin composition for shell mold and resin coated sand for shell mold - Google Patents

Abstract

(57) Abstract: The present invention provides a resin composition for a shell mold that improves mold disintegration after pouring in casting of light alloy castings such as aluminum using a shell mold mold. . A resin composition for a shell mold according to the present invention comprises a phenol / formaldehyde resin 100 for use in the production of easily disintegratable molds for aluminum and light alloy castings.
As a disintegrant, at least one selected from an amino acid or an alkali metal salt of an amino acid, an alkaline earth metal salt, a hydrochloride or a sulfate, an alkyl ester or a hydrochloride of the alkyl ester is used as a disintegrant. It is characterized by containing up to 30 parts by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for improving mold disintegration after pouring in a shell mold used for light alloy castings such as aluminum, and a resin-coated shell mold mold containing the same. About sand.

2. Description of the Related Art Conventionally, when casting a light alloy casting having a low pouring temperature, such as aluminum, using a shell mold, a large amount of labor is required for separating the core (pouring sand) after pouring, especially in a core. I needed it. In the casting of automobile parts having a complicated shape, an increase in working time and man-hours is reflected in productivity, and is a serious problem directly linked to production cost. Therefore, as a method of improving the mold disintegration after pouring, a method of heating the mold after pouring at 400 to 500 ° C. for a certain time or a thermal decomposition accelerator such as a halide in the template binder as a disintegrant is used. Alternatively, a method of adding a carbonization accelerator such as a phosphorus compound, a method of using a special refractory aggregate, and the like have been adopted.

However, the method of heat-treating the mold and the method of using special refractory aggregate have a large burden on energy and raw material costs, and generally employ a method of adding a disintegrant. ing. Here, an inorganic or organic halide, a phosphorus compound, or a peroxide used as a disintegrant has a large effect on template disintegration. However, oxidizing substances generated by thermal decomposition during mold making or pouring may corrode the heating mold or the cast itself, or cause serious health hazards to workers due to irritating odor or toxic gas. In addition, it is not a sufficiently safe substance in terms of environmental considerations outside the manufacturing facilities. In addition, the method of using a carboxylic acid-based alkali metal salt or an alkaline earth metal salt, which is considered to have a relatively small influence as described above, and further using an ester thereof as a disintegrating agent, has a small effect on template disintegration, so that the amount added is large. There is a disadvantage that the characteristics of resin coated sand cannot be exhibited, such as a decrease in mold strength. In view of these problems, the present inventors have researched an ecological mold binder that is particularly environmentally friendly for workers and outside the workplace, and as a result, it has been used as a flavoring ingredient in foods for a long time. Components that meet these objectives have been found in the material. That is, the present invention relates to a resin composition for a shell mold which improves mold disintegration after pouring in casting of a light alloy casting including aluminum using a shell mold mold, and a resin for a shell mold mold containing the same. The purpose is to provide coated sand.

The resin composition for a shell mold according to the first aspect of the present invention is based on 100 parts by weight of a phenol / formaldehyde resin used for manufacturing an easily disintegratable mold for aluminum and light alloy castings. As a disintegrant, 1 to 30 parts by weight of an amino acid or an alkali metal salt of an amino acid, an alkaline earth metal salt, a hydrochloride or a sulfate, and at least one selected from an alkyl ester and a hydrochloride of the alkyl ester is contained. It is characterized by the following. The resin-coated sand for a shell mold according to the second aspect of the present invention is a phenol / formaldehyde-based resin used for producing 100 parts by weight of a refractory aggregate heated to 120 to 180 ° C. and an easily disintegratable mold for aluminum and light alloy castings. Based on 100 parts by weight of the resin, at least one selected from amino acids or alkali metal salts of amino acids, alkaline earth metal salts, hydrochlorides and sulfates, and further alkyl esters and hydrochlorides of the alkyl esters is used as a disintegrant. , 1 to 30 parts by weight, and 0.2 to 10 parts by weight of the resin composition.
0 to 3 parts by weight of hexamethylenetetramine is 0 to 3 parts by weight.
It is characterized by adding 0 parts by weight. According to a third aspect of the invention, there is provided a resin coated sand for a shell mold, wherein the disintegrant according to the second aspect is added as a powder or an aqueous solution. Hereinafter, the present invention will be described in more detail. In a shell mold used for casting a light alloy casting, amino acid or an alkali metal salt of an amino acid, an alkaline earth metal salt, a hydrochloride or a sulfate, further an alkyl ester or the like as a composition for improving mold disintegration after pouring. The hydrochloride of the alkyl ester is used. Specifically, as amino acids asparagine, aspartic acid, alanine, arginine, isoleucine, glycine, glutamine, glutamic acid, cystine, cystine, serine, thyroxine, tyrosine, tryptophan, threonine, valine, histidine, 4-hydroxyproline, δ-hydroxy Lysine, phenylalanine, proline, methionine, lysine, leucine, and potassium aspartate, sodium aspartate, sodium glutamate, potassium glutamate, and the like as an alkali metal salt or alkaline earth metal salt of the amino acid, and as a hydrochloride or a sulfate. Cysteine hydrochloride, arginine hydrochloride, glutamic acid hydrochloride, lysine hydrochloride, etc., and alkyl esters such as ethyl ester and methyl ester of the amino acid. Te hydrochloride salt of the alkyl ester and the like. Further, specific examples thereof include arginine glutamate, lysine glutamate, glycylglycine, and the like, and commercial or household chemical seasonings containing such a composition as a main component. More preferably, sodium glutamate industrially mass-produced is useful. These substances are derived from natural products, their safety is extremely high, and there is almost no mold corrosion problem and little environmental impact. The amount of the composition for improving mold disintegration is 1 to 30 parts by weight based on 100 parts by weight of the phenol / formaldehyde resin used as a binder. More preferably, it is 3 to 10 parts by weight. When the amount is less than 1 part by weight, the disintegration improving effect is extremely small.
If the amount is more than 0 parts by weight, the dispersibility in the resin becomes poor and the strength of the mold is remarkably reduced. Further, the composition for improving the template disintegration used herein is selected from the above-mentioned amino acids or alkali metal salts, alkaline earth metal salts, hydrochlorides and sulfates of amino acids, and further selected from alkyl esters and hydrochlorides of the alkyl esters. At least one type or a combination of a plurality of types may be used. As the phenol / formaldehyde resin used here, novolak resin obtained by an acidic catalyst, resol resin obtained by an alkaline catalyst, or a combination of both, and phenol / formaldehyde resin obtained by modifying urea, melamine, etc. There is no particular limitation.
The outline of the production of the resin-coated sand for a shell mold is as follows. As the phenol / formaldehyde resin used here, novolak resin is generally used, and in this case, hexamethylenetetramine is an essential substance as a curing agent. This hexamethylenetetramine is used as an aqueous solution. That is, a refractory aggregate previously heated to 120 to 180 ° C. is put into, for example, a speed mixer, and phenol /
A formaldehyde resin is charged and the surface of the sand particles is melt-coated. Next, an aqueous solution of hexamethylenetetramine is charged. The kneaded sand changes to a dry state when the sand temperature drops to the melting point of the binder. At this time, a lubricant is further added and mixed, and when the sand temperature of the kneaded sand reaches 70 to 80 ° C, sand is discharged from the mixer to obtain a resin-coated sand. When a resin coated sand for a shell mold is produced using the composition for improving mold disintegration according to the present invention, there are a method of adding the resin coated sand to a phenol / formaldehyde resin in advance and a method of adding the resin coated sand during kneading.
The simplest method of adding the phenol / formaldehyde resin to a phenol / formaldehyde resin in advance is to mix and disperse a composition for improving mold disintegration in a molten resin at the time of granulation molding in the form of a powder. Mold mixers are suitable. On the other hand, as a method of adding at the time of kneading the resin-coated sand, phenol / phenol used as a binder is used.
There is a method in which a formaldehyde-based resin is added at the same time, before or after the addition, or mixed with hexamethylenetetramine to be added as an aqueous solution or solely dissolved in a part of water used as an aqueous solution and then added. Therefore, when the composition for improving the mold disintegration is added at the time of kneading the resin-coated sand,
The form can be either a powder or an aqueous solution.
In particular, in the case of novolak resin, 0.2 to 10 parts by weight of the resin is added to 100 parts by weight of the refractory aggregate and 0 to 30 parts of hexamethylenetetramine is added to the resin.
It is well known to add parts by weight. In producing a resin coated sand for a shell mold containing the composition for improving the mold disintegration property, γ-aminopropylalkoxysilane is used as a silane coupling agent with respect to a phenol / formaldehyde resin used as a binder. (Γ-aminopropyltriethoxysilane), glycidoxypropyltrimethoxysilane,
Addition of epoxycyclohexylsilane or ethyltrimethoxysilane, etc., and ethylene bisstearic acid amide, ethylenebisoleic acid amide, methylene bisstearic acid amide, oxystearic acid amide as a lubricant for kneading sand during resin-coated sand production,
It is conventional to add stearic acid amide, palmitic acid amide, oleic acid amide, calcium stearate, zinc stearate, carbana wax, paraffin wax, and the like. In addition, the refractory aggregate used when manufacturing the resin-coated sand is, for example, silica sand,
Alumina sand, zircon sand, chromite sand, olivine sand,
There is no particular limitation as long as it is used for mold making, such as mullite sand or fly ash.

The present invention will be described in more detail with reference to the following examples. Note that the present invention is not limited to these examples. [Example 1] In a four-necked flask equipped with a stirrer, a reflux condenser and a thermometer, 940.0 parts by weight of phenol, 567.6 parts by weight of 37% formalin, and 9.4 parts by weight of oxalic acid were precisely weighed. The temperature is gradually raised while stirring. After reaching the reflux temperature, the reaction is carried out for 120 minutes. After the distillation reaction, a dehydration reaction is further carried out under vacuum. 1 part by weight of γ-aminopropylalkoxysilane as a silane coupling agent is added and mixed with 100 parts by weight of the resin. After discharging from the flask, the mixture was cooled to room temperature to obtain a novolak-type phenol / formaldehyde resin. Next, after adding a silane coupling agent, sodium glutamate as a disintegrating composition is added and mixed with 3 parts by weight of the novolak resin as powder with respect to 100 parts by weight of the novolak resin, and a novolak-type phenol / formaldehyde resin containing the disintegrating composition I got Example 2 A novolak-type phenol / formaldehyde resin containing a disintegrable composition was obtained in the same manner as in Example 1, except that the amount of sodium glutamate added was 5 parts by weight as the disintegrable composition. Example 3 A novolak-type phenol / formaldehyde resin containing a disintegrable composition was obtained in the same manner as in Example 1 except that the amount of sodium glutamate added was 7 parts by weight as the disintegrable composition. [Example 4] The amount of sodium glutamate added as a disintegrating composition was 5 parts by weight, but it was added as a powder at the same time as the resin was added during the production of a resin-coated sand described later. [Example 5] The amount of sodium glutamate added as a disintegrating composition was 5 parts by weight, but it was mixed and added to a hexamethylenetetramine aqueous solution during the production of a resin-coated sand described below. Comparative Example In a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, 940.0 parts by weight of phenol, 567.6 parts by weight of 37% formalin, and 9.4 parts by weight of oxalic acid were precisely weighed and stirred. While the temperature is gradually rising. After reaching the reflux temperature, the reaction is carried out for 120 minutes. After the distillation reaction, a dehydration reaction is further carried out under vacuum. 1 part by weight of γ-aminopropylalkoxysilane as a silane coupling agent is added and mixed with 100 parts by weight of the resin. After discharging from the flask, the mixture was cooled to room temperature to obtain a novolak-type phenol / formaldehyde resin. [Production of Resin Coated Sand] Comparative Example and Example 1
The method for producing a resin-coated sand using the novolak-type phenol / formaldehyde resin obtained from No. 5 to No. 5 is as follows. 1.5 parts by weight of resin was added to 100 parts by weight of the flattery sand heated to 150 ° C. in advance using a speed mixer for hot coating manufactured by Enshu Tekko. After kneading for 1 minute, 20 parts by weight of a 15% aqueous solution of hexamethylenetetramine was added and further kneaded. When the sand being kneaded changes from a wet state to a dry state, 0.1 part by weight of calcium stearate is added to the sand as a lubricant, the sand is discharged after mixing, cooled to room temperature, and used for a shell mold. Resin coated sand was manufactured. [Preparation of Test Piece] Evaluation of mold disintegration was carried out by a test piece using the resin-coated sand obtained above. That is, using a heating die of 10 × 10 × 60 mm,
A test piece was formed under the conditions of firing at 250 ° C. for 60 seconds and cooled to room temperature. [Evaluation of disintegration property] The test piece obtained as described above was wrapped in aluminum foil, and 500 ° C, 400 ° C, and 3 ° C.
Using an electric furnace heated to 00 ° C., heat treatment is performed for a certain period of time. After cooling to room temperature after the treatment, the aluminum foil was peeled off, and the bending strength of the test piece was measured.
The bending strength before the heat treatment was defined as the initial strength, and the bending strength after the heat treatment was defined as the residual strength. In addition, the strength residual ratio is expressed by the following equation 1.
It was obtained by the formula and was used as an index of disintegration.

(Equation 1) Table 1 shows the results of the disintegration evaluation of Comparative Examples and Examples 1 to 5.

[Table 1] As is clear from Table 1, it is shown that the addition of sodium glutamate as a disintegrating composition is more advantageous than the comparative example in any heat treatment conditions in the residual strength and the residual strength ratio. Further, in these tests, corrosion of the heating mold during preparation of the test piece was not observed by visual observation.

According to the present invention, in the casting of aluminum and other light alloy castings using a shell mold mold, a resin composition for a shell mold which improves mold disintegration after pouring and containing the same. A resin-coated sand for a shell mold can be provided. That is, in a shell mold used for casting of light alloy castings including aluminum, as a composition for improving mold disintegration after pouring, an amino acid or an alkali metal salt, an alkaline earth metal salt, a hydrochloride or a sulfuric acid salt of an amino acid is used. The method using a salt, furthermore an alkyl ester or a hydrochloride of the alkyl ester is extremely high in safety as compared with conventionally used disintegrants, and has almost no problem of mold corrosion and little effect on the environment.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomoyo Muraishi 700 Sukuodarishou, Takasaki City, Gunma Prefecture Inside Gunei Chemical Industry Co., Ltd.

Claims (3)

[Claims] An amino acid or an alkali metal salt, alkaline earth metal salt or hydrochloride of an amino acid or amino acid is used as a disintegrant with respect to 100 parts by weight of a phenol / formaldehyde resin used in the production of an easily disintegratable mold for aluminum and light alloy castings. And sulfates, and at least one selected from alkyl esters and hydrochlorides of the alkyl esters,
A resin composition for shell molds, comprising 30 parts by weight. 2. A refractory aggregate 1 heated to 120 to 180 ° C.
With respect to 100 parts by weight and 100 parts by weight of a phenol / formaldehyde resin used for the production of an easily disintegratable mold for aluminum and light alloy castings, an amino acid or an alkali metal salt, alkaline earth metal salt or hydrochloride of an amino acid is used as a disintegrant And at least one selected from alkyl esters and hydrochlorides of the alkyl esters.
0.2 to 10 parts by weight of the resin composition containing to 30 parts by weight, and further based on 100 parts by weight of the resin composition,
A resin-coated sand for a shell mold, characterized by adding 0 to 30 parts by weight of hexamethylenetetramine. 3. The resin-coated sand for a shell mold according to claim 2, wherein the disintegrant is added as a powder or an aqueous solution.