JP2001219242A - Binder composition for molding sand and casting mold composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binder composition for molding sand which drastically suppresses the formaldehyde smell generated during molding of a casting, greatly improves a working environment, improves the strength of a casting mold, does not form an oxidized film and has good storage stability. SOLUTION: Hydrazine is added to the binder composition for molding sand using a water-soluble phenolic resin and organic ester. The hydrazine is incorporated into a binder containing the water-soluble phenolic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a binder composition for an organic ester-curable molding sand in a self-hardening mold and a gas-curable mold, and more particularly to a water-soluble phenol resin binder. The present invention relates to an improved molding composition sand binder composition used in a process of curing with an organic ester.

[0002]

2. Description of the Related Art As a method for producing a casting mold, a self-hardening molding method in which a binder solution containing a water-soluble phenol resin is used and curing is performed with a liquid organic ester compound, and a room temperature curing using a gaseous or aerosol-like substance. The gas-curable mold method to be effected is known. Since the mold making method using this binder does not contain a sulfur atom in the binder, the mold strength is lower than that of the acid-curable mold making method, and improvement has been desired. Further, when the binder composition containing the water-soluble phenol resin is stored or allowed to stand, the surface of the resin is oxidized and a film is gradually formed, the width of the film becomes thicker, the amount of solid substances increases, and the binder becomes There are problems such as improper measurement at the time of measuring with a machine and uneven mixing at the time of mixing the binder such as sand with the binder. Further, the method of molding a mold using a binder containing a water-soluble phenol resin has a problem in the working environment due to the odor of formaldehyde generated when the mold is manufactured and when the metal is poured into the mold.

[0003]

In order to solve the above-mentioned problems, there is known a method for suppressing the odor of formaldehyde by using urea. When a binder composition containing a water-soluble phenol resin to which urea is added is stored or left, an oxide film is generated in the same manner as when a binder containing a water-soluble phenol resin is stored, and when kneading with molding sand, Problems have occurred and improvements are desired. In addition, urea does not have the effect of increasing the strength of the obtained mold, and it is necessary to improve the strength required for a binder containing a water-soluble phenol resin.

[0004]

The present inventors have conducted intensive studies to solve the above problems, and as a result, found that a water-soluble phenol resin is used as a binder and the binder composition is cured with an organic ester. In, by using hydrazine, significantly reduce the formaldehyde odor generated during the production of the mold, significantly improve the working environment, and
We have found a binder composition for foundry sand that improves the strength of the obtained mold. Also, after adding hydrazine to the binder containing the water-soluble phenol resin, the binder composition does not form an oxide film even when stored or left, and has good storage stability and good molding sand. We have found a binder composition for foundry sand that does not cause problems even during kneading.

That is, the present invention relates to a binder composition for an organic ester-curable foundry sand containing a water-soluble phenol resin and hydrazine as essential components. In a preferred embodiment, the hydrazine content of the water-soluble phenol resin is It is a binder composition for foundry sands having a resin solid content of 0.1 to 5% by weight. The mold composition of the present invention is used in an amount of 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight, of an organic ester curing agent based on 100 parts by weight of the refractory aggregate. A mold composition obtained by kneading a mixture of a caking composition for foundry sand containing a phenol resin solid content of 0.25 to 5 parts by weight.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The water-soluble phenolic resin used in the present invention is a resin curable with an organic ester, such as phenol, cresol, resorcinol, 3,5.
Phenols, including xylenol, bisphenol A, and other substituted phenols, obtained by the reaction of formaldehyde alone or in combination with aldehydes such as acetaldehyde, furfuryl aldehyde and a mixture of aldehydes in the water-soluble nature of large amounts of alkaline substances. Phenolic resins are mentioned, but formaldehyde alone is preferred. Suitable alkaline catalysts used in the production of these water-soluble phenolic resins are alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof. Most preferred. The water-soluble phenol resin may be added in powder form to molding sand or its reclaimed sand.

[0007] The resin solid content of the water-soluble phenol resin is preferably 10 to 60% by weight from the viewpoint of workability at the time of kneading with the aggregate.
The weight average molecular weight is preferably in the range of 500 to 6000, and more preferably in the range of 2000 to 2800, so that the strength of the obtained mold can be easily maintained. The viscosity of the water-soluble phenol resin according to the present invention is 10 to 200 mPa.
・ S is preferred. In a preferred embodiment of the binder composition for foundry sand of the present invention, hydrazine is preferably dissolved in a water-soluble phenol resin solution. The hydrazine used in the present invention is anhydrous hydrazine, hydrated product of hydrazine, or the like, but may also be used in the form of a solution dissolved in an inert solvent which does not adversely affect the performance as a binder. As a preferred embodiment of hydrazine, a 50 to 80% by weight aqueous solution is preferable, and a particularly preferable one is a 50 to 60% by weight hydrazine aqueous solution. When the binder is to be kneaded with the refractory aggregate such as molding sand, the hydrazine of the above-mentioned form may be added.

In the binder composition for molding sands of the present invention, the content of hydrazine is preferably 0.1 to 5% by weight, more preferably 0.5 to 5% by weight, based on the resin solid content of the water-soluble phenol resin. 3% by weight. When the weight percentage of hydrazine is less than 0.1, there is almost no effect of suppressing the formaldehyde odor generated at the time of mold molding. On the other hand, when it exceeds 5 weight%, problems such as inferior casting quality may easily occur. Further, various additives can be added in view of the filling property of the refractory aggregate coated with the resin, the mold releasing property between the obtained mold and the casting, and the like.

As an additive having an effect of improving the filling property of the resin-coated aggregate, various surfactants are effective.
Nonionic surfactants, cationic surfactants, anionic surfactants, amphoteric surfactants and the like can be used. More specifically, examples of the nonionic surfactant include polyoxyethylene-type surfactants such as polyoxyethylene alkyl ether, polyoxyethylene-polyoxypropylene glycol, and polyoxyethylene-polyoxypropylene glycol ethylenediamine; Examples include polyhydric alcohol surfactants such as fatty acid esters, glycerin monofatty acid esters and sorbitan trifatty acid esters, and alkylolamide surfactants such as fatty acid monoethanolamide and fatty acid monoisopropanolamide.

Specific examples of the anionic surfactant include a metal salt of stearic acid, a fatty acid type surfactant such as naphthenic acid, a metal salt of oleic sulfate, a polyoxyethylene alkyl ether sulfate, an aliphatic monoglyceride aliphatic. Ester salts, sulfated oils such as olive oil, fatty acid alkyl sulfates, sulfate ester type surfactants such as aliphatic amide sulfates, sulfonate type surfactants, and phosphate ester type surfactants are used. it can.

Specific examples of the cationic activator include quaternary ammonium salts such as alkylpyridinium salts, alkylquinolinium sulfates and acylaminoethylpyridinium salts, aliphatic triethanolamine, aliphatic triethanolamine formate, Polyoxyethylene fatty acid triethanolamine, fatty acid dibutylaminoethanol, a quaternary ammonium salt having an ester bond amine and an ether bond such as p-isooctylphenoxyethoxyethylbenzylammonium salt are alkylimidazoquine,
1-hydroxyethyl-2-alkylimidazoine, 1
Heterocyclic amine type surfactants such as -acetylaminoethyl-2-alkylimidazoline and quaternary salts thereof can be used.

Examples of the amphoteric surfactant include N-alkyltriglycidin, dimethylalkylbetaine, alkylbetaine, alkyldi (aminoethyl) glycine hydrochloride, dialkyldiethylenetriaminoacetic acid hydrochloride,
N-alkyltaurine salts and the like can be used. In addition, a fluorine surfactant and a silicon-based surfactant can also be used, and the surfactant is not particularly limited. A preferable addition amount of the surfactant is 0.01 to 1 part by weight based on 100 parts by weight (solid content of the resin) of the water-soluble phenol resin.

[0013] A silane coupling agent can be added as an agent for improving the adhesion between the refractory aggregate and the binder. The silane coupling agent is used in an amount of 0.1 to 100 parts by weight (solid resin content) of the water-soluble phenol resin of the present invention.
It is preferred to add 2.0 parts by weight. Specific examples of the silane coupling agent include γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and the like.

In order to produce a mold by a self-hardening molding method using the binder composition for foundry sand of the present invention, a refractory aggregate 1
Organic ester 0.05 to 5 parts by weight
Parts by weight, preferably 0.1 to 2 parts by weight, and a molding sand containing 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight of a water-soluble phenol resin solid content in the binder composition. The binder composition is kneaded by a well-known method to obtain a mold composition, and a mold can be manufactured by using a conventional self-hardening mold manufacturing process as it is.

In the present invention, in order to manufacture a mold by a gas-curing mold molding method, first, a refractory aggregate 10
A kneading sand containing 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight of a water-soluble phenol resin aqueous solution as a solid content is prepared in 0 part by weight, or the model is blown with pressurized air. The mold is manufactured by filling the mixture into the mixture and then blowing and curing 0.05 to 5 parts by weight, preferably 0.5 to 5 parts by weight of a gaseous or aerosol organic ester.

The organic ester as a curing agent used in the template composition of the present invention is derived from a lactone or a monohydric or polyhydric alcohol having 1 to 10 carbon atoms and an organic carboxylic acid having 1 to 10 carbon atoms. A single or a mixture of organic esters is used. In the self-hardening molding method, it is preferable to use γ-butyrolactone, propiolactone, ε-caprolactone, ethyl formate, ethylene glycol diacetate, ethylene glycol diacetate, triacetin, etc. It is preferable to use The binding composition for foundry sand of the present invention is not particularly limited, either by a self-hardening mold molding method or a gas-curable mold molding method. As the refractory aggregate to be used in the mold composition of the present invention, aggregates that can be generally used for casting can be used.Examples include silica sand containing quartz as a main component, chromite sand, zircon sand, and olivine sand. And inorganic refractory granular materials such as alumina sand and the like, but are not particularly limited.

[0017]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. (All parts are by weight) (Production of water-soluble phenol resin) An aqueous solution containing 27.2 parts of phenol and 10 parts of potassium hydroxide was mixed and dissolved. 46.9 parts of a 37% aqueous formaldehyde solution were further added thereto (formaldehyde: phenol molar ratio: 2: 1). The mixture solution was heated under reflux for 3 hours and then cooled to obtain a potassium alkaline phenol / formaldehyde resin aqueous solution. (The resin solid content was 50% by weight and the weight average molecular weight of the resin was 2200.) The solid content was determined by measuring 2.0 ± 0.1 g of a sample in an air circulation furnace.
The measurement was performed by heating at 00 ° C. for 3 hours.

Example 1 A 100% aqueous phenol resin (as solid content) prepared by the above method was mixed with a 50% aqueous solution of hydrazine and γ-glycidoxypropyltrimethoxysilane in the amounts shown in Table 1. One part was added and mixed well to prepare a binder composition (Sample 1). To 100 parts of Fremantle silica sand, 2 parts of the binder composition and 0.4 part of triacetin as a curing agent were added and kneaded for 1 minute to prepare a mold composition, and the formaldehyde odor generated 15 minutes later was organoleptically evaluated. did. After 24 hours, the compression strength of the mold was measured. Table 1 shows the results. Further, a binder composition (sample 1) containing a water-soluble phenol resin was added to 24
It was left for a while and exposed to air, and it was confirmed whether or not a film was formed on the surface of the binder composition. Table 1 shows the results.

[0019]

[Table 1]

Comparative Examples 1 and 2 In Comparative Example 1, no additive was added, and in Comparative Example 2, the hydrazine of Example 1 was added instead of urea. Evaluation criteria for formaldehyde odor are as follows: ◎ Almost no formaldehyde odor. ○ Reduce formaldehyde odor. ×: Formaldehyde odor is strong, and sufficient eye irritation is observed.

[0021]

EFFECT OF THE INVENTION By using the binder composition for molding sand of the present invention to cure with an organic ester, the odor of formaldehyde generated during molding of the casting is significantly suppressed, the working environment is remarkably improved, and high strength is achieved. Can be obtained. By adding hydrazine to the binder containing the water-soluble phenol resin, it is possible to obtain a binder composition for molding sand that does not generate an oxide film and does not cause any trouble during kneading.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 61/04 C08L 61/04

Claims (3)

[Claims] 1. An organic ester curable molding sand binding composition comprising a water-soluble phenol resin and hydrazine as essential components. 2. The caking composition for foundry sand according to claim 1, wherein the content of hydrazine is 0.1 to 5% by weight based on the solid content of the water-soluble phenol resin. 3. An organic ester curing agent of 0.05 to 5 parts by weight based on 100 parts by weight of the refractory aggregate, and a solid content of 0.25 to 5 parts by weight of a water-soluble phenol resin in the binder composition. A mold composition obtained by kneading a mixture comprising the binder composition for foundry sand according to any one of claims 1 to 2.