JP2892466B2 - Binder composition for foundry sand - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a binder composition for molding sand used in a self-hardening mold and a gas-curable mold molding method.

More specifically, the present invention relates to an improved organic ester-curable binder composition for molding sand used in a mold molding method in which a water-soluble phenol resin is used as a binder and cured with an organic ester.

[Conventional technology]

As a molding method for producing a mold such as a main mold and a core using an organic binder, a self-hardening mold method, a cold box mold method, and a cloning method (shell method) are known. In particular, the organic self-hardening molding method is already a general-purpose molding method in place of the inorganic type from the viewpoint of productivity, casting quality, safety and health mainly in the field of mechanical casting.

On the other hand, a cloning method for producing a template by heating and curing a so-called coated sand in which a phenol resin is coated on a granular refractory, that is, a phenol resin is conventionally widely used for producing a template at a medium and high speed.

However, energy saving during mold production, mold production speed,
Further, in order to improve the quality of molds and castings, a cold box mold method of curing at room temperature with a gaseous or aerosol-like material has been seriously attempted in the casting industry as a method of manufacturing a mold instead of a cloning method.

[Problems to be solved by the invention]

As a binder composition used in an organic self-hardening mold molding method and a gas-curable mold molding method, a water-soluble phenol-formaldehyde resin aqueous solution is used as a binder, and this is cured with an organic ester. The product is Japanese
-130627, JP-A-58-154433 and JP-A-58-154
It is known from US Pat.

The mold making method using this binder has advantages such as a smaller tendency of sulfuration as compared with the mold making method using an acid-curable resin because no sulfur atom is contained in the binder, but on the other hand, Compared to the acid-curable mold making method, it has disadvantages such as low mold strength, short pot life, and poor sand reproducibility, and further improvement is desired.

[Means for solving the problem]

The inventors of the present invention have conducted intensive studies to solve the above problems, and found that a water-soluble phenol resin as a binder and a binder composition for molding sand used in a mold molding method of curing this with an organic ester, The inventors have found that the strength of the mold can be greatly improved by adding a specific ratio of the phenol compound monomer to the water-soluble phenol resin, and have completed the present invention.

That is, the present invention provides an organic ester-curable molding sand comprising, as an essential component, a water-soluble phenolic resin and one or more phenolic compound monomers in an amount of 5 to 40% by weight based on the solid content thereof. The present invention provides a binder composition for use.

The content of the phenol compound monomer in the binder composition of the present invention is preferably 7 to 30% by weight based on the solid content of the aqueous phenol resin aqueous solution. According to the present invention, the strength of the mold can be improved by containing the phenol compound monomer in the above specific ratio. If the amount is less than 5% by weight, the effect of improving the strength of the mold is not sufficient, and 40% by weight. Above, the curing speed becomes slow and is not practical.

Phenol compound monomers used in the present invention include, for example, phenol, cresol, resorcinol, xylenol, bisphenol A, cumylphenol, nonylphenol, butylphenol, phenylphenol, ethylphenol, octylphenol, amylphenol, naphthol, bisphenol F, bisphenol C, catechol, hydroquinone, pyrogallol, phloroglucin, bisphenol A residue, cresol residue,
Compounds such as phenols including chlorophenol, dichlorophenol, and other substituted phenols.

The reason why the mold strength can be significantly improved by using the binder composition of the present invention is presumed as follows. That is,
The presence of a specific proportion of phenolic compound monomer induces surface hydrogen bonding between the refractory granular material and the water-soluble phenolic resin, thereby chemically improving the surface properties such as interfacial adhesion. And physically improving, modifying, and improving the permeability and diffusion properties of the cured mold at the composition interface, that is, the solid-liquid and liquid-liquid interfaces, and the properties such as cohesion of the refractory particles. It is thought that.

As a form in which a water-soluble phenol resin and one or a mixture of two or more phenol compound monomers in the above specific ratio are used in combination, the phenol compound monomer is contained in the water-soluble phenol resin in a free state. Or it may be stirred and mixed in the organic ester, or may be separately added to the refractory granular material. At this time, the mixture may be diluted with a known solvent to increase the kneadability and added.

To produce a casting sand mold by a self-hardening molding method using the organic ester-curable molding sand binder composition of the present invention, 100 parts by weight of the refractory granular material, an organic ester 0.05 to 0.05% of a curing agent. 9 parts by weight, preferably 0.1 to 5 parts by weight,
0.4 to 15 parts by weight, preferably 0.5 to 5 parts by weight, of a water-soluble phenolic resin aqueous solution as a solid content, and one or more mixtures of phenolic compound monomers with respect to the solid content of the water-soluble phenolic resin aqueous solution The mold can be produced by incorporating the same in an amount of 5 to 40% by weight, preferably 7 to 30% by weight, kneading by a known method, and utilizing the conventional self-hardening mold production process as it is.

Further, in the present invention, in order to produce a sand mold for casting by a gas-curing mold molding method, first, a refractory granular material 100
In weight parts, water-soluble phenol resin aqueous solution as solid content
0.4 to 15 parts by weight, preferably 0.6 to 5 parts by weight, and 5 to 40% by weight based on the solid content of the aqueous phenol resin aqueous solution,
The kneading sand contained preferably in an amount of 7 to 30% by weight is prepared or filled into a model by blowing with pressurized air, and then 0.05 to 9 parts by weight of gaseous or aerosol organic ester is blown. To produce a mold.

As the organic ester used in the present invention, a lactone or an organic ester derived from a monohydric or polyhydric alcohol having 1 to 10 carbon atoms and an organic carboxylic acid having 1 to 10 carbon atoms alone or as a mixture is used. In the self-hardening molding method, γ-butyrolactone, propionlactone, ε-
It is preferable to use caprolactone, ethyl formate, ethylene glycol diacetate, ethylene glycol monoacetate, triacetin, and the like, and it is preferable to use methyl formate in a gas-curable molding method.

The water-soluble phenol resin used in the present invention is a resin curable with an organic ester, such as phenol, cresol, resorcinol, 3,5-xylenol, bisphenol A, phenols including other substituted phenols, formaldehyde, Phenol resins obtained by reaction with acetaldehyde, furfural aldehyde, a mixture of aldehyde, and the like. Suitable alkaline substances used for the condensation of these phenolic resins are sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof, with potassium hydroxide being most preferred.

As the refractory granular material, inorganic refractory granular materials such as chromite sand, zircon sand, olivine sand, and alumina sand are used in addition to silica sand having quartz as a main component, but are not particularly limited.

Further, a silane coupling agent may be added for the purpose of further improving the mold strength. Preferred silane coupling agents include γ-aminopropyltriethoxysilane and γ- (2-aminoethyl) aminopropyltrimethoxysilane.

The solid content of the water-soluble phenol resin aqueous solution in the present invention is determined by measuring a weighed sample (2.0 ± 0.1 g) in an air-circulating furnace.
Measured by heating to 100 ° C. for hours.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

Examples 1 to 10 and Comparative Examples 1 to 3 The change over time of the mold strength in the self-hardening mold making method was evaluated.

That is, triacetin was added in an amount of 0.25 to 100 parts by weight of silica sand.
A mixture obtained by adding and kneading 1.5 parts by weight of a water-soluble phenol resin having a solid content of 50% by weight and 0.15 parts by weight of various phenolic compound monomers shown in Table 1 and having a diameter of 50 mm
The test piece was filled into a test piece model having a height of 50 mm, and the change in compressive strength with time after kneading was measured.

 The results are shown in Table 1.

Examples 11 to 20 and Comparative Examples 4 to 6 Changes over time in mold strength in a gas-curable mold molding method were evaluated.

That is, a mixture obtained by adding and kneading 2.0 parts by weight of a water-soluble phenol resin having a solid content of 50% by weight and 0.2 parts by weight of various phenol compound monomers shown in Table 2 with respect to 100 parts by weight of silica sand was used. It was filled into a gas-hardening test piece model 50 mm high and 50 mm high. 3.0 parts by weight of gaseous methyl formate was injected into this model, and the change over time in compressive strength after injection was measured.

 Table 2 shows the results.

[Effects of the Invention] As is clear from the above embodiments, according to the production method of the present invention, a mold having a higher strength than that of a mold obtained by a conventional production method can be obtained.

As a result, the amount of binder used can be reduced,
Since the casting sand can be easily collected and the amount of gas generated from the casting mold at the time of casting can be reduced, generation of gas defects can be suppressed and a sound casting can be manufactured, which is practically useful.

Continuation of front page (56) References JP-A-62-252634 (JP, A) JP-A-53-129292 (JP, A) JP-A-49-122424 (JP, A) (58) Fields studied (Int) .Cl. ⁶ , DB name) B22C 1/00-1/26

Claims (3)

(57) [Claims] 1. A water-soluble phenolic resin and one or more phenolic compound monomers of 5 to 40% by weight based on the solid content thereof.
A binder composition for an organic ester-curable molding sand, comprising at least one of the following components as an essential component. 2. The binder composition for foundry sand according to claim 1, wherein the content of the phenol compound monomer is 7 to 30% by weight based on the solid content of the water-soluble phenol resin. 3. The binder composition for molding sand according to claim 1, wherein the organic ester is gaseous.