JP2892468B2 - 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.

[Prior art] As a molding method for producing a mold such as a main mold or 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 present invention has been found to significantly improve the mold strength by using a binder composition for foundry sand obtained by using one or more specific phosphoric esters in combination with a water-soluble phenol resin. Was completed.

That is, the present invention relates to a binder composition for an organic ester-curable molding sand, which comprises a water-soluble phenol resin and one or more phosphoric acid triesters as essential components.

Specific examples of the phosphoric acid triesters used in the present invention include the following.

Trimethyl phosphate, triethyl phosphate, tributyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, trisisopropylphenyl phosphate, tricresyl phosphate, tri-2-ethylhexyl phosphate, and the like.

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 one or more of the above-mentioned phosphoric acid triesters induces surface hydrogen bonding between the refractory granular material and the water-soluble phenol resin, thereby improving surface properties such as improvement in interfacial adhesion. Chemically improved, physically improved and improved properties such as permeability and diffusion at the composition interface of the curing mold, ie, solid-liquid, liquid-liquid interface, and cohesion to refractory particles. It is thought that it was due to quality and improvement.

As a form in which the water-soluble phenol resin and one or more of the above-mentioned phosphate triesters are used in combination, the water-soluble phenol resin may be contained in the water-soluble phenol resin or the aqueous solution, or may be stirred in the organic ester. They may be mixed or added separately to the refractory granular material. At this time, it may be added by diluting it with a known solvent to improve the kneading property.

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 0.6 to 5 parts by weight, and 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, of a phosphoric acid triester are kneaded by a well-known method as a solid, and The mold can be manufactured by utilizing the self-hardening mold manufacturing 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 0.01 to 5 parts by weight of phosphoric acid triesters, preferably 0.05 to 3 parts by weight kneading sand added, or blown with pressurized air model The mold is manufactured by filling the mixture and then blowing 0.05-9 parts by weight of a gaseous or aerosol organic ester to cure the phenolic resin mixture.

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 phenolic resin used in the present invention is a resin curable with an organic ester, such as phenol, cresol, resorcinol, xylenol, bisphenol A, cumylphenol, nonylphenol, butylphenol, phenylphenol, ethylphenol,
Octylphenol, amylphenol, naphthol,
Mixtures of phenols including bisphenol F, bisphenol C, catechol, hydroquinone, pyrogallol, phloroglucin, lignin, bisphenol A residue, cresol residue, chlorophenol, dichlorophenol and other substituted phenols, and formaldehyde, acetaldehyde, furfural aldehyde and 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.

〔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 6 and Comparative Example 1 The change over time in 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.
Parts by weight, 1.5 parts by weight of water-soluble phenol resin and Table 1
The mixture obtained by adding and kneading 0.15 parts by weight of the phosphoric acid triesters shown in (1) above was filled in a test piece model having a diameter of 50 mm and a height of 50 mm, and the change over time in the compressive strength after kneading was measured.

 The results are shown in Table 1.

Examples 7 to 12 and Comparative Example 2 The change over time of the mold strength in the gas-curable mold molding method was 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 phosphoric acid triesters shown in Table 2 with respect to 100 parts by weight of silica sand was used. The test piece for gas hardening, 50 mm in height and 50 mm in height, was filled. 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 the front page (56) References JP-A-62-252634 (JP, A) JP-A-50-96647 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22C 1/00-1/26

Claims (2)

(57) [Claims] An organic ester-curable binder for sands comprising an essential component comprising a water-soluble phenolic resin and one or more phosphoric acid triesters. 2. The binder composition for foundry sand according to claim 1, wherein the organic ester is gaseous.