JPH04118150A - Binder composition for molding sand - Google Patents

Abstract

PURPOSE:To drastically improve mold strength by using a binder composition for molding sand containing one or more kinds of the specific alcohol kind in water-soluble phenol resin. CONSTITUTION:The binder composition for organic ester curing type molding sand contains water-soluble phenol resin and one or more kinds of alcohol as the essential components, and as the alcohol kind, univalent alcohol having 3-12 carbons or the alcohol having at least one of aromatic ring in the molecule is used. Concretely, the following material is used, i.e., propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a binder composition for foundry sand used in self-hardening molds and gas-hardening mold making methods.

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

[Conventional technology]

The self-hardening mold method, the cold box mold method, and the cloning method (shell method) are known as molding methods for producing molds such as main molds and cores using organic binders. In particular, organic self-hardening mold making methods have already become a general-purpose molding method, replacing inorganic ones, from the viewpoints of productivity, quality of castings, and safety and health, mainly in the field of mechanical casting.

On the other hand, conventionally, in order to manufacture molds at medium to high speeds, a cloning method has been widely used in which molds are manufactured by heating and hardening so-called coated sand, in which granular refractories are coated with phenolic resin.

However, in order to save energy during mold manufacturing, mold production speed, and improve the quality of molds and castings, the cold box molding method, in which gaseous or aerosol substances are used to cure at room temperature, has replaced the cloning method. The industry is seriously trying to introduce it.

[Problem to be solved by the invention] As a binder composition used in an organic self-hardening mold making method and a gas hardening mold making method, a water-soluble phenol-formaldehyde resin aqueous solution is used as a binder, and this is mixed with an organic ester. A hardening binder composition for foundry sand was published in Japanese Patent Application Laid-Open No. 1985.
It is publicly known from Japanese Patent Application Laid-open No. 130627, Japanese Patent Application Laid-open No. 58454433, and Japanese Patent Application Laid-open No. 154434/1982.

This mold making method using a binder does not contain sulfur atoms in the binder, so it has the advantage of being less prone to sulfurization than the mold making method using acid-curing resins. Compared to the acid-curing mold making method, this method has disadvantages such as low mold strength, short pot life, and poor sand residing properties, and further improvements are desired.

[Means to solve the problem]

As a result of intensive research by the present inventors to solve the above problems,
In a binder composition for foundry sand used in a mold making method in which a water-soluble phenol resin is used as a binder and the binder is hardened with an organic ester, one or more specific alcohols are added to the water-soluble phenol resin. It has been discovered that mold strength can be significantly improved by using a binder composition for foundry sand in combination, and the present invention has been completed.

That is, the present invention relates to an organic ester-curable binder composition for foundry sand, which contains a water-soluble phenol resin and one or more alcohols as essential components.

The alcohols used in the present invention are preferably monohydric alcohols having 3 to 12 carbon atoms or alcohols having at least one aromatic ring in the molecule.

Specifically, the alcohols used in the present invention include the following.

Propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, 5ec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, isoamyl alcohol, hexyl alcohol,
Heptyl alcohol, octyl alcohol, caprylic alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, allyl alcohol, crotyl alcohol, propargyl alcohol, cyclopentanol, cyclohexanol, benzyl alcohol, cinnamyl alcohol, furfuryl alcohol The reason why mold strength can be significantly improved by using the binder composition of the present invention, which is as follows, is presumed to be as follows.

That is, the presence of one or more of the above alcohols induces surface hydrogen bonding between the refractory granular material and the water-soluble phenolic resin, thereby chemically improving surface properties such as improving interfacial adhesion. physical improvement and modification of properties such as permeability and diffusivity to the composition interface of the hardened mold, i.e. solid-liquid, liquid-liquid interface, and cohesive force for refractory particles. This is thought to be due to the improvement in

The water-soluble phenol resin and one type or a mixture of two or more of the above-mentioned alcohols may be used together, and may be contained in the water-soluble phenol resin or an aqueous solution.
They may be stirred and mixed into the organic ester, or they may be added separately to the refractory granular material. In addition, at this time, it can be diluted with a well-known solvent to improve kneadability and then added.

In order to manufacture a foundry sand mold by the self-hardening mold making method using the organic ester hardening binder composition for foundry sand of the present invention, 100 parts by weight of the refractory granular material is mixed with 0.00 parts by weight of the organic ester as a hardening agent. 0.05 to 9 parts by weight, preferably 0.1 to 5 parts by weight, based on the solid content of the water-soluble phenol resin aqueous solution.
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 alcohol.
A mold can be manufactured by kneading the weight parts by a well-known method and using the conventional self-hardening mold manufacturing process as is.

In addition, in the present invention, in order to manufacture a foundry sand mold by a gas hardening mold making method, first, 100 pieces of refractory granular material are used.
The solid content of the water-soluble phenol resin aqueous solution is 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 parts by weight of the alcohol.
Mixed sand containing ~3 parts by weight is filled into the model by hand or by blowing with pressurized air, and then 0.05 to 9 parts by weight of organic ester in gaseous or aerosol form is blown into the phenolic resin mixture. A mold is produced by curing.

As the organic ester used in the present invention, organic esters derived from lactones or monohydric or polyhydric alcohols having 1 to 10 carbon atoms and organic carboxylic acids having 1 to 10 carbon atoms may be used alone or in mixtures. In the self-hardening mold making method, γ-butyrolactone, propionolactone, ε-
It is preferable to use caprolactone, ethyl formate, ethylene glycol diacetate, ethylene glycol monoacetate, triacetin, etc., and it is preferable to use methyl formate in the gas-curable mold making method.

The water-soluble phenolic resin used in the present invention is a resin that can be cured with an organic ester, such as phenol, cresol, resorcinol, xylenol, bisphenol A, cumylphenol, nonylphenol, butylphenol, phenylphenol, ethylphenol, octylphenol, amylphenol, etc. Phenols, including phenol, naphthol, bisphenol F, bisphenol C1 catechol, hydroquinone, pyrogallol, phloroglucin, lignin, bisphenol A residue, cresol residue, chlorophenol, dichlorophenol, and other substituted phenols, as well as formaldehyde, acetaldehyde, furfuraldehyde, and Examples include phenolic resins obtained by reaction with mixtures of aldehydes and the like. Suitable alkaline materials used in the condensation of these phenolic resins are sodium hydroxide, potassium hydroxide, lithium heptahydroxide, and mixtures thereof, with potassium hydroxide being most preferred.

As the refractory granular material, inorganic refractory granular materials such as chromite sand, zircon sand, oripin sand, alumina sand, etc., as well as silica sand containing quartz as a main component, are used, but are not particularly limited.

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

〔Example〕

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

Examples 1 to 7 and Comparative Example 1 Changes in mold strength over time in a self-hardening mold making method were evaluated.

That is, 0.0% triacetin was added to 100 parts by weight of silica sand.
A mixture obtained by adding and kneading 25 parts by weight, 1.5 parts by weight of a water-soluble phenol resin, and 0.15 parts by weight of various alcohols shown in Table 1 was prepared into a mixture having a diameter of 50 mm and a height of 50 mm.
The mixture was filled into a test piece model, and the change in compressive strength over time after kneading was measured.

The results are shown in Table-1.

Table Examples 8 to 14 and Comparative Example 2 Changes in spinning mold strength over time in the gas hardening mold making method were evaluated.

That is, silica sand 1003! A mixture obtained by adding and kneading 2.0 parts by weight of a water-soluble phenol resin with a solid content of 50% by weight and 0.2 parts by weight of various alcohols shown in Table 2 was mixed with a diameter of 5oIllI11 and a high It was filled into a gas curing test piece model having a diameter of 50 sua. 3.0 parts by weight of gaseous methyl formate was injected into this model, and the change in compressive strength over time after the injection was measured.

The results are shown in Table-2.

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

As a result, it is possible to reduce the amount of binder used, making it easier to recover molding sand, and also reducing the amount of gas generated from the mold during casting, thereby suppressing the occurrence of gas defects. Sound castings can be produced and are useful for practical purposes.

Claims (1)

[Claims] 1. One or two water-soluble phenol resins and alcohols.
An organic ester hardening type binder composition for foundry sand, characterized in that the organic ester hardening type binder composition contains at least one of the above essential ingredients. 2. The binder composition for foundry sand according to claim 1, wherein the alcohol is a monohydric alcohol having 3 to 12 carbon atoms. 3. The binder composition for foundry sand according to claim 1 or 2, wherein the alcohol has at least one aromatic ring in the molecule. 4. The binder composition for foundry sand according to claim 1, wherein the organic ester is gaseous.