JPH04118146A - Binder composition for molding sand - Google Patents

Abstract

PURPOSE:To drastically improve mold strength by using a binder composition for molding sand having the compsn. containing one or more kinds of the specific phosphoric ester in water-soluble phenol resin. CONSTITUTION:By using the binder composition for organic ester curing type molding sand having the compsn. containing water-soluble phenol resin and one or more kinds of the phosphoric triester kind as the essential component, the mold is molded. Further, as the phosphoric triester kind, phosphoric trimethylester, phosphoric triethylester, phosphoric tributyl ester, etc., is used.

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 binder composition for organic ester-cured trace sand used in a mold making method that uses a water-soluble phenol resin as a binder and cures it 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.

[The problem to be solved by the invention is to use a water-soluble phenol-formaldehyde resin aqueous solution as a binder as a binder composition used in an organic self-hardening mold making method and a gas hardening mold making method, and to use an organic ester as a binder composition. 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. 58-154433, and Japanese Patent Application Laid-open No. 154434-1987.

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 regeneration 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 two specific phosphate esters are added to the water-soluble phenol resin. The present inventors have discovered that mold strength can be significantly improved by using a binder composition for foundry sand that uses the above components in combination, and have completed the present invention.

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 kinds of phosphoric triesters as essential components.

Specifically, the phosphoric acid triesters used in the present invention include the following.

Trimethyl ester phosphate, tributyl phosphate, tributoxyethyl ester phosphate, triphenylestenoperic acid, trisisopropylphenyl ester, tricrezino phosphate, tri2-ethylhexyl phosphate, and the like.

The reason why mold strength can be significantly improved by using the binder composition of the present invention is presumed to be as follows. That is, the presence of one or more of the above-mentioned phosphoric acid triesters induces surface hydrogen bonding between the fire-resistant granular material and the water-soluble phenolic resin, thereby improving surface adhesion, etc. Chemically improved properties, as well as physically improved properties such as permeability and diffusivity to composition interfaces, i.e., solid-liquid and liquid-liquid interfaces, and cohesive strength for refractory particles, of the hardened mold. This is thought to be due to the fact that it has been modified and improved.

When using a water-soluble phenol resin and one type or a mixture of two or more of the above-mentioned phosphoric acid triesters, they may be contained in the water-soluble phenol resin or an aqueous solution, or they may be stirred into the organic ester. It may be mixed,
Alternatively, 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 type molding sand binder composition of the present invention, 0 parts by weight of the organic ester as a hardening agent is added to 100 parts by weight of the refractory granular material. .05 to 9 parts by weight, preferably 0.1 to 5 parts by weight
Parts by weight, solid content of water-soluble phenol resin aqueous solution: 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
．． A mold can be manufactured by kneading 05 to 3 parts by weight 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 of phosphoric acid triesters, preferably 0.05 to 5 parts by weight. 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 0.05 parts by weight of organic ester in gaseous or aerosol form is added.
A mold is made by curing the phenolic resin mixture by blowing in 9 parts by weight.

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, T-butyrolactone, propionolactone, ε
- It is preferable to use caprolactone, ethinope 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 phenonopecresonoperesorcinonohexylenol, bisphenol A1 cumylphenonopenonylphenonobebutylphenonobephenyl. Including phenonobe ethylphenol, octylphenonopea milphenonopenaphthol, bisphenol F1 bisphenol 01 catechonobe hydroquinone, pyrogallol, phloroglucin, lignin, bisphenol A residue, cresol residue, chlorophenol, dichlorophenonobe and other substituted phenols. Examples include phenolic resins obtained by reacting phenols with formaldehyde, acetaldehyde, furfuraldehyde, a mixture of aldehydes, and the like. Suitable alkaline materials used in 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, 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 T-aminopropyltriethoxysilane and T-(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 6 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 of 25 parts by weight, 1.5 parts by weight of water-soluble phenol resin, and 0.15 parts by weight of the phosphoric acid triesters shown in Table 1 was kneaded into a mold with a diameter of 53 mm and a height of 5Q.
The mixture was filled into a test piece model having a diameter of 1 mm, and the change in compressive strength over time after kneading was measured.

The results are shown in Table-1.

Table Examples 7 to 12 and Comparative Example 2 Changes in mold strength over time in the gas hardening mold making 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 phosphoric triesters shown in Table 2 to 100 parts by weight of silica sand. was filled into a gas curing test piece model having a diameter of 50 mm and a height of 5 Q mm. 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, the amount of binder used can be reduced, making it easier to recover molding sand, and the amount of gas generated from the mold during pouring can be reduced, suppressing the occurrence of gas defects. Sound castings can be produced, which is useful for practical purposes.

Claims (1)

[Claims] 1. 1. Water-soluble phenol resin and phosphoric triester.
An organic ester-curing binder composition for foundry sand, characterized in that it contains one or more species as essential components. 2. The binder composition for foundry sand according to claim 1, wherein the organic ester is gaseous.