JPH04135035A - Binder composition for molding sand - Google Patents

Abstract

PURPOSE:To obtain a high strength mold by constituting the binder composition for organic ester curing type molding sand of the mixed material of water soluble phenol resin water solution and the specific quantity of novolak type phenol resin. CONSTITUTION:In the binder composition for molding sand using the water soluble phenol resin as the binder and cured with the organic ester, one or more kinds of the novolak type phenol resins are added at 5-40wt.% per the solid part in the water soluble phenol resin. The novolak type phenol resin is dissolved in the water solution or dissolved in solvent in advance, and this is added to the molding sand. The high strength mold is obtd. and as a result, consumption of the binder can be reduced.

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]

A binder composition for foundry sand that uses a water-soluble phenol-formaldehyde resin aqueous solution as a binder and hardens it with an organic ester as a binder composition used in an organic self-hardening mold making method and a gas hardening mold making method. The thing is JP-A-1989.
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 phenolic resin is used as a binder and the binder is hardened with an organic ester, one type of novolak-type phenolic resin or The present inventors have discovered that mold strength can be significantly improved by using a binder composition for foundry sand that is a combination of two or more types, and have completed the present invention.

That is, the present invention provides an organic ester-cured foundry sand characterized in that the essential components are a water-soluble phenolic resin aqueous solution and one or more novolak-type phenolic resins in an amount of 5 to 4 G% by weight based on the solid content thereof. The present invention relates to a binder composition for use.

Preferred novolac type phenolic resins used in the present invention include as phenolic monomers:
For example, phenol, cresol, resorcinone bisphenol A1 bisphenol F1 bisphenol C1
cumylphenonobenonylphenol, butylphenol, phenylphenonobeethylphenol, octylphenol, amylphenonobenaphthol, catechonobehydroquinone, pyrogallonopeflologrinsi,
Examples include phenols including chlorophenol and other substituted phenols, and examples of aldehyde monomers include formaldehyde, furfuranopeglioxal, benzaldehyde, acetaldehyde, trioxane, and acrolein. The product of the present invention is composed of a novolak type phenol resin made of one or more of these phenols and aldehydes, and an aqueous solution of a water-soluble phenol resin. Examples of catalysts for condensing phenols and aldehydes under acidic conditions include acidic substances such as sinuic acid, hydrochloric acid, and sulfuric acid, and metal salts of organic acids.

When using a water-soluble phenol resin and a novolac type phenol resin as described above, they may be dissolved in an aqueous solution of a water-soluble phenol resin, or the viscosity increases significantly when dissolved in an aqueous solution of a water-soluble phenol resin. Those that do not dissolve may be dissolved using a known solvent and then added to the refractory granular material separately from the water-soluble phenolic resin. At this time, the order of addition is not particularly limited.

The composition ratio of the novolak type phenolic resin is 5 to 40% by weight based on the solid content of the water-soluble phenolic resin aqueous solution.

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. 05 to 9 parts by weight, preferably 1.5 to 5 parts by weight, with the solid content of the water-soluble phenol resin aqueous solution being 0.0.
4 to 15 parts by weight, preferably 0.6 to 5 parts by weight, and 5 to 40 parts by weight of one type or a mixture of two or more novolak type phenolic resins based on the solid content of the water-soluble phenolic resin aqueous solution.
A mold can be manufactured by kneading the content in a proportion by weight, preferably 7 to 30 weight%, by a well-known method, and using the conventional self-hardening mold manufacturing process as it 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.
Add 0.4 to 15 parts by weight, preferably 0.6 to 5 parts by weight of a water-soluble phenol resin aqueous solution as a solid content, and a mixture of one or more novolac type phenol resins to the water-soluble phenol resin aqueous solution. 5 to 5 for the solid content of
Mixed sand containing 40% by weight, preferably 7 to 30% by weight, is filled into the model by hand or by blowing with pressurized air, and then a gaseous or aerosol organic ester is added. The mold is manufactured by curing the phenolic resin mixture by blowing in 0.08 to 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, 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, cresonoveresorcinonohexylenol, bisphenol A1 cumylphenonopenonylphenonobebutylphenol, phenylphenonope Ethylphenol, octylphenol, amylphenonohenaphtonobebisphenol F1 bisphenol C1 cateconopehydroquinone, pyrogallol, phloroglucin, lignin, bisphenol A residue, cresol residue, chlorophenonopedic 00 phenolics including other substituted phenols Examples include phenolic resins obtained by reaction 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.

The solid content of the water-soluble phenol resin aqueous solution in the present invention is the sample (2,0±O, Ig
) was measured by heating to 100° C. for 3 hours.

〔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.

[Production of water-soluble phenolic resin]-<A) 50% KO!
(Add phenol in an equimolar ratio to K[lH into the aqueous solution,
Stir and dissolve. While maintaining this solution at 80° C., a 50% formaldehyde aqueous solution having twice the molar amount of phenol was gradually added.

Then, the phenol formaldehyde resin in the reaction solution was reacted at 80°C until it reached a predetermined weight average molecular weight to obtain a water-soluble phenol resin [Manufacture of novolac resin] - (
B> Putty formaldehyde and 0.01 times the mole of oxalic acid were added to phenol and reacted at reflux temperature until a predetermined weight average molecular weight was reached. Next, after stopping the reaction by adding a large amount of cold water, dehydration was performed at normal pressure, and immediately after the dehydration was completed, the reactant was poured into a cooling vat to obtain a novolak resin.

In addition, if the phenol such as O-cresol is solid, it is dissolved in a solvent such as water, and the desired resin is obtained by the same synthesis method.

Moreover, when obtaining a high ortho novolac, a metal salt of an organic acid was used as a catalyst.

Examples 1-5, Comparative Examples 1-3 The mold strength in the self-hardening mold making method was evaluated.

That is, 0.0% triacetin was added to 100 parts by weight of silica sand.
25 parts by weight of the water-soluble phenol resin obtained in (A) above (
Weight average molecular weight 3000) and Table 1 (=50% of the various novolak type phenolic resins shown and obtained in (B) above)
A mixture obtained by adding and kneading 0.3 parts by weight of a methanol solution was filled into a test piece model of 5QmmφX5Qmmh, and the compressive strength was measured 24 hours after kneading.

The results are shown in Table-1.

Examples 6-10 and Comparative Examples 4-6 The mold contact strength in the gas hardening mold making method was evaluated.

That is, to 100 parts by weight of silica sand, 2.0 parts by weight of the water-soluble phenolic resin obtained in the above (A) and 50% of the various novolak type phenolic resins shown in Table 2 and obtained in the above (B).
A mixture obtained by adding and kneading 0.4 parts by weight of a methanol solution was filled into a model for a gas curing test piece measuring 5QmmφX5Qmmh.

3.0 parts by weight of gaseous methyl formate was injected into this model, and the compressive strength was measured 24 hours after the injection.

The results are shown in Table-2.

〔Effect of the invention〕

As is clear from the above examples, according to the manufacturing method of the present invention, a mold with higher strength can be obtained than molds obtained by conventional manufacturing methods.

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

Applicant's agent Kaoru Furutani (3 other people)

Claims (1)

[Scope of Claims] 1. An organic ester curing type characterized in that the essential components are a water-soluble phenolic resin aqueous solution and one or more novolac type phenolic resins in an amount of 5 to 40% by weight based on the solid content thereof. Binder composition for foundry sand. 2. The binder composition for foundry sand according to claim 1, wherein the organic ester is gaseous.