JP2542144B2 - Binder composition for organic ester-curable foundry sand and method for producing mold using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an improved organic ester-curable casting used in a mold making method in which a water-soluble phenolic resin is added as a binder to a refractory granular material and is cured with an organic ester. The present invention relates to a binder composition for sand and a method for producing a mold using the same.

[0002]

2. Description of the Related Art As a molding method for manufacturing a mold such as a main mold or a core using an organic binder, a self-hardening mold method, a cold box mold method, a cloning method (shell Method) is known. In particular, the organic self-hardening mold molding method has already become a general-purpose molding method in place of the inorganic type from the viewpoints of productivity, casting quality, safety and health, etc. mainly in the field of mechanical casting. On the other hand, conventionally, in order to manufacture a mold at a medium or high speed, a phenolic resin is coated on a granular refractory,
A cloning method in which a so-called coated sand is heat-cured to produce a mold is widely used. However, energy saving during mold production, mold production speed, further mold, in order to improve the quality of the casting, cold box mold method to cure at room temperature with a gaseous or aerosol-like substance, as a method of producing a mold that replaces the cloning method, It has been seriously tried to be introduced in the foundry industry.

Further, as a binder used in the organic self-hardening mold making method and the gas-curing mold making method, a water-soluble phenol resin is used as a binder, and the binder composition for foundry sand is hardened with an organic ester. The products are known from JP-A-50-130627, JP-A-58-154433 and JP-A-58-154434. Mold molding method using this binder, since it does not contain a sulfur atom in the binder, while having a feature that the influence of vulcanization is less compared to the mold molding method using an acid-curable resin, Compared with the acid-curable mold making method, it has drawbacks such as low mold strength, short pot life, and poor sand reclaimability, and further improvement is desired.

[0004]

Means for Solving the Problems As a result of intensive research to solve the above-mentioned problems, the present inventors have added a water-soluble phenolic resin to a refractory granular material as a binder and added it with an organic ester. In the binder composition for foundry sand used in the mold molding method for curing, by containing a specific ratio of the phenol compound monomer to the water-soluble phenol resin, without lowering the final strength of the mold,
The inventors have found that the pot life can be greatly extended and have completed the present invention. That is, the present invention is characterized by containing, as an essential component, a water-soluble phenolic resin and one or two or more phenolic compound monomers of 2% by weight or more and less than 5% by weight based on the solid content thereof. Provided are a binder composition for ester hardening type molding sand and a method for producing a mold using the same.

The content of the phenol compound monomer in the binder composition of the present invention is 2% by weight or more and less than 5% by weight, preferably 3 to 4% by weight, based on the solid content of the aqueous water-soluble phenolic resin solution. %, And various phenol compound monomers can be used as the phenol compound monomer, but it is preferable to have two or three phenolic hydroxyl groups in one molecule. According to the present invention,
Since the pot life can be extended by adding the above-mentioned specific proportion of the phenol compound monomer, if the amount is less than 2% by weight, the effect of extending the pot life is not sufficient. Is not practical because the final strength is decreased. Examples of the phenol compound monomer used in the present invention include phenol, cresol, xylenol, cumylphenol, nonylphenol, butylphenol, phenylphenol, ethylphenol, octylphenol, amylphenol, naphthol, resorcin, bisphenol A, bisphenol F, Examples thereof include bisphenol C, catechol, hydroquinone, pyrogallol, phloroglysin, and the like, and a phenol compound including resorcin residue, bisphenol A residue, chlorophenol, dichlorophenol, and other substituted phenols can also be used.

The reason why the pot life can be greatly extended by using the binder composition of the present invention without lowering the final strength of the mold is presumed as follows. That is, by allowing a specific proportion of a phenol compound monomer to be present in an organic ester, the activation and polymerization of the water-soluble phenol resin due to the hydrolysis of the ester was delayed and the pot life was extended and activated. Since the phenol compound monomer is incorporated into the water-soluble phenol resin, it is considered that the final strength of the mold does not decrease. Further, it is considered that the phenolic hydroxyl group is deeply involved in the delaying effect and the ease of incorporation into the resin, and it is considered that two or more phenolic hydroxyl groups are contained than one having one phenolic hydroxyl group in one molecule. The one having a phenolic hydroxyl group is more effective. As a form in which the water-soluble phenol resin and the mixture of one or more phenol compound monomers in the above-mentioned specific proportions are used in combination, the phenol compound monomer is contained in the water-soluble phenol resin in a free state. Alternatively, it may be added to the refractory granular material separately from them. or,
At this time, it is also possible to add it after diluting it with a known solvent to improve the kneading property.

In the present invention, in order to manufacture a sand mold for casting by a self-hardening molding method, 0.05 to 9 parts by weight, preferably 0.1 to 5 parts by weight of organic ester as a curing agent is added to 100 parts by weight of a refractory granular material. , Water-soluble phenol resin aqueous solution (solid content concentration: 40 to 80% by weight) 0.4 to 15 parts by weight, preferably 0.6 to 5 parts by weight, and 1 of phenol compound monomer
Or more than 2% by weight, preferably less than 5% by weight, based on the solid content of the water-soluble phenolic resin aqueous solution.
Preferably, the mold can be produced by adding 3 wt% or more and 4 wt% or less , kneading by a known method, and using the conventional self-hardening mold production process as it is.

The water-soluble phenolic resin used in the present invention is a resin curable with an organic ester, such as phenol, cresol, resorcinol, 3,5-xylenol, bisphenol A, and phenols including other substituted phenols. Phenolic resins obtained by reacting with a mixture of formaldehyde, acetaldehyde, furfural aldehyde and aldehyde in a large amount of an aqueous solution of an alkaline substance. or,
A monomer capable of formaldehyde condensation such as urea, melamine, and cyclohexanone may be co-condensed with these to such an extent that they do not become the main constituent units in a weight ratio. Suitable alkaline substances used in the production of these water-soluble phenolic resins are sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof, with potassium hydroxide being particularly preferred.

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 is used alone or in a mixture. However, in the self-hardening molding method, γ-butyrolactone, propionolactone,
It is preferable to use ε-caprolactone, ethyl formate, ethylene glycol monoacetate, ethylene glycol diacetate, triacetin, dimethyl glutarate and the like. As the refractory granular material, in addition to silica sand containing silica as a main component, inorganic refractory granular materials such as chromite sand, zircon sand, olivine sand, and alumina sand are used, but are not particularly limited.

Conventionally, a silane coupling agent has been widely used as a part of a binder because it is effective for improving the mold strength. Known silane coupling agents are used in the present invention,
Preferred are γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane and the like. In the present invention, it is preferable to use this silane coupling agent together with a binder composition.

[0011]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Examples 1 to 9 and Comparative Examples 1 to 4 The pot life of the mold strength in the self-hardening mold making method was evaluated. That is, 0.38 parts by weight of dimethyl glutarate, 1.5 parts by weight of a water-soluble phenol resin having a solid content of 50% by weight, and 100 parts by weight of silica sand, various phenol compound monomers shown in Table 1 are added to the resin. A test piece model having a diameter of 50 mm and a height of 50 mm was filled with the mixture prepared by adding and mixing the weight% of the water-soluble phenolic resin shown in Table 1 to the solid content of the water-soluble phenol resin. The compression strength of the molded product after standing was measured. Table 1 shows the results. The solid content of the water-soluble phenolic resin aqueous solution is 100 ° C for 3 hours in a weighed sample (2.00 ± 0.1g) in an air circulation furnace.
It was measured by heating to.

[0012]

[Table 1]

* 1 Compressive strength: The compressive strength of a mold after molding and standing for 24 hours, measured under conditions of a temperature of 35 ° C. and a humidity of 60% RH. * 2 Evaluation result: ◎ = The pot life is very long and the final compressive strength does not decrease. ◯ = The pot life is long and the final compressive strength does not decrease. × = Beauty time is short, or final compressive strength is low. From the results shown in Table 1, the molded product made of the mixture using the binder composition of the present invention was 30% more molded immediately after kneading than the comparative product.
It can be seen that there is almost no difference in compressive strength between the molded product after being left for a minute and the pot life is evaluated well.

[0014]

As is apparent from the above examples, by using the binder composition of the present invention, a mold having a long pot life can be obtained as compared with the mold obtained by the conventional composition. . As a result, in the summer or when the sand temperature is high, or when molding a large mold or a mold with a complicated shape, when more work life is required, molds should be molded without lowering the mold strength. It becomes possible and practically useful.

Claims (4)

(57) [Claims] 1. An organic compound containing, as an essential component, a water-soluble phenolic resin and at least 2% by weight and less than 5% by weight relative to the solid content of one or more phenolic compound monomers. Ester hardening type binder composition for molding sand. 2. The binder composition for an organic ester-curable foundry sand according to claim 1, wherein the number of phenolic hydroxyl groups in one molecule of the phenol compound monomer is 2 or 3. . 3. The binder composition for organic ester-curable foundry sand according to claim 1, wherein the phenol compound monomer is contained in the organic ester. 4. A method for producing a mold using the organic ester-curable binder composition for molding sand according to any one of claims 1 to 3.